A Supplemental HCVF Assessment on the Sumatran Tiger ...

FINAL REPORT Tiger <strong>HCVF</strong> <strong>Supplemental</strong> <strong>Assessment</strong> – Serapung FMU
Table 3 Selected population modelling results from Tilson et al. (1994) showing the
probability of extinction (Pe) of tigers using different population sizes and carrying
capacity with or without the effects of inbreeding (Inb H). Carrying capacity and
inbreeding are shown to have major impacts on Pe. The expected population after one
hundred years is the mean value of surviving populations. The results of the effects
catastrophes and poaching are not shown.
Starting
Population
Carrying
Capacity
Deterministic
Growth Rate
Inb H Pe 100 yrs Expected Population
after 100 yrs
25 25 0.086 No 0.404 20
25 50 0.086 No 0.042 44
75 100 0.086 No 0.004 90
25 25 0.086 Yes 0.944 11
25 50 0.086 Yes 0.324 26
75 100 0.086 Yes 0.000 82
2.4.3 Habitat Utilisation by the Tiger
Providing certain conditions are met the tiger is capable of surviving within a wide
range of habitat types - from coniferous-deciduous forests of Russia, tropical
forests of Southeast Asia, to grassland habitats of India. The Sumatran subspecies
is similarly adaptable, and found to be present in most major natural ecotypes
occurring on the island of Sumatra, including peat-swamp forests. In
addition the Sumatran tiger is also known to make use of low intensity agricultural
systems, particularly where this is associated with a low density of people. On the
other hand there is currently no evidence that the Sumatran tiger can utilize either
industrial timber plantations or anything other than the forested peripheries of oilpalm
estates. In light of this STCP has assumed, for the purposes of this
assessment, that all natural forests (both degraded and intact) represent potential
tiger habitat, and that HTI and oil-palm estates are non-tiger habitat.
Karanth et al. (2004) found a functional relationship between abundances of
tigers and their prey under a wide range of ecological conditions. This supports
Johns (1983) statement that the congregation of browsing mammals that feed on
the ground vegetation of recently logged forest causes an associated rise in the
densities of tigers. Franklin (2002) found that although the Sumatran tiger
showed a significant preference for closed canopy rather than open
forest/grassland, both Franklin (2002) and Kawanishi (2002) noted that tigers will
utilize abandoned roads and trails wherever they are available. Smith et al.
(1989) found Bengal tigers marked along a network of trails, roads, dry
streambeds and ridge tops that are used for travel through their territories.
Franklin (2002) has suggested that the use of the roads and trails by tigers is for
their ease of movement through difficult terrain and vegetation (which optimises
efforts to defend territories and prey resources) and high visibility for hunting.
2.4.4 Social and community impacts in relation to tigers
In Sumatra, as the second most populated island in Indonesia after Java, and
one of Indonesia’s biologically most diverse (Whitten et al. 1987), the conflict
between people and wildlife is predictably intense. The Sumatran tiger has
epitomised the nature of this conflict (Nyhus 1999, Tilson et al. 2001).
Historically tiger-human conflict has been common in Sumatra. While some
authors suggest tiger-attributed human deaths are rare (McDougal 1987) the
earliest European explorers described tigers as numerous and dangerous,
Sumatran Tiger Conservation Program Pg 17/68