The conservation of tigers and other wildlife in oil palm plantations

Occupancy surveys
A variation of the patrol transects, which continually monitored specific areas of the
landscape, was a one-off occupancy survey designed to rapidly assess wildlife status
and threats across the entire landscape over a short period of time. The occupancy
survey operated at two levels. Firstly, presence or absence of target species (medium
and large mammals) and threats across the landscape were measured. This was done
using repeated sampling to estimating detection probabilities for different species or
threats, thus allowing confidence levels to be calculated, as described by MacKenzie
et al. (2002). Secondly, occupancy surveys also recorded rates at which species were
detected across the landscape, giving a crude measure of distribution.
The occupancy survey was carried out in April-May 2005 using teams of two people
to search 36 randomly placed 3x3 km cells for wildlife. Each cell was independently
surveyed three times by three different teams, with six hours spent by each team in
each cell and repeats carried out on consecutive days to reduce the possibility that
animal movements and rainfall during the survey affected results. The objective within
each cell was not to achieve total coverage of the 9km 2
but to establish whether the
target species were present or not, and if so how many times they were independently
recorded in each cell. Therefore, within cells teams were free to search selectively and
ignore areas they deemed unlikely to contain wildlife. Data were then analysed by
building detection history matrices for each cell and analysis using PRESENCE
software version 2.0 (Pledger 2000). For species with sufficient data the naïve estimate
of occupancy, detection probability and proportion of area occupied was calculated
using the “single group, constant p” model which had the best fit in every case.
Camera-trapping
Camera-trapping is an increasingly widely used technique used for measuring relative
abundance (Carbone et al., 2001), minimum population sizes based on individual
recognition or sophisticated estimates of density based on capture mark recapture if
data are sufficient (Karanth, 1995). They are suitable for a range of medium to large
mammals, with previous studies focussing on tigers (Karanth and Nichols, 1998),
bears (Mace et al., 1994), small carnivores (Moruzzi et al., 2002) and ungulates (O'Brien,
Wibisono and Kinnaird, 2003). In this study a mixture of “Camtrakker” and
“Photoscout” cameras were used with passive sensors. In almost all cases, cameras
were attached to trees about 1-2m from the expected path of the animal and generally
about 30-70cm above the ground (depending on vegetation length). Cameras were
aimed at an animal the size of a crawling or crouching human.
Wildlife conservation in oil palm plantations 17