Tigers and Their Prey in Bukit Rimbang Bukit Baling: Abundance Baseline for Effective Wildlife Reserve Management

Managing the critically endangered Sumatran tiger (Panthera tigris sumatrae) needs accurate information on its abundance and availability of prey at the landscape level. Bukit Rimbang Bukit Baling Wildlife Reserve in central Sumatra represents an important area for tigers at local, regional and global levels. The area has been recognized as a long-term priority Tiger Conservation Landscape. Solid baseline information on tigers and prey is fundamentally needed for the management. The objective of this study was to produce robust estimate of tiger density and prey a vailability in the reserve. We used camera traps to systematically collecting photographic samples of tigers and prey using Spatial Capture Recapture (SCR) framework. We estimated density for tigers and calculated trap success rate (TSR; independent pictures/100 trap nights) for main prey species. Three blocks in the reserve were sampled from 2012 to 2015 accumulating a total of 8,125 effective trap nights. We captured 14 tiger individuals including three cubs. We documented the highest density of tigers (individuals/100 km2) in southern sampling block (based on traditional capture recapture (TCR) : 1.52 ± SE 0.55; based on Maximum Likelihood (ML) SCR:0.51 ± SE 0.22) and the lowest in northeastern sampling block (TCR: 0.77 ±SE 0.39; ML SCR: 0.19 ± SE 0.16). The highest TSR of main prey (large ungulates and primates) was in northeastern block (35.01 ± SD 8.67) and the lowest was in southern block (12.42 ± SD 2.91). The highest level of disturbance, as indicated by TSR of people, was in northeastern sampling block (5.45 ± SD 5.64) and the lowest in southern (1.26 ± SD 2.41). The results suggested that human disturbance strongly determine the density of tigers in the area, more than prey availability. To recover tigers, suggested strategies include controlling human disturbance and poaching to the lowest possible level in addition to maintaining main prey availability.Keywords: Capture-Mark-Recapture; closed population; habitat management; population viability; tiger recovery Harimau dan Mangsanya di Bukit Rimbang Bukit Baling: Basis Informasi Kelimpahan untuk Pengelolaan Suaka Margasatwa yang EfektifIntisariMengelola spesies kunci seperti harimau Sumatera (Panthera tigris sumatrae) yang dalam kondisi kritis, memerlukan informasi terkait populasi satwa tersebut dan ketersediaan satwa mangsanya pada tingkat lanskap. Suaka Margasatwa Bukit Rimbang Bukit Baling di Sumatera bagian tengah merupakan sebuah kawasan penting untuk harimau baik pada tingkat lokal, regional, maupun global. Kawasan ini telah diakui sebagai sebuah kawasan prioritas jangka panjang Tiger Conservation Landascapes (TCL). Informasi dasar yang sahih mengenai populasi harimau dan mangsanya sangat dibutuhkan untuk pengelolaan efektif satwa tersebut dan kawasan habitatnya. Tujuan dari studi ini adalah untuk menghasilkan perkiraan kepadatan populasi harimau dan ketersediaan mangsanya di kawasan suaka margasatwa tersebut. Kami menggunakan perangkap kamera untuk mengumpulkan sampel gambar harimau dan mangsanya secara sistematis menggunakan kerangka kerja Spatial Capture Recapture (SCR). Kami memperkirakan kepadatan harimau dan menghitung angka keberhasilan perangkap atau trap success rate (TSR: gambar independen/100 hari aktif kamera) untuk satwa mangsa utama. Tiga blok di dalam suaka margasatwa telah disurvei dari tahun 2012 hingga 2015 mengakumulasikan keseluruhan 8,125 hari kamera aktif. Kami merekam 14 individu harimau termasuk tiga anak. Kami mendokumentasikan kepadatan tertinggi harimau (individu/100 km2) di blok sampling selatan (berdasarkan pendekatan analisa capture recapture tradisional (TCR) 1.52 ± SE 0.55; berdasarkan Maximum Likelihood (ML) SCR 0.51 ± SE 0.22) dan terendah di utara-timur (TCR: 0.77 ±SE 0.39; ML SCR: 0.19 ± SE 0.16). TSR tertinggi dari mangsa utama (ungulate besar dan primata) adalah di blok sampling utara-timur (35.01 ± SD 8.67) dan terendah adalah di blok sampling selatan (12.42 ± SD 2.91). Tingkat gangguan tertinggi, sebagaimana diindikasikan oleh TSR manusia, adalah di blok sampling utara-timur (5.45 ± SD 5.64) dan terendahnya di blok sampling selatan (1.26 ± SD 2.41). Hasil studi ini mengindikasikan bahwa gangguan manusia yang sangat tinggi sangat menentukan kepadatan harimau di kawasan ini, melebihi pengaruh dari ketersediaan satwa mangsa. Untuk memulihkan populasi harimau, disarankan beberapa strategi termasuk mengendalikan gangguan manusia dan perburuan hingga ke tingkat terendah, selain tetap memastikan ketersediaan satwa mangsa utama yang memadai

Population Status of a Cryptic Top Predator: An Island-Wide Assessment of Tigers in Sumatran Rainforests

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

Tigers Need Cover: Multi-Scale Occupancy Study of the Big Cat in Sumatran Forest and Plantation Landscapes

The critically endangered Sumatran tiger (Panthera tigris sumatrae Pocock, 1929) is generally known as a forest-dependent animal. With large-scale conversion of forests into plantations, however, it is crucial for restoration efforts to understand to what extent tigers use modified habitats. We investigated tiger-habitat relationships at 2 spatial scales: occupancy across the landscape and habitat use within the home range. Across major landcover types in central Sumatra, we conducted systematic detection, non-detection sign surveys in 47, 17×17 km grid cells. Within each cell, we surveyed 40, 1-km transects and recorded tiger detections and habitat variables in 100 m segments totaling 1,857 km surveyed. We found that tigers strongly preferred forest and used plantations of acacia and oilpalm, far less than their availability. Tiger probability of occupancy covaried positively and strongly with altitude, positively with forest area, and negatively with distance-to-forest centroids. At the fine scale, probability of habitat use by tigers across landcover types covaried positively and strongly with understory cover and altitude, and negatively and strongly with human settlement. Within forest areas, tigers strongly preferred sites that are farther from water bodies, higher in altitude, farther from edge, and closer to centroid of large forest block; and strongly preferred sites with thicker understory cover, lower level of disturbance, higher altitude, and steeper slope. These results indicate that to thrive, tigers depend on the existence of large contiguous forest blocks, and that with adjustments in plantation management, tigers could use mosaics of plantations (as additional roaming zones), riparian forests (as corridors) and smaller forest patches (as stepping stones), potentially maintaining a metapopulation structure in fragmented landscapes. This study highlights the importance of a multi-spatial scale analysis and provides crucial information relevant to restoring tigers and other wildlife in forest and plantation landscapes through improvement in habitat extent, quality, and connectivity

Estimates of β for the logit link function based on best and univariate models for tiger probability of habitat use (ψ_1-km) within acacia plantations in central Sumatra for landscape covariates.

<p><u>Note</u>:</p><p>*indicates strong or robust impact, that is 95% confidence intervals as defined by ±1.96×SE not overlapping 0; italics indicate opposite from <i>a priori</i> prediction. AltDEM = altitude; Precip = precipitation;Dtwater = distance to freshwater body; dtfedge07 = distance to forest edge; dtpacr = distance to centroid of protected areas; Dtmprd = distance to major public road; dtf05cr = Distance to nearest centroid of forest block greater than 50,000 ha.</p

Estimates of β for the logit link function based on best and univariate models for tiger probability of habitat use (ψ_1-km) within forest areas in central Sumatra for manual covariates.

<p><u>Note</u>:</p><p>*indicates strong or robust impact, that is 95% confidence intervals as defined by ±1.96×SE not overlapping 0; italic indicates opposite from <i>a priori</i> prediction.</p

Estimated probability of habitat use (ψ_1-km) by tigers in six land cover types.

<p>These estimates were produced from the best model for each landcover (bars) and ratio of plantation's probability of use (diamonds) relative to forest based on a) landscape covariates and b) manual covariates.</p

Summary of survey effort and detection of tigers in five landcover types in Riau Province, central Sumatra.

<p>*number of sites where the species was detected divided by total number of sites surveyed.</p

Map of probability of tiger occupancy in the central Sumatra landscape.

<p>This map is constructed from the best occupancy model developed based on the landscape-scale survey in 17×17 km grid cells representing forest and other major landcover types.</p

Top models depicting tiger probability-of-occupancy (ψ_{17×17 km}) at the landscape-scale with 17×17 km grid-level landscape covariates in Riau Province, central Sumatra.

<p>Psi = probability of site occupancy/habitat use; p = probability of detection; thta0 = spatial dependence parameter representing the probability that the species is present locally, given the species was not present in the previous spatial replicate; thta1 = spatial dependence parameter representing the probability that a species is present locally, given it was present at the previous spatial replicate. AltDEM = Altitude; dtf05cr = Distance to nearest centroid of forest block greater than 50,000 ha; LCFor = Code for forest (1) or non forest (0); For07Area = Area of forest in the grid based on 2007 data; dtpacr = distance to centroid of protected area; Def0607 = Deforested area from 2006 to 2007 in each grid cell; Precip = Precipitation; Dtmprd = Distance to major public road.</p