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COSTA RICA FOREST RESEARCH
PROGRAMME (CRF)
Osa Peninsula, Costa Rica
Eretmochelys imbricata (LINNÉ, 1766)
CRF Phase 153 Science Report
15 June 2015 – 14 September 2015
Peter Brakels, Charlotte Armitage, Rachel Curran, Eleanor Flatt, Emily Neville
& Charles Wheeler
Staff Members
Alex Foulkes (AF) Project Manager (PM) – Until July
Peter Brakels (PB) Principal Investigator (PI)
Charlotte Armitage (CA) Assistant Research Officer (ARO)
Jackson Shanks (JS) Assistant Research Officer (ARO)
Rachel Curran (RC) Assistant Research Officer (ARO)
Eleanor Flatt (EF) Assistant Research Officer (ARO)
Emily Neville (EN) Assistant Research Officer (ARO)
George Shankar (GS) Field Communication Officer (FCO)
Charles Wheeler (CW) Conservation Apprentice (CA)
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Table of Contents
1. Introduction ............................................................................................. 4
1.1 Natural History of Costa Rica and Wildlife Conservation ...................................... 4
1.2 Osa Peninsula .......................................................................................................... 4
1.3 Aims and Objectives of Frontier CRF ..................................................................... 5
2. Training .................................................................................................... 7
2.1 Briefing Sessions ..................................................................................................... 7
2.2 Science Lectures ...................................................................................................... 7
2.3 Field Training .......................................................................................................... 8
2.4 BTECs ...................................................................................................................... 8
3. Research Work Programme ................................................................... 9
3.1 Survey Areas ............................................................................................................ 9
3.2 Local Population Density of the Four Primate Species Coexisting in Costa Rica 12
3.2.1 Introduction .................................................................................................. 12
3.2.2 Methodology ................................................................................................ 12
3.2.3 Results .......................................................................................................... 13
3.2.4 Discussion .................................................................................................... 18
3.4 Neotropical River Otter Habitat Preferences of Reutilised Latrine Sites and the
Role of Scat Deposition in Intra-Specific Communication ............................... 20
3.4.1 Introduction .................................................................................................. 20
3.4.2 Methodology ................................................................................................ 21
3.4.3 Results .......................................................................................................... 21
3.4.4 Discussion ..................................................................................................... 22
3.5 A baseline study assessing the impacts of habitat disturbance on the distribution
and abundance of six focus species (including four endemic) of the Osa
Peninsula: .......................................................................................................... 22
3.5.1 Introduction .................................................................................................. 22
3.6.2 Methodology ................................................................................................ 24
3.6.3 Results ...............................................................................................................
Discussion .............................................................................................................. 27
3.7 CRF and the Osa Conservation Sea Turtle Conservation Programme .................. 29
3.7.1 Introduction .................................................................................................. 29
3.7.2 Methodology ................................................................................................ 30
3.7.3 Results .......................................................................................................... 34
3.7.4 Discussion .................................................................................................... 35
Additional Projects .................................................................................... 36
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5. Proposed Work Programme for Next Phase ..................................... 37
6. References ............................................................................................ 37
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1. Introduction
1.1 Natural History of Costa Rica and Wildlife Conservation
Despite covering an area of just 50,000 km2, the Central American country of Costa Rica has
high levels of biological diversity, with some 12,000 species of plants, 1,239 species of
butterflies, 838 species of birds, 440 species of reptiles and amphibians, and 232 species of
mammals, which represent around 5% of the world’s species, with only 0.1% of the worlds land
mass (Sánchez-Azofeifa et al., 2002). The extraordinary biodiversity observed here has been
attributed to two main factors; the geographical location and climatic conditions of the region.
Costa Rica lies about halfway between the Tropic of Cancer and the equator, with an annual
average temperature of 27 °C, fluctuating little throughout the year. This small variance means
that seasons in the tropics are defined by the amount of rainfall, which is much more variable
than temperature, providing distinct wet and dry seasons, particularly in the southern Pacific
lowlands, which receive an average annual rainfall of 7,300 mm . The dry season begins around
November/December and continues through to April/May, after which the rainy season
commences (Baker, 2012).
Costa Rica is one of the world’s leading countries in environmental sustainability and
conservation (Fagan et al., 2013), however, this has not always been the case. Up until the
1960s, activities such as logging and hunting seriously threatened biodiversity in this region,
resulting in over half of the country’s forests being cut down and many species being driven to
the verge of extinction (Henderson, 2002). The poaching of turtles for the fatty calipee and
collection of turtle eggs, has severely depleted populations of endangered black turtles
(Chelonia mydas) and vulnerable olive ridley turtles (Lepidochelys olivacea) that use Costa
Rica’s coastlines as nesting sites. Similarly, the hunting of Costa Rica’s wild cat species,
peccaries and tapirs for their meat, skins and other body parts, has significantly reduced wild
populations.
Since the 1960s, some of these issues have been controlled through the implementation of
several reforestation programmes, legislation, education and the creation of protected areas,
representing almost 27% of the country’s surface area (The World Bank Group, 2015). Costa
Rican law currently protects 166 species from hunting, capture and sale, yet illegal hunting still
occurs, including in protected areas (Baker, 2012). Deforestation and habitat fragmentation
outside of the country’s protected areas and national parks is still a significant problem, due to
expanding human populations and related increases in economic pressure. Additionally, the
projected impacts of climate change are also likely to have significant adverse effects on Costa
Rican biodiversity (Baker, 2012). Due to the high levels of biodiversity and multiple threats
placed on Costa Rica it is important to conduct research to determine the health of the
ecosystem and its encapsulated species.
1.2 Osa Peninsula
The Osa Peninsula is located at the southern end of the Southern Pacific lowlands and covers an
area of 1093 km² (Henderson, 2002). It is the region where the last remnants of tropical
broadleaved evergreen lowland rainforest on the Pacific slope in Central America are found
(Kappelle et al. 2002). It is a unique ecosystem in terms of endemic species like the Cherrie’s
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Tanager (Ramphocelus costaricensis), the Red-backed squirrel monkey (Saimiri oerstedii)), the
Golfo Dulce poison dart frog (Phyllobates vittatus) as well as possessing rich biodiversity, with
over 2.5% of the planets species, making this peninsula an ideal location for scientific research
(Larsen & Toft 2010).
The Osa Peninsula consists of Tropical Wet, Premontane Wet and Tropical Moist forest types,
with elevations ranging between 200 and 760 m (Santchez-Azofeifa et al., 2002). Due to its
diverse topography, the peninsula has a variable climate, with an average annual rainfall of 5500
mm, a mean temperature of around 27°C and humidity levels almost never falling below 90%
(Cleveland et al, 2010).
The Osa Peninsula has a population of around 12,000 people, mainly located in small scattered
settlements. The major sources of income in the region are agriculture (rice, bananas, beans and
corn), livestock (cattle), gold mining, logging and more recently, the expanding eco-tourism
industry (Carrillo et al., 2000). The peninsula’s population is increasing at a rate of 2.6%
annually, compared to 1.3% in the rest o the country and 1.14% globally (Sánchez-Azofeifa et
al., 2001). Since the 1990s, there has also been a dramatic rise in the number of hospitality
businesses opening along the road, from Puerto Jimenez to Carate, as a result of the growing
popularity of ecotourism (Minca and Linda, 2002). This has caused growing concern for the
sustainability of the region’s environmental resource demands (Sánchez-Azofeifa et al., 2001).
Frontier’s Costa Rica Forest Research (CRF) programme began in July 2009 in collaboration
with the local non-governmental organisation Osa Conservation at the Piro site (N 08°23.826,
W 083°20.564) in the southeast of the Osa Peninsula. The site is located within a 1700 ha
private forest reserve, managed by the administrative unit of ACOSA (Osa Conservation Area)
within the National System of Conservation Areas (SINAC). The site is a prime location for
carrying out both forest and shoreline surveys, as there is relatively easy access to both the
primary and secondary forest, as well as pristine beach habitat. The long term objectives of the
project are to investigate the effects of climate change, deforestation and other anthropogenic
impacts on the terrestrial communities of Costa Rica and on the country’s network of protected
areas. There are five core faunal study groups within CRF; primates, sea turtles, wildcats,
neotropical otters and birds.
1.3 Aims and Objectives of Frontier CRF
Under the umbrella of the research programme, the specific aims and objectives of Frontier
CRF are:
1. To estimate the density of the four primate species within the Osa Conservation site at
Piro and its boundaries.
2. To compare primate behaviour between different forest types throughout Piro
3. To assess Neotropical river otter habitat preferences of reutilised latrine sites and
investigate the role of scat deposition in intra-specific communication.
4. To compare the abundance of six endemic birds species between young secondary and
mature primary forest of the Osa Peninsula.
5. To monitor the activity and health of nesting marine turtles on Piro and Pejeperro
beaches and to support the management of the hatchery under the Osa Conservation
Sea Turtle Conservation Programme.
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2. Training Volunteer Research Assistants (RAs) and newly appointed staff receive a number of briefing
sessions on arrival (Table 1), followed by regular science lectures (Table 2) and field training
(Table 3) throughout their deployments. The CRF research programme also supports candidates
completing the BTEC Advanced Certificate and Advanced Diploma in Tropical Habitat
Conservation and the Certificate of Personal Effectiveness (CoPE) (Table 4).
2.1 Briefing Sessions
All new arrivals to CRF are introduced to the aims of the research programme, the
methodologies and the research output of the individual projects. They are also provided with an
update on the achievements of CRF. This information is delivered via the ‘Introduction to the
Frontier Costa Rica Forest Research Programme presentation’. Additionally, all volunteers and
staff are given a full health, safety and medical briefing, which they are tested on before
participating in field activities. Volunteers undertaking a BTEC and/or CoPE qualification are
given an introductory briefing before they begin the assessments.
Table 1. Briefing sessions conducted during Phase CRF151
Briefing Session Presenter
Introduction to the Frontier Costa Rica Forest Research
Programme
PB
Health and Safety Briefing and Test ALL
Medical Briefing and Test ALL
Introduction to the BTEC and CoPE Qualifications ALL
Introduction to Surveying and Monitoring PB
Camp Life and Duties ALL
2.2 Science Lectures
A broad programme of science lectures is offered at CRF providing information and
training in various aspects of research. Lectures are typically presented utilising
PowerPoint and give an opportunity for greater understanding of the ecology and
identification of focal species, methods of data analysis used by CRF and considerations
when planning research projects.
Lectures are scheduled with the following objectives:
To allow every volunteer and member of staff to attend each presentation at least
once during deployment, regardless of length of stay.
To meet the time requirements for BTEC assessments.
To avoid conflict with other activities, maximizing attendance.
Workshops provide detailed training on specific software and applications used
in conservation.
Attendance of lectures is compulsory.
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Table 2. Science lectures delivered during Phase CRF153
Science Lecture Presenter
Survey Planning: BTEC E07 Preparation ALL
Surveying and Monitoring: BTEC E09
Preparation
ALL
Bird Call Identification CA
Primates of the Osa, identification,
ecology and behaviour
PB
Mammal track survey workshop PB
GPS workshop PB
2.3 Field Training
All volunteers and newly appointed staff receive field training. Training is hands-on and
provides an opportunity for participants to become familiar with field equipment.
The following topics are covered:
Specific training sessions to prepare volunteers and staff for accurate data collection
Identification of flora and fauna
Survey method training
Skills and tools used for research
- Turtle tagging
- Proper maintenance of equipment
Table 3. Field training provided during Phase CRF152
Field Training Provider
Turtle Patrol Data Collection ALL
Primate Surveys by total counts PB
Bird Surveys by Point Surveys CA, EF
Field Equipment: GPS PB
Identification of Neotropical Otters and their Signs,
and Recording River Attributes
ALL
Studying Primate Behaviour ALL
Staff Turtle Training Osa Conservation
Wildlife Track Recording and Identification PB
2.4 BTECs
Frontier offers volunteer Research Assistants an opportunity to gain internationally recognised
qualifications based around teamwork, survey techniques, environmental conservation and
effective communication of results. The BTEC in Tropical Habitat Conservation may be studied
as an Advanced Certificate (four week program) or Advanced Diploma (ten week program). See
Table 4 for the BTECs undertaken during this phase.
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Table 4. BTECs Undertaken in Tropical Habitat Conservation during Phase CRF152
Name BTEC Title and Type Mentor
Holly Coleman Primate behaviour – Comparison between
habituation levels and behavioural profiles of all four
primate species on the Osa Peninsula between two
locations, Carate & Piro.
RC
Thomas Humphreys Turtle beach patrols and community awareness in
Carate
PB
3. Research Work Programme
3.1 Survey Areas
Field research is conducted within an 11.83 km2 privately-owned property in Piro, Osa
Peninsula and its boundaries (8°23’-8°26’N, 83°18’-83°25’W) (Figure 1). Located largely
within the Golfo Dulce Forest Reserve and Osa Conservation Area (ACOSA) Wildlife Refuge,
this property is owned by NGO Osa Conservation (OC). The landscape is heterogeneous,
composed of lowland moist primary, secondary and coastal forest. Dominant tree species
include; Ficus insipida, Ceiba pentandra, Attalea butyracea, Carapa guianensis, Castilla tunu,
Spondias mombin, Hyeronima alchorneoides, Chimarrhis latifolia, Fruta dorada, Caryocar
costaricense, Ocotea insularis, Pouteria torta, and Inga allenii. The property also borders dense
forest and pastoral properties to the southeast and encompasses pochote (Pachira quinata) and
teak (Tectona grandis) plantations in the north and northeast, each occupying 0.4 km2. There are
two biological research stations within the survey area, Cerro Osa station in the northwest and
Piro station in the southern region of the property. Mean annual rainfall and temperature for the
area is 5,000-6,000 mm and 26-28 °C respectively; the dry season extends from the end of
December until March.
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Figure 1. The Frontier Costa Rica Forest Research Programme study area with
research: beaches, rivers and trails marked. LS: Laguna Silvestre; FD: Rain Forest
Discovery; AL: Attalea; LT: Las Tortugas; CO: Ocelote ; AT: Ajo; TA: Tangara; CO:
Cerro Osa; NB: Northern Border; CT: Chicle.
A forest trail network covers most of the southern and north eastern portions of the site. The
majority of the trails are narrow and machete-cut. Exceptions to this are Cerro Osa, which is an
old logging road, and the north-south segment of Northern Border and Laguna Silvestre, which
are both 5 m wide cleared tracks. Attalea is the most recently cut trail and is approximately one
year old, while all other trails are more than five years old with the Rainforest discovery trail
over 2 years old.
The property is bordered to the south by the Pacific Ocean and the coastline is separated into
two beaches – Playa Piro (2 km) and Playa Pejeperro (4.5 km). The primary rivers intersecting
the property are the Rio Piro and the adjoining Quebrada Coyunda; the mouth of the former is at
approximately the centre of Playa Piro.
The trails run to a diversity of habitats with different degrees of usage and disturbance (table 5).
The forest trails are used as survey transect for the different monitoring projects.
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Table 5. Current trails present in Piro with description on habitat and frequency of use
Transect
Name (code)
Transect
Length (km)
Habitat Description,
Trail Type and disturbance
Ajo (AT) 2.0 Trail through secondary and mature, primary broad-
leaved evergreen lowland forest. Frequently used by
researchers and volunteers.
Ocelot (OC) 1.4 Trail through secondary and mature primary broad-
leaved evergreen lowland forest. Frequently used by
researcher and volunteers.
Cerro Osa
(CO)
1.4 Old logging road and forest trail through secondary
and mature, primary broad-leaved evergreen lowland
forest, abandoned pochote (Pachira quinata)
plantation and across a branch of the Quebrada
Coyunda River
Laguna
Silvestre
(LS)
2.6 Access road through secondary and primary broad-
leaved evergreen lowland forest. Road used by local
farmers, transport by horse and occasionally by truck
(dry season)
Las Tortugas
(LA)
1.6 Trail through secondary riparian and coastal forest
with a variety of palm species and main access road
dissecting secondary forest. Daily use by researchers
and volunteers.
Tangara
(TA)
1.3 Trail through secondary and mature, primary broad-
leaved evergreen lowland forest. Frequently used by
researchers and volunteers.
Chicle (CT) 1.9 Forest ridge trail through primary broad-leaved
evergreen lowland forest and across Quebrada
Coyunda River.
Northern
Border (NB)
4.9 Old logging road through a pochote (Pachira
quinata) plantation and trail through mature, primary
broad-leaved evergreen lowland forest. Trail along
border is used by locals, hunting likely present.
Forest
discovery
(FD)
2.5 Trail through secondary forest and main access road
dissecting secondary forest. Trail in close vicinity
parallel to the mean access road Puerto Jimenez –
Carate. Frequently used by researchers and
volunteers.
Attalea (AL) 1.8 Trail through secondary coastal broad-leaved
evergreen lowland forest dominated by palms of the
species Attalea butyracea (Royal Palm) &
Astrocaryum standleyanum (Black Palm) and
pasture.
Total 21.4
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3.2 Local Population Density of the Four Primate Species Coexisting in Costa Rica
3.2.1 Introduction
There are four species of primate found in Costa Rica; the Central American squirrel monkey
(Saimiri oerstedii), mantled howler monkey (Alouatta palliata), geoffroy’s spider monkey
(Ateles geoffroyi) and white-faced capuchin (Cebus capucinus). All four species are present at
the study site in Piro. A. geoffroyi is listed as Endangered and S. oerstedii as Vulnerable (IUCN
2015). Population declines exceeding 50% over 45 years have been reported for A. geoffroyi,
principally driven by stress-induced habitat loss (Cuarón et al., 2008b). S. oerstedii has a limited
distribution, restricted to Panama and Costa Rica, this makes populations which are exploited
for the pet trade and those experiencing habitat loss and degradation more vulnerable to
stochastic events. Land conversion for agriculture and development, clear cutting, selective
logging, hunting and the pet trade have implications for all four Costa Rican primate species
(Cropp and Boinski, 2000). Populations of A. palliata and C. capucinus are thought to be stable
and not in declined, they are therefore listed as least concern, however monitoring is necessary
as they are exposed to the same threats as other, more endangered primates (IUCN, 2015).
The primate guild in Costa Rica is vital to forest structural integrity. All four species perform
important roles as seed dispersers (Julliot, 1997; Garber et al., 2006) and the Osa Peninsula is
the only part of Costa Rica where all four species occur together (Carrillo et al., 2000).
Frontier CRF has been surveying the presence and abundance of all four species in
collaboration with Osa Conservation since March 2010. The overall aim of this research is to
provide an insight into the habitat use and behaviour of primates in the area to better inform
management and policy decisions at a local level. The principal and foremost objective of this
project is to produce estimates of population density for each of the four species. Density
estimates are lacking for two of the four primate species, the Central American squirrel monkey
and the white-faced capuchin, which are therefore key to survey, however focus is also on the
red listed spider monkey and squirrel monkey. This phase we aimed to conduct a total count of
the species, identify the different groups and their minimum (sub) group size in order to
estimate the density of all the species within the protected area of Piro (Burgiere & Fleury
2000). The long term monitoring of home range size and primate total counts are considered the
most reliable method in deriving primate densities (Hassel-Finnegan et al. 2008; Marshall et al.
2008; Plumptre & Cox 2006; Burgiere & Fleury 2000; Fashing & Cords 2000). This method is
especially effective working in areas of small fragmented forest with habituated primates
(Pruetz & Leasor 2002).
3.2.2 Methodology
Data is collected by walking transects and conducting total counts of all primates encountered
(Hassel-Finnegan et al. 2008; Marshall et al. 2008; Plumptre & Cox 2006; Burgiere & Fleury
2000; Fashing & Cords 2000). The transects are sampled equally across times of day. Surveys
started between 6:00-7:00am hours to cover peak primate activity, increasing the detection
probability. Transects include, for the most part, combinations of different forest trails.
Transects sampled (Table 5) are walked by two observers at a constant speed of 1.5 – 2 km per
hour including regular stops between every 100-200m as recommended by Peres (1999). No
transect is surveyed more than once on the same day and sampling is only conducted in fair
weather due to the reduction in detection probability in adverse weather conditions. Transects
were surveyed evenly once a month. To assure reliable total count a minimum observation time
of 30 minutes was set to assure that all individuals within the (sub)group could be counted
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(Pruetz & Leasor 2003). The research was non-invasive and adhered to the legal requirements
of Costa Rica (Costa Rican Government Decree 31514-MINAE). Any and all aggressive
behaviour towards the observers by individual primates was responded to by moving on as
quickly as possible.
All primates observed were recorded and the spatial location noted using GPS. The number of
individuals within the target group was recorded. All individuals visible at the same time and
exhibiting the same general behaviour (e.g., resting, moving or foraging) were considered to be
part of the same group (Chapman et al., 1995). Agreement upon group size was made between
the observers where the group could be counted together; otherwise the observers split their
search effort into non-overlapping areas (e.g., left and right of the trail) and made independent
counts which were then summed. Where possible, secondary data on group composition (i.e.
gender and age group; adult, juvenile, infant) was also recorded, however vocal detections were
not included. Furthermore, the behaviour upon encounter, duration of observation and distance
from the trail and direction travelling was noted. Primate home ranges are based on field
observations, where primates are encountered and the direction they travel. Data on group
composition as well as the occurrence of identifiable individuals (scars, missing limbs,
pigmentation etc.) is collected making it possible to identify different groups. When primate
troops are 'recaptured' it will be included in the spatial database and minimal home ranges per
troops are drawn in google earth on the basis of habitat availability and the average home ranges
of the species known from previous studies. For spider monkeys this ranges between 0.73 – 2.2
km2 (Fedigan et al. 1988), Central American squirrel monkey range is on average 2 km
2, white-
faced capuchin up to 1 km2 (but usually less
) and mantled howler monkeys have the smallest
home range ranging between 0.27 – 0.6 km2
on average. Primate minimum density was
calculated as the total number of individuals for the different groups encountered divided by the
surface area of the study site (11.83 km2).
3.2.3 Results
Primate total counts data was collected since the start of this phase. All trails are surveyed at
least once a month, resulting in a total of 3 surveys for this phase. Primate encounters from
previous phases were added to compile a map with all primate records and the identification of
the different troops and their size. This will result in a reliable actual minimum density of the
primates present in Piro Conservation Area. By surveying evenly and thoroughly throughout the
whole study area with an emphasis on primate group composition, we were able to identify and
map previously unrecorded primate groups. Below, the different primate groups within each
species are listed with home ranges displayed on the accompanying maps (Figures 2-5). These
represent the groups that have only been encountered once and 'total' numbers have not been
confirmed yet, or of situations where total counts were not possible because of the conditions in
the field (e.g. distance or dense foliage) and the behaviour of the group (e.g. fleeing or group
spread).
Central American Spider monkey (SP)
In total a minimum number of nine different groups are estimated to occur within the property
of Piro (see fig 2 and table 6). The largest minimum subgroup (based on not knowing if an
entire family has been observed) count was 23 individuals from a group that occurs on the
northern border. Four new groups were identified during this phase; G1, G4, G6 & G9.
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Table 6. Number of Spider monkey groups, group size, characteristics and location
SP Group ID Minimum
subgroup size
Characteristics, location and estimated home range size
(small/average/large)
Group 1 8 Attalea forest (small)
Group 2 20 Habituated group, field station and camp (small)
Group 3 20 Ocelot group, group size underestimated (average)
Group 4 14 Chicle group (large/ unknown)
Group 5 12 Discovery/Laguna Silvestre group (average)
Group 6 8 Upstream Quebrada coyunda/ Cerro Osa group
(unknown)
Group 7 18 Laguna Silvestre group (large), likely more than one
group
Group 8 >10 Upstream Piro river group
Group 9 23 Northern Border group (average)
Total: 133
Density:
11,2/km2
Figure 2. Map with spider monkey encounters (pin points), and estimated home ranges
(circles) per group (numbers). Red line represents boundary of study area. Yellow line
main road Puerto Jimenez - Carate
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Central American Squirrel Monkey (SQ)
In total 11 possible different groups have been identified (see table 7). The groups appear to be
highly variable in size, with two large (>30) groups visiting the two different field stations of
OC. Five new groups were recorded this phase; G1, G8, G9, G10 & G11. Squirrel monkeys
represent the highest density of all four species of primates in Piro, with 19 individuals per km2.
Table .7 Number of Squirrel monkey groups, group size, characteristics and location
SQ Group ID Minimum
subgroup size
Characteristics, location and estimated home range size
(small/average/large)
Group 1 16 Attalea forest (average)
Group 2 32-52 Habituated group visit Frontier camp (small)
Group 3 23 Tortugas trail and nearby road (small)
Group 4 >15 Possible same group as 3 (average)
Group 5 25 Possible same habituated group as 2, Visits OC site east
side (small)
Group 6 >10 Possible same group as 5, Ocelot group (small)
Group 7 20 Possible same group as 2, Discovery trail, along road
Group 8 10 Reforestation area group (average)
Figure 3. Map with squirrel monkey encounters (pin points), and estimated home
ranges (circles) per group (number). Red line represents boundary of study area.
Yellow line main road Puerto Jimenez - Carate
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Group 9 15 Laguna Silvestre group (large)
Group 10 >30 Cerro Osa group, visit CO field station (large)
Group 11 >10 Northern border group (large)
Total: 226
Density:
19,1/km2
White-faced capuchin (CA)
Capuchins are the least encountered primate species in Piro and they appear to present
the lowest primate density for all species, although have been found to occur throughout
the whole study area. In total nine different groups have so far been identified
representing a total density of 8.3/km2.
Table 8. Number of Capuchin monkey groups, group size, characteristics and location
CA Group ID Minimum
subgroup size
Characteristics, location and estimated home range size
(small/average/large)
Group 1 15 Tortugas trail group, crossing road (average)
Group 2 10 Habituated group, visits Frontier camp (average)
Group 3 10 Ocelot group (unknown)
Figure 4. Map with capuchin encounters (pin points), and estimated home ranges
(circles) per group (number). Red line represents boundary of study area. Yellow line
main road Puerto Jimenez - Carate
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Group 4 >10 Chicle group (unknown)
Group 5 12 Discovery trail group near road (unknown)
Group 6 >10 Cerro Osa group, visits field station (unknown)
Group 7 10 Upstream Piro river group (unknown)
Group 8 10 Norther border group (unknown)
Group 9 >10 Attalea group (unknown)
Total: 98
Density:
8,3/km2
Mantled howler monkey (HO)
This species represents the highest group density within the study area; so far at least 18
distinct groups have been identified, although this is likely to be an underestimation (see
table 9). With 16 individuals per km2
howler monkeys are well represented within the
study area.
Figure 5. Map with howler monkey encounters (pin points), and estimated home ranges
(circles) per group (number). Red line represents boundary of study area. Yellow line
main road Puerto Jimenez - Carate
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Table 9. Number of Howler monkey groups, group size, characteristics and location
HO Group ID Minimum
subgroup size
Characteristics, location and estimated home range size
(small/average/large)
Group 1 27 Attalea group (at least 2 groups)
Group 2 ? >5 Beach group south of road
Group 3 13 Tortugas group, beach group 2
Group 4 11 Tangara trail, near field station
Group 5 24 Behind Frontier camp
Group 6 13 Ajo group
Group 7 10 Ocelot – Cerro Osa junction group
Group 8 9 Chicle group
Group 9 13 Discovery group
Group 10 16 Possible same group as 9
Group 11 ? >3 Cerro Osa group, Quebrada Coyunda valley
Group 12 A=15 B=7 Laguna silvestre groups, likely more than one group
Group 13 9 Northern border east group
Group 14 > 5 Laguna silvestre upper part
Group 15 A= > 5 B= > 5 Northern border west group, two distinct groups
Total: 190
Density:
16,1/km2
3.2.4 Discussion
Group counts for Spider monkeys are very hard since this species lives in fission-fusion
societies where the whole group is hardly ever complete (Di Fiore, A. & Campbell C.
2007) Spider monkeys split up in several sub groups (2-6 individuals on average) in the
early morning when leaving the sleeping tree and return to the same tree to join the rest
of the group before nightfall. Sometimes however, subgroups stay separate from the rest
of the group for more than a day (Youlatos 2008). Therefore, total counts might not be
the ideal measure to calculate the population density of spider monkeys in an area.
Squirrel monkey group composition is also very difficult to determine, because of the
difficulty in distinguishing males from females, and the fact that troops are large, the
animals move rapidly, and are widely spread (Boinski 1992). For this reason the
estimations of these two species surveyed in this study need to be regarded as relative
minimum numbers and are likely to be underestimated.
In order to conduct a total count for a large group of squirrel monkeys, ideally,
researchers would be split into several survey teams, spread out depending on the
spread of the squirrel monkey group. For spider monkeys, distance-sampling might be
an alternative method, as although it is an extrapolation of a sample of encounters,
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density numbers can be derived relatively quickly. The accuracy of these numbers
should obviously be critically assessed. For all four species, but especially the squirrel
and spider monkeys, the number of groups and their home ranges need to be more
precisely mapped.
The number of groups for the two latter species is likely to be overestimated, since both
species can occupy large home ranges and travel over relatively large distances of up to
2-4 km per day. A solution to this problem would be to have several survey teams and
to survey simultaneously in different part of the study area. The density estimation in
this study is considerably less than that of our previous study using line-transect
sampling, which was 34.36 individuals/km2. Obviously, both methods can't be
compared one on one, as they are meant to be used complementary to each other to
derive more accurate estimations (Plumptre 2000, Plumptre & Cox 2006). Distance
density estimates are likely to overestimate the primate density since numbers will be
extrapolated from a sample throughout the whole area. Assuming that the sample is
representative for the study site and suitable habitat is continuous, the primates are
present throughout the whole area.
The home ranges depicted per species are indicative and have to be regarded as rough
boundaries and are by no means accurate. Furthermore, home ranges of our primate
study species are likely to overlap to a considerable degree. Since we are restricted to
the trails, troops cannot be followed and therefore home ranges cannot be accurately
mapped.
Group size of spider monkeys can be in the range of 20-40 (Campbell 2008). The
biggest group count in this study is 23 individuals. The minimum density of spider
monkeys in Piro, based on subgroup counts, was calculated to be 11.2 individuals/km2.
However, if the spider monkey density is calculated based on a minimum group size of
20 individuals, this would result in a density of over 15 individuals/km2. The squirrel
monkeys occur in groups of 23-54 and have been recorded to be over 65 in some areas
(Boinski 1988). Research staff counted only two large groups and one average sized
group (see table 7), there are potentially more large groups (>20) in the study area,
however, group counts for the other groups are based on only a few and some a single
encounter(s). White-faced capuchins live in smaller family groups than their smaller
relatives, ranging from 10-20 on average. All groups identified in this study, except one,
have the minimum count of +/- 10 individuals. White-faced capuchins were the least
encountered species and total counts for most groups are based on only a single
encounter. This could possibly result in an underestimation of the group size, since with
several encounters of the same group different counts can be averaged. Mantled howler
monkey group size, like capuchins, range between 10-20, with an average of 12,9
individuals (Chapman & Pavelka 2005). Two large groups have been encountered with
24 and 27 individuals, these groups are likely to consist of the two different groups. It is
not uncommon for mantled howler monkeys to have overlapping home ranges. Howler
monkeys are territorial primates, males set their home range boundaries by howling
before sunset, which would cease of any other males entering their home range. No
aggression or any other signs of a dispute was observed within the group; why these
howler monkeys are so tolerable at these sites needs further studying. Howler monkey
density in Piro was estimated to be 30.8 individuals/km2, that's almost 50% more than
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the estimate based the total counts. The total count estimation is clearly underestimated,
since only a fragment of the howler population within the property has likely been
encountered. Certain parts of the area cannot be accessed due to the lack of trails (NW
part of the property).
Overall this pilot can be considered a success, the first results are promising with
several new groups identified this phase. Some group counts are not complete however,
and are based only on a few sightings, therefore more survey work is required to
complete some group counts and distinguish groups from each other in order map their
home ranges more precisely. It is likely that more howler monkey groups will be
discovered/identified in the future. Howler monkeys are probably the most difficult to
detect since they spent most of the time motionless in the canopy of the forest and are
therefore easily missed. This possibly explains why we haven't recorded any howler
monkeys in the Piro river valley upstream from Frontier camp so far.
3.4 Neotropical River Otter Habitat Preferences of Reutilised Latrine Sites and the
Role of Scat Deposition in Intra-Specific Communication
3.4.1 Introduction
The Neotropical River Otter (Lontra longicaudis) is a solitary species that can be found
in a variety of habitats including swamps, streams and lagoons from Mexico to Uruguay
(Emmons and Feer, 1997; Quadros et al., 2002; Gori et al., 2003; Santos et al., 2012).
Despite this, otters are an adaptive species and have been reported to inhabit irrigation
ditches in rice and sugar cane plantations in Guyana (IOSF, 2012). Their low
reproductive potential and dependence on healthy aquatic environments means that the
species cannot respond quickly to population crashes and are sensitive to environmental
change (Cezare et al., 2002; Waldemarin and Alvarez, 2008). Despite their wide
distribution, little is known about the species’ ecology, local distribution and population
status, hindering the development of appropriate conservation strategies; the
Neotropical river otter is currently listed as “Data Deficient” on the IUCN Red List of
Threatened Species (Waldemarin and Alvarez, 2008). This is because relatively little
research effort has been devoted to the study of the species throughout its range, and
detailed habitat and ecology information is lacking.
Otters are secretive and difficult to observe, thus necessitating alternative methods to
monitor their status and distribution. In contrast, otter latrines or haul-outs; places along
the shoreline where otters eat, defecate, urinate, roll and deposit anal sac secretions, are
often obvious evidence of otter activity (Bowyer et al., 1995; Crowley et al., 2012).
Latrines are located several meters from the water on high ground (e.g. logs, rocks)
(Quadros and Montiero-Filho, 2002; Stevens and Serfass, 2008; Depue and Ben-David,
2010) and mark territorial boundaries within otter home ranges (Melquist and
Hornocker, 1983; Remonti et al., 2011). The exact purpose of latrines is not
conclusively known, but they are believed to play a role in intraspecific communication
(Melquist and Hornocker, 1983; Rostain et al., 2004; Kasper et al., 2008), signalling
reproductive state to the opposite sex (Rostain et al., 2004), marking areas of key
resource use (Kruuk et al., 1986; Kruuk, 1992) and conveying the social status of males
(Rostain et al., 2004).
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Numerous environmental characteristics such as water depth (Anoop and Hussain,
2004; Depue and Ben-David, 2010; Remonti et al., 2011; Carrillo-Rubio and Lafón,
2004), water edge topography (Swimley et al., 1998; Bowyer et al., 1995; Anoop and
Hussain, 2004) and vegetation structure (Prenda and Granada-Lorencio, 1996), are
reported to influence latrine site selection, however, discrepancies exist regarding the
importance of each factor. Therefore, habitat preference studies are essential to better
comprehend the distribution, abundance, and requirements of the Neotropical Otter.
3.4.2 Methodology
Two linear transects were established along the course of the Rio Piro and Quebrada
Coyunda measuring 5.2 km and 2.8 km respectively (Fig.5). Each river was surveyed
once a week, typically as two distinct transects. One began at CRF camp and ran 3.5 km
north on the Rio Piro. The other began at CRF camp and started 1.7 km south on the
Rio Piro to the river mouth and then ran 2.8 km east of the Quebrada Coyunda from the
intersection with Rio Piro. Surveyors walked within the river course and typically began
sampling early morning.
Figure 5. Map of otter transects along Rio Piro and Quebrada Coyunda.
During the course of the survey all reutilised sites such as rocks, logs, fallen trees, roots
and river margins were actively searched for otter spraints. Research staff defined
reutilised latrines as sites having two or more scats present. The substrate diameter
where the spraint was deposited, stream depth adjacent to the substrate and distance to
the waterline was recorded. At each site, GPS data was collected and river width and
river depth at 1 m intervals of the river cross-section was measured. The
presence/absence of mucous in spraint was also recorded and escape cover distance,
defined as the distance from the water’s edge to the point where the undergrowth
started, was collected for both river margins.
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3.4.3 Results
Data collection still progress
3.4.4 Discussion
Data collection still progress
3.5 A baseline study assessing the impacts of habitat disturbance on the distribution
and abundance of six focus bird species (including four endemic) of the Osa
Peninsula:
3.5.1 Introduction
The highly multifaceted and heterogeneous environments of Costa Rica have many
species-rich communities; particularly those within the avian families (Herzog et al.,
2002). Due to their sensitivity to change, birds are well known as important indicators
of the ecosystem health in which they reside. The avifauna of Costa Rica are infamous
for their wealth in diversity, with over 800 species documented (Henderson, 2010),
however, populations are becoming more threatened with pervasive human influences.
The complex myriad of interactions between trees and the birds that destroy or disperse
their seeds play crucial roles in these ecosystems (Howe, 1980), yet reductions in bird
population levels show a correlation to falling pollination and seed dispersal rates, both
process that are fundamental to any stable ecosystem (Pejchar et al., 2008). This,
combined with high levels of endemism within Costa Rica highlights the need to
regularly and closely monitor the bird communities. Trends are impossible to measure
unless some baseline is first established (Bibby et al., 1998), followed by the
assessment of biotic and abiotic factors on bird distribution, which has been
successfully undertaken by many authors (Blake & Loiselle, 2000). Therefore, by
conducting a study in the Osa Pennisula of focus bird species we can begin to establish
the health of bird populations here and therefore the ecosystem as a whole. This study
also aims to identify the potential effects of disturbance on these endemic bird species,
which little information is known.
Due to population growth in Costa Rica, large areas of forest have been cleared to allow
the expansion of agriculture and other industries. This has resulted in Costa Rica
currently suffering from one of the world’s highest rates of deforestation of unprotected
forest (Powell et al. 2000), creating dramatic alterations to the ecosystems. With this in
mind, and the fact that there are knowledge gaps in the understanding of tropical bird
communities (Herzog et al. 2002), this project aims to support the ongoing assessment
of tropical bird communities of the Osa Peninsula. The project started in early October
2014, after some initial pilot studies, with the intention of assessing the species
distribution of six focus species of the Osa Peninsula in order to start a baseline survey.
In order to provide a more concise study we selected six individual bird species as focus
species unique to this study, with four being endemic to the area. The six focus species
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23
are listed in Table 6 with additional details of their conservation status and species
range taken from IUCN Red List (2014) and Henderson (2010). Four of these, the
Fiery-billed Aracari (Pteroglossus frantzii), Riverside Wren (Thryothorus semibadius),
Cherries Tanager (Ramphocelus costaricensis) and Orange-Collared Manakin (Manacus
aurantiacus) are endemic to the region of South West Costa Rica and western Panama.
It was determined that those species of the Manakin family found in the region,
including the Blue Crowned (Lepidothrix coronate) and Red Capped Manakin (Pipra
mentalis), should also be assessed over the course of the study. Focal species were
chosen to eliminate bias that was present in past studies when researching all bird
species. This bias arises as some calls are much more distinct than others, leading to
particular species of bird being recorded more than others; focal species allow a more
succinct and accurate analysis. The specific focal species were chosen as they allow a
study of endemic birds in the region but also allow the analysis of different members of
the same family (Manakins).
Table 6. Six Focus Species IUCN Red List (2014) and Henderson (2010)
Species Endemic Range IUCN
Status
Pop Trend
Fiery-billed Aracari
(Pteroglossus frantzii)
SW Costa Rica to W
Panama
Least
Concern Decreasing
Riverside Wren
(Thryothorus
semibadius)
SW Costa Rica to W
Panama
Least
Concern Unknown
Cherries Tanager
(Ramphocelus
costaricensis)
SW Costa Rica to W
Panama
Least
Concern Stable
Red-Capped Manakin
(Pipra mentalis) Belize to Panama
Least
Concern Decreasing
Blue-Crowned Manakin
(Lepidothrix coronate) Costa Rica to Brazil
Least
Concern Decreasing
Orange Collared
Manakin (Manacus
aurantiacus)
SW Costa Rica to W
Panama
Least
Concern Decreasing
The aim of this project is to be the start of many feeder projects assessing differences in
the communities of the six focus species across different habitat gradients, particularly
human created gaps, using the definition of Levey (1988), whereby a gap is a “vertical
hole in the forest extending through all levels down to within an average of 2 m above
ground” (Levey 1988:252). By selecting points which are effected by human
disturbance our study can begin to establish how bird species are responding to these
changes and subsequently the wider ecosystem. It is hoped the project can focus on
sampling the populations at dawn, and possibly dusk in the future over the coming
phase. Trails examined encompass primary and secondary forest as well as swamp and
river habitats (Table7).
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Table 7. Overview of point counts with habitat type
Trail Point Description
Ajo
1 Forest Edge
2 Secondary Forest
3 Secondary Forest
Ocelot
1 Forest Edge
2 Gallery Forest
3 Primary Forest
Tangara
1 Secondary Forest
2 Secondary Forest
3 Primary Forest
Discovery
trail
1 Secondary Forest
2 Secondary Forest
3 Swamp
Northern
Border
1 Secondary Forest
2 Secondary Forest
3 Secondary Forest
Cerro Osa
1 Secondary Forest
2 Primary Forest
3 Forest Edge
Rio Piro (S)
1 Gallery forest
2 Gallery forest
3 Gallery forest
Tortugas
Trail
1 Forest Edge
2 Secondary Forest
3 Forest Edge
3.6.2 Methodology
Point counts were conducted along six trails/transects (Tortugas trail, Discovery trail,
Cerro Osa, Ajo, Tangara, Ocelot, Northern Border and a river transect down Rio Piro)
and consist of four different habitat types; primary forest, secondary forest, gallery
forest and forest edge. Point counts were conducted in a similar manner to Blake &
Loiselle (2000). Observers visited set points where they listened and watched for the
focal species, as well as noting additional species. Volunteers were trained to recognise
the calls and physical characteristics of the selected target species, as well as other
species, in order to increase the accuracy of data collection during each survey. Each
point count lasted 10 minutes at each of the marked points, which included a minute
settling period prior to starting. Points were marked prior to data collection along each
of the trails using a handheld GPS, selected in order to assess different habitat types.
Surveys were conducted in the morning, with the three point counts undertaken at 0530,
0600 and 0630am, to coincide with the dawn chorus. All birds seen or heard were noted
down with particular attention paid on the six focal species highlighted above.
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When noting down the species name and whether it was heard or seen, distance bands
were also used in order to ascertain where the bird lay in relation to the trail. This will
aid in establishing whether birds are found near or further away from man-made gaps in
the forest canopy layers. Distance band 1 encompassed a bird sighted or heard within 2
m of the trail, band 2 was between 2 and 10 m of the trail, and band 3 was beyond 10 m
(Figure 6).
Figure 6. Survey distance bands to established the location of the bird in relation to the point count
It is noted within the literature that even highly experienced observers can introduce a
variety of bias into the results due to varying identification skills between species, as
well as differences in observation technique (Herzog et al. 2002). In order to avoid this,
observer bias was minimised with the same trail leader conducting the survey each time.
All volunteers are made familiar with the calls and physical characteristics of each of
the target species before conducting a survey. The potential for the birds to have
different calls from those learnt is also an important point to recognise, which could be
mitigated against by taking recordings for further analysis. Baldo & Mennill (2011)
found that Great Curassow birds had many different calls and it is highly likely that the
species under focus on this study also possess many variants of the calls learnt to
identify them, potentially introducing error and the chance of missing certain birds. Due
to the dense canopies overhead birds can also go unnoticed if they are not seen or heard,
especially when there is heavy rain, which is accounted for by cancelling surveys under
these conditions .
3.6.3. Results
In total 155 point counts were conducted since the 24th
of October 2014, which started
during the previous phase. The number of points counts conducted among different
forest types were uneven, with 16 in primary forest, 52 in secondary forest, 31 at the
forest edge, and 56 along gallery forest. These include point counts conducted by a
BTEC candidate that was studying 5 different species including Riverside Wren, Blue-
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26
Crowned manakin and yet another endemic species the Blue-black grosbeak but also
two red listed species the Great Currasow and the Great Tinamou.
The highest species richness was found in gallery and secondary forest, while the lowest
was found in primary forest and at the edge of the forest .The riverside wren was
recorded in all four forest types but most frequently within the gallery forest. The blue
crowned manakin was recorded in gallery, secondary and primary forest and was the
most frequently observed bird in primary forest among the focal birds. The red capped
manakin was only recorded once, in gallery forest. Cherries tanagers were heard and
seen in gallery, secondary and forest edge habitat. The Fiery-billed araḉari has been
recorded in secondary forest and gallery forest. The Orange collared manakin has not
yet been recorded so far in any point count. Three IUCN red listed bird species were
also recorded during the point counts, the Vulnerable Great Currasow (Crax rubra) and
the two Near threatened birds the Baird's Trogon (Trogon bairdii) and the Great
Tinamou (Tinamus major). The Great Currasow was recorded only five times and the
two latter species 17 times and 42 times respectively. All three red list species were
found in a range of forest types, especially the Great Tinamou, which appeared to be
versatile as it was recorded in primary, secondary and gallery forest habitats.
3.6.4. Discussion
All of the focal species, with an exception of the cherries tanager, mainly occur in
mature and tall wet second growth forest and not at the forest edge. The cherries tanager
however, is said to be more common in open areas, often in disturbed habitats with
thickets & shrubs (Stiles & Skutch 1989). The riverside wren was seen in all forest
types, as stated in Stiles & Skutch 1989. This particular wren is known to forage low in
dense vegetation inside mature wet forests and at forest edges, despite the name, which
0 5 10 15 20 25
Forest Edge (N=25)
Primary Forest (N=10)
Secondary Forest (N=30)
Gallery (N=30)
Frequency of Focus Bird Species found at Different Habitat Types
Riverside Wren Blue Crowned Manakin Red Capped Manakin
Cherries Tanager Fierey Billed Aracari Orange Collared Manakin
Figure 11. Frequency of focus bird species found at different habitat types
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27
is conclusive with our results. The blue crowned manakin is said to be a typical forest
bird, which frequents the understory of humid mature forest and tall secondary forest
(Stiles & Skutch 1989). The secondary forest within our study area is generally tall and
regarded as old secondary forest, where blue crowned manakins were frequently
encountered. Not much is known about the ecology of this bird so with the continuation
of this study we hope to able to obtain information on this. The red capped manakin was
not as frequently encountered as the blue crowned manakins, which may be related to
their tendency to stay in upper understory and sub-canopy habitat (Stiles & Skutch
1989). The fiery-billed araḉari is commonly found in the middle to upper level of semi
open second growth forest often adjacent to clearings (Stiles & Skutch 1989). This
corresponds to our findings, where 50% of the point counts in secondary forest were
located at natural clearings
The blue-black Grosbeak was only recorded once in Primary forest, which could
suggest a preference for this forest and as low numbers were sited, that deforestation has
impacted this species in this area. However more point counts are required to draw any
conclusions for this species. The few sightings of Great Currasow could be explained by
the fact that they are generally uncommon, especially in areas that were previously
unprotected like this study site. However, this species is also hard to survey since it
possess a large variety of different calls (Baldo & Mennill 2011) and can therefore be
easily missed by the inexperienced surveyor.
The Great Tinamou (Tinamus major) was recorded quite frequently in this study and
during the BTEC study, with no obvious habitat preference found. The Great Tinamou
is heavily targeted for its meat throughout its range, mainly outside protected areas and
tt is likely that this bird profits from the fact that there is no hunting present in the study
site. The Baird’s trogon (Trogon bairdii) doesn’t appear to be as common, however, it is
a species that frequents the canopy in tall forests (Stiles & Skutch 1989) and since only
a few point counts were conducted in tall mature primary forests, this could partially
explain the few recordings of Baird’s trogon.
The point counts are uneven amongst the different types of forest, with primary forest
being underrepresented. The number of point counts conducted so far is not sufficient to
determine the presence or absence and habitat preference of the focal species. The
orange collared manakin was regularly seen within our study site and is considered
quite common by local residents, although it has not yet been recorded in our study
(Pers. Comm. Sanchez. M). More point counts need to be conducted to evenly cover the
different forest types, thereby increasing the representativeness of the whole study site.
Having undertaken this project in its pilot stage some changes have been suggested
moving onto the next phase. Very little is known about these endemic birds so before
trying to understand the effects of humans on these populations it has been decided that
increasing our knowledge of their ecology is our primary concern. Once we begin to
understand the bird’s preferences we can begin to establish a baseline which will then
allow us to study factors such as human disturbance more thoroughly. In light of this,
the six focal species will remain the same but point counts will be conducted at
locations which allow better habitat comparison; more points will be chosen in primary
forest habitat types to diminish the current bias in the point counts and allow us to more
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28
accurately compare different forest types. There are also plans to expand the project to
focus on other threatened species in the area, such as the Great Currasow and the Great
Tinamou.
3.7 CRF and the Osa Conservation Sea Turtle Conservation Programme
3.7.1 Introduction
Sea turtles are a flagship species for conservation, due to their iconic nature, and being
an excellent indicator species for climate change. This is due to their temperature-
dependant sex determination, whereby increased temperatures create a sex bias skewed
toward females, which could cause entire populations to collapse. Additionally,
temperature-induced changes in plant community composition, together with rising sea
levels, may result in increased incidences of beach erosion and inundation of nests
(Janzen, 1994). Late maturation in conjunction with anthropogenic threats, such as
beach development, long line fishing and pollution, mean that turtle populations are
highly vulnerable and often unstable (Govan, 1998). Poaching, and the illegal trade of
turtle eggs causes further reductions in turtle populations, which may result in entire
clutches being destroyed. Turtle hunting was widespread between the 1950s and 70s,
with half of the world’s turtle catches being conducted in Mexico, where as many as
350,000 turtles were harvested annually (Marquez et al., 1996).
A number of conservation strategies have been established throughout Costa Rica,
including limited legal commercial egg harvesting on a nesting beach in Ostional during
the first 36 hours of wet season arribadas (mass arrival of turtles) (Campbell, 1998) and
an annual catch of 1,800 black turtles being granted to fishermen in Limόn (Troëng and
Rankin, 2004). Though the latter may have increased extractive use along with illegal
hunting in the mid 1990s, the ban on black turtle fishing and increased law enforcement
since 1999 may have increased female turtle survivorship (Troëng and Rankin, 2004).
In other regions such as Tortuguero, the Costa Rican government has made egg
poaching illegal, in addition to prohibiting the trade of calipee, the edible part of the
shell (Government of Costa Rica 1963 and 1969; Troëng and Rankin, 2004).
Meanwhile, the growing ecotourism industry in Costa Rica has provided locals with an
alternative source of income and has promoted conservation throughout the country. To
evaluate the effectiveness of such strategies, it is imperative that monitoring
programmes are long term as it can take decades for species with late maturity to show a
population response (Troëng and Rankin 2004; Bjorndal et al., 1999).
On the Osa Peninsula where turtles are threatened primarily from predation by dogs,
coastal development, illegal trade of eggs and, to a lesser extent, turtle meat (Drake,
1996), NGO Osa Conservation have been patrolling Piro and Pejeperro beaches since
2003. Their aim is to monitor the frequency and health of the local nesting turtle
population and manage nest relocations to the associated hatchery. The Frontier Costa
Rica Forest research programme works in partnership with the Osa Conservation Sea
Turtle Conservation programme, protecting the four species which nest here: olive
ridley (Lepidochelys olivacea), Pacific black turtle (Chelonia mydas agassizii),
leatherback (Dermochelys coriacea) and hawksbill (Eretmochelys imbricata). The latter
two rarely nest on these two beaches. The olive ridley is most commonly found nesting
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29
here and is listed by the IUCN as ‘vulnerable’, whilst the black turtle is listed as
‘globally endangered’ (Troëng and Rankin 2004; Honarvar et al., 2008; IUCN, 2013).
3.7.2. Methodology
Now in peak olive ridley season, night and morning patrols were conducted on both
Playa Piro and Playa Pejeperro, managed between Frontier and Osa Conservation.
Morning patrols commenced at 04:00 am on Playa Piro and 03:00 am on Pejeperro
(high tide permitting) to minimise surveyor exposure to direct sunlight and high
temperatures. Night patrols typically started at 19:30 pm on both beaches. To minimise
disturbance to nesting females, surveyors used red lights during night patrols and survey
teams were limited to six people.
The survey area for both beaches was divided into 100 m sectors; this constituted a 2
km stretch of Playa Piro and 4.4 km stretch of Playa Pejeperro. For every turtle track
encountered, data such as patrol date, name of data recorder, beach sector number and
time were recorded. Nest data was also collected, for example; the nest type associated
with the tracks (in situ IS, false crawl FC; i.e., turtle returned to sea without nesting or
NA when the nest type could not be determined) and track symmetry (symmetrical S or
asymmetrical A) and the nest distance to the vegetation. The track was then crossed
through with a deep heel drag in the sand to avoid the track being recorded again in
subsequent patrols. Track characteristics were used as an indicator of species where the
turtle was absent (i.e., asymmetrical tracks suggest olive ridley, symmetrical tracks
suggest black). If a turtle was encountered, the species and distance to the tide was
recorded, a health assessment conducted and tagging of both the individual’s flippers
completed.
In-situ nests were confirmed by inserting a stick into the sand to locate the egg chamber
(indicated by a marked change in resistance when pressure applied) followed by careful
digging to confirm the presence of eggs. A false crawl was defined by the absence of a
nest or where it was clear that the turtle returned to sea without digging a nest. In the
case of predated nests, typically evident by the presence of predator tracks, egg shells
and signs that the nest had been dug up, the predator was identified by the tracks and
number of egg shells recorded.
Flipper Tagging and Health Assessments
All turtles encountered pre- or mid-nesting were tagged whilst they were laying, during
which time the female enters a haze and therefore associated stress is reduced. To
reduce the risk of infection during tagging, the tag sites were washed firstly with water,
then alcohol and iodine before applying the alcohol-cleaned tag. National’s ear tags
(National Band and Tag Co., KY, USA), each with a unique identifying number
engraved, were used. Two tags were used, one on each front flipper; both through the
third nail from the body (Figure 7).
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Figure 7. Diagram of Turtle flipper tag placement
While the turtle was laying (or at latest when returning to the ocean, stopping the turtle
en route by covering the eyes and kneeling in front of her), a health assessment was
completed. In addition to the date, flipper tag number and beach sector number, the
following health parameters were assessed; head (including the eyes, ears and nostrils),
front and rear flippers, carapace and skin, fibropapillomas (e.g., barnacles) and body
fat.
i) The features of the head are checked for swelling, cuts, lesions, sunken in eyes,
wounds and other deformities.
ii) The flippers are checked for symmetry, wounds, deformities; such as missing digits,
cuts, missing limbs, scars from tags torn out, and fibropapillomatosis, a form of the
herpes virus which has a cauliflower-like appearance and may, in addition to being
commonly found on the skin, be found on the eyes.
iii) The carapace is also noted for wounds, mating scars, boat strike wounds, defects and
any exposed bones or flesh. Any epibionts such as barnacles, leeches and algae on the
carapace are also counted.
iv) A body condition score is given, using integers from 1-3 where 1 indicates a thin and
emaciated turtle and 3 indicates one which is overweight. The condition can most
clearly be determined by inspecting the area around the neck and shoulder area.
Nest Triangulation
Nest triangulation was carried out only on those nests between sector 10 and 20 on
Playa Piro for the close monitoring of individual nests and their respective incubation
periods and hatchling success. When a nest was in situ the egg chamber was located
through probing the sand with a stick, as above, and in effect a chimney was then dug to
reach the surface of the eggs. In this chamber, a piece of flagging tape noting the date
and a unique nest number to identify it was placed inside before the nest was covered
again with the sand originally removed. From the point on the sand surface directly
above the centre of the egg chamber, the distance to the three nearest trees was
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measured, one central, i.e., approximately 90° relative to the nest, and one each to the
east and west of this point. These trees were also marked with flagging tape noting the
date, nest number and whether they are central (C), east (E) or west (W) of the nest. The
height of the tape in the tree from the ground was also recorded for precise nest location
referencing. Finally, the angle from the tree to the nest was recorded, again for C, E, and
W.
Nest Relocations and Hatchery Management
Osa Conservation has restored the use of the hatchery to be included in the programme.
Turtle nests that are at risk of flooding or erosion by the ocean’s tide are relocated to the
hatchery. These were deemed to be found between sector one and 10 of Playa Piro.
Considering this, the hatchery is located in sector 16 of Playa Piro. The hatchery is
divided into 300 quadrats, lettered from A-O on one axis and 1-20 on the other. Each
quadrat has a specific marker (e.g., A1, A2, and so on) in order to identify individual
nests.
A maximum of three nests are to be relocated to the hatchery per day. Any additional
nests may be relocated to sectors 11 and greater of Playa Piro, where they are not at risk
of high tides. When relocations away from one of the at-risk sectors are necessary, but
the time of day means that the ambient temperature becomes too high, or in the case that
three nests have already been relocated to the hatchery that day, nests may also be
relocated to these ‘safe’ sectors in order to avoid heat damage whilst transferring eggs.
When an in situ nest is found, the first step is to locate the egg chamber by probing the
sand. Next, wearing latex gloves, the surveyor digs out the eggs very carefully. Wet
sand found in the nest is placed into a clean bucket, to provide cushioning for the eggs
to be relocated. One by one the eggs are taken out of the nest and placed into the bucket,
in the same upright position they were found in to avoid any damage to the embryo. The
eggs are then covered by wet sand from the nest, again to avoid damage. The egg
chamber’s depth and width are measured so that a new egg chamber, approximately
identical in size and depth, can be dug during relocation. Date, sector in which the nest
was found, number of eggs and time of relocation are to be noted on a ticket allocated to
each nest, accompanied by the chamber measurements. Place of relocation is noted on
the nest ticket by circling either ‘Relocated to A’ (hatchery) or ‘B’ (other, e.g., sector
11). In either case, the egg buckets are carefully carried to their new location.
In the case of the hatchery, a pre-appointed quadrat is marked with red flagging tape by
the previous surveyor, following a chequered pattern to allow space for working and for
hatchlings between nests. The nest code (e.g., A1) is noted on the nest ticket, and all its
information is transferred to a data sheet along with the time of arrival at the hatchery.
A new egg chamber is dug, again whilst wearing latex gloves, in accordance with the
stated procedure.
The sex of hatchlings has been shown to be determined by the temperature in the nest.
Therefore, a plastic tube perforated with holes - to allow for air exchange, and long
enough to reach the top of the nest - is inserted into the middle of the chamber of each
new nest to house the thermometer inserted after egg deposition. This is in order to
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record temperatures in the nests and to estimate the percentage of male and female
hatchlings at the end of the season. The same process of transferring the eggs to the
bucket is reversed to fill the nest. The wet sand from the bottom of the bucket is initially
used to cover the eggs and is patted down. More wet sand is then used to cover the rest
of the hole and patted down, and the remaining exposed pipe is covered with a bottle
cap so that air exchange does not occur between the nest and the ambient air. Finally, a
mesh is placed on top of the sand around the egg chamber. A ring around the nest is dug
out to approximately 10cm depth to insert the bottom edges of the mesh. The top is tied
with string in order to allow for easy opening when taking nest temperatures and to
protect the nest from flies or predators. The red flagging tape is moved to the next
quadrate to be used for relocation.
The temperature in each nest was checked three times per day: at 0600, 1400 and 2200
hours. Slowly, the thermometer is pulled out and the temperature read immediately, to
allow for an accurate recording, before being carefully replaced in its original position.
A rain gauge is also set up at the hatchery to be checked every morning at 0600, and
emptied thereafter. Nest codes and temperatures (°C) as well as rain measurements
(mm) are kept on a separate spreadsheet managed by Osa Conservation.
Whenever a surveyor visited the hatchery for temperature readings, all nests were
checked for hatchlings that had emerged from the nest and were on the surface of the
sand. When hatchlings were present, the nest code is noted and a total of 20 hatchlings
are measured. The mesh is removed and with gloves the hatchlings are placed in a clean
bucket. The mesh was replaced if any eggs or live pipped hatchlings remained in the
nest. A clean Ziploc bag was clipped onto a handheld microscale (50g). The scale was
calibrated to 0g. One by one each hatchling was placed in the bag and its weight was
noted. Next, the hatchlings’ carapace length and width is measured using a calliper and
noted. Once all necessary hatchlings were measured, they were re-placed into the bucket
and all were released on the beach. If the necessary number of hatchlings was not
obtained from a single emergence, the next hatchlings to emerge from the same nest
were measured until this number was obtained. This data is managed by Osa
Conservation.
When relocating to sector 11 of Playa Piro, a new chamber was dug according to the
previous measurements that were taken. Eggs were transferred from the bucket into the
nest, as described above, as soon as possible to reduce any effect of egg temperature
change whilst eggs remained in the bucket. This was particularly important during
warmer hours of the morning. Once the chamber was full, wet sand from the bottom of
the bucket was packed over the eggs, and the remaining space filled with more wet
sand. The nest is then triangulated according to the triangulation procedure above. No
temperature measurements were taken for nests outside of the hatchery.
Nest Excavations
Triangulated nests were excavated after the expected hatch date to determine hatch
success, emergence success and embryology. This data was combined with the data
collected at the time of nesting, and where possible linking with data of individual
turtles (i.e., tagging and health assessment). These data are essential for quantifying
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hatching and emergence success, which are integral components in understanding
population trends. Excavations, as described below, were also performed for non-
triangulated nests when the hatchlings emerged; indicated by the presence of hatchling
tracks or emerging hatchlings.
Any egg shells on the surface (greater than 50% of the entire shell) were counted and
recorded as predated. The area was searched for any live or dead hatchlings outside of
nests and these were recorded separately before beginning the excavation. If a live
hatchling was found in the nest, it was removed and put on the surface of the sand to
make its own way to the sea. The hatchling could be assisted by moving it closer to the
sea if the sand was very hot, but as it is believed that for the hatchling to become
imprinted on its natal beach to which it will return to nest as an adult (Lohmann et al.,
2008) , the hatchling must enter the water on its own. All of the remaining contents of
the nest were removed separating unhatched eggs from empty egg shells. Unhatched
eggs which varied from the normal white colouration and/or had large impressions
present and were very soft-shelled were deemed dead - a lesson learned from years of
professional experience gained by Osa Conservation and other expert parties - and were
opened to ascertain the stage of development; white unhatched eggs were returned to
the nest. There were five developmental stages which were determined by the
percentage that the embryo occupied within the egg, graduated at 25% intervals
whereby a Stage 1 occupied 0-25% of the egg (and had blood vessels and an eye spot
present), Stage 2 occupied 26-50% and so on. The fifth category was for undeveloped
eggs which were identified as an egg yolk with no signs of an embryo or eye spot.
Protective latex gloves were worn at all times.
3.7.3. Results
This phase, a total of 89 turtle patrols was conducted at Piro beach and 47 patrols on
Pejeperro beach by Frontier and Osa Conservation. On Piro beach 41 night patrols were
conducted during this period and 22 in Pejeperro beach. Oliver Ridley turtles largely
outnumbered the Black Pacific sea turtles this phase. On Pejeperro beach a third more
turtle tracks were found oppose to Piro while the patrol effort on Piro was double as
much (see table). This phase a critically endangered Hawksbill turtle laid 3 nests on Piro
beach on the 23th
of June, 5th
of July and her last nest on the 17th
of July.
Table 8. Summary of all turtle data collected this phase. LO: Lepidochelys olivacea;
CM: Chelonia mydas agassiz; S: symmetrical tracks; AS: asymmetrical tracks, FC:
False crawls.
Piro (LO-AS) Peje (LO-AS) Piro (CM-S) Peje (CM-S)
Tracks (FC) 117 141 11 19
Nests 326 536 5 17
Total tracks 443 677 16 36
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Hatchling success hatchery
In total 159 nests have been relocated to the turtle hatchery at the time of writing. The
first nest being moved on the 9th
of June and the latest nest moved (at the time of
writing) on the 13th
of September. Hatchling success for the first 38 nests is 89%; these
represent all the nests laid up until the first of August. In total 3275 hatchlings (N=38)
have been released successfully. Hatchling success for August and September has yet to
be analysed.
3.7.4 Discussion
The peak of the nesting season of the Pacific Green turtle is December – March and of
the Olive Ridley turtle August – October in Piro and Pejeperro (Pers. Comm. Manual
Sanchez, Osa Conservation). Although there can be yearly variation in the nesting
activity of the sea turtles and an overlap between the species, with the first turtles
arriving 2-3 months before the ‘peak’ of the nesting season (Pers. Comm. Manual
Sanchez, Osa Conservation). At Playa Naranjo, Guanacaste, Costa Rica, the peak of
Green turtles is October-March (Cornelius 1986). This phase largely overlaps with the
nesting season of the Olive Ridley turtles, which explains the higher numbers of this
species found during this time of the year. On beaches shared with other nesting turtles
species, Pacific green turtle nesting occurs after the nesting peak of the Olive Ridley
turtle (Alvarado et al. 1985). This may reduce competition for nesting space. Both
species can’t be compared based on their numbers. Olive Ridley turtles are known to be
the most abundant sea turtle species globally, especially in the Eastern Pacific ocean,
where they are known to outnumber the Pacific green turtles. (Cliffton et al. 1982,
Alvarado-Díaz et al. 2001, Márquez et al. 1976, Solís et al. 2007) This is also reflected
by their different global status, Vulnerable for the former and Endangered for the latter
(Seminoff 2004, Abreu-Grobois & Plotkin 2008).
Hatchling success from the ex-situ nests in the hatchery will be discussed when all data
has been compiled.
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Additional Projects
N/A
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Brakels P, Armintage, C., Stanish, T., Shanks, J., Rachel, C. & Natalie D.
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5. Proposed Work Programme for Next Phase
Primate surveys will continue, sampling evenly across all trails and times of day until
sufficient data (group composition, home range boundaries) is collected for all four primate
species. Hopefully we can pick up the line-transect sampling again next phase so accurate
density estimates can be made of spider monkeys and squirrel monkeys (in particular) with
the complementary data of actual group counts.
The monitoring program of the otter project will continue until there is sufficient data to
analyse. This will provide a greater insight into the distribution and habitat selection of the
species in Piro river. Next phase we aim to report our first findings of this year’s otter data.
Next phase we will be approaching the end of the nesting season of the Olive Ridley turtles
and we will get the first Pacific green turtles to come nest on the beaches.
The bird project will carry on collecting point count data to analyse the encounters and
abundance of endemic birds between different types of habitats across the trail.
Track surveys will be continued next phase, with the main focus on the distribution and
abundance of wild cats and their prey throughout the Piro property.
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