IUCN / SSC Cat Specialist Group - Digital Cat Library |
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| Maddox, T.M.; Priatna, D.; Gemita, E.; Selampassy, A. | |
| Pigs, Palms, People, and Tigers Survival of the Sumatran Tiger in a commercial landscape | |
| 2005 Full Book | |
Research objectives for 2003-4 targeted understanding the relationship between tigers, their probable main prey (wild pigs, _Sus scrofa_) and their role of prey species as pests on the plantation. The results show more than 40 medium and large sized mammals using the oil palm concession and borders, with other mammals of conservation interest including tiger (_Panthera _tigris) dhole (_Cuon alpinus)_, sun bear (_Helarctos malayanus), _Malayan tapir (_Tapirus indicus)_, clouded leopard (_Neofelis nebulosa) _and fishing cat (_Prionailurus viverrinus) _with little difference between the plantation concession and the more intact forest concession. However, use of the oil palm crop itself is limited and almost all species are restricted to the unplanted habitats bordering the oil palm or the Asialog forest concession. However, the degraded scrub habitats showed higher presence of many species than the apparently less degraded forest concession, including the Sumatran tiger. Prey studies were based on night transects and randomly placed camera trap surveys. These confirmed wild pigs (_Sus scrofa_) to be the dominant ungulate and likely tiger prey present, with abundance far outweighing any other species, although at least 19 potential tiger prey species exist on site. Line transects estimated density within the oil palm and scrub habitats to be around 2.5 pigs/km2 and agreed with camera trapping studies that densities in the forest were negligible in comparison. These densities are comparable to other pig studies but much lower than the only other oil palm study where predators were absent. Pigs were also one of the few species to show higher abundance inside the oil palm crop compared to outside in the scrub. However, studies of abundance were not as complete as hoped with the failure of capture mark recapture studies following unsuccessful trapping attempts. Line transects are thought to be underestimating true densities and further work estimating absolute density is also required for calibrating camera trap results. Consequently, these estimates are only considered to be preliminary results. As a result of problems capturing pigs, other aspects of the prey study were also delayed and planned assessments of pig impact on the plantation are still underway. Prey movements were investigated with two radio collared wild pig (_Sus _scrofa) and one tapir (_Tapirus indicus _). Wild pig do not wear collars well, the first releasing itself after two weeks and the second, thanks to a modified harness attachment, lasted two months. Data may not be complete, but indicate range use of approximately 5-6 km2, both focussing on scrub / oil palm border areas. The tapir continues to be tracked well and shows a surprisingly small range of about 6 km2, based entirely in the plantation scrub and not in the forest. Research on the tigers based on density calculations from camera trapping rates and individual recognition of camera trap photos show that a minimum of nine and possibly even sixteen tigers have used the plantation concession and bordering areas within the last three years, suggesting densities comparable to many protected areas. At least four of the tigers were breeding residents living within the plantation concession. However, camera trap rates fell sharply in 2003-4 despite prey species and other large mammals apparently remaining stable and based on recent data the tiger population looks to be in severe trouble. Various avenues still need to be explored before conclusions drawn (for example an expanded survey is needed into the forest concession) but it appears likely that illegal land clearance is looking the most likely cause. Tiger movements were also assessed by camera traps and all appeared to use both the plantation and forest concessions. One tiger was also successfully captured and radio collared, the first ever in Sumatra. Despite some complications receiving the signal in certain habitats, data were collected for 7 months before the tiger slipped out of the collar. During this time the tiger spent most of its time in plantation scrub, apparently never venturing into the oil palm. However, estimates of tiger ranges were not particularly improved by the radio tracking data. |
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