A Supplemental HCVF Assessment on the Sumatran Tiger ...

FINAL REPORT Tiger <strong>HCVF</strong> <strong>Supplemental</strong> <strong>Assessment</strong> – Serapung FMU
(Smith et al. 1989). In PSF the localised concentration of tiger activity as suggested by
secondary signs and “scent-marking” may be accentuated as undisturbed PSF is more
restricting in terms of ease-of-movement in comparison to other lowland forest types.
The paths along the canals within the FMU offer the same ease-of-movement but,
being newly developed and subject to intense disturbance from illegal logging, may not
yet be fully exploited by tigers. Previous studies have shown some species, including
tigers, become more nocturnal in their activity in order to avoid encounters with
humans (Ojasti 1991, Griffiths and van Schaik 1993, Guggisberg 1975) and Kawanishi
(2002).
The relative abundance of tiger sign found within and outside the FMU was also
reflected in the number of remote camera photographs obtained, with all 14
photographs taken along the Yos Trail. However, it should be noted that the number of
camera trap days was 50% greater along the Yos Trail in comparison to the FMU, due
to theft of cameras within the FMU and a limited number of locations where cameras
could be placed due to illegal logging activities.
The rate of photo-capture for all cameras both inside and outside the FMU was 0.093
tiger photographs per camera day (10.7 days/photograph). Comparison with other
studies (Figure 23) identifies this as the highest rate achieved by any published study
on the Sumatran tiger in Indonesia, greater than capture rates from the high-density
tiger population in Way Kambas NP (0.025 photographs/camera day, 39.9
days/photograph) and comparable to capture rates achieved in the exceptionally high
tiger density areas of India and Nepal’s flagship national parks (including Kaziranga,
Nagarahole and Chitwan).
Although photographic capture rates of tigers have been shown to be correlated with
their density (Carbone et al. 2001), due to limitations of study time and camera
coverage, no attempt is made here to relate results to such estimates of density. An
accepted minimum level of sampling effort for such an extrapolation is considered to be
1,000 camera trap days (Carbone et al. 2001) which, under the study conditions of this
assessment, would require extension of field time by a factor of 9. However,
photographic capture rates were qualitatively similar to rates found in other quality
habitats of Sumatra, at least suggesting that tiger density in Serapung is not outside
the range of density previously observed elsewhere.
If the high frequency of tiger secondary signs and photo-captures is considered
alongside the frequent reports of tiger sightings by local people, it is clear that tigers
are exceptionally active around the Serapung FMU and particularly within the
immediate vicinity of the Yos Trail. Further study is required to confirm that these high
levels of tiger activity relate to a corresponding high tiger density, or whether this
abundance of data is a result of the geographically restricted ranging of a smaller
number of individuals. However, during the time available this assessment could find
no evidence in support of the latter hypothesis, where no obvious boundaries to tiger
movement were observed, and where no qualitative differences in habitat could be
identified between the Yos Trail and adjacent areas. Given the overwhelming weight of
evidence collected during this assessment, it appears that the peat swamp forests of
Serapung and Siak-Pelalawan provide tiger habitat at least comparable to other
optimal lowland forests sites in Sumatra.
Further work should be conducted as a matter of urgency to accurately measure the
carrying-capacity of PSF in relation to the Sumatran tiger. Evidence collected during
this assessment, in contrast to previous studies, suggests that PSF should not be
considered suboptimal habitat for tigers as a general rule. If tigers are confirmed to be
capable of living at high densities in PSF then this will have a significant impact on
future Sumatra-wide conservation strategies for the species.
Sumatran Tiger Conservation Program Pg 46/68