Mammalia 76 (2012): 57–65 © 2012 by Walter de Gruyter • Berlin • Boston. DOI 10.1515/MAMM.2011.105 Prey selection by smooth-coated otter ( Lutrogale perspicillata) in response to the variation in fish abundance in Upper Gangetic Plains, India Asghar Nawab 1 and Syed Ainul Hussain 2, * 1 Freshwater and Wetlands Programme, World Wide Fund for Nature – India, 172-B Lodi Estate, New Delhi-110003, India 2 Wildlife Institute of India, Post Box 18, Chandrabani, Dehra Dun – 248001 Uttarakhand, India, e-mail: hussain@wii.gov.in * Corresponding author Abstract The dietary diversity of carnivores often varies inversely with prey abundance. Slight environmental perturbations, anthro- pogenic or otherwise, leading to lower prey availability, could affect the continued existence of mammalian carnivores in human-dominated landscapes. We examined the selection of prey by the smooth-coated otter in response to the variations in abundance of fish in Corbett Tiger Reserve in the Upper Gangetic Plains, India. Sixteen fish species were recorded from the Reserve; 14 from the lotic and five from lentic sys- tems. In the lotic systems, the river cat ( Glyptothorax pec- tinopterus) was most abundant during summer followed by ticto barb ( Puntius ticto) and mahseer ( Tor spp.), while dur- ing winter mahseer was most abundant followed by chaguni ( Chagunius chagunio) and minnow (Labeo dyocheilus). The diet of otter included four prey categories, among which fish were the most dominant prey (84%). The other preys were amphibians, crabs and birds which were taken occasionally. There was no difference in the overall proportion of differ- ent prey categories utilized among seasons and sites. In the Reserve, eight fish species from the families Cyprinidae and Sisoridae were used. The ticto barb, chaguni, minnow and river cat were the most utilized species. The species used and their preference by otters varied from river to river depending on their availability in different seasons. The ticto barb was most utilized during summer, followed by river cat and hill trout. In winter river cat, chaguni and mahseer were the most utilized species. The otters used hill trout ( Barilius bendelisis), sucker head ( Schizothorax richardsonii) and ticto barb during summer and chaguni and minnow during winter more than their availability, indicating their preference. Keywords: corbett tiger reserve; mustelids; prey selection; river ecosystems; smooth-coated otter. Introduction Mammalian carnivores are important ecosystem components, but are prone to extinction because of their small populations, slow growth rates, large area requirements (Dalerum et al. 2009) and reduced prey availability. Their dietary diversity often varies inversely with prey resource abundance (Tinker et al. 2008). Thus, slight environmental perturbations, anthro- pogenic or otherwise, leading to lower prey availability, could easily upset their energy balance (Carbone et al. 2007) affect- ing their existence. In areas of high human densities, such as India, the human population density is positively associated with the extinction of many species. Overall, large-bodied, rare and habitat-specialist mammals have had higher extinction probabilities (Karanth et al. 2010). The smooth-coated otter ( Lutrogale perspicillata, Geoffroy 1826), a semi-aquatic carni- vore distributed throughout south and southeast Asia (Hussain 1996, Hussain and Choudhury 1997), is now restricted to a few protected areas and increasingly getting rarer because of changes in riverine ecosystems (Hussain 2002). It is now listed as “ Vulnerable” in the IUCN Red List (Hussain et al. 2008) and Appendix II of CITES, indicating that it is conser- vation dependent. It is a large otter weighing around 8–11 kg (Pocock 1941) and is found in large rivers and lakes (Kruuk et al. 1994). Information on its ecology is scanty which hin- ders the development of appropriate conservation measures. Most otter species belonging to the genera Lutra, Lutrogale and Lontra have generally been described as fish specialists (e.g., Mason and Macdonald 1986, Hussain and Choudhury 1997). However, several studies have suggested that they may be better defined as opportunistic predators, with their feeding behavior being dependent on the availability of prey. In rivers with a low diversity of prey, otters tend to feed on fewer species; however, where prey populations are diverse, an otter’s diet may include several prey categories, though many of these will be eaten in small amounts (Hussain and Choudhury 1998). Differences in selection of microhabitats by otters may also influence the susceptibility of a prey spe- cies to otter predation (Remonti et al. 2010). Fish migrations, whether for spawning or for overwintering can temporarily increase the availability or biomass of some species (Carss et al. 1990). Observations on the diet of otters are useful for their conservation and for determining the species’ response to changes in aquatic ecosystems, both in terms of the prey population and habitat quality. Materials and methods Study area The Upper Gangetic Plains lie in the alluvial plains of the Ganges and Yamuna rivers with an area of approximately Brought to you by | Bibliotheque de l'Universite Laval Authenticated Download Date | 3/4/15 7:57 PM