A Supplemental HCVF Assessment on the Sumatran Tiger ...

FINAL REPORT Tiger <strong>HCVF</strong> <strong>Supplemental</strong> <strong>Assessment</strong> – Serapung FMU
2.4 Sumatran Tiger Status, Threats and Ecology
Both the status and ecology of the Sumatran tiger in the wild remains poorly
understood and this presents a serious constraint to effective conservation efforts
(Tilson & Traylor-Holzer 1994, Tilson & Nyhus 1998). Conservation of the tiger in a
constantly changing, human-dominated landscape requires an understanding of the
species’ limits and capabilities (Sunquist et al. 1999). The tiger is clearly an adaptable
species, persisting in a diversity of habitat types, tolerating a range of climatic and
rainfall regimes. They are capable of rapidly increasing their numbers given suitable
conditions. As a predator they are capable of capturing prey of widely differing sizes,
altering their hunting strategies to accommodate the composition of the available prey
base (Sunquist et al. 1999).
2.4.1 Status of the Sumatran Tiger and threats
Sumatran tigers, once numbering in the thousands, are today listed in Appendix I
of CITES and designated as critically endangered by the IUCN. They represent
the last of three Indonesian subspecies of tiger, with both the Bali (P. t. balica)
and Javan (P. t. sondaicus) subspecies going extinct during the last 50 years.
Within the last century Sumatra has been transformed from an island of extensive
Dipterocarp-dominated forests, containing scattered agricultural settlements and
small towns (Whitten et al. 1987, Collins et al. 1991, Jepson et al. 2001), to a
region characterised by intense development led by the forestry, plantation,
agriculture, and mining sectors. Since 1960 government sponsored
transmigration programmes have facilitated the large-scale relocation of people
to Sumatra from densely populated islands such as Java, Bali and Madura and,
in so doing, significantly altered the distribution and status of the remaining
biodiversity (Whitten 1987, Gillis 1988, Collins et al. 1991). By the time the need
for additional protected areas was recognised much of the optimum habitat for
conservation had already been converted (Collins et al. 1991, Fearnside 1997).
In 1992 a Sumatra-wide population and habitat viability analysis (PHVA) was
carried out for the wild Sumatran tiger (Seal et al. 1994, Tilson et al. 1994). The
viability of any population depends on a number of parameters, which include
intrinsic factors such as population size, reproductive rate, demographic
structure; and extrinsic factors including prey density, habitat quality, and human
impacts. Genetic factors, such as inbreeding, are also considered important. The
interplay of these parameters with random chance events (stochasticity) can be
modelled to predict how a population may increase or decline in the future. The
stochastic population simulation programme VORTEX (Lacey 1993, Ellis & Seal
1995) was used to study the interaction of the multiple variables and to predict
the effects of various management scenarios on the probability of tiger population
viability (Seal et al. 1994, Wiese et al. 1994). Ecological parameters used in the
model were derived from studies on the Bengal and other tiger subspecies, from
unpublished data contributed by the workshop participants, from direct
observations by Indonesian Forestry Department staff and from data extrapolated
from Sumatran tiger captive-breeding studbooks. The results of the population
simulations were combined with a landscape-level spatial model of Sumatran
tiger distribution and potential habitat developed using GIS (Faust & Tilson 1994)
to provide an overall population status assessment for the Sumatran tiger.
A total of 26 protected areas were identified where tigers were present,
representing 45,600 km 2 and accounting for 9.6% of the total land area of
Sumatra. Based on density estimates obtained for tigers in similar ecological
settings, and direct sightings by Forestry Department staff, the population of wild
Sumatran tigers was estimated at 500 individuals. Of these approximately 100
Sumatran Tiger Conservation Program Pg 15/68