Impact of prey occupancy and other ecological and anthropogenic factors on tiger distribution in Thailand's western forest complex

Abstract

Despite conservation efforts, large mammals such as tigers ( Panthera tigris ) and their main prey, gaur ( Bos gaurus ), banteng ( Bos javanicus ), and sambar ( Rusa unicolor ), are highly threatened and declining across their entire range. The only large viable source population of tigers in mainland Southeast Asia occurs in Thailand's Western Forest Complex (WEFCOM), an approximately 19,000 km 2 landscape of 17 contiguous protected areas. We used an occupancy modeling framework, which accounts for imperfect detection, to identify the factors that affect tiger distribution at the approximate scale of a female tiger's home range, 64 km 2 , and site use at a scale of 1‐km 2 . At the larger scale, we estimated the proportion of sites at WEFCOM that were occupied by tigers; at the finer scale, we identified the key variables that influence site‐use and developed a predictive distribution map. At both scales, we examined key anthropogenic and ecological factors that help explain tiger distribution and habitat use, including probabilities of gaur, banteng, and sambar occurrence from a companion study. Occupancy estimated at the 64‐km 2 scale was primarily influenced by the combined presence of all three large prey species, and 37% or 5,858 km 2 of the landscape was predicted to be occupied by tigers. In contrast, site use estimated at the scale of 1 km 2 was most strongly influenced by the presence of sambar. By modeling occupancy while accounting for imperfect probability of detection, we established reliable benchmark data on the distribution of tigers in WEFCOM. This study also identified factors that limit tiger distributions; which managers can then target to expand tiger distribution and guide recovery elsewhere in Southeast Asia.

Spatial Modeling of Forage Crops for Tiger Prey Species in the Area Surrounding Highway 304 in the Dong Phayayen-Khao Yai Forest Complex

“…GLMs provide good predictions for virtual species distributions because they can deal with many types of predictors (Brotons et al, 2004;Engler et al, 2004). Duangchatrasiri et al (2019) assessed whether human activity had an impact on the occurrence of wildlife by using the distance from villages and roads because wildlife is sensitive to hunting and a range of other environmental conditions such as disturbance variables inside protected areas (Lynam et al, 2012). In addition, distance to rivers and streams have also been included as covariates that reflect habitat quality near streams (Linkie et al, 2006).…”

Weights of gaur (Bos gaurus) and banteng (Bos javanicus) killed by tigers in Thailand

“…HKK combined with adjacent reserves, Thung Yai Naresuan East Wildlife Sanctuary and Thung Yai Naresuan West Wildlife Sanctuary, is considered a source for re‐establishing tigers throughout the region. Much of the rest of WEFCOM is subject to prey depletion from poaching, and therefore, it is estimated that tigers occur in only 37% of WEFCOM (Duangchatrasiri et al, 2019). HKK is composed of four main vegetation types: mixed deciduous forest (48.3%), dry evergreen forest (24.7%), hill evergreen forest (13.4%), and dry deciduous dipterocarp forest 6.9% (Trisurat, 2004).…”

“…Our study suggests that gaur and banteng are important target species for conservation efforts that restore the tiger's prey base in South‐East Asia. Furthermore, Duangchatrasiri et al (2019) and Jornburom (2016) have shown that the restoration of these bovids can have a major impact on the distribution of tigers in WEFCOM.…”

“…HKK combined with adjacent reserves, Thung Yai Naresuan East Wildlife Sanctuary and Thung Yai Naresuan West Wildlife Sanctuary, is considered a source for re-establishing tigers throughout the region. Much of the rest of WEFCOM is subject to prey depletion from poaching, and therefore, it is estimated that tigers occur in only 37% of WEFCOM (Duangchatrasiri et al, 2019).…”

Wetlands are keystone habitats for jaguars in an intercontinental biodiversity hotspot

“…Prey availability is a key determinant of the distribution and abundance of large carnivores [14–15], including jaguars [16–17]. Among terrestrial mammalian species, jaguars tend to prefer capybara ( Hydrochoerus spp.)…”