ORIGINAL PAPER

Influence of habitat management on the abundanceand diet of wild rabbit (Oryctolagus cuniculus algirus)populations in Mediterranean ecosystems

Catarina Ferreira & Paulo Célio Alves

Received: 9 July 2008 /Revised: 11 February 2009 /Accepted: 16 February 2009 /Published online: 2 April 2009# Springer-Verlag 2009

Abstract During the last decades wild rabbit (Oryctolaguscuniculus) populations have been progressively declining inthe Iberian Peninsula as a result of several factors, namelyhabitat deterioration. Hence, habitat management hasbecome one of the most commonly used managementtechniques to restore wild rabbit populations. To test theefficacy of some of these measures (creation of pastures,opening firebreaks) in rabbit populations, two managed(M1 and M2) and two control areas (C1 and C2) wereselected in the Portuguese Southwest (SW) Coast. In eachstudy area, the influence of habitat management was testedassessing temporal changes in rabbit abundance obtainedfrom pellet counts and in rabbits’ diet through micro-histological analysis of fecal pellets. Rabbit densities werehigher in managed than in control areas (mean annualvalues: M1–1.08 pellets/m2; M2–1.60 pellets/m2; C1–0.69pellets/m2; C2–0.40 pellets/m2). In general, Gramineae wasthe most consumed plant group throughout the year and inall study areas. In control areas, consumption of alternative

species with low nutritive value (e.g., Cistus ladanifer) wasobserved, especially in summer. Our data suggest a positiveinfluence of habitat management on rabbit populationssince in managed areas individuals presented an overallhigher abundance and a more nutritive diet. In addition,there was no evidence that sown species were consumed indetriment to naturally occurring grasses, suggesting that inMediterranean semi-arid regions clearing vegetation insidethe scrubland might be sufficient to improve habitatconditions for rabbits.

Keywords Oryctolagus cuniculus algirus .

Microhistological analysis . Relative abundance .

Habitat management . South Portugal

Introduction

The European wild rabbit (Oryctolagus cuniculus) has beendescribed as a successful colonizer as is widely spread in adiverse range of environments (Myers et al. 1994). In someregions where the species was introduced, exceptionalecological conditions favored its rapid colonization turningit into a pest (Cooke 2008). In these regions (e.g., Australia)control programs for the species have been continuouslyimproved and new methods to prevent population growthhave emerged. In contrast, in the Iberian Peninsula, wherethe species is native and plays an important ecological andsocial role (e.g., Delibes-Mateos et al. 2008a), the wildrabbit has steadily declined around 30% since the early1990s due to several factors, namely viral epizootics asmyxomatosis and rabbit hemorrhagic disease (RHD),raising general concern on the future of its populations(Alves and Ferreira 2002; Delibes-Mateos et al. 2008b).Moreover, large-scale changes in land use have also causeda significant loss of landscape mosaics, especially inter-spersed pastureland and Mediterranean scrub, which isrequired by the species (e.g., Moreno et al. 1996).

Eur J Wildl Res (2009) 55:487–496DOI 10.1007/s10344-009-0257-4

Communicated by: C. Gortázar

C. Ferreira (*) : P. C. AlvesCIBIO, Centro de Investigação em Biodiversidade e RecursosGenéticos, Universidade do Porto,Rua Padre Armando Quintas,4485-661 Vairão, Portugale-mail: catferreira@gmail.com

P. C. AlvesDepartamento de Zoologia e Antropologia,Faculdade de Ciências da Universidade do Porto,Rua do Campo Alegre, s/n,4169-007 Porto, Portugal

Present address:C. FerreiraInstituto de Investigación en Recursos Cinegéticos(CSIC-UCLM-JCCLM),Ronda de Toledo, s/n,13071 Ciudad Real, España

Consequently, habitat deterioration and/or fragmentation isalso held as one of the most important factors responsiblefor wild rabbit’s decline throughout the Iberian Peninsula(Moreno and Villafuerte 1995).

Conservation strategies of wild rabbit populations inPortugal and Spain have usually been based on restockingoperations and habitat management. However, restockingsare frequently unsuccessful since they require several stepsthat are rarely undertaken (Calvete et al. 1997). Alterna-tively, habitat management is thought to represent anadequate technique for promoting population growth dueto its general low cost and simple application, withoutinducing short- or long-lasting negative biological effects innative populations, bearing a global positive impact onbiodiversity by beneficiating not only target but also severalother species (Faragó et al. 2001). These measures aim toincrease the availability of basic ecological resources,improving habitat quality and the carrying capacity of agiven area. In the case of the wild rabbit, the ameliorationof shelter conditions promotes a quantitative and qualitativeincrease of breeding sites and improves refuge cover frompredators, which affects the species’ social behavior byincreasing the effectiveness of group vigilance (Villafuerte1994). On the other hand, given that the onset of rabbitreproduction, and thus its influence on rabbit density, isrelated to an increase in high food quality, it is veryimportant that its diet includes items of high protein andwater content (e.g., Villafuerte et al. 1997). Therefore, theestablishment of feeding patches as a habitat managementtechnique is particularly important in areas where vegeta-tion composition does not meet the rabbit’s basic nutritionalrequirements. Overall, if primary ecological needs are met(such as refuge and food), it is possible that rabbit densitywill increase to a level that the population itself willmaintain habitat characteristics that favor the speciesoccurrence. In fact, the role of the wild rabbit as an“ecosystem engineer” has already been described given itseffect on landscape structure through grazing disturbance,seed dispersal, and contribution to soil fertility (throughwarren building and latrines establishment; Gálvez et al.2008 and Delibes-Mateos et al. 2008a), suggesting thatpotentially favorable environments can be perpetuated bythe species itself after reaching certain abundance levels. Inthis context, habitat management in areas with low rabbitdensities is aimed at artificially mimicking the species’ability to impose structural alterations in the environmentwhen abundant.

Despite general perception that managing habitat canimprove population density, there is little research from theIberian Peninsula on the real impact of these measures inrabbit populations (e.g., Moreno and Villafuerte 1995;Cabezas and Moreno 2007; Catalán et al. 2008). Particu-larly in the south of Portugal, a semi-arid Mediterranean

region, where habitat management techniques are broadlyused by game managers in hunting reserves as one of thefirst approaches to recover wild rabbit populations, theknowledge of the effect of these measures and of how thisspecies responds to this type of interventions is veryimportant. Thus, the main goals of this work were (a) toassess the effects of habitat management techniques(mainly through the establishment of new feeding areas)on wild rabbit abundance and diet and (b) to evaluate thedifferential influence of two management techniques, theopening of firebreaks only vs. augmenting fire breaks withsown pasture grasses by studying the variation of wildrabbit’s diet in this region.

Materials and methods

Study area

Data collection was carried out between May 2001 andOctober 2002 in the Parque Natural do Sudoeste Alentejanoe Costa Vicentina (PNSACV; Portuguese SW Coast), anatural reserve established along the South PortugueseAtlantic coast (36° 59′ N; 8° 40′ W). This area is includedin the Mediterranean–Iberoatlantic biogeographic zone(Rivas-Martínez et al. 1990), with mean annual temper-atures varying from 15°C to 17.5°C and rainfall concen-trated between November and March (400–600 mm).

Study sites

Four study sites were selected on the basis of (a) theirhomogeneity and similarity in terms of vegetation structureand type and (b) previous knowledge on wild rabbitabundance (Oliveira 2000; Pinto 2000; Ferreira 2001). Allsites presented typical Mediterranean vegetation, primarilycomposed of evergreen sclerophyllous scrubland dominatedat most locations by Cistus ladanifer. Each site hadapproximately 300 ha and was at least 3 km apart fromthe nearest site. On two of these sites (M1—Vilarinha andM2—Cabeços da Bordeira) habitat was managed bycreating firebreaks in February 2001. This involved cuttingout all vegetation along strips about 5 m wide inside thescrubland. The length of these strips was variable since itdepended on the slope and vegetation density in a givensite. No further management procedures were employed onsite M1, but on M2, some sections of the firebreaks wereplanted using a mixture of Secale cereale, Trifoliumsubterraneum, and Avena barbata, which are the plantspecies typically employed by hunters in this region forgame feeding. These ultimately provided strips of pasturewithin the scrubland about 5 m wide and 30 m long. Theother two study sites were kept unmanaged and their

488 Eur J Wildl Res (2009) 55:487–496

natural vegetation intact (no firebreaks and no pastures)and therefore considered control areas (C1—Cadaveiro andC2—Monte Serrada).

Wild rabbit abundance

Among indirect methods to estimate wild rabbit relativeabundance, pellet counts are the simplest and mostcommonly used technique to monitor low density rabbitpopulations (e.g., Palomares 2001). Each of the four studysites comprised three UTM 1×1 km squares, on which400 m long transects per UTM square were set in a total ofthree transects per study site. In the managed areas, two ofthese transects were established in scrubland areas and thethird one on a firebreak or pasture, according to the type ofintervention (M1 or M2). This transect distribution wasintended to ensure that an increase on rabbit relativeabundance could be associated with habitat managementand not due to a displacement of the individuals to therecently cleared areas. Each transect comprised 40 samplingplots fixed at 10 m intervals. Monthly pellet counts wereperformed in a total of one hundred and twenty 0.78 m2

circular plots (diameter=1 m) in each study site. All pelletsfound within each plot were collected to avoid recountingand for the purpose of diet analysis.

Rabbit relative abundance was expressed as a pelletabundance index (PAI), which corresponded to the averagenumber of pellets counted in the 120 plots per square meter(±SE) per month. Annual PAI was also estimated using theaverage of monthly values for each study site. Seasonalvalues were pooled to compare pellet density between sites.All data were log-transformed before analysis [log (x+1)]due to a right skewed distribution of the data sets. Repeated-measures ANOVA analysis was carried out on seasonal PAIvalues using the Statistica v. 5.0 package. Missing data weredue to periods of high precipitation that prevented reliablecounts (due to pellets being washed away by rain) orbecause of logistic constraints to perform field work.

Diet composition

A reference collection of microphotographs of the epider-mis from the plant species found in the four study sites wasestablished using the mechanical detachment methodfollowing Maia et al. (1996). Briefly, a sub-sample of 15rabbit pellets (variable in shape, size and color), per studysite for each alternate month, was selected randomly formicrohistological examination, following the methods ofChapuis (1979) and Vavra and Holecheck (1980). Afterchemical preparation of the fecal material, a grid composedof forty 16 cm2 squares was used. A sample of the first bestpreserved ten epidermal fragments from each square wasexamined using an optical microscope, providing a total of

400 epidermal fragments for each sample. Wheneverpossible, fragments were identified to species level; other-wise, a more general taxonomic classification was registered.A total of 24 samples (six for each study site) were collected,and their analysis was performed for the following months ineach study area: M1 (Dec01, Feb02, Apr02, Jun02, Aug02,Oct02), M2 (Oct01, Dec01, Feb02, Jun02, Aug02, Oct02),C1 (Oct01, Dec01, Feb02, Apr02, Aug02, Oct02), and C2(Oct01, Dec01, Apr02, Jun02, Aug02, Oct02).

Relative frequency for each food item was determined asthe number of fragments of a given food item divided bythe total number of fragments identified. Aside fromspecies’ description, plant species were also divided intofive functional groups: grasses, other monocotyledons,herbs, shrubs, and broad leafed trees. Diet diversity in eacharea and for each study period was estimated throughBrillouin diversity index (BDI, Margalef 1995), accordingto the following formula:

BDI ¼ 1=Nð Þ log2 N !�Σ log2 Ni!ð Þ

N being the total number of food items consumed and Nithe individual proportion of each item (Carretero 2004).Maximum diversity (Hmax) was also calculated to relativelycompare the observed diversity index values. Thesecalculations were performed using MENJA software forMS-DOS, developed by Carretero et al. (unpublished).Schoener Similarity Index (SSI) between areas and studyperiods was also calculated to evaluate temporal and spatialsimilarities in the diets (Schoener 1968):

SSI ¼ 100� 1=2Σ pij � pik��

��

where pij and pik are the percentages of occurrence of thespecies that are common to the four dietary regimes. Thisindex ranges from 0 to 100, the maximum valuecorresponding to totally identical diets.

Assessing the influence of habitat management

In order to assess the influence of habitat management tech-niques on rabbit abundance we performed a multi-dimensional non-metric analysis, multi-dimensional scaling(MDS), distinguishing two periods: T0—year 2000, con-sidered as the reference year when all four sites conservedtheir natural vegetation without human intervention (habitatmanagement was first performed in February 2001; Oliveira2000; Pinto 2000; Ferreira 2001) and T1—years 2001+2002, post-intervention (present data which included datafrom the two types of study sites, C and M). All abundancedata (from T0 to T1) were obtained using the samemethodology (40 sampling plots along 400 m transects). Toassess differences in rabbit abundance before and afterhabitat management (T0 and T1) and between treatments

Eur J Wildl Res (2009) 55:487–496 489

(C and M throughout T1), a density matrix comprising meanpellet density per square meter for each season and each areawas converted to a similarity matrix using Euclidiandistances. Significance of differences between periods wastested using ANOSIM, which is comparable to adistribution-free two-way ANOVA (Clarcke and Warwick1994).

Results

Wild rabbit abundance

In general, mean pellet density per square meter was higherin managed areas than in control areas (Fig. 1). The four sitesdiffered significantly in seasonal pellet density (ANOVA,DF=4, F=26.58, p<0.01). Tukey HSD test showedsignificant differences between managed and control areas(p<0.01) and between the two managed sites (p<0.05).Although significant differences in monthly mean pelletdensity was detected between sites (ANOVA, F=46.75, p<0.01), no overall differences were found between sites from2001 to 2002 (ANOVA, F=3.36, p>0.05).

Table 1 shows mean annual pellet density per square meterin each study site from 2000 to 2002. In 2000 (reference year),mean annual pellet density was variable between study siteswith rabbit abundances being increasingly higher from M1<C1<M2<C2. In 2001 (when firebreaks were first opened andpastures established), M2 presented the highest mean pelletdensity. Proportionally, the greatest increases in mean pelletdensity from 2000 to 2001 were registered for both managedareas, and they were twice those registered in control areas. In2002, there was a general decrease in mean pellet density,which was less evident in managed areas (M1 and M2). Inaddition, when comparing to 2000, in 2002 rabbit abundancewas higher in M1 (+100%), similar in M2 (+5%), whereaslower (almost half their initial abundance) on both controlareas (C1: −56%; C2: −62%).

Diet composition

A total of 151 plant species (39 families) was identified andcollected in the four study sites, and approximately 500microphotographs were taken from the epidermis of theirreproductive and vegetative parts. In general, 80 plantspecies were consumed by wild rabbits (Table 2), which

Fig. 1 Monthly variation ofwild rabbit abundance (meanpellet density per square meter(+SE)) in each of the study sites:M1 (firebreaks), M2 (firebreaksand pastures), C1 and C2(controls). Missing values areassociated with periods of heavyrain or logistic constraints toperform field work

490 Eur J Wildl Res (2009) 55:487–496

corresponded to more than 50% of the plant speciesobtained in the reference collection. A total of 9,600epidermal fragments were examined, more than 90% ofwhich were positively identified.

On managed areas, autumn and winter diets revealedgrasses as major feeding components (Fig. 2), even if insome periods other plant groups such as leguminosae andalternative species (like Malva hispanica and C. ladanifer)greatly contributed to dietary diversity during these sea-sons. The importance of grasses such as Dactylis glomerataand Cynosurus echinatus became increasingly evident inM1 and M2 since this plant group consistently dominatedthe rabbits’ diet during the rest of the sampling period. Inthese areas, a resource bipartition was evident for most ofthe sampling period since the consumption of grasses wasstrongly complemented with dicotyledons. On the otherhand, apparently, the species sown in the pastures in M2were not particularly preferred by rabbits since they werefound only in low frequencies. It should be noted, however,that S. cereale was the only species sown that developedand grew normally, while T. subterraneum, for example, didnot germinate at all. In control areas, grasses were alsoimportant components of rabbit’s diet throughout the wholesampling period, in spite of the inclusion of an importantarray of other alternative plant groups, particularly in autumnand summer (Fig. 2). Cistaceae, such as C. ladanifer,leguminosae and compositae were among the most com-monly consumed groups in C1 and C2, especially duringsummer. The green parts of plants were the most significanttrophic components of rabbit’s diet. On average throughoutthe sampling period, leaves represented more than 50% ofthe total plant parts in all study sites. In general, theconsumption pattern of plant components was similaramong sites. Reproductive parts, such as buds and flowers,were mostly preferred during autumn and spring, especiallyin managed areas, while during the rest of the samplingperiod, these structures were consumed less than 10%.

Brillouin diversity index was moderately high for allstudy sites during the whole sampling period (Table 2). InM1, the index ranged from 3.8 (Hmax=5.1) in April 2002 to5.0 (Hmax=6.1) in June 2002. In M2 it varied between 3.9(Hmax=5.4) in October 2001 and 4.5 (Hmax=5.7) in August2002. In C1, it ranged from 3.8 (Hmax=5.2) in April 2002to 4.4 (Hmax=5.8) in October 2002, and in C2 from 3.2(Hmax=5.4) in April 2002 and 4.6 (Hmax=5.7) in June2002. In general, Schoener’s similarity index showedrelatively low similarity between the four study sites. Whenconsidering the overall sampling period, the most similardiets found were between M1 and M2 (SSI=69.38),followed by C2 (SSI=57.75) and C1 (SSI=32.50). In M1,diet is most identical between April and August 2002 (SSI=61.25), whereas dissimilarity is higher between Februaryand June 2002. In M2, SSI is higher between Februaryand October 2002 (57.50) and lowest between October2001 and February 2002. In C1, diets are more similarbetween August and October 2002 (SSI=69.38) and theleast identical between October 2001 and April 2002. InC2, diets were closest between April and August 2002(SSI=56.00) and the least identical between December2001 and June 2002.

Assessing the influence of habitat management

Results from the MDS analysis show a significant temporalvariation of mean pellet density in the four study sitesbetween T0 and T1 (two-way ANOSIM; p<0.1%; R=0.719), suggesting that there are differences in rabbitabundance before (T0) and after (T1) habitat management.However, there were no statistical differences betweenmanaged and control sites during T1 period (two-wayANOSIM; p>0.5%; R=−0.051), which means that duringthe period habitat management was performed there wereno differences between study sites. Nevertheless, rabbitabundance in the four sites is different from 2000 to 2001+2002 (also see Table 1).

Discussion

Wild rabbit abundance

Rabbit abundance found in all study sites was generallyvery low comparing to other areas in the Iberian Peninsula(e.g., Lombardi et al. 2003), which is in accordance withprevious data from this region (e.g., Palma et al. 1999).Factors such as vegetation structure and composition,incidence of viral diseases and predation have been pointedout as playing a cumulative role (Trout and Tittensor 1989),preventing wild rabbit populations in the Iberian Peninsulafrom recovering former numbers. In particular, RHD may

Table 1 Mean annual rabbit pellet density per square meter for eachof the study sites and years, 2000 being the reference year, i.e., beforeany habitat management in any of the managed areas. Interannualchanges in pellet densities are shown in parenthesis

Study sites 2000 2001 2002

M1 (with firebreaks) 0.54a 1.29b (+139%) 1.08b (−16%)

M2 (with firebreaksand pastures)

1.52a 3.55b (+134%) 1.60b (−55%)

C1 0.91c 1.07b,c (+18%) 0.40b (−63%)

C2 1.81a 2.23b (+23%) 0.69b (−69%)

a Oliveira (2000) and Pinto (2000)b Present workc Ferreira (2001)

Eur J Wildl Res (2009) 55:487–496 491

Tab

le2

Relativefrequencies(≥

2%)of

plantspeciesandfunctio

nalgrou

psprov

ided

bythemicrohistolog

icalanalysisof

wild

rabb

itfaecalpelletsbetweenOctob

er20

01andOctob

er20

02in

the

managed

(M1:

firebreaks;M2:

firebreaks

andpastures)andcontrolareas(C1;

C2).Total

numberof

speciesidentifiedandBrillo

uindiversity

indexarealso

presented

Month

Oct-01

Dec-01

Feb-02

Apr-02

Jun-02

Aug-02

Oct-02

Annualaverage

Study

area

M2

C1

C2

M1

M2

C1

C2

M1

M2

C1

M1

C1

C2

M1

M2

C2

M1

M2

C1

C2

M1

M2

C1

C2

M1

M2

C1

C2

Grasses

Agrostis

sp.

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.80

0.00

0.00

0.00

0.00

3.30

0.00

2.00

0.00

3.50

0.00

0.00

0.00

0.00

0.50

8.30

0.00

1.10

Avenula

sp.

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

5.30

0.00

0.00

0.00

0.00

0.00

0.00

3.00

0.00

0.00

0.00

0.00

0.00

0.00

0.90

0.50

0.00

0.00

Avena

barbata

0.00

0.00

0.00

0.00

2.70

0.00

2.30

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

7.30

0.00

0.00

0.00

0.00

0.00

0.40

0.00

1.60

Briza

maxima

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.00

0.00

0.00

0.00

0.30

0.00

Briza

minor

3.30

5.00

4.50

0.00

2.30

0.00

8.80

2.50

0.00

0.00

4.50

0.00

0.00

0.00

000

0.00

10.8

13.3

0.00

10.3

3.80

000

0.00

0.00

3.60

3.10

0.80

3.90

Briza

sp.

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

3.80

0.00

000

0.00

0.00

0.00

0.00

2.80

0.00

000

0.00

0.00

0.00

0.00

0.00

1.10

Chaetopogon

fasciculatus

0.00

0.00

0.00

0.00

0.00

0.00

2.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.30

Cynosurus

echinatus

3.30

10.0

3.80

0.00

0.00

0.00

0.00

0.00

0.00

0.00

7.80

0.00

0.00

2.00

0.00

0.00

0.00

5.50

0.00

0.00

0.00

0.00

0.00

0.00

1.60

1.50

1.70

0.60

Cynosurus

sp.

5.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.30

0.00

0.00

0.00

0.00

0.00

0.00

0.00

1.20

0.00

0.00

Dactylis

glom

erata

9.00

0.00

4.50

5.00

12.0

3.30

6.30

11.0

2.00

2.80

17.0

3.80

0.00

3.50

0.00

0.00

18.8

6.80

0.00

5.50

14.3

8.00

0.00

7.50

11.6

6.30

1.60

4.00

Festuca

sp.

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

4.30

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.70

0.00

Digita

riasp.

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.30

0.00

0.00

Holcussp.

4.50

0.00

3.20

3.50

0.00

0.00

0.00

0.00

0.00

0.00

2.30

0.00

0.00

0.00

0.00

0.00

2.00

0.00

0.00

0.00

0.00

6.00

0.00

2.80

1.30

1.80

0.00

1.10

Hordeum

leporinum

0.00

2.00

2.00

0.00

0.00

0.00

3.30

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.30

0.90

Hordeum

murinum

0.00

0.00

0.00

0.00

0.00

0.00

2.50

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

1.40

Hordeum

sp.

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.00

2.00

4.30

0.00

0.00

0.00

0.00

0.00

0.00

0.30

0.70

0.00

0.30

Lam

arckia

aurea

0.00

0.00

0.00

0.00

0.00

0.00

2.50

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.40

Micropyrum

sp.

4.80

0.00

3.80

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.50

0.00

4.50

0.00

0.00

0.00

3.00

0.00

5.00

0.00

0.00

2.50

2.30

0.80

1.30

0.80

1.80

Phalarissp.

4.80

0.00

4.30

0.00

4.70

0.00

0.00

0.00

2.30

0.00

0.00

3.30

0.00

4.80

0.00

0.00

3.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

1.30

190

0.50

0.70

Secale

cereale

0.00

0.00

4.80

0.00

3.70

0.00

25.5

4.00

2.50

2.50

0.00

2.00

0.00

0.00

3.80

0.00

2.00

0.00

0.00

0.00

3.00

0.00

0.00

0.00

1.50

1.70

0.80

5.00

Other

Gramineae

7.80

8.50

11.0

12.3

19.7

18.5

21.3

25.3

15.5

16.5

21.8

13.5

17.1

6.80

9.80

5.50

13.5

8.30

8.50

21.0

17.5

16.5

11.8

10.3

16.2

12.9

12.9

14.4

Totalgrasses

42.3

25.5

42.3

20.8

45.0

21.8

80.3

42.8

22.3

26.0

61.3

25.0

21.0

21.5

13.5

10.8

52.0

50.3

8.50

55.3

38.5

30.5

16.3

22.8

39.5

34.0

20.5

38.7

Other

Monocotyledons

Liliaceae

0.00

0.00

0.00

2.80

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

3.80

0.00

0.00

0.00

3.30

0.50

0.00

0.00

1.20

Ornith

ogalum

broteroi

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

4.30

0.00

2.30

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.70

0.00

0.00

0.40

Ornith

ogalum

unifo

lium

0.00

0.00

2.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.30

Totalother

Monocotyledons

0.00

0.00

2.00

2.80

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

4.30

0.00

2.30

0.00

0.00

0.00

3.80

0.00

0.00

0.00

3.30

1.20

0.00

0.00

1.90

Herbs

Andryalasp.

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

5.30

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.90

0.00

0.00

0.00

Andryalaarenaria

4.80

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.80

0.00

0.00

Carduus

tenuiflorus

0.00

0.00

3.30

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.50

Caryophyllaceae

3.50

7.30

4.50

3.30

0.00

5.50

0.00

0.00

0.00

14.3

0.00

0.00

0.00

6.00

10.8

4.50

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.30

1.50

2.40

4.50

1.90

Centaurium

sp.

0.00

0.00

0.00

3.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.00

0.00

0.00

0.00

0.80

0.00

0.00

0.00

Centaurium

erythraea

subesp.grandiflo

rum

0.00

0.00

0.00

0.00

2.70

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.40

0.00

0.00

492 Eur J Wildl Res (2009) 55:487–496

Com

positae

0.00

0.00

2.30

2.00

0.00

0.00

0.00

0.00

0.00

2.50

2.00

0.00

7.60

2.80

0.00

0.00

0.00

0.00

0.00

3.30

2.50

2.30

0.00

0.00

1.50

0.40

0.40

2.20

Echium

sp.

0.00

0.00

0.00

3.30

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.50

0.00

0.00

0.00

Lavandula

luisierii

6.30

2.50

2.30

4.80

0.00

0.00

0.00

0.00

0.00

5.30

5.00

0.00

0.00

0.00

0.00

0.00

0.00

5.50

0.00

0.00

0.00

7.80

3.00

4.00

1.60

3.30

1.80

1.00

Legum

inosae

0.00

0.00

0.00

7.30

0.00

3.80

0.00

4.50

6.00

4.50

2.80

17.5

8.60

2.50

4.00

14.0

5.30

3.50

17.0

2.00

0.00

7.00

14.0

8.30

3.70

3.40

9.50

5.50

Lotus

sp.

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.30

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.40

0.00

Malva

hispanica

0.00

0.00

0.00

5.00

2.00

0.00

0.00

4.50

4.50

0.00

0.00

3.50

0.00

3.30

0.00

0.00

0.00

0.00

0.00

0.00

19.0

3.50

2.30

0.00

5.30

1.70

1.00

0.00

Orchismascula

0.00

0.00

0.00

2.30

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.40

0.00

0.00

0.00

Ornith

opus

sp.

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.00

0.00

0.00

2.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.70

0.00

0.00

0.00

Papaver

somniferum

0.00

0.00

0.00

0.00

0.00

2.00

0.00

0.00

0.00

2.30

0.00

3.50

0.00

0.00

0.00

0.00

3.00

0.00

2.80

0.00

0.00

0.00

0.00

0.00

0.50

0.00

1.80

0.00

Pulicaria

odora

11.3

3.80

2.80

2.00

11.0

0.00

0.00

0.00

0.00

0.00

0.00

0.00

22.4

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

3.80

0.00

0.00

0.30

4.30

0.60

4.20

Raphanusraphanistrum

2.50

4.30

0.00

0.00

0.00

0.00

0.00

0.00

0.00

6.00

2.00

0.00

6.70

0.00

7.30

0.00

250

6.00

0.00

0.00

0.00

0.00

0.00

0.00

0.80

2.60

1.70

1.10

Rum

exsp.

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.30

0.00

0.00

0.00

0.40

0.00

0.00

0.00

Sanguisorbaminor

0.00

4.50

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.80

0.00

Sesamoidespurpurascens

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.80

0.00

0.00

0.00

0.50

0.00

0.00

0.00

Sinapisarvensis

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

5.30

0.00

0.00

0.00

0.00

0.00

0.00

0.00

16.5

0.00

0.00

0.00

3.60

Trifo

lium

sp.

0.00

0.00

2.80

13.0

3.00

3.30

0.00

9.30

6.00

4.00

8.30

10.00

10.00

2.0

2.80

4.00

4.50

0.00

9.00

0.00

0.00

5.50

6.50

2.80

6.20

2.90

5.50

3.30

Total

herbs

28.3

22.3

17.8

45.8

18.7

14.5

0.00

18.3

16.5

38.8

22.0

34.5

55.2

18.5

24.8

27.8

20.5

15.0

31.0

5.30

28.5

29.8

25.8

33.8

25.6

22.2

27.8

23.3

Shrubs

Cistaceae

0.00

0.00

2.00

0.00

2.30

0.00

0.00

0.00

6.00

0.00

2.00

0.00

0.00

4.50

2.30

5.80

3.30

0.00

0.00

2.80

0.00

2.00

3.00

3.50

1.60

2.10

0.50

2.30

Cistusladanifer

2.30

5.50

0.00

0.00

4.00

143

3.00

6.00

10.3

0.00

0.00

10.8

0.00

2.30

0.00

0.00

0.00

0.00

8.00

0.00

0.00

0.00

6.50

0.00

1.40

2.80

7.50

0.50

Cistussalvifo

lius

0.00

10.3

0.00

0.00

0.00

6.50

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.30

0.00

3.0

0.00

4.50

0.00

0.50

0.00

3.90

0.00

Cynaracardunculus

0.00

0.00

0.00

0.00

0.00

2.30

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.40

0.00

Cynarasp.

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.50

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.40

0.00

0.00

Daphnegnidium

0.00

2.00

0.00

0.00

0.00

0.00

0.00

0.00

2.80

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.00

0.00

0.00

0.00

0.00

0.00

0.00

0.50

0.70

0.00

Erica

umbella

ta0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

4.00

6.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.70

0.00

1.00

Ericaceae

0.00

2.00

630

0.00

0.00

4.00

0.00

0.00

2.50

0.00

0.00

2.30

2.90

2.50

4.00

3.50

0.00

0.00

2.00

3.00

0.00

0.00

0.00

0.00

0.40

1.10

1.70

2.60

Genista

sp.

0.00

0.00

0.00

4.30

0.00

0.00

0.00

0.00

4.00

0.00

0.00

0.00

0.00

0.00

6.50

0.00

0.00

0.00

3.30

0.00

0.00

0.00

3.50

0.00

0.70

1.80

1.10

0.00

Halimium

halim

ifoliu

m0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

4.30

0.00

2.00

0.00

0.70

0.00

0.30

Lavateraolbia

0.00

3.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.00

0.00

0.00

0.00

0.00

0.00

0.00

4.00

0.00

3.00

2.80

0.00

3.30

0.50

0.50

150.50

Phillyreaangustifo

lia0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

2.30

0.00

0.00

0.00

0.00

2.00

0.00

0.00

0.00

0.00

0.00

0.40

0.00

0.30

Thymus

camphoratus

0.00

0.00

0.00

0.00

0.00

0.00

0.00

8.80

0.00

0.00

0.00

3.50

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

1.50

0.00

0.60

0.00

Thymus

sp.

0.00

0.00

0.00

2.00

0.00

0.00

0.00

0.00

6.30

0.00

0.00

0.00

0.00

0.00

4.00

0.00

0.00

0.00

8.00

0.00

0.00

2.00

2.50

0.00

030

2.00

1.80

0.00

Total

shrubs

2.30

22.8

8.30

6.30

6.30

27.0

3.00

14.8

31.8

0.00

2.00

18.5

2.90

9.30

25.5

15.3

3.30

0.00

29.5

7.80

6.00

11.0

20.00

8.80

6.90

12.8

19.6

7.60

Broad

leaf

trees

Fagaceae

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

3.50

0.00

0.00

0.00

0.00

0.00

0.00

2.00

0.00

0.00

0.00

0.90

0.00

0.00

Total

broadleaf

trees

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

0.00

3.50

0.00

0.00

0.00

0.00

0.00

0.00

2.00

0.00

0.00

0.00

0.90

0.00

0.00

Unidentifiedepidermis

5.30

12.5

13.5

6.00

7.00

10.5

6.50

6.80

5.50

930

5.00

9.30

9.50

9.80

9.50

10.5

6.80

10.5

7.50

8.50

6.00

7.50

8.00

7.50

6.70

7.50

9.50

9.30

Total

numberof

species

51.0

45.0

46.0

43.0

45.0

49.0

26.0

49.0

51.0

49.0

33.0

38.0

22.0

69.0

45.0

48.0

42.0

50.0

49.0

42.0

58.0

50.0

55.0

55.0

49.0

48.7

47.5

39.8

Brillo

uindiversity

index

3.90

4.40

4.50

4.40

4.00

4.10

3.30

3.80

4.30

4.20

3.80

3.90

3.30

5.10

4.40

4.60

4.10

4.50

4.20

4.10

4.00

4.20

4.50

4.40

4.20

4.20

4.20

4.00

Eur J Wildl Res (2009) 55:487–496 493

be exerting a strong influence in the species’ ability to over-come adverse conditions. This disease was first described inPortugal in 1989 although there is no quantitative informa-tion available (Muller et al. 2009). Nevertheless, RHD hadan initial high impact in Iberian wild rabbit populations(Villafuerte et al. 1995) and is generally reported by gamemanagers and hunters as responsible for local extinctions ofthis species (unpubl. data). On the other hand, the observedgeneral seasonal pattern of rabbit abundance is in line withthe ones described elsewhere in the Iberian Peninsula (e.g.,Beltrán 1991). Particularly in summer, abundance reductionis usually associated to impoverishment of food resources(Villafuerte et al. 1997), and this is also observed in ourstudy.

Wild rabbit diet

A large spectrum of plant species was consumed by rabbits,which confirms the generalist character of this lagomorph

(e.g., Homolka 1988). This is also corroborated by themoderately high levels of diversity found in all study sites,suggesting that this species explores different vegetationstrata and is able to adapt its feeding strategy to thequantity and quality of the resources available (Chapuis1979). Nevertheless, diets between areas and samplingperiods were not very similar overall since Schoener’sindex was relatively low for all study sites. Of the totalplant species consumed, grasses were preferred, in accor-dance with previous findings (e.g., Martins et al. 2002). Incontrol areas, rabbits fed mainly on herbs during winter,being the consumption of alternative groups such asCistaceae rather high for the rest of the sampling period.Therefore, in these areas, it is possible to observe adisplacement of rabbit’s diet towards a higher consumptionof shrub-like dicotyledons like gum cistus (C. ladanifer),which present a low nutritional value and are of difficultdigestion because of their high fiber content. This is inagreement with Martins et al. (2002) who also observed anincrease of the ingestion of gum cistus during particularlycritical periods such as summer, which could have repercus-sions on the species’ reproductive behavior. Under thesecircumstances, survival may also be jeopardized since poorphysical condition can increase predation risk and influencesusceptibility of individuals to epizootic events (Villafuerte1994). In managed areas, grasses are consistently consumedin high proportions, which could be associated with ahigher food availability provided by the opening of fire-breaks in M1 and additionally the installation of greenpastures in M2. In the managed areas, reproductive parts ofplants were also more frequently ingested. Particularly inautumn and spring, these correspond to important dietarycomponents, for their high water and protein content,essential for reproduction (Gonçalves et al. 2002). Sponta-neous graminoides, like D. glomerata, were also present inhigh frequencies at different moments in all study sites,suggesting that in this region this could be an essentialtrophic component for the wild rabbit, probably due to theplant’s high palatability and nutritional value (Marques andMathias 2001). Additionally, at the functional group level,diet composition between M1 and M2 showed somesimilarities (Table 2) and seemed to be more diverse (atleast at maximum peaks), suggesting that opening fire-breaks (or glades) inside the scrubland could be sufficientto promote the growth of adventitious grasses, which haveproven to be important complementary food items.

Influence of habitat management on wild rabbit populations

Our results suggest a positive influence of the implemen-tation of habitat management on wild rabbit abundancesince mean annual pellet density was higher in managedareas in 2002, when comparing to the year 2000, and the

Fig. 2 Temporal variation in average relative frequencies (percent) offunctional plant groups obtained from microhistological analysis ofwild rabbit fecal pellets between October 2001 and October 2002 inmanaged (a) and control (b) areas

494 Eur J Wildl Res (2009) 55:487–496

MDS analysis indicated that these differences were signif-icant. The question to whether these differences could bedue to habitat management alone was, however, not fullyaddressed by our data.

Although the MDS-algorithm provided evidence for asignificant difference between the periods before (T0) andafter (T1) habitat management, it showed no significantdifferences among the four study sites throughout the T1period (2001+2002). This can be due to the fairly highfitness stress value (0.21) of this analysis, which is probablyrelated to the low number of replicates analyzed pertreatment (management vs. control), and thus, these resultsshould be cautiously interpreted (Clarcke and Warwick1994). Nevertheless, after a general reduction in rabbitabundance observed from 2001 to 2002, managed areasseemed to present the lowest decreases and still maintain ahigher density (Table 1). In this context, one may suggestthat habitat management improved, in general, habitatconditions, consequently favoring rabbit abundance, pro-viding individuals with a greater ability to overcomeadverse factors. Even if it was not possible to completelyunderstand what factor(s) caused the overall decrease inrabbit abundance in the four study sites between 2001 and2002 (possibly incidence of diseases, predator pressure,and/or differential impact of both factors in each studyarea), evidence suggests that in managed areas rabbits wereable to cope better with the incidence of this (these)factor(s), improving their recovery in critical periods.

On the other hand, some authors have suggested thatplanting crops could be advantageous for rabbit populations(Moreno et al. 1996) and the significant differences foundin abundance between M1 and M2 during our study couldpotentially corroborate this. However, in our case, meanpellet density in M2 was already higher prior to habitatintervention (year 2000) and so attention should be paid tothe fact that previous differential rabbit abundance couldproduce different after-management effects (Villafuerteet al. 1995) although this relationship is not always evident(Delibes-Mateos et al. 2008b). In addition, plant speciessown in the pastures in M2 were only residually found inrabbits’ diet, and so, it is not completely certain thatdifferences between M1 and M2 can be related to habitatmanagement alone. In semi-arid Mediterranean regions, therecommended period for crop plantation is autumn andearly winter. The fact that pastures were planted in Februarymay have had negative effects on the grasses’ developmentdue to late seedling, which could have prevented theincorporation of these plants in rabbit’s diet. Under thesecircumstances, planting crops would not be advisable.Subsequently, it is extremely important to carefully selectthe crops used in the pastures in relation to their require-ments (soil type, germination period, and climatic con-ditions; Havet and Granval 1996), bearing in mind that if

some of these specificities are not met, then it is probablypreferable not to sow crops at all. Overall, the ingestion ofalternative and more palatable food items (particularly inthe summer) in managed areas ascertains for the assumptionthat clearing vegetation alone inside the scrubland (e.g.,firebreaks) could be enough to provide a positive influenceof habitat management.

This work has provided evidence for the positive influenceof habitat management in wild rabbit populations, mainly byimproving feeding conditions closer to shelter patches(through the establishment of strips inside the scrubland),improving global habitat quality. This parameter stronglyinfluences population survival and is determinant for thesuccess of other management techniques used to increasewild rabbit abundance, namely restocking operations(Moreno and Villafuerte 1997). Therefore, habitat manage-ment should always be a priority when considering the arrayof rabbit management techniques since in fact measuressuch as scrub management and crop for game species havebeen described as frequent activities undertaken in areaswhere rabbit populations seem to be recovering (Delibes-Mateos et al. 2008b). Finally, until rabbits reach anabundance peak capable of producing modifications onlandscape structure by themselves, neglecting the need tosupervise and maintain these feeding areas could compro-mise the success of these measures. Therefore, patchesshould be cleared regularly in order to reduce plantcompetition and to promote continuous grass growth.

Further research should focus on more detailed andcarefully planned experimental designs that consider factorssuch as number and minimum area of replicates, experi-mental scale, and methods used to avoid problems of rabbitsfeeding outside the study plots so that clearer results couldbe obtained. Also, other aspects of the rabbit’s biology at alocal scale should be addressed, namely the epidemiology ofviral diseases and predator–prey dynamics, and how habitatmanagement could reduce the impact of these factors.

Acknowledgments This work was partially funded by the Instituto daConservação da Natureza e da Biodiversidade (ICNB, Portugal). Wewish to thank the Director of the Parque Natural do Sudoeste Alentejanoe Costa Vicentina for all the support given during field work.We are alsograteful to F. Barreto Caldas, J. Honrado, and R. Silva from the BotanicDepartment of Porto University for help in plant identification, J.Paupério for help in diet analysis, M. Carretero and A.Múrias for helpfulcomments on the statistical analysis, and B. Cooke and R. Villafuerte forvaluable comments on an early draft of the manuscript.

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