Download Large mammal abundance and distribution patterns in relation to

Large mammal abundance and distribution patterns in relation to habitat
characteristics of Mayan forests: Project overview
Dr Kathy Slater, Operation Wallacea
Calakmul is a large expanse of tropical forest that is continuous with the Maya Biosphere Reserve in
the Petén Province of Northern Guatemala. Calakmul biosphere reserve covers an area of 723,000
hectares, but is attached to two state reserves Balam-kim and Balam-ku which run the entire length
of the western side of the biosphere. The total area covered by these connected reserves is
1,200,000 hectares, but these reserves are surrounded by more forest giving rise to over 4 million
hectares of forest. Over 20,000 people live in and around Calakmul and with more people moving
into the area, developments are starting to affect the landscape and hunting rates. Hunting is strictly
prohibited inside the reserve, but in the surrounding forest, indigenous communities are permitted
to hunt certain species (e.g. peccary and deer). Although these species are abundant, they are the
preferred prey of jaguar and puma and a reduction in their preferred prey can lead to increased
likelihood of felid attacks on livestock in buffer zone communities (Forster et al., 2010). A study of
the habitat preferences of ungulates in hunted and non-hunted areas of Calakmul indicated that
each species preferred different habitats and that the habitat preferences of each species changed
when they were in hunted areas compared to non-hunted areas (Reyna & Tanner, 2005).
Consequently all types of forest in hunted and non-hunted areas must be preserved in order to
maintain the ungulate population and corresponding felid population.
Large mammal density at Calakmul Biosphere Reserve is very high and the forest is one of the last
remaining strongholds of endangered mammals such as spider monkeys, jaguar and tapir. The
tropical semi-deciduous forest in Calakmul Biosphere Reserve is unusual in that areas close to Mayan
Ruins contain unusually high densities of large fruiting trees (the result of Ancient Mayan agroforestry) in comparison to other areas (Ross & Rangel, 2011). These large fruiting trees are a major
attraction for primates, and both howler and spider monkeys tend to me concentrated in these
areas (Estrada et al., 2004). As there are no rivers or streams in the reserve, forest structure is also
heavily affected by distance from the few permanent water sources in the reserve known as
aguadas. In addition, there is a steady increase in mean annual precipitation from the north to the
south of the reserve that has a notable effect on tree species composition and forest structure.
The aim of the large mammal research project is to investigate the relationship between habitat
characteristics and large mammal abundance and ranging. The project also aims to provide reliable
estimates of population density by collecting data in different sections of the forest with and without
aguadas and ruins. Projects can focus just on primates and terrestrial mammals or just one of the
two. Projects focussed on terrestrial mammals may chose to focus on certain species such a tapir
that are known to adjust their range according to proximity to water, or large predators (eg. jaguar
and puma) and their prey (peccary and deer).
Methods
Data collection will be carried out in 5 different locations with the Calakmul Biosphere Reserve
(Figure 1). These camp locations have been chosen due to their accessibility during the wet season
and because they cover the full geographical and vegetation range of the reserve. Each camp will
contain four 2km long transect lines for data collection that have been mapped using a GPS unit. Five
sample sites for habitat surveys will be located along each transect line at 500m intervals, giving rise
to 100 sample sites across the 5 research camps in the reserve. Each sample site will consist of a
20m x 20m area adjacent to the transect line. These sample sites will be marked and the GPS
location recorded.
Figure 1: Location of research camps in Calakmul
Primates and large terrestrial mammals will be surveyed along line transects (that are not placed
with any pre-determined knowledge of the distribution of the animals: Peres, 1999), using distance
sampling (Buckland et al., 2001). The entire length of the transect line will be walked by small groups
of 3-4 observers walking quietly and slowly (500-1,000 m/hr), starting at 6.30am when the majority
of animals are most active and are easiest to detect. Each time an animals is encountered the
species, whether the animals was seen or heard, number of individuals (visual sightings only),
perpendicular distance from the individual to the transect line, habitat, time, distance travelled
transect along the transect line and weather conditions will be recorded. Each line must be surveyed
on four separate occasions.
The distance sampling method is only suitable when animals are relatively easy to detect and is
therefore unsuitable for monitoring elusive species living a low densities such as jaguar. Thus, an
additional two methods will be used to monitor these species: patch occupancy sampling
(Mackenzie, 2005) and camera trapping. Patch occupancy sampling involves detecting animals based
on tracks and faeces rather that visual or vocal sightings of the animals. These data will be collected
as students walk back along the transect line to camp (i.e. after the distance sampling). Camera traps
will be placed in areas of the forest, close to some of the research camps, but in areas that will not
be visited by human observers conducting survey work. It will therefore be possible to compare
density estimates from transect surveys with density estimates from camera traps, but as the
camera traps are part of a different ongoing study, it is not possible to change to location of the
traps to better suit individual projects.
Habitat surveys will be conducted in each of 20m x 20m survey sites to investigate tree diversity and
basal area, and to estimate carbon tonnage within the reserve. Surveys will generally be conducted
in the afternoons. Numbered metal tags will be attached to each tree in the plot, and the species,
DBH, height of each tree, and whether the tree is alive or dead will be recorded on datasheets with
the corresponding tree tag number. Where species cannot be identified in the field, photographs of
leaves, fruit (if available leaves and bark will be taken for later identification from textbooks. If
identification is not possible from photographs, then samples may be taken from the tree at a later
date for full examination. DBH will be measured using 50m tape measures and tree height will be
calculated using SUUNTO clinometers and tape measures (tree height can be estimated based on the
distance of the observer from the base of the tree and the angle from the observer to the top of the
tree). In addition, understorey vegetation will be measured using a 3m graduated touch pole in lines
bisecting the plot and in leaf litter depth and canopy openness (measured using a canopy scope) will
be recorded 1m in from each corner of the plot and in the centre of the plot.
Each large mammal track can then be linked to the nearest habitat plot along the transect providing
a corresponding set of habitat variables for each track. From this, habitat preferences of each
species may be calculated and the habitat variables effecting large mammal abundance at each plot
can also be investigated.
Suggested Reading
Buckland, S.T., Andersen, D.R., Burnham, K.P., Laake, J.L., Borchers, D.L., & Thomas, L. 2001.
Introduction to Distance Sampling: Estimating Abundance of Biological Populations. Oxford: Oxford
University Press.
Colchero, F., Conde, D.A., Manterola, C., Chavez, C., Rivera, A, & Ceballos, G. 2011. Jaguars on the
move: modeling movement to mitigate fragmentation from road expansion in the Mayan forest.
Animal Conservation 14: 158–166.
Estrada, A.J., Luecke, L., Van Belle, S., Barrueta, E. & Rosales-Meda, M. 2004. Survey of black howler
(Alouatta pigra) and spider (Ateles geoffroyi) monkeys in the Mayan sites of Calakmul and Yaxchilan,
Mexico and Tikal, Guatemala. Primates 45:33–39
Forster. C.R, Vaughan. C. 2002. Home range, habitat use, and activity of Baird’s tapir in Costa Rica.
Biotropica. 34 (3): 423-437
Forster, R.J., Harmsen, B.J., & Doncaster, P.C. 2010. Habitat use by sympatric jaguars and pumas
across a gradient of human disturbance in Belize. Biotropica 42: 724-731.
MacKenzie, D.I., Nicols, J. D., Royle, J.A., Pollack, K., Bailey, L., & Hines, J.E. 2006. Occupancy
Estimation and Modelling: Inferring Patterns and Dynamics of Species Occurrence. London: Elsevier
Publishing.
Peres, C.A. 1999. General Guidelines for standardizing line-transect surveys of tropical forest
primates. Neotropical Primates 7(1):11-16.
Ross, N.J. & Rangel, T.F. 2011. Ancient Maya agroforestry echoing through spatial relationships in
the extant forest of NW Belize. Biotropica 43(2): 141–148.
Reyna-Hurtado, R., & Tanner, G.W. 2005. Habitat preferences of ungulates in hunted and nonhunted
areas in the Calakmul Forest, Campeche, Mexico. Biotropica 37(4): 676–685 2005