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The smooth-coated otter (Lutra perspicillata) is one of the most endangered and threatened mammals of India (Tikader, 1983) and faces a great threat due to ever increasing human disturbance in preferred habitats. The smooth-coated otter is distributed throughout India from Himalayas southwards and has been reported from the states of Karnataka, Kerala, Andhra Pradesh, Madhya Pradesh, Maharastra, Gujarat, Punjab, Himachal Pradesh, Uttar Pradesh, Bihar, West Bengal and Mizoram (Prater, 1971; Hussain and Choudhary, 1988; Hussain, 1993; Foster-Turley and Santiapillai, 1990). It is seen to inhabit large rivers and their associated tributaries, estuaries and coastal mangrove swamps, and requires undisturbed forest or scrub adjacent to the water (Mason, 1990).
Hussain (1993) reported the lack of information on the status of otter populations in India. According to Foster-Turley and Santiapillai (1990), all three species of otter present in India are more or less restricted to National Parks and Wildlife Sanctuaries and are threatened in many areas due to reduction in their prey biomass, poaching and habitat degradation. Little information exists on otter populations outside protected areas in India, and with this in mind a study was carried out to assess the distribution of smooth-coated otters in both protected and unprotected areas in Andhra Pradesh, India.
STUDY AREA AND METHODS
To ascertain the present status and distribution of smooth-coated otter in Andhra Pradesh, India, a survey was conducted covering coastal areas, wetlands, riverine habitats, perennial and non-perennial water tanks and other potential otter habitats. Surveys were conducted in selected tracts of the state after considering the distribution trends of the otter in the past. Otter presence or absence was recorded through direct and indirect evidence. During the surveys, care was taken to ascertain that all the study sites were of comparable size. In each habitat, group structure composition and habitat conditions were recorded. The relative status of otter populations at positive sites was estimated by a combination of visual records and indirect evidence. Depending on the relative density of the estimated otter population and occurrence of positive otter signs, the status of otter populations at these sites were categorised as abundant, normal or sparse. Interviews with local people and fishermen were also conducted to evaluate the distribution of the species.
RESULTS AND DISCUSSION
In Andhra Pradesh, the smooth-coated otter has a more or less patchy distribution, with the strongest population in the mangrove and estuarine habitat of East Godavari District within the limits and adjacent areas of Coringa Wildlife Sanctuary; followed by Kolleru Lake in Krishna District and Mantralayam in Kurnool District (Fig. 1).
Of the 23 districts in the state, 10 had positive signs of otters, recorded at 35 sites (Table 1). All the other sites surveyed (n=39, 52.7%) remained negative with no evidence of otter occurrence. Regarding habitat, signs were registered most frequently around water tanks (14.9%), followed by riverine habitats (13.5%), mangrove and estuarine habitats (9.4%), reservoirs (6.8%) and estuaries (2.7%) (Table 2).
The number of groups sighted varied between 3 and 22. Groups varied between 2 and 16 individuals at the study sites, with total estimated populations ranging between 15 -450 animals. Regarding population status, 8 (22.9%) sites showed abundant distribution, 13 (37.1%) sites showed normal distribution, and 14 (40.0%) sites showed sparse distribution of otters.
The smooth-coated otter is abundantly distributed along the mangrove and estuarine habitats of East Godavari district with healthy population recorded from 6 sites. This can probably be attributed to increased prey availability during the tidal influxes. Similar observations elsewhere in the world (Foster-Turley, 1992; Chakraborti, 1993) point out that prey availability is the main requirement for good populations in these types of habitats. Similar habitat is to be found in Nizampatanam, in Guntur district. Here, a rather large population of about 100 otters was also recorded (Prasad, 1992).
At estuarine habitats, where mangrove vegetation was sparse as a result of large scale clearance for development of aquaculture farms, such as Intheru, Pedapatnam and Kona in Krishna district, the otters were considered as normally distributed.
In the case of riverine habitats, distribution was abundant, with about 150 otters, only at Mantralayam, in the Kurnool district, downstream of the river Tungabhadra. At other sites (along the rivers Godavari and Krishna) populations ranged from normal to sparse. It was noted that the frequency of sightings of otters at these sites was higher with respect to their population density. This can be attributed to the availability of preferred prey along the river course and the adjacent paddy fields, as recorded at Ravulapalem in East Godavari District.
The population status of the smooth-coated otter at water tanks and reservoirs was maximal at Kolleru wetland, whilst the status varied at other sites in Warangal, Medak and Adilabad districts. Most of these water tanks are perennial and are connected to major rivers, or their tributaries, and are utilised by the State Fisheries Department for piscicultural activities. Availability of food and escape routes, in the form of numerous canals originating from these tanks and reservoirs make them good potential otter habitats. At Pakhal tank, though otters were seen, sightings were sporadic when compared to the sightings in the canal system associated with the tank.
Habitat suitability, as well as human disturbance factors, cannot be over looked as factors affecting the utilisation patterns of these water tanks and their associated canals. Otters have been reported as completely missing from areas where a good population previously existed. This is mainly attributed to the increase in pollution levels and acidity in the waters of these regions. Mason and Macdonald (1989) described a direct correlation between water pH levels and otter usage and indicated that the Eurasian otter (Lutra lutra) avoided waters with low pH.
However, it is important to note that smooth-coated otters have tolerated a little alteration in their habitats (in the form of aquaculture and pisciculture farms) as shown by the populations existing at the mangrove and estuarine habitats in Andhra Pradesh, where they remain in high numbers compared to other habitats. This is mainly due to the availability of alternative food in the surrounding areas and the relative safety due to inaccessibility of habitat. Studies conducted by Macdonald and Mason (1983) and Chehébar et al. (1986) indicate that the otters have disappeared from areas where no suitable habitat remains, and when habitat destruction goes on the otters are compelled to make use of small reservoirs and canals with less disturbance, ample food and good vegetation cover, as found in the cases discussed by Macdonald et al. (1986) and Melquist (1984).
Based on the survey, the following conservation measures will enhance the survivability of otters, both within and outside various protected areas in Andhra Pradesh:
In the aquatic ecosystem where it abounds, the otter represents an apex animal of the ecological pyramid. There is increasing realisation that small mammal conservation has taken a back seat to general conservation measures that emphasise large predator mammals. Keeping in view the Fishery/Wildlife and Wildlife/Man interface, such status surveys should be regularly taken up. The information reported herein should serve as base-line data for the future management and conservation needs of this endangered species.
ACKNOWLEDGEMENTS - We express our heartfelt gratitude to Prof. J. V. Ramana Rao, the driving force behind us in all our research endeavours. We are thankful to the Andhra Pradesh State Forest Department and Andhra Pradesh State Fisheries Department for providing necessary information. We also extend our gratitude towards the fishermen and locals of the areas surveyed without whose help the task would have been difficult to accomplish.
Chakraborti, K. (1993). An ecological review of otter in the Mangrove ecosystem of Sunderbans. Tigerpaper 20 (1): 19-21.
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