| PROJECT SUMMARY
The Baird's Tapir Project is studying the population dynamics of an undisturbed, non-hunted population of Baird's
tapirs in Costa Rica's Corcovado National Park. The underlying philosophy of the study is that with a better understanding of the ecology of an intact,
healthy tapir population, we will be better equipped to identify irregularities in populations that are influenced by human activities. This information can
then be used to design appropriate management strategies to correct those specific abnormalities. Towards this end, a population of tapirs is being
monitored via radiotelemetry and direct observations to measure the following parameters: a) reproductive rate, b) offspring and adult sex ratios, c)
offspring and adult survival rates, d) juvenile dispersal behavior, e) spatial distribution, f) population density, g) mortality, and h) genetic variability.
The results of this study can be directly applied to the health assessment of other tapir populations and will influence new and existing conservation
programs such as reintroduction, translocation, and the designation of new protected areas. In addition, we are collecting data on of site-specific parameters (home
range size, habitat use, etc.), which will be vital for management plans for tapirs in Corcovado.
INTRODUCTION
Once common in practically all ecosystems from southern Mexico to northern Colombia,
the Baird's tapir is now in danger of extinction throughout its range (the
species is already considered extinct in El Salvador). Illegal hunting is
reducing many tapir populations to dangerously low levels while deforestation is
isolating these populations in smaller and smaller patches of forest fragments.
As the sizes of tapir populations decrease and isolation interrupts the
exchange of genetic material, the probability of local extinction will increase
dramatically. The future survival of the Baird's tapir will depend on the
protection of large expanses of habitat supporting tapir populations and, in
many cases; the implementation of management plans to repair the damage done by
human influence.
For years IUCN categories of threat have been based on the results of population
viability analysis (PVA) of target populations. PVAs are also important when
making management decisions for the conservation/preservation of endangered
species. However, this analysis requires a demographic model of the population
and data on the year-to-year variability of each of the parameters of the
model. The Baird's Tapir Project is providing the first set of data from a
free-ranging tapir population towards the development of just such a model. Radiotelemetry
and direct observations are being used to monitor the movements and behavior of
a small tapir population in Costa Rica's Corcovado National Park. The data
collected is analyzed to describe a) home range size, b) habitat use, c)
juvenile dispersal, d) activity patterns, e) population density, f) spatial
distribution, g) territoriality, h) reproductive rate, i) mating system, j)
adult and offspring sex ratios and k) survival rates.
The population being studied inhabits the area surrounding
the Sirena Biological Station in the heart of Corcovado National Park. This
site was chosen because it is one of the
few places left in Central America where a large population of Baird's tapirs
exists without unnatural pressure from deforestation or hunting. This
characteristic is crucial because our goal is to document the "behavior" of an
undisturbed population. The underlying philosophy behind the study is that with
a better understanding of how an intact, healthy tapir population functions, we
will be better equipped to identify abnormalities in populations influenced by
human activities. This information can then be used to design management plans
to address those specific problems.
The Baird's Tapir Project is the largest and longest-running
field study of tapir ecology in the world. Initiated in 1995, the study has
radiocollared and monitored the movements and behavior of more than 30 tapirs.
Five adult tapirs (3 female, 2 male) were captured and radiotagged in 1995 and
monitored for 12 months. The objectives during this time were to test data
collection methods and gather data on habitat use, home range size, activity
patterns and foraging behavior of tapirs. The results were presented for
Charles Forester's Master's degree in Wildlife Management from the National
University of Costa Rica. In 1997 and 1998 the study area was expanded to its
present size and 13 more adult tapirs were added to the study. Between 1996 and
2000, we developed a new anesthetic protocol for the immobilization of
free-ranging tapirs that has proven safe for the animals as well as the
researchers.
The data set on home range size, habitat use and activity pattern has been entered into the Corcovado National Park database for
consideration in any future management decisions involving tapirs. Although the
study has collected an extensive amount of information on reproduction,
survival, mortality, and juvenile dispersal, the slow reproductive rate and
longevity of the tapir requires us to continue monitoring the population in
order to fully understand the dynamics of the population.
STUDY AREA
Corcovado National Park (41,789 ha) is located on the
western coast of the Osa Peninsula of Costa Rica. Created in 1975, Corcovado
protects the largest remaining tract of Pacific lowland tropical rainforest in
Central America and supports more than 500 species of large trees, 367 bird
species, 140 mammals, 51 amphibians and 64 reptiles. Temperatures range from 23° and 26.5° and annual rainfall
varies between 3,800 mm in the lowlands to 6,500 mm in the mountains. The rainy
season extends from May through November and the dry season from December
through April.
The core study area for this project is 20 km2 of lowland rainforest surrounding the Sirena ranger station / biological station.
Two major rivers drain the region: the Rio Claro in the south and the Rio
Sirena in the north. The region north and northwest of the Sirena station has
alluvial, well-drained soils and vegetation corresponding to tropical wet
forest. It is estimated that approximately 1,800 ha had been deforested in the
Sirena area (principally in 1-17 ha parcels) before it was declared a National
Park in 1975. The resulting habitat now, 28 years later, is a mosaic of primary
and regenerating secondary forest patches.
METHODS
Data collection is directed towards enhancing conservation efforts on two levels: a) site-specific data (critical habitats, population
density, etc.) relevant mainly to the tapir population in Corcovado, and b)
demographic data (reproductive rate, sex ratios, etc.) applicable to tapir
populations throughout Central and South America.
--Immobilization for Radiocollar Attachment:
Study animals are immobilized to either: a) replace radiocollars before battery failure, or b) place radiocollars on offspring of
radiocollared females. Collars are attached leaving a two-finger width gap
between the neck and collar material. Offspring are first radiocollared at
12-months of age, just before they begin to move independently from their
mother. Juveniles are visually checked continuously to make sure their collar
has not become too tight. All captures are conducted during the day and
telemetry equipment is used to locate the target animals. The tapirs are
immobilized with a mixture of 40 mg of Butorphanol and 100 mg of Xylazine,
delivered in a 5 cc dart (Pneu-Dart) with a CO2 pistol (Dan-Inject).
Naltrexone (Trexonil, Wildlife Laboratories) is injected intramuscularly at a
mean dose of 150 mg to reverse the Butorphanol. Tolazoline (Lloyd laboratories)
is administered intramuscularly to reverse the alpha-2 agonist effects of
Xylazine. A complete report on the protocol can be found in the Journal of
Wildlife Disease: 36(2): pp. 335-41, 2000, or
http://www.ivis.org/special_books/Heard/foerster2/chapter_frm.asp.
To date 44 immobilizations have been conducted without complications using this
new protocol. Biological samples collected during the first five years were
used to report reference ranges for hematology, serum chemistry, mineral
levels, skin histopathology, infectious disease antibody rates and
ectoparasites for the population.
--Radiotelemetry:
Movements of the study animals are monitored via
radiotelemetry. Transmitter bearings are estimated for the strongest signal
from at least two of 160 receiving stations established along research trails
in the study area. The animal's coordinates are estimated by triangulation.
Each month, 6 diurnal (0600-1759 hr) and 15 nocturnal (1800-0059 hr) locations
are estimated for each tapir (250 locations/year). This sampling design is
based on data from the previous 5 years, which show tapirs in the Sirena area
are predominantly nocturnal and that 15 locations per month are sufficient to
measure movement patterns without having problems with autocorrelation of data.
Telemetry data is used to determine: a) home range size, b) habitat use, c)
activity pattern, and d) distance and direction of juvenile dispersal.
-- Home range size:
Seasonal and annual home range sizes are estimated for each
tapir. Results are pooled into 5 categories for analysis: a) all tapirs
combined, b) all adults, c) all juveniles, d) all male adults, and e) all
female adults. Home ranges locations and sizes are further analyzed to estimate
population density, territoriality, and spatial distribution of the animals.
Home range overlap between individuals is also used an initial indication of
their mating system.
Results to date:Average annual home range size for all adult tapirs
combined is 117.4 ha. (n=31). Average wet- and dry-season home range sizes are
82.8 ha (n=44) and 92.1 ha (n=49) respectively. No significant differences have
been noted in home range sizes between seasons or between sexes. As expected,
home ranges of juveniles (average: 67 ha.) are much smaller than adults.
--Habitat availability and use:
Habitat availability for each tapir is determined by
overlaying its home range boundary on the habitat map of the study area
(right). Seasonal and annual habitat use is calculated as the percentage of
telemetry locations in each habitat type.
Results to date:Secondary forest is the most utilized
habitat by all study animals. This is probably due to the higher density of
understory vegetation and an abundance of pioneer plant species, which are
generally more palatable. Primary forest, the second most utilized habitat
type, is used mostly for daytime resting sites and in the wet season when fruit
production is higher. In general, tapirs were located more often on flat or
gently sloping terrain, and near permanent water sources. Habitat use of
juveniles closely follow that of adults.
--Offspring independence and Juvenile dispersal:
Adult females with offspring by their side are located every
2 weeks to monitor survival and development. Dispersal is defined here as the
movement of an individual away from its natal range upon reaching the age of
independence. Dispersal behavior is evaluated in terms of age, distance and
direction. Offspring of collared females are radiotagged at 10-12 months of
age. This is the stage of development when an offspring begins to move more
independently of its mother (although it will remain in the same home range
until 3 years old). At 3 years of age, a new radiocollar with a new battery is
placed on the animal in anticipation of it leaving the study area. Once an
animal has left the core study area, monthly flights are made to locate them
from the air and estimate their position. Locations are collected in this way
until 3 months prior to estimated collar failure. At that time, the animal is
found, immobilized and the collar removed.
Results to date:
Independence and dispersal of juvenile tapirs appears to be
dependent on age and reproductive behavior of the mother. If the mother becomes
pregnant, the offspring will begin to move independently 1 to 2 months before
the birth. It will, however, remaining within its maternal home range for
another 2 or 3 years. Between 3 and 4.5 years of age juveniles tapirs inhabit
the "no-mans land" between adult territories just outside their maternal home
range. Finally, between 4.5 and 6 years of age the juveniles move completely
away to establish their own territory. To date, six juvenile tapirs have been
monitored during the dispersal process. Four females dispersed an average of 18 km from their original home ranges (range: 5-30 km). One male has traveled 16 km and another 5 km. However,
these males have not yet become completely established and may disperse to
different locations.
--Mortality:
All radiocollars are equipped with a mortality sensor, which
doubles the pulse rate of the signal after 12 consecutive hours of inactivity.
In such a case, telemetry equipment is used to locate the transmitter and
verify the animal's death. Cause of death is investigated based on physical
evidence found on site and, when possible, through necropsy. At minimum, the
skull of the tapir is collected. Teeth wear and closure of cranial sutures are
evaluated to place the animal in the proper age class.
Results to date One female and three male study animals have died since
1995. The female was found in December of 2000 and is thought to have died of
old age based on extensive wear of her molars. She also had multiple infections
in her canines and molars. A 2.5 year old juvenile male fell 20 m into a rocky
canyon and died of traumatic injuries. No evidence was found to indicate why
the animal fell. It is possible he was trying to escape from a predator or the
ground simply gave way underfoot. One adult male was found in December of 2001
with no obvious external injuries. The only abnormality noted was a slight
infection of his lower right canine. A second adult male died in January 2002.
He had been observed severely underweight for the previous 18 months. Again,
the only abnormality found was infections in one lower canine and upper molar.
The population needs to be studied for a longer period to increase our data on
survival rate, age-dependent mortality, sex-dependent mortality and causes of
death.
--Population density in core study area:
An estimation of the population density (number of
individuals per km2) of tapirs in the core study area is based on
radiotelemetry data. Locations for all adults during a single year are plotted
on a map and the area calculated with a minimum convex polygon. This area is
then divided into the total number of adults monitored during that time.
Results to date Based on adult home range size alone, the population
density of tapirs in the Sirena area is estimated at 0.88 tapirs/km2.
However, when home range overlap is considered, the density estimate increases
to 2.54 tapirs/km2. The population needs to be monitored for more
time to increase our data set.
--Reproductive rate:
Telemetry equipment is used to locate adult females on a
monthly basis to check for the presence of an offspring.
Results to date Sixteen offspring have been born to five radiocollared
females with an average birthing interval of 20 months. The sex ratio of
offspring has been 8 male, 5 female and 3 unknown. The overall birth rate has
been 0.51 offspring/female per year. The birth rate of male offspring has been
0.24 males/female per year while the birth rate of female offspring has been
0.20 females/female per year. No birthing season has been noted since births
have been recorded in all months except February, May and October.
--Offspring survival:
Females with young are visited bi-weekly to appraise
offspring development and to monitor survival rate.
Results to date
Thus far, tapir offspring have a 100% survival rate to the
age of 4 months (n=16); 91% to 1 year (n=11); 86% to 2 years (n=7); 67% to 3
years (n=6); 50% to 4 years (n=4) and 33% to 5 years (n=3). More time is needed
to obtain a larger sample size from older juveniles.
-- Genetic evaluation:
Skin samples for DNA analysis are collected from each
radiocollared tapir at time of immobilization. Jim Norton, a geneticist with
the Brookfield Zoo, is using these samples to develop molecular microsatellite
markers. Using several of these markers it is possible to identify individuals
based on the combinations of variable markers in their genome. These markers
will be used to genotype all the samples collected from the study animals and
evaluate genetic variability within the population. In addition, relatedness
between individuals will be determined based on level of frequencies of shared
markers. With enough samples it may then be possible to look for certain
aspects of tapir social structure such as juvenile dispersal and mating system.
Radiotelemetry data on dispersal and spatial distribution (home range overlap,
etc.) will be used to support these findings.
So far 6 potential microsatellites have been identified.
Preliminary results have not shown much variability. Preliminary results show
no significant differentiation between samples collected in Panama and the
radiotagged tapirs in CNP. This implies that prior to habitat destruction and
fragmentation, gene flow was connecting the Darien and CNP, effectively making
them one single panmictic population. So far, only juvenile females have
dispersed from the area. Home range overlap appears to indicate tapirs live in
small family groups consisting of an adult female, and adult male, and their
offspring. DNA samples from 4 mother-offspring pairs have been collected.
Additional samples are needed from other
populations to be able to assess whether the lack of variability is a
characteristic of the microsatellite markers or of the Corcovado population.
More DNA samples from known mother-offspring pairs are necessary to identify
the sires of those offspring. More mother-offspring samples are needed. More
juveniles need to be followed to determine sex-dependent dispersal behavior.
Also, more home range data is needed to define spatial distribution patterns.
--Biologists training:
The project employs only Latin American biologists, although
U.S. and European volunteers have participated. Thus far, 3 field assistants
have gone on to graduate schools in ecology and 2 other are currently employed
as parataxonimists in Corcovado. The primary investigator conducts telemetry
workshops twice a year for university students on field courses in the park. An
agreement between the project and the Wildlife Management Master's Program at
the Universidad Nacional of Costa Rica whereby students are welcome to conduct
his/her field project with tapirs in Corcovado. This year a young Costa Rican
will investigate the influence of tapir foraging behavior on the structure and
diversity of the forest.
CONSERVATION IMPACT
The success of this project does not stop with the analysis
of the data. The central theme around which this project was created is
providing information that will aid in the conservation of Baird's tapirs and
their habitat throughout their range. This implies making the methodology, the
data, and the results available to local, regional, national and international
decision makers.
On a local level, all results are communicated to the central office of the Osa Conservation Area of which
Corcovado is the most important component. To date no specific action has been
taken to manage the tapir population but recent studies are bringing to light
the hunting pressures felt by tapirs near the park boundaries. Results of this
study will be crucial in demonstrating the detrimental affect this will
certainly have on the population as a whole. If needed, we will be able to show
concrete data on the reproductive potential of the tapir and how the population
cannot endure even minimal hunting. Also, short-term projects would likely
demonstrate the differences in densities and behavior between the study
population and those found near the borders of the park. This type of quality
information will make it much easier to justify the implementation of programs
to reduce the hunting of tapirs (environmental education, patrols, etc.).
Informally, our study methods, results and general observations are made known to the towns and
villages surrounding the park. A local newspaper, "Sol de Osa", has carried
several stories about the project with natural history data on the tapir. We
have great hopes for the new environmental education department within the park
administration. This will be a fantastic opportunity to convey a conservation
message to the people of the Osa Peninsula, with a slight bias towards tapirs.
Ideally, the tapir can be used as a flagship species to bring attention to the
importance of the park. On a very local level, visitors to the park (national
and international) are always informed about the project and its goals.
On a regional and national level, copies of our
results are periodically sent to the Universidad Nacional, which maintains
Costa Rica's best library of ecological material. Final results of certain
aspects of the study are sent to the National Library, the National Museum and
the Ministry of Natural Resources. This project and the study animals are
regularly featured on national television broadcasts and newspapers
highlighting the biodiversity of the nation. We have a good relationship with
several newspapers and television stations and expect to continue having
tapirs, their natural history and their conservation issues presented to the
Costa Rican public.
Tapirs are found in many parts of Costa Rica, but mainly their populations are isolated in National
Parks or other protected areas. Our results will be made available to park
officials and those responsible for the management of these areas. Although
tapirs are found in a wide range of ecosystems in Costa Rica, our results on
demographic parameters will provide decision makers with the tools needed to
evaluate the populations under their charge and design management strategies if
they are needed.
On an international level, the results of this study will be sent to the Ministries of Natural resources of each range
country of the Baird's tapir. The primary investigator is a graduate of the
National University of Costa Rica's Wildlife Management Master's Program which
educates and trains students from all over Latin America. As a result, we have
strong ties to important decision makers in many Central and South American
countries. Our results and recommendations will be sent directly to these
influential people. In addition, our results have been, and will continue to be
presented at international meetings and symposiums. This project has been the
focus of several international television broadcasts shown on The Discovery
Channel and Animal Planet. Most recently, the BBC filmed a portion of their
herbivore documentary with David Attenborough using our study animals. The primary
investigator is also the deputy chair of the IUCN/SCC Tapir Specialist Group,
with contacts all over the world interested in tapir ecology and conservation. |
