Large carnivores living in tropical rainforests are under immense pressure from the rapid conversion of their habitat. In response, millions of dollars are spent on conserving these species. However, the cost-effectiveness of such investments is poorly understood and this is largely because the requisite population estimates are difficult to achieve at appropriate spatial scales for these secretive species. Here, we apply a robust detection/non-detection sampling technique to produce the first reliable population metric (occupancy) for a critically endangered large carnivore; the Sumatran tiger (Panthera tigris sumatrae). From 2007–2009, seven landscapes were surveyed through 13,511 km of transects in 394 grid cells (17×17 km). Tiger sign was detected in 206 cells, producing a naive estimate of 0.52. However, after controlling for an unequal detection probability (where p = 0.13±0.017; ±S.E.), the estimated tiger occupancy was 0.72±0.048. Whilst the Sumatra-wide survey results gives cause for optimism, a significant negative correlation between occupancy and recent deforestation was found. For example, the Northern Riau landscape had an average deforestation rate of 9.8%/yr and by far the lowest occupancy (0.33±0.055). Our results highlight the key tiger areas in need of protection and have led to one area (Leuser-Ulu Masen) being upgraded as a ‘global priority’ for wild tiger conservation. However, Sumatra has one of the highest global deforestation rates and the two largest tiger landscapes identified in this study will become highly fragmented if their respective proposed roads networks are approved. Thus, it is vital that the Indonesian government tackles these threats, e.g. through improved land-use planning, if it is to succeed in meeting its ambitious National Tiger Recovery Plan targets of doubling the number of Sumatran tigers by 2022.
- Wikramanayake E, Dinerstein E, Seidensticker J, Lumpkin S, Pandav B, et al. (2011) A landscape-based conservation strategy to double the wild tiger population. Con Lett 4: 219–227.
- 2.Linkie M, Guillera-Arroita G, Smith J, Rayan DM (2010) Monitoring tigers with confidence. Integr Zool 5: 342–350.
- 3.Wibisono HT, Pusparini W (2010) Sumatran tiger (Panthera tigris sumatrae): A review of conservation status. Integr Zool 5: 313–323.
- 4.Linkie M, Chapron G, Martyr DJ, Holden J, Leader-Williams N (2006) Assessing the viability of tiger subpopulations in a fragmented landscape. J Appl Ecol 43: 576–586.
- 5.WWF-Indonesia (2010) Sumatra's Forests, their Wildlife and the Climate. Windows in Time: 1985, 1990, 2000 and 2009. A quantitative assessment of some of Sumatra's natural resources submitted as technical report by invitation to the National Forestry Council (DKN) and to the National Development Planning Agency (BAPPENAS) of Indonesia. Jakarta, Indonesia.
- 6.Tilson RL, Soemarna K, Ramono W, Lusli S, Traylor-Holzer K, et al. (1994) Sumatran Tiger Population and Habitat Viability Analysis Report. Indonesian Directorate of Forest Protection and Nature Conservation and IUCN/SSC Conservation Breeding Specialist Group, Apple Valley, Minnesota.
- 7.Seidensticker J, Gratwicke B, Shrestha M (2010) How many wild tigers are there? An estimate for 2008. Tilson, Ronald and Nyhus, Philip J., Tigers of the world: the science, politics, and conservation of Panthera tigris. New York: Elsevier/Academic Press. pp. 295–299.
- 8.Karanth KU, Nichols JD, Seidensticker J, Dinerstein E, Smith JLD, et al. (2003) Science deficiency in conservation practice: the monitoring of tiger populations in India. Anim Conserv 6: 141–146.
- 9.MacKenzie DI, Nichols JD, Lachman GB, Droege S, Royle JA, et al. (2002) Estimating site occupancy rates when detection probabilities are less than one. Ecology 83: 2248–2255.
- 10.Karanth KU, Gopalaswamy AM, Kumar NS, Vaidyanathan S, Nichols JD, et al. (2011) Monitoring carnivore populations at the landscape scale: occupancy modelling of tigers from sign surveys. J Appl Ecol. in press.
- 11.Rabus B, Eineder M, Roth A, Bamler R (2003) The shuttle radar topography mission – a new class of digital elevation models acquired by spaceborne radar. J Photogrammetry Remote Sensing 57: 241–262.
- 12.Hines JE, Nichols JD, Royle JA, MacKenzie DI, Gopalaswamy AM, et al. (2010) Tigers on trails: Occupancy modeling for cluster sampling. Ecol Appl 20: 1456–1466.
- 13.Royle JA (2006) Site occupancy models with heterogeneous detection probabilities. Biometrics 62: 97–102.
- 14.Guillera-Arroita G (2011) Impact of sampling with replacement in occupancy studies with spatial replication. Methods Ecol Evol 2: 401–406.
- 15.Sunquist ME (1981) The social organisation of tigers (Panthera tigris) in Royal Chitawan National Park, Nepal. Smithsonian Contrib Zool 336: 1–97.
- 16.GTI (2010) Global Tiger Initiative National Consultations - the Road to the Tiger Summit, National Tiger Recovery Program, INDONESIA. Unpublished report, Washington DC, USA.
- 17.Ministry of Forestry of Indonesia (2010) The National Tiger Recovery Program: The Road to the Tiger Summit. The Ministry of Forestry of Indonesia and the Global Tiger Initiative National Consultation, Jakarta, Indonesia.
- 18.Government of Indonesia (2008) Kesepakatan bersama seluruh Gubernur Sumatera untuk penyelamatan ekosistem pulau Sumatera [Joint agreement by all Sumatran Governors to save the Sumatra island ecosystem]. Government of Indonesia document, Jakarta, Indonesia.
- 19.ATBC (2011) Resolution Opposing Road Construction through Kerinci Seblat National Park, Indonesia. The Association for Tropical Biology and Conservation (ATBC)[http://www.tropicalbio.org/index.php?option=com_content&view=article&id=494:resolution-opposing-road-construction-through-kerinci-seblat-national-park-indonesia&catid=51:resolutions&Itemid=79].
- 20.Nyhus PJ, Tilson R (2004) Characterizing human-tiger conflict in Sumatra, Indonesia: implications for conservation. Oryx 38: 68–74.
- 21.Government of Aceh (2007) Logging moratorium (temporary cessation on logging) in Nanggroe Aceh Darussalam. Instruction of the Governor of Nanggroe Aceh Darussalam, Number: 05/instr/2007, Aceh.
- 22.Clements RG, Sayer J, Boedhihartono AK, Venter O, Lovejoy T, et al. (2010) Cautious optimism over Norway-Indonesia REDD pact. Conserv Biol 24: 1437–1438.