Integrative Zoology 2017; 12: 211–227 doi: 10.1111/1749-4877.12240 1 ORIGINAL ARTICLE 1 2 2 3 3 4 4 5 5 6 Density and carrying capacity in the forgotten tigerland: Tigers 6 7 7 8 8 9 in the understudied Nepalese Churia 9 10 10 11 11 12 12 13 Kanchan THAPA1,2 and Marcella J. KELLY1 13 14 14 1 2 15 Department of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, Virginia, USA and Conservation Science Unit, WWF 15 16 Nepal, Baluwatar, Kathmandu, Nepal 16 17 17 18 18 19 19 20 20 21 Abstract 21 22 While there are numerous wildlife ecology studies in lowland areas of Nepal, there are no in-depth studies of 22 23 the hilly Churia habitat even though it comprises 7642 km2 of potential wildlife habitat across the Terai Arc. We 23 24 investigated tiger, leopard and prey densities across this understudied habitat. Our camera trapping survey cov- 24 25 ered 536 km2 of Churia and surrounding areas within Chitwan National Park (CNP). We used 161 trapping lo- 25 26 cations and accumulated 2097 trap-nights in a 60-day survey period during the winter season of 2010–2011. In 26 27 addition, we walked 136 km over 81 different line transects using distance sampling to estimate prey density. 27 28 We photographed 31 individual tigers, 28 individual leopards and 25 other mammalian species. Spatial capture– 28 29 recapture methods resulted in lower density estimates for tigers, ranging from 2.3 to 2.9 tigers per 100 km2, than 29 30 for leopards, which ranged from 3.3 to 5.1 leopards per 100 km2. In addition, leopard densities were higher in 30 31 the core of the Churia compared to surrounding areas. We estimated 62.7 prey animals per 100 km2 with forest 31 32 ungulate prey (sambar, chital, barking deer and wild pig), accounting for 47% of the total. Based on prey avail- 32 33 ability, Churia habitat within CNP could potentially support 5.86 tigers per 100 km2 but our density estimates 33 34 were lower, perhaps indicating that the tiger population is below carrying capacity. Our results demonstrate that 34 35 Churia habitat should not be ignored in conservation initiatives, but rather management efforts should focus on 35 36 reducing human disturbance to support higher predator numbers. 36 37 37 38 Key words: camera trapping, carrying capacity, churia habitat, Panthera tigris tigris, spatially explicit capture 38 39 recapture 39 40 40 41 41 42 INTRODUCTION 42 43 43 44 The tiger [Panthera tigris tigris (Linnaeus, 1758)] is 44 45 the top predator in the Indian subcontinent (Sunquist & 45 46 Sunquist 2002) and plays an important role in shaping 46 47 prey assemblages in the lower trophic levels (Karanth 47 48 Correspondence: Kanchan Thapa, Department of Fish and & Sunquist 1995). Despite their ecologically signifi- 48 49 Wildlife Conservation, Virginia Tech, 146 Cheatham Hall, cant role in ecosystem health (Ritchie et al. 2012) and 49 50 Blacksburg, 24061, VA, USA. the history of concern for their survival, tiger popula- 50 51 Email: [email protected] tions are still being decimated (Seidensticker 2010) and 51 © 2016 International Society of Zoological Sciences, Institute of Zoology/ 211 Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd K. Thapa and M. J. Kelly 1 their range has collapsed to less than 7% of their histor- nected at varying degrees (Wikramanayake et al. 2004; 1 2 ic range (Sanderson et al. 2006; Walston et al. 2010). Wikramanayake et al. 2010). The Churia, also called the 2 3 In addition to the tiger, the sympatric leopard [Pan- Siwalikhs in India, is one of the youngest of 5 moun- 3 4 thera pardus fusea (Meyer, 1794)], has also experienced tain ranges in Nepal (Hagen 1961) (Fig. 1) and occu- 4 5 range reduction to only 65% of its historic range (Rip- pies 13% of the total land surface (LRMP 1986) extend- 5 6 ple et al. 2014). The primary drivers of declines for both ing from the Brahmaputra River in the east in India to 6 7 carnivores include habitat loss and fragmentation, de- the Indus River in the west in Pakistan (Jhingran 1981). 7 8 pletion of natural prey, and direct persecution by peo- Forest density within the Churia is high (73% intact for- 8 9 ple (Karanth & Stith 1999; Balme et al. 2010; Walston est cover) (DFRS 2015) and conservation of the Chu- 9 10 et al. 2010). Conservation of these carnivores has been ria is critical to maintain landscape connectivity across 10 11 a global priority due to their vulnerability to extinction Nepal and India (Wikramanayake et al. 2004; Seiden- 11 12 and their potential ability to structure ecosystems (Rip- sticker et al. 2010; Jhala et al. 2011; Barber-Meyer et 12 13 ple et al. 2014), and because they also serve as umbrella al. 2013). Unfortunately, the Churia of Nepal suffers 13 14 species across a wide range of habitats (Wang & Mac- from degradation and overexploitation via agricultural 14 15 donald 2009). In South Asia, tigers and leopards occu- encroachment and poaching (Paudel et al. 2013; FRA/ 15 16 py a wide range of habitats, including alluvial floodplain DFRS 2014). 16 17 grasslands (Smith 1993), seasonally dry sub-tropical, The Churia range extends through a majority of tiger 17 18 deciduous lowland forests (Seidensticker 1976; Odd- habitat across the Terai Arc, yet the classic studies on ti- 18 19 en et al. 2010), the porous bhabhars (Thapa et al. 2014), ger ecology (ecological separation [Seidensticker 1976], 19 20 temperate areas up to alpine regions in the Himalayas dispersal and behavior [Smith 1985, 1993] and social 20 21 for leopards (Wang & Macdonald 2009), and mangrove organization [Sunquist 1981]) have focused instead on 21 22 deltas for tigers in the Sunderbans (Seidensticker 1987; the lowland areas comprised of alluvial floodplain grass- 22 23 Loucks et al. 2010). lands, riverine forests and climax Shorea robusta forests 23 24 The Terai Arc Landscape (hereafter referred to as (Peet et al. 1999; Dinerstein 2003). Thus, Churia habi- 24 25 the Terai Arc) is a high priority landscape for tiger con- tat remains a “forgotten tigerland” as its ecological role 25 26 servation containing 12 potential sub-populations con- in tiger conservation has been overlooked because it is 26 27 27 28 28 29 29 30 30 31 31 32 32 33 33 34 34 35 35 36 36 37 37 38 38 39 39 40 40 41 41 42 42 43 43 44 44 45 45 46 46 47 47 48 48 49 49 50 Figure 1 Churia physiographic range in Nepal covers 639 km2 within Chitwan National Park and covers 7,642 km2 across the Terai 50 51 Arc Landscape. 51 212 © 2016 International Society of Zoological Sciences, Institute of Zoology/ Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd Tiger, leopard and prey in Churia habitat 1 generally seen as unsuitable or marginal habitat. spatially explicit capture–recapture methods; (ii) esti- 1 2 The first systematic tiger census carried out in Chit- mate potential prey density in the Churia habitat using a 2 3 wan National Park (CNP) did not sample the Churia distance sampling approach; and (iii) predict tiger abun- 3 4 habitat (Karki et al. 2009). Following that, Karki et al. dance within the Churia by extrapolating prey density 4 5 (2013), recorded a few individual tigers within the Chu- to the entire area and relating prey biomass to predator 5 6 ria in CNP during a camera survey. However, whether energy needs. We address a gap in knowledge of tigers, 6 7 tigers frequented the extensive Churia hills was still un- their co-predators and prey in this important yet lit- 7 8 known. A subsequent tiger census (Dhakal et al. 2014) tle known habitat. We expect our study will reveal that 8 9 sampled some Churia habitat but did not provide em- there are more tigers in CNP than previously thought, 9 10 pirical evidence of the contribution of Churia habitat to and, thus, will be positive news for tiger conservation 10 11 tiger numbers in CNP. Thus, we provide the first sys- across Nepal. 11 12 tematic study of the Churia habitat examining tiger and 12 13 leopard population ecology, and the prey base support- MATERIAL AND METHODS 13 14 ing these predators. Habitat and site-specific assess- 14 15 ments are needed to make better informed conservation Study area 15 16 management decisions for these endangered species in 16 17 This study was conducted within CNP in central Ne- 17 Nepal. 2 18 pal (Fig. 2). The hilly Churia habitat covers 639 km and 18 The objectives of this study are to: (i) estimate den- 19 is divided into 2 areas: one stretching between the low- 19 sities of tigers and leopards in the Churia habitat using 20 20 21 21 22 22 23 23 24 24 25 25 26 26 27 27 28 28 29 29 30 30 31 31 32 32 33 33 34 34 35 35 36 36 37 37 38 38 39 39 40 40 41 41 42 42 43 43 44 44 45 45 46 46 47 47 48 48 49 49 50 Figure 2 Study area showing camera trap and line transect spatial location in Chitwan National Park. Note that the hidden line is 50 51 underneath the dark and grey lines in part of the figure. 51 © 2016 International Society of Zoological Sciences, Institute of Zoology/ 213 Chinese Academy of Sciences and John Wiley & Sons Australia, Ltd K.