Population densities, group size and biomass of ungulates in a lowland tropical rainforest forest of the eastern Himalayas K. Muthamizh Selvan, Salvador Lyngdoh, Govindan Veeraswami Gopi ⇑ , Bilal Habib, Syed Ainul Hussain Wildlife Institute of India, Chandrabani, PO Box 18, Dehradun 248001, India article info Article history: Received 24 July 2013 Revised 15 January 2014 Accepted 8 May 2014 Keywords: Arunachal Pradesh Biomass Carnivores Density Distance Eastern Himalayas Ungulates Group size Sambar Gaur Muntjac abstract Large ungulate population monitoring is a crucial wildlife management tool as ungulates help in structuring and maintaining the large carnivore populations. Reliable data on population status of major ungulate prey species are still non-existent for most of the protected areas in the Indian part of the eastern Himalayan biodiversity hotspot. Twenty transects were monitored over a period of three years (2009–2011) totaling 600 km with an average length of 2 km. The estimated mean density of ungulates was 17.5 km À2 with overall density of 48.7 km À2 . The wild pig Sus scrofa had the highest density (6.7 ± 1.2 km À2 ) among all the prey species followed by barking deer Muntiacus muntjak (3.9 ± 0.6 km À2 ), sambar Rusa unicolor (3.8 ± 0.5) and gaur Bos gaurus (3.5 ± 0.9 km À2 ). The estimated total ungulate biomass density was 2182.56 kg km À2 . This prey biomass can support up to 7.2 tigers per 100 km À2 . However, with two other sympatric carnivores sharing the same resources, the actual tiger numbers that can be supported will be lower. The estimated minor prey species was 31 km À2 signifi- cantly 30.6% crop damages were reported by wild pig (p = 0.01) and 35.4% was elephant (p = 0.004). This data on ungulate densities and biomass will be crucial for carnivore conservation in this understudied globally significant biodiversity hotspot. Ó 2014 Ecological Society of China. Published by Elsevier B.V. All rights reserved. 1. Introduction Large ungulates are involved in fundamental ecological process of seed dispersal, influence spatial patterns of vegetation and form potential prey species for carnivores [48]. Abundance, distribution and activity pattern of large carnivore is determined by different size of the prey species [31] and the mean body size of large carni- vores are mainly determined by the frequency distribution of available prey [51]. Prey distribution, density and biomass within a given area represent measurable amounts of energy potentially available as food to carnivores. Predator–prey relationships amongst large mammals have complex interactions in ecological system [21]. Less preferred prey might have reduced mortality risk when it co occurs with a favored prey if the predator concentrates its attack on the preferred species [18]. The rate of carnivore pop- ulation growth should be dependent on both the density of prey and prey conspecifics [19]. Several studies have suggested main- taining a healthy herbivore population both in terms of biomass and community structure is essential for conserving a viable carni- vore population [30,50]; Karanth and Stith, 1999; [29]. Overhunting in tropical forests compounded with little knowl- edge on population ecology of large herbivores in South East Asia is a major problem [20,48]. In Arunachal Pradesh, prey depletion due to hunting and livestock depredation by carnivores that leads to retaliatory killing of the latter is common [2,22]. This study pro- vides baseline information on ungulate prey species available for large carnivores in Pakke Tiger Reserve. The recent study conducted by the Wildlife Institute of India in Pakke–Nameri TR has documented a decline of tiger occupied areas from 1100 km À2 to 371 km À2 [26]. Depletion of prey is the major reason for carnivore decline especially for tiger throughout the species range [32] and we suspect the same to be true for these tiger reserves in Arunachal Pradesh. Based on available studies in South East Asia ([24,7,44,45,34]), in this paper we focus on biomass, density, population structure and composition of the major prey species in PTR. Our study high- lights certain important observations and we recommend likewise key measures for long-term survival of prey species in the region. 2. Materials and methods The study was carried out in Pakke Tiger Reserve (PTR) 26°54 0 – 27°16 0 N, 92°36 0 –93°09 0 E in the foot hills of east Himalayan region, http://dx.doi.org/10.1016/j.chnaes.2014.05.003 1872-2032/Ó 2014 Ecological Society of China. Published by Elsevier B.V. All rights reserved. ⇑ Corresponding author. Address: Department of Endangered Species Manage- ment, Wildlife Institute of India, India. E-mail address: gopigv@wii.gov.in (G.V. Gopi). Acta Ecologica Sinica 34 (2014) 219–224 Contents lists available at ScienceDirect Acta Ecologica Sinica journal homepage: www.elsevier.com/locate/chnaes