Abstract
Living in different aquatic ecosystems, otters play a vital role in maintaining aquatic species assemblages, particularly fish communities. Thus their wellbeing indicates the health of wetland ecosystems. Smooth-coated Otter Lutrogale perspicillata, a piscivorous mustelid, is widely distributed across Asia. Its population is declining due to habitat transformation, pollution and hunting. This study aimed to understand the ecological requirements of the species by assessing its distribution and its determinants, population and diet composition along the Cauvery River in Hosur and Dharmapuri Forest Divisions. Through monthly extensive surveys between December 2010 and February 2011, covering 62.5 km of Cauvery from the Karnataka border to Palar River junction, this study identified and mapped a 31 km stretch from Dubguli (Yellolapatti) to Biligundlu (Musulumaduvu) as an otter distribution area. Comparison of ecological parameters including bank type, water depth, river width, human disturbance, vegetation cover and water current with the distribution pattern of otters across 125 blocks revealed that water depth and vegetation cover influenced otter distribution positively, while human disturbance had negative influence (these three variables explained 54% of variation in otter distribution). Based on direct sightings, seven different groups consisting of 36 individuals were estimated as the minimum population. The mean group size was 3.8 ± 0.16 (range: 2–7) individuals. Twenty-one otter spraints were analyzed to determine diet composition, revealing that otters feed on insects, molluscs, crabs, fish, frogs, reptiles and birds. Fish constituted the bulk of otter diets. Conservation measures like reducing anthropogenic pressures (e.g., fishing, cattle pens, tourism), increasing awareness of sustainable fishing to stakeholders, and instituting long-term monitoring programs are suggested for the long-term conservation of otters in the study area.
Highlights
Otters are piscivorous mustelids belonging to the family Mustelidae and subfamily Lutrinae
Factors influencing distribution Otter were observed to be significantly concentrated in river stretches with higher water depth (K-W χ2= 11.358, df= 2, P
Further comparison of otter abundance recorded in the five blocks with the ecological factors prevailed in the respective block revealed that water depth (Coefficient±SE= 0.133 ± 0.034, P
Summary
Otters are piscivorous mustelids belonging to the family Mustelidae and subfamily Lutrinae. Living in different aquatic ecosystems (Pardini 1998), otters play a major role in maintaining aquatic species communities, fish communities (Sivasothi 1995; Anoop & Hussain 2005) They are health indicators of wetland ecosystems, being sensitive to degradation of habitat and the food chain (Erlinge 1972). The Smooth-coated Otter is presently listed as a ‘Vulnerable’ species on the IUCN Red List (de Silva et al 2015), Appendix I in CITES (CoP 2019) and is protected under Schedule II in Indian Wildlife (Protection) Act (1972). Despite their wide distribution and vital role in the wetland ecosystem, not much attention has been paid to understand their ecology. Systematic data on their habitat, distribution, population, and feeding ecology are essential for conservation planning and management of the species in India
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