A Supplemental HCVF Assessment on the Sumatran Tiger ...

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FINAL REPORT Tiger <strong>HCVF</strong> <strong>Supplemental</strong> <strong>Assessment</strong> – Serapung FMU Several studies have been conducted on the effects of logging on wildlife in the forests of Southeast Asia, though again PSF has suffered from relatively little attention. Comparisons between pre- and post-logging wildlife abundance have shown conflicting results between studies (Bennett & Dahaban 1995, Meijaard et al. 2005). Some of this variation may well have exposed a critical feature of postlogging ecological modification, that of the effect of microhabitat creation along newly opened logging roads (Bennett & Dahaban 1995, Johns 1989, 1992). Meijnaard et al. (2005), through an extensive literary review on the effects of logging, has suggested that almost as many mammal species declined in the aftermath of logging, as those that increased. The most tolerant, or advantaged, species were identified as herbivores and omnivores where diet consists of considerable secondary growth foliage. With respect to abundance of tiger prey species in the Siak-Pelalawan forest block, it is possible that the sub-optimal nature of climax stage PSF habitat has been somewhat “improved” relative to its original condition, if only temporarily, by the effects of widespread logging, rail creation and other causes of canopy disturbance that opens the forest to increased light levels and hence leads to increased productivity at ground-level. Figure 4. Past and present HPH concessions in the Siak-Pelalawan forest block Sumatran Tiger Conservation Program Pg 14/68
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
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