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Save the Elephants – South Africa

soon to become

Vegetation and Questionnaire Report

2013

by Dr. Michelle Henley

Table of Contents Background .................................................................................................................................................. 4

Introduction .................................................................................................................................................. 4

Aim............................................................................................................................................................... 6

Methods ........................................................................................................................................................ 6

Wire netting of trees ..................................................................................................................................6 Study sites of large trees monitored throughout the APNR.......................................................................7 Vegetation monitoring methods.................................................................................................................8 Questionnaire surveys .............................................................................................................................11 Photographic examples of aspects of the vegetation surveying methods ................................................12 Data analysis ...........................................................................................................................................15 Large tree surveys and tree nesting bird surveys ....................................................................................15 Questionnaire surveys .............................................................................................................................16

Results and discussion................................................................................................................................ 17

VLAKGEZICHT.......................................................................................................................................17 Overall type of elephant impact, impact intensity and impact age..................................................... 17

Contrasting wire protected trees with unprotected trees ................................................................... 22

NTSIRI .....................................................................................................................................................24 Overall type of elephant impact, impact intensity and impact age..................................................... 24


DE LUCA ................................................................................................................................................31 Overall type of elephant impact, impact intensity and impact age..................................................... 31


CHARLOSCAR........................................................................................................................................37 Overall type of elephant impact, impact intensity and impact age..................................................... 37


ROCK FIG...............................................................................................................................................44 Overall type of elephant impact, impact intensity and impact age..................................................... 44


SUMATRA ...............................................................................................................................................50 Overall type of elephant impact, impact intensity and impact age..................................................... 50


LARGE TREES WITH TREE NESTING BIRDS .................................................................................... 57

QUESTIONNAIRE SURVEYS................................................................................................................. 59

General statistics .....................................................................................................................................59 Plant species of concern with in relation to elephant impact..................................................................60 Bush encroachment and tall tree loss (STE-SA survey) ..........................................................................60

Conclusion.................................................................................................................................................. 66

Acknowledgements .................................................................................................................................... 67

References .................................................................................................................................................. 67

Background This report combines the results of three datasets along a common theme which considers the interaction between elephants and the vegetation. The datasets were obtained from:

(1) The large tree surveys conducted at specific study sites throughout the Associated Private Nature Reserves (APNR)

(2) The survey of the large trees used as nesting sites by raptors and vultures within the Klaserie Private Nature Reserve

(3) Questionnaire surveys were distributed to landowners, managers and tourist in 2003, 2007 and 2012, with tourists being included in the survey only in 2012.

The details relating to the methods, results and discussion of (2) are only briefly highlighted as the scientific manuscript entitled Direct and indirect effects of elephants (Loxodonta africana) on large trees used by vultures and raptors as nesting sites, South Africa is presently under review and will be distributed to all interested parties once accepted by the scientific journal. As for (3), only the results of the questions which relate to the vegetation in the questionnaire surveys are discussed here to avoid repetition with the comprehensive report that will be circulated in conjunction with Adam Edge, a BSc (Hons.) candidate from Western Kentucky University, USA who is still conducting his analyses.

Introduction Large trees are of aesthetic significance to managers and the public at large as they are considered important landscape features with certain species typifying the lowveld region in which they occur (Owen-Smith et al. 2006). Over and above their aesthetic importance, large trees have an important ecosystem function and are associated with a stable ecological state, which implies that they can function as suitable key indicators of ecosystem change (Druce et al. 2008). Large trees play a significant role in nutrient cycling (Ludwig et al. 2008, Treydte et al. 2008). Together with other woody vegetation, large trees provide shade and shelter for wildlife; reduce evapotranspiration and conductance in species growing beneath tree crowns and are, in themselves, an important food source to many herbivores (Belsky 1994).

Elephants are known to bark strip particular woody species, break large branches and uproot trees (Barnes 1982, Lewis 1986). Consequently elephants have the ability to increase habitat complexity by modifying the woody structure (Pringle 2008). Their feeding habits can thus lead to physiognomic vegetation change and result in ‘hedging effects’ (Smallie & O’Connor 2000, Styles & Skinner 2000, Lombard et al. 2001), changed tree shapes, reduced canopy height and volume and thereby increase the vegetation’s sensitivity to fire (Jacob and Biggs 2002b, Gauargis & Van Rooyen 2009). Elephant impact can decrease the structural diversity of the landscape and in combination with various confounding factors, lead to the loss of tall trees (Van Wyk & Fairall 1969, Coetzee et al. 1979, Pellew 1983, Fenton et al. 1998, Trollope et al. 1998, Eckhardt et al. 2000). In certain landscapes of the Kruger National Park (KNP) the Thresholds of Potential Concern (TPC) for the large tree component has already been exceeded (Jacob and Biggs 2002a&b). Some studies have shown that elephants’ structural modification of the landscape favours certain invertebrate and vertebrate communities (Govender 2005, Palmer et al. 2008, Pringle 2008) while others have found negative consequences to biodiversity (Cumming et al. 1997). Hence the activities of elephants on large trees can potentially threaten the biodiversity targets of the KNP and requires intense monitoring (Biggs et al. 2008).

Changes in the woody structure and composition could have significant implications for bird species (Herremans 1995, Cumming et al. 1997, Motsumi 2002, Kemp et al. 2003, Ogada et al. 2008). Various tree-nesting raptors which have been listed as vulnerable in the Red Data Book of Birds of South Africa, Lesotho and Swaziland (Barnes 2000) are potentially susceptible to the loss of nesting sites due to elephant impact (Botha 2005). For certain tree-nesting birds such as the Southern Ground Hornbill (Bucorvus leadbeateri), elephants may be removing potential or existing nesting sites by felling large trees. Elephants may also compromise the survival rate of important nesting trees by extensive ring-barking which may not be immediately apparent. Studies have shown that vultures select tall trees for nesting (Monadjem & Garcelon, 2005). It is also generally recognised that raptors are susceptible and sensitive to ecological changes and disturbance (Herremans et al. 1999, Bridgeford & Bridgeford 2003). Hence, elephant feeding habits could either be detrimental to the nesting sites of particular species of birds, have no effect at all or alternatively elephants could, by breaking primary branches, actually play a facilitating role in the creation of nests for species such as Southern Ground Hornbills (Henley & Henley 2005). A dearth of information concerning the nesting sites of savanna raptors necessitates research on the outcomes of elephant-raptor interactions (Kerley et al. 2008). Management interventions to reduce elephant impacts to large trees Management interventions aimed at reducing elephant impacts and the consequential response of biodiversity should be investigated (Kerley et al. 2008). Elephant impacts are modulated by resource availability and, consequently, spatially and temporarily altering elephants’ access to resources could modify their impact on the vegetation and promote heterogeneity.

Plant refuge areas either occur naturally where water is scarce (Echardt et al 2000), where steepness prevents access to certain vegetation types by specific herbivores (Bond & Loffell 2001, Edkins et al. 2007) or where bee hives are present (Vollrath & Douglas-Hamilton 2005a&b, King et al. 2007). Manipulating the distribution of water sources has been proposed as an important management tool which could be used to influence the distribution of elephants and ultimately their impact on the vegetation (Owen-Smith 1996, Chamaille-Jammes et al. 2007, O’Connor et al. 2007, Loarie et al. 2009b, Shannon 2008). Vegetation refugia can also be created artificially by using fences. Accordingly, exclusion plots could be erected around particularly vulnerable species and, if properly designed, these exclusion plots would not only protect rare species but could also provide much needed data on how climate and other herbivores affect recruitment rates. It would however, be important to remember that exclosures and exposures represent extremes of continuums and that historical perspectives would still be critical to determine which landscape features managers hope to achieve (Cowling & Kerley 2002).

Individual large trees can also be protected artificially by the direct application of wire netting to the mature stems in order to prevent these trees from being bark-stripped by elephants (Gordon 2003, Henley & Henley 2004). This method not only has very little visual impact but also does not prevent elephants and other herbivores from using the area entirely for other means. However, as wire-net protected trees can still be felled or uprooted by elephants, the absolute use or avoidance of protected trees may not be as important as the degree to which the tree-protection measure increases the survival rate of large trees (Grant et al 2007). A questionnaire survey conducted in 2003, 2007 and 2012 revealed that landowners within the Associated Private Nature Reserves (APNR) had expressed their concern about the impact of elephants on especially Sclerocarya birrea (Marula), Acacia nigrescens (Knob thorn) and Lannea schweinfurthii (False marula) trees. This report looks at the wire netting of specific tree

species to evaluate the effectiveness of this method in preventing the bark stripping of the monitored specimens. If this relatively simple technique effectively deters elephants from bark-stripping mature trees then it could be of importance for the following reasons: • Various large trees around camps and lodges are of aesthetic importance to landowners and

managers. Protecting these individuals would ensure the maintenance of the aesthetic features of the landscape.

• Protecting numerous trees within a relatively small area would create localised woodland refugia that would maintain the structural diversity of the landscape and prevent biodiversity loss at a larger scale.

• Woodland refugia may function as important seed reserves for future recolonisation of other areas.

Hence irrespective of the method that is used to restrict the spatial use of resource availability to elephants, artificial tree sanctuaries with large specimens can act as valuable seed banks to populate surrounding areas (Western & Maitumo 2004) and also preserve the aesthetic features of the landscape (Owen-Smith et al. 2006). The extent and intensity of use of plant refuges will depend on both the density and range use patterns of the herbivore under consideration. Elephants restrict their foraging distance, and consequentially their impacts on the vegetation, in relation to the distribution of water, but there is a difference between the sexes. Breeding herds are less likely to move more than 5 km from water than bulls (Stokke & Du Toit 2002, Wittemyer et al. 2007). Hence differences in movement patterns and feeding behaviour between the sexes are likely to influence the placement and efficacy of artificially maintained tree sanctuaries. Management interventions aimed at protecting large trees need to be evaluated in terms of the survival rate of large trees as valued aesthetic and ecological assets in relation to sex-related distinctions in habitat use by elephants and the consequential efficacy in preserving the nesting sites of large tree nesting birds.

Aim • To contribute towards the improved management of elephants by providing information

on the impact of elephants as drivers of ecosystem change in relation to indicator species such as large trees (primary) and selected tree nesting birds (secondary).

• To describe the societal distribution of human value systems that underlie ecosystem changes brought about by either human or elephant impact by means of questionnaire surveys.

Methods

Wire netting of trees Trees, defined as single stemmed woody plants, more than 2 m tall were considered suitable for treatment with wire netting. At some study sites all trees within a defined area were wire netted while at others wire netting was placed on some trees while leaving others as controls. At the Vlakgezicht, Ntsiri and Rock Fig study sites bird wire (13mm mesh, 1.8m tall) was wrapped around the tree trunk about 50cm off the ground to a height of approximately 230cm. On average 1.25m of wire was used per tree. The ends of the netting were stapled on the tree trunk with 25mm wire fencing staples. At the Sumatra study site part of the wire netting was folded double before stapling the two ends together to make allowance for the natural expansion of the tree

over time. When placing wire netting around a tree, care was taken to cut a few loops of wire around the entrances of any holes left by squirrels or smaller nesting birds to ensure easy and safe passage for these inhabitants in and out of the tree trunks. At the Charloscar study site diamond mesh with a 50 mm diameter was nailed onto the trees using 3 inch nails. At the De Luca study site bird wire with a 50 mm diameter was stapled onto the trees often at a height more than 50 cm off the ground.

Study sites of large trees monitored throughout the APNR Six study sites have been established within the APNR (Figure 1). On the Vlakgezicht property in the Timbavati a selection of 64 trees were initially monitored in July 2004. In November-December 2004 this study site was extended to include an additional 51 trees. In October 2005 a further 129 trees were incorporated into the monitoring programme. In February 2007 a total of 850 trees were labelled which were again monitored in 2008 and 2012. On Ntsiri in the Umbabat 100 trees have been monitored since 2005 with 10 additional trees added in February 2007 and subsequent surveys repeated in 2008 and 2012. At the De Luca study site in the Umbabat, certain trees were netted in November 2006 while stones were packed at the base of others more than six years ago. Monitoring of the trees at the De Luca study site took place in March 2007 and surveys were repeated in 2008 and 2012. In the Klaserie at the Charloscar study site 315 trees were monitored in February 2007 after they had all been wire netted in April 2006. In May 2008 an additional 300 trees (unprotected by wire netting) on the periphery of the block with wire-protected trees were added to the sample as control trees and all trees were again surveyed in 2012. At the Rock Fig study site in the Timbavati 38 trees were monitored in February 2007 after they had all been wire netted in November 2006, with subsequent monitoring in 2008 and 2012. The Sumatra study site was first surveyed in 2008 with 1346 trees surveyed in 2012. Over time a limited number of new study trees have been added at some of the study sites whilst in the search for particular trees that could not be found or were presumed dead due to various factors.

Figure 1 Location of the six study sites within the Associated Private Nature Reserves on the border with the Kruger National Park.

Figure 2 Location of large trees monitored for tree nesting vultures and raptors in the Klaserie Private Nature Reserve (KPNR). In the Klaserie Private Nature Reserve (KPNR) 100 large trees with either raptor or vulture nests have been monitored since 2008 (95 Acacia nigrescens and five Combretum imberbe, Leadwood trees). Trees with nests were initially located by means of previously recorded GPS coordinates that were obtained during census operations (Figure 2). In 2011 the stem circumference and height of all Acacia nigresens, Combretum imberbe (Leadwood), Sclerocarya birrea, Spirostachys africana (Tambotie) and Philenoptera violacea (Apple-leaf) tree species, known to be used by vultures and raptors as nesting sites within the KPNR, were measured in a 20 m radius around the main stem of the centrally located large tree with a nest. The stem diameters of these trees were measured at 50cm from the ground as standard DBH measurements were not possible for younger age classes. Measurement of trees in a 20 m radius of trees with nests provided an indication of the potential regeneration of the surrounding vegetation and the future replacement of trees with nests. In 2012 an additional 200 Acacia nigrescens control trees without nests but in close proximity to the trees with nests were monitored as control trees.

Vegetation monitoring methods The following methods, developed by Greyling (2004) and Henley & Henley (2007), with subsequent categorisation of data were used to monitor trees: 1) Each tree was labelled by hammering a numbered washer at breast height into the tree.

Where two trees were less than one metre apart, one label was used for both trees. 2) The number on each washer was recorded on the datasheet. 3) The tree species was recorded with the focus being on monitoring Acacia nigrescens,

Sclerocarya birrea and Lannea schweinfurthii trees. If the tree was a Sclerocarya birrea

tree the sex was determined (M-male, F-female) by looking for fruit kernels on the ground.

4) The tree location was recorded by writing down the GPS co-ordinates (decimals degrees h dd. ddd) while standing as close to the tree as possible after waiting for the GPS reading to record the location with an accuracy of at least a 5m radius.

5) Stem diameter was recorded at breast height (DBH) in cm 6) The height of the tree canopy was estimated at <1m, 1-2m, 2-3m, 3-5m or >5m. In 2012,

tree heights and volumes were determined using the method developed by Barret et al. (2012).

7) The impact type was recorded as: BS-bark stripping BBA-Primary branch breaking to access smaller plant parts

MS-Main stem breakage as the main stem has been snapped off UR-Uprooting, where the main stem had been pushed over 8) The extent of the impact for each of the different impact types were recorded according

to the following classes: Class 1: none

Class 2: < 1% Class 3: 1-5% Class 4: 5-10% Class 5: 10-25% Class 6: 25-50% Class 7: 50-75% Class 8: 75-90% Class 9: 90-99% Class 10: 100%

• Bark stripping (BS) was estimated according to the above mentioned impact classes by looking at the proportion of the circumference stripped of bark and not the length of bark that had been stripped. A tree that had been totally ring-barked fell within class 10, for example.

• Primary branch breaking to access smaller plant parts (BBA) was estimated according to the proportion of primary branches that had been broken. If for example a tree only had two primary branches and one of these had been broken then the impact category for BBA was class 6 or 7, depending on whether the broken branch was the smaller or larger of the two branches.

• If the tree was uprooted (UR) or the main stem broken (MS) within the past season and the tree was still alive (test by piercing the bark) or had just re-coppiced, then the impact was placed into the 90-99% (class 9) category. If the woody plant had subsequently died then the impact was scored at 100% (class 10). If the tree crown was still attached to a tree whose MS had been damaged but it was still alive, it would receive an impact class of 8. If the tree was uprooted, or the main stem snapped long enough ago for the re-coppicing material to form the main feature of the tree, then the impact class was scored according to the amount of re-coppice material present. If, for example, if the main stem was snapped but the re-coppiced material now made up 2/3 of the tree, the impact would be MS class 7. Uprooted trees that were alive but with half of their roots in the ground and the other half showing received an impact class of 8. If an uprooted tree was alive and still had all its roots in the ground but was

clearly pushed down, it was given an impact class of 7. If an uprooted tree was alive but just leaning with all its roots were still in the ground, it was given an impact class of 6.

9) The persistence of a tree to the next monitoring period was gauged and recorded according to the following criteria:

• Trees with no elephant impact were recorded as ‘no impact’ • A record was kept on the presence of shelf fungus (class Basidiomycetes), termite

(Coptotermes species), woodborer (Cerambycidae species), or other insect activity. Termite damage appears present when the bark is covered with red tunnel-like structures (5mm in diameter) radiating from the ground along the trunk of the tree whereas other insect damage was visible in the form of holes of various sizes bored into the inner bark. Shelf fungus was typically recognized as dark shelf-like structures present on the trunk or branches of a tree.

• Trees with elephant impact in the lower impact classes (2-6) were categorised as ‘light to moderate’

• Trees with elephant impact in the higher impact classes (7-10) were categorised as ‘moderate to heavy’

• BS die-back was recorded in the persistence column for all bark-stripping (BS) events in the ‘moderate to heavy’ category and where die-back on the branch tips was visible.

• BS alive was recorded in the persistence column for all bark-stripping (BS) events that fell in the ‘moderate to heavy’ category but where no die-back was recorded on the branch tips. For Sclerocarya birrea trees this often occurred due to healing of the debarked area.

• Unless otherwise specified in the field, ‘hedged’; was recorded in the persistence column where primary branch breaking to access smaller plant parts (BBA) events fell into the ‘moderate to heavy’ category and where the tree’s height had been altered from above 5m to below 5m. The sex of most Sclerocarya birrea that had been hedged, were recorded as ‘unknown’ as these trees did not bear fruit or alternatively fruit kernels beneath these trees were either very old or rare. Hence they could have incidentally been carried there by elephants or by baboons.

• Pollard (O’Connor et al. 2007) was recorded in the persistence column where the main stem (MS) had been snapped and the tree had either re-coppiced or the bark was still found to be alive (moderate to heavy). The sex of all Sclerocarya birrea that had been pollard more than one year ago was recorded as ‘unknown’ for the same reasons as outlined above.

• Uprooting (UR) was recorded where the tree had been uprooted (moderate to heavy). UR-r was recorded in the persistence column for all uprooted trees that had re-coppiced. The sex of all Sclerocarya birrea that had been uprooted more than one year ago was recorded as ‘unknown’ for the same reasons as outlined above.

• ‘Dead’ was recorded in the persistence column for all trees that had died due to extensive bark-stripping or snapping of the main stem by elephants in the past. ‘Dead-natural’ was recorded for all trees that had died due to insect attack, wind toppling or fire and which had no or very little other signs of elephant impact (light to moderate) during pervious surveys. ‘Dying-natural’ was recorded for all trees that had signs of die-back on the branches due to insect attack, wind toppling or fire and which had no

or very little other signs of elephant impact (light to moderate) during pervious surveys.

• ‘Not found’ (NF) was recorded for trees that could not be found in subsequent surveys and these missing trees were allocated to being killed by elephants if they had ‘moderate to heavy’ elephant impact recoded in previous years. If in previous years elephant impact was recorded as ‘light to moderate’ but other impact types (fire, insect attack, wind toppling etc.) had been noted, cause of death was allocated to any of these factors. In incidences where a missing tree could not be explained by either of the above, they were recorded as ‘NF-unkown’.

10) Tusk entry height: These measurements were only applicable where bark stripping had occurred and scars were visible where the tusk entered the tree. The height above the ground of the tusk entry point was measured. These measurements were only taken if the scar represented a tusk entry point otherwise it was preferably omitted.

11) Age of impact: Recent or current season impact was distinguished from old impact by the pinky fleshy colour of the exposed stem in the former: • Recent (within the past month) • Within the past dry season (6 month period) • Within the past year (past 12 months) • More than a year old (more than 12 months)

12) ‘Treatment’ was recorded as ‘none’, ‘wire-netting’, ‘natural protection by other plants’ or ‘protection by stone packing’, either alone or together with wire-net protection.

13) Additional ‘notes’ that were made included any healing that had subsequently occurred (especially for old Sclerocarya birrea bark-stripping events). The condition of the treatment method and whether it had deteriorated (wire rusted or too loose) was recorded. Notes were made on whether the wire had been penetrated by an elephant tusk (scaring on the bark beneath) or merely tested by an elephant (eye of the wire stretched but bark left untouched beneath).

14) The presence of a large bird nesting site such as the Southern Ground Hornbill, vultures or raptors (if possible by species). Where nests were present, a record was kept on whether the nest was considered active i.e. when a bird was sitting on the nest or if fresh bird droppings were visible in the vicinity of the nest.

Questionnaire surveys Identical questionnaires were distributed to landowners, shareblock holders and managers (reserves, shareblocks and lodges) within the APNR. The questionnaire was available in either English or Afrikaans and was circulated via email in 2003, 2007 and 2012. Respondents had up to three months to respond and could either post, hand deliver or return the questionnaire via email. The formulated questions were initially used to identify which woody plant species need to be monitored for elephant impact based on the concerns raised by landowners and managers alike. The questionnaires were also used to gather information on the perceptions of various parties in relation to:

• vegetation monitoring and changes in the vegetation structure (bush encroachment and tall tree loss);

• elephant research, water-point closure and the removal of the western boundary fence; • trophy hunting, green hunting and the culling of elephants; and

• ranking of various plant species that were found to constitute large dietary proportions of both bull and cow groups of elephants within the APNR (Greyling 2004).

In 2012 an additional survey was circulated simultaneously to not only the same affected parties of the APNR but also to tourists visiting the lodges within the Reserves. The additional questionnaire aimed to understand the perceptions of the different interest groups (managers, residents and tourist) towards elephants and large trees as well as towards the available management options concerning the conservation of elephants within South Africa. Questions were formulated to specifically contribute towards the ongoing large tree and elephant tracking project within the APNR and will form part of a B.Sc. (Hons) project conducted by Adam Edge.

Photographic examples of aspects of the vegetation surveying methods

Wire netting and label - Charloscar site Wire netting tested by elephant

Wire netting penetrated by elephant (<1% bark-stripping) Healing after bark-stripping

Pollarding (with re-coppice) – main stem snapped off Uprooting - the main stem is pushed over

Hedging – primary branches broken but main stem intact Die-back on branches after bark-strip

Mortality due to fire at Ntsiri study site. Note the empty wire cage

Mortality due to insect attack as no other signs Acacia nigrescens with a vulture nest in the crown

of elephant impact visible

Vulture incubating on its nest in an Acacia nigrescens

Data analysis

Large tree surveys and tree nesting bird surveys The frequency of occurrence of a specific impact type was determined across tree species for each site individually. The proportion that each of the impact types contributed to the total across all impact types within a specific size category (diameter at breast height) was determined irrespective of the species. Likewise, the proportion that each of the impact intensity classes contributed to the total across all impact classes within a specific size category (diameter at breast height) and for each impact type separately was determined irrespective of the species.

Species specific proportions of trees were grouped as either having no elephant impact,

light to moderate bark-stripping (BS) and/or primary branch breaking to access smaller plant parts (BBA), or moderate to heavy BS. Trees that were either hedged, pollard or uprooted in the higher impact classes, were grouped as being ‘structurally changed/modified’ by elephants. Trees that were heavily impacted upon by elephants which eventually lead to their death, or which could not be found in subsequent years of surveying, were described as having died due to elephant effects. Trees with no elephant impact or that were impacted upon in the lower elephant intensity classes but died after having signs of insect attack, fire scaring or wind toppling, were grouped as having died due to other causes. Included in this category were trees that died due to unknown causes (possibly shifting water tables etc.) or which could not be found in a particular year but were not heavily impacted upon by elephants in previous years.

To predict what proportion of a particular species which was still alive at the last survey may be more susceptible to mortality in future years, species specific proportions of trees were determined by combining trees with no to little elephant impact (<50%), or moderate to heavy elephant impact (>50%) with the presence or absence of other external signs of agents which could compromise the survival rates of trees in future (insects, fungus, fire or wind). Trees that had moderate to heavy elephant impact together with the presence of other external agents were considered to be the most vulnerable in future years.

Survival curves were used to test tree persistence and nest persistence of large tree nesting birds by means of the Mantel-Cox test. This nonparametric test was used for the analysis of survival curves on the basis of the hazard rate using censored data (Fry, 1992). The following survival curves were contrasted for each of the study sites separately: (1) tree persistence where only elephant induced tree mortalities were considered versus mortalities of trees irrespective of the underlying cause of death (2) tree persistence where trees were wire-net protected versus unprotected trees where only elephant induced mortalities were brought into consideration (3) tree persistence for trees with large tree nesting birds’ nests versus nest persistence within these trees.

The proportion of Sclerocarya birrea trees of a particular sex which were subjected to the various types of impact of different intensities were determined by counting the frequency of a particular impact intensity for each impact type and for each of the sexes. Fisher’s exact test was used to test for significant associations between impact and sex of the tree for each of the impact types after grouping impact intensity classes into either with or without impact to account for low frequencies.

Pie-charts were used to contrast wire-net protected and unprotected trees in terms of the relative contribution of each impact type across species, irrespective of the age of the impact where trees had died in previous years of surveying. Chi square tests were used to test for associations between impact type and tree protection method. Trees that were alive as well as

trees that had died due to having undergone BBA, MS or UR were grouped as structurally modified prior to analysis to account for small sample sizes in some categories. Binary logistic regression with backward selection of significant variables (tree height, DBH, impact category and termite , fungus or insect presence was used to determine the relationship between elephant impact and bird nesting sites as well as the abandonment of a tree previously used as a nesting site. The data of the 100 trees with nests and the 200 control trees were used for the analysis of tree selection while for the abandonment of trees previously used as nesting sites only the 100 trees with nests’ data was used in the analyses.

Questionnaire surveys With the questionnaire surveys, Chi square tests were used to test for differences between categories (differences in opinions between years and differences between resident/manager/tourist types within a year for each of the questions that were asked). Small frequencies within certain categories of the questionnaire prevented the use of Chi square tests. We here report on the percentage of respondents which agreed, disagreed or were neutral in their opinions on:

• vegetation monitoring and changes in the vegetation structure (bush encroachment and tall tree loss)

• ranking of various plant species that were found to constitute large dietary proportions of both bull and cow group of elephants (Greyling 2004).

Prior to analyses, questionnaires were grouped into those received from landowners and shareblock owners (seen as residents), managers of reserves, lodges or shareblocks and tourists. Shareblock owners or managers were either from Olifants River-, Olifants North Game Reserve, Ingwelala, Ntsiri or Ndlophu. GraphPad Prism 5.02 (GraphPad Software Inc. 2007) was used for statistical analysis and curve fitting. For binary logistic regression analysis on the influence of elephant impact, IBM SPSS Statistics 19 was used. General Linear Model analyses was conducted using MiniTab Statistical Software 13.31 (MiniTab Inc. 2000).

Results and discussion The same analyses are repeated for each of the study sites due to the interest of particular landowners.

VLAKGEZICHT The Vlakgezicht study site is predominately located on the vegetation type described as Terminalia sericea woodland on sandy soils (simplified map of the APNR). A total of 257 tree stems (including multi-stemmed species predominately found amongst Lannea schweinfurtii) have been protected by means of wire sleeves while 717 trees without wire protection have been monitored over time.

Overall type of elephant impact, impact intensity and impact age The most common impact type across all size/age categories and irrespective of the species under consideration was primary branch breaking to access smaller plant parts (BBA), followed by bark-stripping (BS). Main-stem breakage (MS) occurred in smaller size/age categories while the same applied to uprooting events (UR). Relatively few trees were found in the largest size/age category with one out of these five trees having been uprooted but still found to be alive. In general, relatively few trees were found to have no impact during the last survey (2012).

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Figure 3 The proportion of different impact types accumulative over time but irrespective of the plant species, and in relation to size classes as reflected by the DBH. When considering the intensity of elephant impact in 2012, similar trends were found with most trees showing a gradient of intensity of use across all size/age classes in the BBA and BS impact types. Irrespective of the impact type, smaller/younger age classes of trees appeared to be more

intensely used by elephants with regards to MS and UR. Although the latter two impact types occurred less frequently they were more inclined to be severe in nature (Figure 4).

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Figure 4 The proportion of various impact types (BS, BBA, MS and UR from top to bottom) in accordance with the intensity. Irrespective of the impact type, most elephant impact could be considered having occurred more than a year ago with relatively infrequent fresh impact (less than a month old) occurring within any particular year of surveying (Figure 5)

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BS BBA MS UR

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Figure 5 The frequency with which various impact types occurred and according to when the impact type took place, ranging from recent to more than a year ago. When contrasting the degree of elephant impact between first and most recent years of monitoring in which sample sizes were of equal proportions, trends in terms of ‘light to moderate’, ‘moderate to heavy’ and ‘structural changes’ per species type, were similar between years. Light to moderate elephant impact and structural changes to trees were the most prolific effects that elephants had on trees of all species and over time. However, a relatively large proportion of species had died over time due to either elephant impact or other causes such as fire, insect attack, wind toppling or other unknown causes, e.g. shifting water tables. Sclerocarya birrea appears to have suffered the highest relative proportion of mortalities when compared to other species. Approximately twice the proportion of trees, irrespective of the species, were lost due to elephant impact alone although death due to other causes did account for at least one third of the mortalities that were recorded across all species (Figure 6). Although a large proportion of the remaining trees had only no to little elephant impact (impact intensity of <50%) with no other signs of possible factors that could influences their survival rate in the long run, a substantial proportion of trees have no to little elephant impact or moderate to heavy elephant impact (impact intensity of >50%) together with other signs of external factors that could compromise their survival in the long run. Trees with moderate to heavy impact together with the presence of other external factors (fire, insect attack, wind toppling etc.) are expected to die within the medium to long term, thereby representing a potential loss of up to 12% across all species (Figure 7).

2007

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Marula

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2012

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Structure Changed

Moderate to Heavy BS

Light to Moderatedamage

No Impact

Figure 6 Species specific proportion of trees which had either no elephant impact, light to moderate or moderate to heavy elephant impact. Trees that were either structurally modified due to hedging, pollarding or uprooting or which had died directly due to elephant impact or other external factors (fire, insect attack, wind toppling or unknown causes) are also contrasted between years.

0%10%20%30%40%50%60%70%80%90%

100%

All spp. Combined

Knobthorn

Marula

False Marula

Other spp.

>50% elephant damage +external influences

>50% elephant damage +no external influences

<50% elephant damage +external influences

<50% elephant damage +no external influences

Figure 7 Proportion of different tree species affected by elephants or other external factors such as fire, insect attack or wind toppling in combination with various intensity of elephant use.

The results mentioned above were corroborated by comparing the survival curves of trees that were affected by elephant impact only with those which were affected by elephants and other agents as well (fire, insect attack, wind toppling or unknown causes). Over the eight year period of monitoring, survival rates of trees had dropped to 55.3±3.9% (mean ± SEM) whilst including the influence of other agents further lowered the survival rate to 40.3±3.8% (mean ± SEM) since the study was initiated (Figure 8). The effects of external factors other than elephants did have a significant influence on the survival rate of trees overall as the two curves were found to be significantly different from each other (Log rank Mantel-Cox Test, Chi square = 26.85, df=1, P<0.0001). It is important to note that many trees were found with either fire scarring or burnt to the ground during the 2008 survey (1383 days after the study was initiated). During this survey period 61 individual trees were found with fire scarring while 37 of these trees were found dead with indications of being burnt to death. The steep decrease in the survival curve following this point in time indicates that trees’ overall survival rate declined sharply after being subjected to fire. The effects of elephants prior to the fire could have made the trees more vulnerable to mortality by either lowering the tree canopy through hedging, pollarding and uprooting or by exposing the heartwood due to bark-stripping.

Figure 8 Changes in survival rates of large trees subjected to elephant effects and the combined effects of elephants and other agents such as fire, insects and wind or alternative unknown causes of mortality. As in previous years, male Sclerocarya birrea trees were more plentiful than female trees even if most of the trees classified as being of an unknown sex were to be considered female trees. Regardless of sex, comparatively few trees fell within the higher impact classes (Figure 9). Hemborg & Bond (2006) found that female Sclerocarya birrea trees were generally more injured than male trees, our results, however, were confounded by the comparatively large proportion of trees that could not be sexed due to having been hedged, pollard or uprooted (cf. methods). The lower frequency of female trees could possibly be attributed to higher mortality rates for this sex

over time. For the remaining trees, no significant differences in associations could be found between the sex of the tree and the presence or absence of impact when impact levels were pooled and tested for each of the impact types (‘bark-stripping’, ‘primary branch breaking’, ‘main stem snapping’ or ‘uprooting’) using Fisher’s exact test.

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Figure 9 Sex related impact levels for each of the four major impact types in Sclerocarya birrea

Contrasting wire protected trees with unprotected trees As agents such as insects, fire and wind should not be affected by the wire-net protection of large trees, survival rates for trees with and without wire-net protection were contrasted in cases where tree mortality could directly be ascribed to elephant impact. Wire-net protected trees had significantly higher survival rates when compared to unprotected trees. Over the eight year period of monitoring wire protected trees’ survival rate had dropped to 72.9±5.3% (mean ± SEM) whilst unprotected trees’ survival rate was found to be 42.8±7.2% (mean ± SEM). The two curves were significantly different from each other (Log rank Mantel-Cox Test, Chi square = 52.65, df=1, P<0.0001). Trees without wire declined more rapidly than wire-net protected trees after the 2008 survey, possibly indicating that fires not only make trees more vulnerable to subsequent attack by other agents (such as insects and wind) as well as elephants (Figure 10). Trees that were wire-net protected had a higher proportion of them left untouched, more of their primary branches broken to access smaller plant parts (BBA) and a lower relative proportion of mortalities (irrespective of the impact type) when compared to unprotected trees (Figure 11). Overall the association between wire-net protected and unprotected trees with impact type proved to be significant when impact classes relating to structural modification of the tree both for surviving as well as dead trees were grouped together (BBA, MS and UR) to enable Chi square analyses (Chi square = 62.5, df=7, P<0.0001).

Figure 10 Changes in survival rates of wire-net protected versus unprotected large trees that were subjected to elephant effects. For the wire-netting to continue offering the tree protection from elephant effects, it is important to maintain the wire cage around the tree. Baboons were found to pull the wire down over time, especially while climbing female Sclerocraya birrea trees to access the fruit. Furthermore elephants can rub up against a tree while a trees’ natural expansion with an increase in stem diameter over time can also open the wire ends around the tree trunk, thereby rendering it ineffective. On average, 8% of all trees protected by wire were either tested or penetrated (cf. photographic records) per survey year by elephants’ tusks.

Wire protected

13%

3%

31%32%

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none

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Alive with MS only

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Alive with combination of variousimpact typesDead with BS

Dead with BBA

Dead with MS

Dead with UR

Dead with a combination of elephantimpact typesDead from other causes

Figure 11 Relative proportions of various impact types for trees that were wire-net protected and unprotected at the Vlakgezicht study site. Bark-stripping (BS) on wire protected trees was inflicted prior to protecting the trees.

NTSIRI The Ntsiri study site is predominately located on the vegetation type described as Acacia nigrescens, Combretum apiculatum tall woodlands on deep soils (simplified map of the APNR). A total of 62 tree stems have been protected by means of wire-netting while 65 trees without wire protection have been monitored over time.

Overall type of elephant impact, impact intensity and impact age At the Ntsiri study site trees in the smaller and larger size categories were not included. Impact generally decreased with an increase in size although the proportion of trees with main stem breakage, irrespective of the species appeared to increase in the 50-59cm DBH category. The results for the larger size categories of trees was, however, constrained by small sample sizes. Uprooting occurred in relatively large proportions relative to other impact types in the lower size/age categories of trees (Figure 12)

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port

ion

of tr

ees

None BS BBA MS UR

Figure 12 The proportion of different impact types (BS- bark stripping; BBA- primary branches broken to access smaller plant parts; MS- main stem breakage; UR- uprooting) accumulative over time but irrespective of the plant species, and in relation to size classes as reflected by the DBH. As with other study sites, BBA and BS occurred relatively more frequently than other impact types and also showed more of a gradient in terms of proportional intensity of use. Main stem breakages and uprooting events all occurred in the higher impact classes (Figure 13). Most impact occurred more than a year ago although recent feeding events (within the past month) did occur on a number of occasions within specific impact types (Figure 14).

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Figure 13 The proportion of various impact types from top to bottom (BS-bark stripping; BBA-primary branches broken to access smaller plant parts, MS-main stem breakage; UR-uprooting) and in accordance with the intensity.

0

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BS BBA MS UR

> 1year

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< 6months

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Figure 14 The frequency with which various impact types occurred and according to when the impact type took place, ranging from recent to more than a year ago. When contrasting the degree of elephant impact between first and most recent years of monitoring in which sample sizes were of equal proportions, trends in terms of no impact, ‘light to moderate’ and ‘moderate to heavy’ were similar between years for all the species combined and for Acacia nigrescens. Across all species there was a marked increase in the relative proportion of trees killed by elephants or due to other causes. Changes in Lannea schweinfurtii impact types reflect the life history of a single specimen and can not be seen to be representative of the wider population (Figure 15).

2007

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2012

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Structure Changed



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A relatively small proportion of the remaining trees had no to little elephant impact (impact intensity of <50%) with no other signs of possible factors that could influences their survival rate in the long run. A substantial proportion of trees have no to little elephant impact together with other signs of external factors that could compromise their survival in the long run. Trees with moderate to heavy impact (impact intensity of >50%) together with the presence of other external factors (fire, insect attack, wind toppling etc.) are expected to die within the medium to long term, with Sclerocarya birrea trees looking particularly vulnerable at this study site (Figure 16).

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>50% elephant damage+ external influences

>50% elephant damage+ no externalinfluences

<50% elephant damage+ external influences

<50% elephant damage+ no externalinfluences

Figure 16 Proportion of different tree species affected by elephants or other external factors such as fire, insect attack or wind toppling in combination with various intensity of elephant use. Survival rates of trees had dropped to 65.8±4.9% (mean ± SEM) when only considering mortalities that could directly be attributed to elephants. Including the influence of other agents (such as fire, insect attack and wind toppling) further lowered the survival rate to 52.3±4.8% (mean ± SEM) since the study was initiated (Figure 17). The effects of external factors other than elephants influenced the overall survival rate of trees as the two curves were found to be significantly different from each other (Log rank Mantel-Cox Test, Chi square = 6.635, df=1, P<0.01). In September-October 2006 a management fire passed through the study site which meant that more than 50% of the Acacia nigrescens trees were found to be severely burnt while almost a quarter which had burnt to death, had no previous record of elephant impact when surveyed in 2005. The survival curve declined more sharply after the first survey post the burning event i.e. February of 2007 representing 557 days after the study was initiated. A similar trend was found for the Vlakgezicht study site when comparing pre-and post burning survival rates although the decline in survival rate post the fire for the latter study site was found to be steeper when compared to Ntsiri. These differences could possibly be explained in terms of the

intensity of the fire as the Vlakgezicht site which would have a higher fire load when compared to Ntsiri and consequentially result in a hotter burn.

Figure 17 Changes in survival rates of large trees subjected to elephant effects and the combined effects of elephants and other agents such as fire, insects and wind or alternative unknown causes of mortality. Compared to other study sites, male and female Sclerocarya birrea trees were more evenly numbered. Male trees were subjected to uprooting more frequently than female trees, which experienced heavier impact when considering all other impact types. However, no significant differences in associations could be found between the sex of the tree and the presence or absence of impact when impact levels were pooled and tested for each of the impact types using Fisher’s exact test.

.

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Figure 18 Sex related impact levels for each of the four major impact types (BS-bark-stripping; primary branch breaking-BBA; main stem snapping-MS or uprooting-UR) in Sclerocarya birrea

Contrasting wire protected trees with unprotected trees As agents such as insects, fire and wind should not be affected by the wire-net protection of large trees, survival rates for trees with and without wire-net protection were contrasted in cases where tree mortality could directly be ascribed to elephant impact. Over the seven year period of monitoring wire protected trees’ survival rate had dropped to 71.0±5.6% (mean ± SEM) whilst unprotected trees’ survival rate was found to be 56.4±9.8% (mean ± SEM). However, these differences did not prove to be significant (Log rank Mantel-Cox Test, Chi square = 3.48, df=1, P=0.062). Trees without wire declined more rapidly than wire-net protected trees after the 2007 survey, possibly indicating that fires not only make trees more vulnerable to subsequent attack by other agents (such as insects and wind) as well as elephants (Figure 19).

Figure 19 Changes in survival rates of wire-net protected versus unprotected large trees that were subjected to elephant effects. Trees that were wire-net protected had a higher proportion of them left untouched, more of their primary branches broken to access smaller plant parts (BBA), less bark-stripping (BS) and uprooting (UR) and a lower relative proportion of mortalities (especially in the ‘other causes’ category but which had fire scarring in previous years) when compared to unprotected trees (Figure 20). Overall the association between wire-net protected and unprotected trees with impact type proved to be significant when impact classes relating to structural modification of the tree both for surviving as well as dead trees were grouped together (BBA, MS and UR) to enable Chi square analyses (Chi square = 17.7, df=7, P=0.013). On average, 3% of all trees protected by wire were either tested or penetrated (cf. photographic records) per survey year by elephants’ tusks.

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none

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Figure 20 Relative proportions of various impact types for trees that were wire-net protected and unprotected at the Ntsiri study site. Bark-stripping (BS) on wire protected trees was inflicted prior to protecting the trees.

DE LUCA The De Luca study site is predominately located on the vegetation type described as Colophospermum mopane dense woodland and shrubveld (thicket) (simplified map of the APNR). A total of 22 trees have been monitored at this study site since 2007 of which 15 have been protected by means of wire sleeves or stone packing around the base of the tree.

Overall type of elephant impact, impact intensity and impact age All trees have been impacted upon at the De Luca study site with primary branch breaking to access smaller plant parts being the most prolific impact type. A number of trees in the lower size/age classes were bark stripped (BS) while one Sclerocarya birrea tree died due to being pollard by elephants. (Figure 21)

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ortio

n of

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s

None BS BBA MS UR

Figure 21 The proportion of different impact types (BS- bark stripping; BBA- primary branches broken to access smaller plant parts; MS- main stem breakage; UR- uprooting) accumulative over time but irrespective of the plant species, and in relation to size classes as reflected by the DBH. The majority of bark stripping (BS), with the exception of one individual tree, has occurred in the lower impact categories. Primary branch breaking to access smaller plant has also occurred at a low intensity. No uprooting events have occurred but one individual in the lower size/age categories has been pollard (Figure 22). Most impact occurred more than a year ago although recent feeding events (within the past month) included bark stripping as well as primary branch breaking to access smaller plant parts (Figure 23).

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> 1 year

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Figure 23 The frequency with which various impact types occurred and according to when the impact type took place, ranging from recent to more than a year ago. When contrasting the degree of elephant impact between first and most recent years of monitoring in which sample sizes were of equal proportions, ‘light to moderate’ impact has increased while ‘moderate to heavy’ were similar between years for all the species combined and for Sclerocarya birrea.. One specimen of the latter species has died due to elephant impact since the study was initiated (Figure 24).

2007

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Knobthorn Marula Other spp.

2012

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Dead (Elephant)

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No Impact

Figure 24 Species specific proportion of trees which had either no elephant impact, light to moderate or moderate to heavy elephant impact. Trees that were either structurally modified due to hedging, pollarding or uprooting or which had died directly due to elephant impact or other external factors (fire, insect attack, wind toppling or unknown causes) are also contrasted between years. A substantial proportion of the remaining Sclerocarya birrea and Lannea schweinfurthii trees had no to little elephant impact (impact intensity of <50%) with no other signs of possible factors that could influences their survival rate in the long run. A substantial proportion of trees have no to little elephant impact together with other signs of external factors that could compromise their

survival in the long run. A relatively small proportion of Sclerocarya birrea trees with moderate to heavy impact (impact intensity of >50%) but with no other external factors (fire, insect attack, wind toppling etc.) present, could be considered vulnerable in the near future (Figure 25).

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Knobthorn Marula FalseMarula





Figure 25 Proportion of different tree species affected by elephants or other external factors such as fire, insect attack or wind toppling in combination with various intensity of elephant use. As no trees had died due to other agents (fire, insect attack or wind toppling), a comparison could not be drawn between the survival curves of trees affected by elephants as opposed to other factors. Male Sclerocarya birrea trees were bark-stripped more frequently than female trees. Female trees appeared to be more prone to being pollard by elephants than male trees as one female tree was lost due to this impact type while another was heavily impacted upon in this impact category (Figure 26)

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Contrasting wire protected trees with unprotected trees Over the five year period of monitoring, wire protected trees’survival rate had dropped to 93.3±6.4% (mean ± SEM) whilst unprotected trees’ survival rate was found to be remain 100%. However, these differences did not prove to be significant (Log rank Mantel-Cox Test, Chi square = 0.40, df=1, P=0.527) and the differences can be attributed to the one Sclerocarya birrea tree which was felled by elephants. Wire-net protection was primarily employed to increase the survival rate of trees by preventing bark stripping but it was not thought to prevent the felling or uprooting of trees by elephants. Hence the small sample sizes of surveyed trees at this study site have confounded the interpretation of the results with regards to the efficacy of the wire-netting technique (Figure 27).

Figure 27 Changes in survival rates of wire-net protected versus unprotected large trees that were subjected to elephant effects. Both wire-net protected and unprotected trees had substantial proportions of bark stripping events in combination with primary branch breaking to access smaller plant parts. However, it should be noted that trees were often wire-net protected after they had been bark-stripped in the past. Hence any bark stripping events post wire-net protection of a tree was recorded as ‘penetration’ events while the stretching of the eyes of the wire to try and reach the bark but without actual contact with the tree stem, was recorded as a ‘testing’ event. Consequently, the bark-stripping proportions indicated on wire-protected trees refer to bark stripping events prior to the application of tree protection techniques. In addition, a large proportion of trees with wire-netting were tested in 2012 (33%) while almost all wire-net protected trees required maintenance as 87% of the trees’ wire had been rubbed open by elephants. With consequential recent bark-stripping were the wire had been removed (Figure 28). Small sample sizes in various impact categories prevented Chi square tests for association between impact and treatment (wire-net or unprotected) type.

Wire protected7%

46%

40%

7%

Unprotected

0%

71%

BS only

BBA only

Combination of variouselephant impact types

MS only

Figure 28 Relative proportions of various impact types for trees that were wire-net protected and unprotected at the De Luca study site. Bark-stripping (BS) on wire protected trees was inflicted prior to protecting the trees.

CHARLOSCAR The Charloscar study site is predominately located on the vegetation type described as Acacia nigrescens, Combretum apiculatum tall woodland on deep soils (simplified map of the APNR). A total of 621 trees have been monitored since 2007 of which 324 have been protected by wire-netting

Overall type of elephant impact, impact intensity and impact age At the Charloscar study site a relatively large proportion of trees have not been impacted upon by elephants. Overall, trees in the larger size/age categories were bark-stripped, uprooted and pollard less than younger trees. The bark stripping of the largest size/age category is represented by two individual trees with light to moderate elephant impact (Figure 29).

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0-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89 larger

DBH (cm)

Prop

ortio

n of

tree

s

None BS BBA MS UR

Figure 29 The proportion of different impact types (BS- bark stripping; BBA- primary branches broken to access smaller plant parts; MS- main stem breakage; UR- uprooting) accumulative over time but irrespective of the plant species, and in relation to size classes as reflected by the DBH. A small proportion of trees have undergone main stem breakage (MS) in the higher impact categories while the majority of bark-stripping (BS) and primary branch breakage events to access smaller parts (BBA) have been of light to moderate intensity. Uprooting events occurred more frequently on younger trees and were generally of moderate to heavy intensity (Figure 30). In comparison to the other study sites, Charloscar has experienced relatively little elephant feeding effects, of which most were of low intensity. As with other sites, most impact occurred more than a year ago with relatively few recent bark-stripping, primary branch breaking to access smaller plant parts and main stem breakage events (Figure 31).

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100%

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90+cm

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8 (75‐90%)

7 (50‐75%)

6 (25‐50%)

5 (10‐25%)

4 (5‐10%)

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2 (<1%)

1 (0%)

Figure 30 The proportion of various impact types from top to bottom (BS-bark stripping; BBA-primary branches broken to access smaller plant parts, MS-main stem breakage; UR-uprooting) and in accordance with the intensity. .

0

50

100

150

200

250

300

BS BBA MS UR

> 1 year

< 1 year

< 6 months

< 1 month

Figure 31 The frequency with which various impact types occurred and according to when the impact type took place, ranging from recent to more than a year ago.

When contrasting the degree of elephant impact between first and most recent years of monitoring in which sample sizes were of equal proportions, trends in terms of none and ‘light to moderate’ impact intensity per species type, were similar between years. Acacia nigrescens trees experienced the least change between years when compared to other species. A proportion of almost 10% relative to the other impact intensities could be ascribed to mortalities directly related to elephants. A substantially smaller proportion of mortalities were due to agents other than elephants which included insects, fire or wind toppling. (Figure 32). Trees at the Charloscar study site appear to be particularly susceptible to the effects of insects as most trees had insects present (63%) with termites and borers being the most prevalent. Many of the trees were found to be hollow inside which could be indicative of a shortened lifespan. A large proportion of trees had light to moderate elephant impact together with the presence of external agents which could compromise the survival of the trees. Overall just below 10% of all species had moderate to heavy elephant impact together with the presence of other impact agents which would mean that this proportion of trees relative to other impact intensity classes could be expected to die within the medium to long term (Figure 33). Sclerocarya birrea trees appear to be more vulnerable than Acacia nigrescens. When comparing the survival curves of trees that were affected by elephant impact only with those which were affected by elephants and other agents as well (fire, insect attack, wind toppling or unknown causes), survival rates of trees had dropped to 87.2±1.6% (mean ± SEM) whilst including the influence of other agents further lowered the survival rate to 84.8±1.7% (mean ± SEM) since the study was initiated (Figure 34). Despite the substantial presence of other agents which can influence the longevity of the trees, the effects of external factors other than elephants did not have a significant influence on the survival rate of trees overall as the two curves were found to be similar (Log rank Mantel-Cox Test, Chi square = 1.35, df=1, P=0.246). The Charloscar study site had one of the highest survival rates compared to other study sites with comparatively little elephant impact (Figure 34) which could probably be ascribed to the lack of permanent water within the study site and the absence of fire in recent years.

2008

0%

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All spp.Combined


2012

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Dead (Elephant)

Structure Changed



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All spp.Combined



>50% elephant damage + noexternal influences


<50% elephant damage + noexternal influences


Figure 34 Changes in survival rates of large trees subjected to elephant effects and the combined effects of elephants and other agents such as fire, insects and wind or alternative unknown causes of mortality. Male Sclerocarya birrea trees were predominant on Charloscar. Near equal proportions of moderate to heavy elephant impact in terms of primary branch breakage to access smaller plant parts, main stem breakage and uprooting occurred in greater proportions on male trees as opposed to female trees (Figure 35). No significant differences in associations could be found between the sex of the tree and the presence or absence of impact when impact levels were pooled and tested for each of the impact types (‘bark-stripping’, ‘primary branch breaking’, ‘main stem snapping’ or ‘uprooting’) using Fisher’s exact test.

BS

0

50

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Male Female Unknown

Heavy Impact

Light Impact

No Impact

BBA

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50100

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MS

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100

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Male Female Unknown

Heavy Impact

Light Impact

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UR

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Male Female Unknown

Heavy Impact

Light Impact

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Contrasting wire protected trees with unprotected trees As agents such as insects, fire and wind should not be affected by the wire-net protection of large trees, survival rates for trees with and without wire-net protection were contrasted in cases where tree mortality could directly be ascribed to elephant impact. Wire-net protected trees did not have significantly higher survival rates when compared to unprotected trees. Over the five year period of monitoring wire protected trees’ survival rate had dropped to 92.5±1.5% (mean ± SEM) whilst unprotected trees’ survival rate was found to be 87.9±1.9% (mean ± SEM) since the study was initiated (Figure 36). The two curves were not significantly different from each other (Log rank Mantel-Cox Test, Chi square = 3.79, df=1, P=0.051).

Figure 36 Changes in survival rates of wire-net protected versus unprotected large trees that were subjected to elephant effects. Trees that were wire-net protected had a higher proportion of them left untouched, with less of them bark stripped, pollard or uprooted. There was also far less proportions of trees with combinations of elephant impacts on wire protected trees (Figure 37). Overall the association between wire-net protected and unprotected trees with impact type proved to be significant when impact classes relating to structural modification of the tree both for surviving as well as dead trees were grouped together (BBA, MS and UR) to enable Chi square analyses (Chi square = 24.7, df=7, P=0.0009). On average, 5% of all trees protected by wire were either tested or penetrated (cf. photographic records) per survey year by elephants’ tusks.

Wire protected

29%

13%39%

1%

1%

6%

1%

1%

1%5% 1% 2%

Unprotected

18%

14%

32%

2%

4%

15%

2%

1%

3% 5%

1%

3% none

Alive with BS only

Alive with BBA only

Alive with MS only

Alive with UR only

Alive with combination of various impact types

Dead with BS

Dead with BBA

Dead with MS

Dead with UR

Dead with a combination of elephant impact types

Dead with unknown causes

Figure 37 Relative proportions of various impact types for trees that were wire-net protected and unprotected at the Charloscar study site. Bark-stripping (BS) on wire protected trees was inflicted prior to protecting the trees.

ROCK FIG The Rock Fig study site is predominately located on the vegetation type described as Acacia nigrescens, Combretum apiculatum tall woodland on deep soils (simplified map of the APNR). A total of 38 trees have been protected by means of wire netting.

Overall type of elephant impact, impact intensity and impact age All trees have been impacted upon at the Rock Fig study site. In general, the proportion of impact declined with an increase in the size/age of the tree. One tree was pollard and two trees uprooted, one of which due to construction work in the surrounding area. Three of the trees are within the camp boundaries to which elephants don’t have free access (Figure 38).

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0-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89 larger

DBH categories (cm)

Prop

ortio

n of

tree

s

None BS BBA MS UR

Figure 38 The proportion of different impact types (BS- bark stripping; BBA- primary branches broken to access smaller plant parts; MS- main stem breakage; UR- uprooting) accumulative over time but irrespective of the plant species, and in relation to size classes as reflected by the DBH. The intensity of the different impact types was relatively low with the exception of the three individual trees that have subsequently died and which are mentioned above. Moderate to heavy impact occurred in the smaller size classes trees that were bark-stripped by elephants (Figure 39). However, it should be noted that no fresh impact by elephants occurred and hence bark-stripping events refer to the extent of bark stripping that occurred prior to the application of the wire-netting. The bark-stripping event that occurred within the past year was due to humans utilizing the bark of Cassia abbreviata (Figure 40).

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1

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4

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7

8

BS BBA MS UR

> 1 year

< 1 year

< 6 months

< 1 month

Figure 40 The frequency with which various impact types occurred and according to when the impact type took place, ranging from recent to more than a year ago. When contrasting the degree of elephant impact between first and most recent years of monitoring in which sample sizes were of equal proportions, two trees had died due to elephant impact while two deaths were caused due to anthropogenic influences. A tree had died due to insect attack (Figure 41).

2007

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Knobthorn

Marula

False Marula

Other spp.

2012

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All spp. Combined

Knobthorn

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False Marula

Other spp.

Dead (Other)

Dead (Elephant)

Structure Changed



No Impact


A substantial proportion of the remaining trees had no to little elephant impact (impact intensity of <50%) with no other signs of possible factors that could influences their survival rate in the long run. Similarly, a large proportion of trees (especially Sclerocarya birrea) had no to little elephant impact together with other agents that could impact on the trees’ survival rate. Only a very small proportion of Acacia nigrescens trees had moderate to heavy elephant impact together with other signs of external factors (fire, insect attack, wind toppling etc.) and which are consequently expected to die within the medium to long term (Figure 41).

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All spp.Combined






Figure 41 Proportion of different tree species affected by elephants or other external factors such as fire, insect attack or wind toppling in combination with various intensity of elephant use. Survival rates of trees had dropped to 89.3±5.1% (mean ± SEM) when only considering mortalities that could directly be attributed to elephants. Including the influence of other agents (such as fire, insect attack and wind toppling) further lowered the survival rate to 78.9±6.6% (mean ± SEM) since the study was initiated (Figure 42). The effects of external factors other than elephants didn’t influenced the overall survival rate of trees to a large extent as the two curves weren’t found to be significantly different from each other (Log rank Mantel-Cox Test, Chi square = 1.418, df=1, P=0.234). Male and female Sclerocarya birrea trees occurred in equal proportions but female trees were generally more utilised than male trees (Figure 43). Small sample sizes in various impact categories prevented Chi square tests for association between impact type and sex.

Contrasting wire protected trees with unprotected trees Wire protected and unprotected trees could not be contrasted with each other as all trees were wire-net protected at this site. Although a few trees have been severely impacted nearly half of the trees have not been affected by elephants (Figure 44). On average, 5% of all trees protected by wire were either tested or penetrated (cf. photographic records) per survey year by elephants’ tusks. Up to 39% of the wire-net protected trees at this site require maintenance as the wire has either been rubbed open by elephants or gradually pulled down by baboons.

Figure 42 Changes in survival rates of large trees subjected to elephant effects and the combined effects of elephants and other agents such as fire, insects and wind or alternative unknown causes of mortality.

BS

0

1

2

3

Male Female Unknown

Heavy Impact

Light Impact

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Heavy Impact

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Male Female Unknown

Heavy Impact

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No Impact


Wire protected

49%

24%

21%

3% 3%

none BS only

BBA only MS only

UR only

Figure 44. The proportions of various impact types for trees that were wire-net protected and at the Rock Fig study site. Bark-stripping (BS) on wire protected trees was inflicted prior to protecting the trees.

SUMATRA The Sumatra study site overlays predominately two vegetation types described as Colophospermum mopane - Combretum apiculatum woodland in the west and Colophospermum mopane dense woodland and shrubland (thicket) in the east (simplified map of the APNR). A total of 839 trees have been wire-net protected together with 506 unprotected trees.

Overall type of elephant impact, impact intensity and impact age A relatively small proportion of trees have been left unutilised by herbivores. The most common impact type across all size/age categories and irrespective of the species under consideration was primary branch breaking to access smaller plant parts (BBA). The proportion of bark-stripping (BS) per size/age category increased from the 10-19 up until the 80-89 DBH categories. Both main stem breakage (MS) and uprooting (UR) increased to its highest proportion in the 30-39 DBH category, thereafter decreasing again (Figure 45). Trees broader than 70 DBH generally had fewer impact types with the impact being of low intensity with the exception of a small proportion of large trees that were intensely bark-stripped and uprooted in these larger size/age categories. Most trees showed a gradient of intensity of use across all size/age classes in the BS and BBA impact type with the latter impact type being most prevalent and of the highest intensity in smaller/younger trees (Figure 46).

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0-9 10-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89 larger

DBH (cm)

Prop

ortio

n of

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s

None BS BBA MS UR

Figure 45 The proportion of different impact types accumulative over time but irrespective of the plant species, and in relation to size classes as reflected by the DBH.

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Figure 46 The proportion of various impact types (BS, BBA, MS and UR from top to bottom) in accordance with the intensity.

Irrespective of the impact type, most elephant impact could be considered as having occurred more than a year ago with relatively infrequent fresh impact (less than a month old) occurring within any particular year of surveying and in this instance, only in the primary branch breakage to access smaller plant parts (BBA) category (Figure 47)

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Figure 47 The frequency with which various impact types occurred and according to when the impact type took place, ranging from recent to more than a year ago. When contrasting the degree of elephant impact between first and most recent years of monitoring in which sample sizes were of equal proportions, a number of trees have died due to elephant impact and other agents (fire, insect attack and wild toppling) over the five year period. The proportion of trees that have died due to other factors has been lower than those trees that have died due to elephant effects. A proportion of Sclerocarya birrea which were alive but structurally modified in 2008 have died in recent times. Compared to the other species that were surveyed, Sclerocarya birrea, Acacia nigrescens and Lannea schweinfurtii are more affected by elephants in decreasing order of severity. As these species are found in lower densities than the surrounding Colophospermum mopane trees, they are probably used more often than reflected by their relative abundance and could consequently be considered favoured species. (Figure 48). Although a large proportion of the remaining trees had only no to little elephant impact (impact intensity of <50%) with no other signs of possible factors that could influences their survival rate in the long run, a substantial proportion of trees have no to little elephant impact or moderate to heavy elephant impact (impact intensity of >50%) together with other signs of external factors that could compromise their survival in the long run. Trees with moderate to heavy impact together with the presence of other external factors (fire, insect attack, wind toppling etc.) are expected to die within the medium to long term, thereby representing a potential loss of over 10% across all species (Figure 49).

2008

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2012

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<50% elephant damage + noexternal influences


Comparing the survival curves of trees that were affected by elephant impact only with those which were affected by elephants and other agents as well (fire, insect attack, wind toppling or unknown causes), showed that over a five year period, survival rates of trees had dropped to 86.4±0.94% (mean ± SEM) whilst including the influence of other agents further lowered the survival rate to 83.2±1.03% (mean ± SEM) since the study was initiated (Figure 50). The effects of external factors other than elephants did have a significant influence on the survival rate of trees overall as the two curves were found to be significantly different from each other (Log rank Mantel-Cox Test, Chi square = 5.14 df=1, P=0.023).

Figure 50 Changes in survival rates of large trees subjected to elephant effects and the combined effects of elephants and other agents such as fire, insects and wind or alternative unknown causes of mortality. Male Sclerocarya birrea trees were more plentiful than female trees and also appeared to be utilized more heavily by elephants when compared to female trees (Figure 51). Overall, both male and female trees frequently had their primary branches broken to access smaller plant parts. These results corroborate with the high proportion of Sclerocarya birrea trees which were found to be structurally modified at the Sumatra study site (Figure 51). No significant differences in associations could be found between the sex of the tree and the presence or absence of impact when impact levels were pooled and tested for each of the impact types (‘bark-stripping’, ‘primary branch breaking’, ‘main stem snapping’ or ‘uprooting’) using Fisher’s exact test.

BS

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Contrasting wire protected trees with unprotected trees As agents such as insects, fire and wind should not be affected by the wire-net protection of large trees, survival rates for trees with and without wire-net protection were contrasted in cases where tree mortality could directly be ascribed to elephant impact. Wire-net protected trees had significantly higher survival rates when compared to unprotected trees (Figure 52). Over the five year period of monitoring, the wire protected trees’ survival rate had dropped to 89.0±1.1% (mean ± SEM) whilst unprotected trees’ survival rate was found to be 82.1±1.7% (mean ± SEM). The two curves were significantly different from each other (Log rank Mantel-Cox Test, Chi square = 12.5, df=1, P=0.0004). Trees that were wire-net protected had a higher proportion of them left untouched and with less trees main stems broken or uprooted. Overall, wire-net protected trees had a lower relative proportion of mortalities (irrespective of the impact type) when compared to unprotected trees. The relatively large proportion of bark stripping which is reflected on the wire-net protected trees refers to bark stripping that occurred prior to wire-net protecting the tree (Figure 53). The association between wire-net protected and unprotected trees with impact type proved to be significant when impact classes relating to structural modification of the tree both for surviving as well as dead trees were grouped together (BBA, MS and UR) to enable Chi square analyses (Chi square = 77.2, df=7, P<0.0001). On average, 3% of all trees protected by wire were either tested or penetrated (cf. photographic records) per survey year by elephants’ tusks.

Figure 52 Changes in survival rates of wire-net protected versus unprotected large trees that were subjected to elephant effects.

Wire protected

10%

7%

53%

2%

2%

14%

1%

2%3%

3% 1% 2%

Unprotected

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1%

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1%

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4%1% 4%

4%

none

Alive with BS only

Alive with BBA only

Alive with MS only

Alive with UR only


Dead with BBA

Dead with MS

Dead with UR


Figure 53 Relative proportions of various impact types for trees that were wire-net protected and unprotected at the Sumatra study site. Bark-stripping (BS) on wire protected trees was inflicted prior to protecting the trees.

LARGE TREES WITH TREE NESTING BIRDS The results from the study with the vulture and raptor nesting sites in the KPNR can be bulleted as follows:

• Bark-stripping as an impact type was most prolific on large trees with nesting sites • Elephant impact did not differ between trees with nests and control trees without nests

but trees with nests were taller and a larger proportion of these trees had lower elephant impact and were less affected by insects and fungus

• Overall elephant impact was low, irrespective of tree or nesting bird type. Of the trees with nests there were significantly more trees in lower impact classes with few in higher impact classes (>50%)

• Impacted trees with vulture nests had relatively lower elephant impact compared to trees with raptor nests as 90% of trees with vulture nests had low elephant impact while only 71% of impacted trees with raptor nests had low elephant impact. Vultures may be more sensitive to the die-back of the nesting tree as they build their nests on the upper crown and require a fine network of branches to enable sufficient buoyancy to carry the nest. Raptors prefer to build nests in the fork of the upper branches.

• Higher elephant impact classes increased the chances of recording insects and fungus. • A tree with larger DBH and an absence of insect activity had higher survival rates • Elephants could indirectly be influencing survival rates of large trees as accumulated

elephant impact on older trees could render these trees as unusable as potential nesting sites because of increased arthropod and fungus evasions over time.

• In 2008, at the start of the study, all monitored trees were still alive and had active nest sites. The survival rate of nests declined significantly more than trees (Log rank Mantel-Cox Test, Chi square = 131.2 df=1, P<0.0001).with as much as 79%of the nests being lost by 2012. Over the five year period, survival rates of trees had dropped to 78.5±3.58% (mean ± SEM) whilst the survival rate of nests was 21.3±3.04% (mean ± SEM) since the study was initiated (Figure 53).

Figure 53 Survival curves for trees with vultures and raptors and for nest found within these large trees respectively.

• Overall, there is a high generation/recruitment of potential nesting sites on which elephants have a negligible influence as an inverse J-shape was found with most trees in younger age classes (Figure 54)

0

200

400

600

800

1000

1200

≤10 11-19 20-29 30-39 40-49 50-59 ≥60

DBH (cm)

Num

ber o

f ind

ivid

uals

Figure 54 The frequency of seedlings and younger trees found in the immediate vicinity of the centrally located large trees with nesting sites

QUESTIONNAIRE SURVEYS General statistics For the questionnaire distributed by Save the Elephants – South Africa (STE-SA), a total of 76, 131 and 89 questionnaires were returned in 2003, 2008 and 2012 respectively. Questionnaire responses from resident stake holders of the APNR were grouped into those received from landowners, shareblock owners and managers of the Reserves, shareblocks or lodges respectively. For the questionnaire distributed by Western Kentucky University (WKU) in 2012, an additional questionnaire which was distributed together with the STE-SA questionnaire to the same affected parties within the APNR, 83 were returned. In addition 138 questionnaires were returned from tourists from Kings Camp, Tanda Tula Safari Camp, Umlani Bush Camp and Rock Fig in the Timbavati Private Nature Reserve. In Balule Private Nature Reserve, tourist respondents came from Tora Yaka Bush lodge, Tremisana Game Lodge, Ezulweni River lodge and Naledi Enkoveni. All tourist surveys were distributed in hard copy by the lodge managers and collected over time. In general we had more than a 20% return on the questionnaires that were distributed to residents via email. However, if one includes that Shareblock managers may have distributed the questionnaire to all their members or if all shareblock members were to have responded to questionnaires surveys posted on the respective websites, then returns may have dropped to just over 10% for each of the years. The general statistic relating to the 2012 questionnaires are depicted in Table 1.

Table 1 Summary of the number of questionnaires distributed and returned to STE-SA and WKU respectively in 2012.

STE‐SAResident Resident Tourist

Sent (known) 350 350 485Sent (presumed) 644 644Recieved 89 83 138

25.43% 23.71% 28.45%13.82% 12.89%

Return %

WKUSent/Recieved

Most resident respondents were South African citizens, males and retired (over 60 years of age). In contrast, most tourist respondents were non-South Africans, females and younger than 60 years of age (Table 2).

Table 2 The nationality, Gender and age of resident and tourist respondents of both the STE-SA and WKU questionnaire

Demographic Nationality Gender Age SA Non-SA Male Female Under 50 50 and Over

Resident 66 18 77 15 31 53 Tourist 36 101 64 75 73 65

For the resident respondents of both the STE-SA and WKU questionnaire, the majority of the resident respondents to both the STE-SA and WKU questionnaire were resident for more than

five years but less than 20 years but infrequent visitors to the APNR (Table 3&4). Tourists were mainly return visitors to South Africa (Table 4).

Table 3 Number of resident respondents that were either landowners, Shareblock owners or managers in the APNR, including the number of years of residency or ownership in the area.

Residency Resident Position Years of Residency

Landowner Shareblock Manager Other 5 and Under 6-20 21+46 30 13 2 17 40 33

Table 4 Residents number of visits to the APNR in contrast with those of tourists based at the lodges when questionnaires were distributed by WKU.

'Visits'

Permanent / SA Resident

Frequent / Been to

SA before

Infrequent / First time to

SA Resident 21 33 36 Tourist 37 86 9

Plant species of concern with in relation to elephant impact The abovementioned questionnaire survey distributed in 2003 identified three plant species of particular concern with regards to elephant impact. Consequently, the vegetation surveys focussed on elephant impacts on Sclerocarya birrea, Acacia nigrescens and Lannea schweinfurtii as these species are utilized in a similar way (bark-stripped for the two former species and large branch breakage or felling for all three species) and are often sought after by elephants in the presence of other species at particular times of the year (favoured species). Both Sclerocarya birrea and Acacia nigrescens were listed as two of five of the most important species in the KNP because collectively these species made up 80% of the total tree population (Van Wyk & Fairall 1969). In addition, Sclerocarya birrea has cultural, medicinal and economic uses (Roberts 1990, Palgrave 1993) while Acacias are often favoured by white backed vultures (Gyps africanus) as nesting sites (Murn et al.2002). Hence the vegetation study will continue using these species as key indicators of environmental change. Across all affected parties within the APNR, concerns increased for some species while for others it declined over the ten year period (Figure 55). The interaction between species of concern and time proved to be significant with the greatest relative concern being for Sclercarya birrea and Acacia nigrescens (Chi square = 19.6, df=10, P=0.033). These subtle changes over time where primarily driven by managers’ opinions as there has been a decline in concern for other species (including Grewia spp.) together with a concurrent increase in concern for Sclerocarya birrea, Acacia nigrescens and Lannea schweinfurtii.

Bush encroachment and tall tree loss (STE-SA survey) When considering how opinions of landowners, shareblock holders and managers have changed over time with regards to whether bush encroachment is taking place in the APNR, there was only an interaction between type of affected party and their opinion in 2003 (Chi square = 14.7,

df=4, P=0.005). A large proportion of landowners disagreed that bush encroachment was taking place while most shareblock owners remained neutral on the topic. There is a general trend towards more affected parties agreeing that the bush has thickened with less parties being neutral on the topic as time has progresses (Figure 56).

Landowners

0%10%20%30%40%50%60%70%80%90%

100%

2003 2007 2012

Grewia spp.

A. nigrescens

C. mopane

S. birrea

L. schweinfurthii

Other spp.

Shareblock

0%10%20%30%40%50%60%70%80%90%

100%

2003 2007 2012

Grewia spp.

A. nigrescens

C. mopane

S. birrea

L. schweinfurthii

Other spp.

Managers

0%10%20%30%40%50%60%70%80%90%

100%

2003 2007 2012

Grewia spp.

A. nigrescens

C. mopane

S. birrea

L. schweinfurthii

Other spp.

All

0%10%20%30%40%50%60%70%80%90%

100%

2003 2007 2012

Grewia spp.

A. nigrescens

C. mopane

S. birrea

L. schweinfurthii

Other spp.

Figure 55 Relative importance of various plants species identified as of concern to landowners, shareblock owners and managers within the APNR.

Bush Encroachment

0%

20%

40%

60%

80%

100%

Land

owners

Shareblocks

Managers All

Land

owners

Shareblocks

Managers All

Land

owners

Shareblocks

Managers All

2003 2007 2012

Agree

Neutral

Diasgree

Figure 56 Perceptions of affected parties within the APNR over time and with regards to whether the bush has undergone encroachment.

When considering how opinions of landowners, shareblock holders and managers have changed over time with regards to tall trees that have been lost to the system, there was only an interaction between type of affected party and their opinion in 2003 (Chi square = 9.95, df=4, P =0.041). A large proportion of landowners agreed that bush encroachment was taking place while most shareblock owners remained neutral on the topic. There is a general trend towards more landowners agreeing that tall trees have been lost to the system while shareblock owners have become less neutral about the topic. Across all years, there have been a larger proportion of shareblock owners and managers who have been neutral about tall tree loss when compared to land owners. (Figure 57). In contrast to opinions regarding bush encroachment, the same landowners that completed the questionnaire over the 10 year period, have become less neutral on the topic of tall tree loss in latter years although the interaction effects between opinion and time was not significant (Figure 58).

Large Tree Loss

0%10%20%30%40%50%60%70%80%90%

100%

Land

owners

Shareblocks

Managers All

Land

owners

Shareblocks

Managers All

Land

owners

Shareblocks

Managers All

Land

owners

Shareblocks

Managers All

2003 2007 2012 All

Agree

Neutral

Diasgree

Figure 57 Perceptions of affected parties within the APNR over time and with regards to whether the tall trees have been loss from the system.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

2003Bush

Encroachment

2007 2012

2003Tall Tree Loss

2007 2012

Agree

Neutral

Disagree

Figure 58 Perceptions of the same 10 respondents that answered the questionnaire three times over a 10 year period with regards to whether bush encroachment has taken place and whether tall trees have been loss from the system.

Perceptions on photos of various landscape types (WKU survey) There was a significant association between landscape type and the different opinions of the respondents, whether residents or tourists (Chi square = 138.4, df=4, P<0.0001). Respondents were more frequently positive in attitude towards a photograph depicting a savannah landscape with tall trees and long grass, when comparing their response to scrubveld with no tall trees or a Colophospermum mopane dominated landscapes (Figure 59). Both residents and tourists evaluated scrub lands and savannas similarly and although tourists appeared to be more negative towards landscapes depicting savannas with tall trees than residents, the interactions between opinions of residents versus tourists and landscape type were not significantly different for these two landscape types. However, residents were more negative towards landscapes dominated by Colophospermum mopane (Chi square = 31.9, df=2, P<0.0001) than tourists (Figure 60). These results indicate that residents and tourists do have different aesthetic perceptions of what the landscape should look like and which vegetation types and structures are favoured.

0%

50%

100%

Scrub Savannah Mopani

Positive

Neutral

Negative

Figure 59 Perceptions of respondents towards photographs depicting a scrubland with no tall trees (scrub), a photograph of tall trees with waving grass (savannah) and a photograph of dense Colophospermum mopane veld (mopane). Respondents were asked to score the photos from 1-5 with ‘5’ representing the most favourable score. Scores below ‘3’ were taken as negative, ‘3’ as neutral and larger than ‘3’as positive.

0%

20%

40%

60%

80%

100%

Scrub

Savann

ah

Mop

ani

Scrub

Savann

ah

Mop

ani

Resident Tourist

Positive

Neutral

Negative

Figure 60 Perceptions on how residents versus tourists responded to photographs depicting a scrubland with no tall trees (scrub), a photograph of tall trees with waving grass (savannah) and a photograph of dense Colophospermum mopane veld (mopane). Respondents were asked to score the photos from 1-5 with ‘5’ representing the most favourable score. Scores below ‘3’ were taken as negative, ‘3’ as neutral and larger than ‘3’as positive.

Perceptions of large trees that have or have not undergone structural modification (WKU survey) There was a significant association between large tree impact and the different opinions of the respondents, whether residents or tourists (Chi square = 154.0, df=4, P<0.0001). Respondents were positively orientated towards an undamaged tree where as bark-stripped trees were less favoured and pollard trees were the least favoured (Figure 61). When considering the difference in opinion between residents as opposed to tourists, trends were similar but with residents feeling more strongly opposed to trees that had been impacted upon by elephants than tourists. Tourists were more inclined to not to be strongly opinionated and were consequently more frequently neutrally orientated towards the same set of questions as residents. There was a significant interaction between respondent type (resident versus tourist) and opinion with regards to trees with no impact, trees that were bark-stripped and trees that were pollard (Chi square = 16.6, df=2, P<0.0002, Chi square = 7.65, df=2, P<0.022 and Chi square = 7.85, df=2, P<0.020 respectively) as some tourists were opposed to undamaged trees while many were neutral in their opinion. Fewer tourists were opposed to bark-stripped and pollard trees but more were neutrally orientated when compared to residents. (Figure 62). These results indicate that residents and tourists do have different aesthetic perceptions on the visual consequences of elephant effects.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Undamaged Tree Brak‐strippedTree

Broken Tree(MS)

Positive

Neutral

Negative

Figure 62 Perceptions of respondents towards photographs depicting a tall tree that has not been impacted upon by elephants (undamaged), a tree that has been bark-stripped and a tree that has been pollard (broken tree MS). Respondents were asked to score the photos from 1-5 with ‘5’ representing the most favourable score. Scores below ‘3’ were taken as negative, ‘3’ as neutral and larger than ‘3’as positive.

0%

20%

40%

60%

80%

100%

Und

amaged

Bark‐

Stripp

ed

Broken

Und

amaged

Bark‐

Stripp

ed

Broken

Resident Tourist

Positive

Neutral

Negative

Figure 63 Perceptions on how residents versus tourists responded to photographs depicting a tall tree that has not been impacted upon by elephants (undamaged), a tree that has been bark-stripped and a tree that has been pollard (broken tree MS). Respondents were asked to score the photos from 1-5 with ‘5’ representing the most favourable score. Scores below ‘3’ were taken as negative, ‘3’ as neutral and larger than ‘3’as positive.

Table 5 Summary of the survival statistics per study site as well the proportion and number of trees by type which have been identified as vulnerable to mortality in future. The average proportion of trees with wire-netting that have been tested or penetrated by elephant tusks per survey period, has also been provided. Study Site Survival Rate of

Large Trees Efficiency of Protection

Vulnerability of Trees Average % Trees Tested/Penetrated per Survey Period

Elephant effects only

87.2% With Wire 92.5% Proportion 10%

All causes 84.8% Unprotected 87.9%

Charloscar

Difference significant?

No Difference Significant?

No

Number and Type 18 Knobthorn 49 24 Marula 7 False Marula

5%


n/a With Wire 93.3% Proportion 0%

All causes n/a Unprotected 100%

De Luca


n/a Difference Significant?

No


33%




Ntsiri


Yes Difference Significant?

No


3%


89.3% With Wire n/a Proportion 4%

All causes 78.9% Unprotected n/a

Rock Fig


No Difference Significant?

n/a


5%




Sumatra



Yes


3%

%




Vlakgezicht



Yes


8%

Conclusion • Impact intensity differed between sites with survival rates of trees (when considering

elephant impact only) varying from as low as 55.3% to as high as 89.3 %. • The Ntsiri and Valkgezicht study sites had the lowest survival rates over time but both

these properties were also monitored for the longest period of time (seven and eight years respectively).

• Not only were a large portion of trees lost on the Ntsiri and Vlakgezicht properties due to elephant effects, but other causes of mortality also contributed significantly to the decline in survival rates over time. The survival curves for large trees based on elephant effects only, was significantly higher than the survival curves which accounted for all causes of mortality i.e. including death due to fire, insect attack, wind or other unknown causes.

• The Ntsiri and Vlakgezicht study site both had 10% of the large trees identified as vulnerable to future mortalities as these individuals had elephant impact in the moderate to high, impact categories concurrently with the presence of other external agents (fire scarring, insect attack, wind-toppling effects) which could compromise the survival of a tree. At the Ntsiri study site more Sclerocarya birrea were vulnerable than Acacia nigrescens while at the Vlakgezicht study site more Lannea scweinfurthii was vulnerable than Sclerocarya birrea.

• The study sites with the highest proportional mortality figures for large trees (Ntsiri and Vlakgezicht) have two factors in common which could explain the comparatively large loss of trees at these sites. Ntsiri experienced a management fire in 2006 while Vlakgezicht burnt in 2008. Both properties survival curves declined more steeply after these events. Furthermore, both these study areas have water points in amongst and in the immediate vicinity of the study sites which could be the cause of a elephants frequently encountering the large trees on their way to the water points.

• The survival rate of wire-net protected versus unprotected trees was significantly higher on the Sumatra and Valkgezight properties. Wire-net protection resulted in a survival rate difference between the wire-net protected and unprotected trees of 6.8% and 30.1% for Sumatra and Vlakgezicht respectively. Considering the vulnerability of some of the trees on Vlakgezight, the wire-netting of trees does offer important protection to large trees.

• Across all the study sites, wire-net protection generally lead to lower mortalities rates in trees and higher proportions of untouched trees, increased frequencies of primary branch breakage to access smaller plant parts concurrently with reduced proportions of trees that were either bark-stripped, uprooted or pollard.

• Properties were most wire-netting required maintenance (De Luca), experienced high proportions of testing /penetration of the wire-netting by elephants (up to 33% per year of survey). Hence maintenance of wire-nets is important to ensure the efficacy thereof over the long run.

• Study sites with no recent history of fire and where the large trees were monitored that were not in the immediate vicinity of a water point, generally experience comparatively low large tree mortalities (87.2 % Survival rate for Charloscar).

• Large trees mortality rates appear to be much slower that what nests of tree nesting birds are disappearing.

• Changes in nesting sites can not be solely attributed to changes in tree survival but indicate other factors may be at play.

• The tree species that are being monitored are in keeping with the landowners, share block owners and managers concerns.

• Over time, managers have become more concerned about the elephant impact to Sclerocarya birrea and Acacia nigrescens than to other species

• The proportion of affected parties agreeing that tall tree loss is taking place in the APNR, has gradually increased over time.

• Across all parties, savannah landscapes and undamaged tall trees are preferred probably with residents being more strongly opinionated compared to tourists who prefer to be neutral in their opinion in larger proportions.

Acknowledgements Tanda Tula Safari Camp, Transfrontier Safaris and Umlani Bush Camp provided invaluable logistical support at various stages of the project. The US Fish and Wildlife Services as well as the Environmental Society of South Africa provided financial support. The following landowners and managers are thanked for permission to work on their land and for not only purchasing the wire netting for the trees but also for making their labour available to fit the trees with wire netting: Nick and Timothy Hancock (Vlakgezicht), Carl van der Berg and Mark Griffiths (Ntsiri), Paul de Luca, Koos Malan (Charloscar), Marlene McCay, Pat and Eileen Donaldson, Bruce Jenkins and Martin and Adri Stone (Rock Fig) and Tokkie and Rosa Scholtz (Sumatra). Cornelius van der Waal is thanked for coordinating the wire-netting of the trees on Sumatra. The Van Tienhoven Foundation for International Nature Protection financially supported the wire-netting of the trees on this property. Colin Rowles, is thanked for making Lamson Monareg available while working within this Reserve. Jacques Brits is thanked for making Frans Inyati available on occasion while working while working within the Timbavati Private Nature Reserve. Craig Hay from the South African Wildlife College is thanked for arranging for Khutani Bulunga from SANParks. The following people are thanked for their indispensable contribution towards the collection of data and their assistance with field work within particular years since the study was initiated: Adam Edge, Alexander Munro, Christine McCagh, Francois van der Merwe, Joel Sitole, Kelly Derham and Kerri Dyer. The following people helped out on an ad hoc basis: Adam Baugh, Andreas Liebenburg and the Dartmouth students, Amy Clark, Andrea Webster, Andrew de Luca, Brett Marneweck, Catherine Gordon, Dan Hibbett, Ellery TuckerWilliams, Jennifer Zerbel, Josh Hibbett, Steve Henley and Trish Pontynen. For the surveys of the tree nesting birds Daniel van der Vyver, Gabrielle Simmons, Kate Meares, Sieglinde Rode and Susanne Vogel were instrumental. The following people provided fieldwork assistance for various lengths of time: Adam Edge, Blair Zoghoy, Francois van der Merwe, Kelly Derham, Prince Nakuna, Roni Makukule and Sarah Bergs. Leslie Brown and William de Boer provided additional scientific advice and supervised Sieglinde Rode and Susanne Vogel respectively. A very special word of thanks to Hannah Malin who spent many hours checking datasets and kindly assisted with the analyses of both the large tree and questionnaire surveys. Kelly Derham and Adam Edge assisted with data entry and analyses of the large tree and questionnaire surveys respectively under the additional supervision of Bruce Schulte and Jerry Daday respectively.

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