FOOD HABITS AND ACTIVITYPATTERNOF THE COMMON OTTERLUTRA LUTRA NAIR CUVIER) (F. ATPICHAVARAM,TAMILNADU, SOUTHINDIA 1 G.Umapathy2 Key words: Common otter, Lutra lutra nair foodhabits, activity pattern, , Pichavaram mangrove forests Food habitsand activitypattern ofthecommon otter(Lutra lutra)werestudied in Coleroon and Uppanarrivers,in Pichavarammangroveforest,inTamilNadu,duringDecember 1991 to March 1992. Atotal of2,552recordsofdiurnal activitieswerenotedthroughgroupscan ofapopulation infreshwaterhabitat.Twospraintswerecollectedfrombrackishwatersand 176fromtheadjoining freshwater habitats. Swimming or moving was the major diurnal activity, followed by resting. Scat analysis showed that fish was the major food item in the diet, followed by crustaceans. Introduction c. 5 km stretchofthe Coleroon river and 15 km stretch of the Uppanar river (11° 25' N, 74° Otters are considered as health indicators 47' E). The study area at Coleroon was about ofwetland habitats (Foster-Turley et al. 1990). 2 km south ofPichavaram village and is called The otter population is declining in many Block1.ThewidthofthebackwatersatColeroon m wetlands due to pollution, deforestation and ranged from 250 to 300 and depth from 2 to conversion of wetlands into agricultural and 5 m, during the dry season. Both banks were aquaculture lands (op. cit.). Studies on the mostly covered with prawn culture farms and European otter (Lutra lutra) have indicated that narrow strips of thick bushes. The site at humandisturbanceisamajorfactorinthedecline Uppanarrivercoveredabout 8 kmoffreshwater of its population (Joint Otter Group 1977). habitat (Block II) and 7 km ofestuarine habitat Studies on the population and feeding ecology (BlockIII) andis tothe northofColeroonriver. ofIndianotters arevery limited(Hussain 1992). BlocksIIandIIIwereseparatedbyacheckdam, Thispaperreportssomeobservationsonthefood which formed a small reservoir of fresh water habits ofthe common otter Lutra lutra nair in used for agricultural purposes and which UppanarandColeroonrivers, atPichavaram, on provided a goodhabitatfor otters. The width of the east coast of India, in Tamil Nadu, from Uppanarrivervaried from 10to 15mand depth December 1991 to March 1992. from 1 to 5 m. The freshwaterhabitat(BlockII) hadavillage(1 kmstretch),paddyfields(3 km) Study Area and thick bushes (2 km) on its banks’ The estuarine habitat (Block III) was covered with The study area adjoins the Pichavaram paddy fields (2 km), prawn farm(2 km), thorny mangrove forest in South Arcot district, Tamil bushes (2 km) and open land (2 km). The Nadu, on the east coast ofIndia. It comprises a Uppanar river mouth was occupied by an extensive stretch ofmangrove forest. 'AcceptedJanuary,1999 departmentofZoology,UniversityofMadras, MaterialandMethods GuindyCampus,Chennai600025,TamilNadu,India. PresentAddress:CentreforCellularandMolecularBiology, Theottersoccurringinthestudyareawere W-l12,GroundFloor,UppalRoad,Hyderabad500007, AndhraPradesh,India. identified as Lutra lutra nair (Krishnan 1977). JOURNAL, BOMBAYNATURAL HISTORYSOCIETY, 97(3), DEC. 2000 367 FOODHABITSANDACTIVITYPATTERNOFTHECOMMONOTTER They were located by frequent surveys during Block III (68.2%), and second most common in A early hours. total of 176 fresh spraints (less Block II (36.4%) (Table 1). Crustaceans (crabs than a week old) were collected from these and prawns) were common in the spraints in localities. Thesewerewashedinafinesieve; the Block I and II, while crabs were most common various components were separatedandbroadly in Block II (45.5%). 3% to 12% insects were identifiedas fish, crab, prawn, insectandothers. found in the spraints. Whether the frequency of The percentage frequency of the various prey occurrenceofvariousfooditemsinotterspraints itemswascollectivelycalculatedforallspraints, canbeinterpretedastheproportionoffoodintake foreachblock. Time spentbyotters ondifferent is confounded by many factors, such as activitieswas estimatedbygroup scan(Altmann differences in prey size and proportion of 1974),atintervalsof10minutes,onlyfromBlock indigestibility (Macdonald and Mason 1986). II since visibility in other areas was poor. The Fish is a major food item ofthe European activities were categorized into feeding, resting, otterLutralutra(Kruuketal. 1987), andsmooth movingorswimming,playingandothers. Success Indian otterLutraperspicillata (Hussain 1992). rates of foraging dives were also estimated. All Table observations were made from dawn to dusk, for PERCENTAGEOCCURRENCE1 OFDIFFERENTFOOD six days each month, from December 1991 to ITEMS INOTTERSPRAINTSCOLLECTEDINTHE March 1992. Since the animals were shy and PICHAVARAMAREA, EASTCOASTOFTAMILNADU aquatic,itwasdifficulttofollowdiemcontinuously, Fooditem Percentageoccurrenceoffood items but an average of4 to 5 hrs ofobservation was BlockI BlockII BlockIII possible in a day (range 2 to 8 hrs). The number recordedper scanvaried from3 to 6. Fish 71.54 36.36 68.18 Percent time spent on an activity was Crab 14.30 45.45 9.10 calculated for each day from: T =n x 100IN Prawn 7.15 12.50 13.62 where — % Insect 3.44 5.70 9.10 T^ time spent on activity a — Nna—ntoutmalbenrumobferrecoofrdrsecwoirtdhsacftoirvtihtyeadaaynd NOtuhmebrserofspraints 3.57 0.00 0.00 analysed 80.00 32.00 64!00 An average ofthese percentages over the studyperiod was usedas an estimate ofthe time In the former species, some habitat differences spent on each activity. in the food preference were seen, with the crustaceans forming the main food item ResultsandDiscussion (Macdonald and Mason 1987). Fifty-fourfeeding dives were recorded, of Atotalof2,552recordsofdiurnalactivities which 39 dives (72.0%) were successful. Ofthe weremadein24 days. Movingorswimmingwas successful dives, otters captured fish on 22 themajoractivity, taking42.84%ofthedaytime occasions (56.4%), crabs on 8 (20.5%), prawn (range 30.1% to 53,7%). Resting was second, once (2.5 %) and unidentified items on eight taking 30.87% ofthe day time (range 26.4% to occasions (20.5%). This observation on feeding 34.8%), while feeding was 20.3% (range 15.7% also indicates the dominance offish in the diet. to 24.3%). Playing and other activities The differences between direct observation of constituted 3.79% and 2.14% respectively. feeding and spraint analysis in the Block II Fish was the most common food item in population, may be due to the otter feeding on the spraints collected in Block I (71.5%) and smallerprey (mostly crabs) under water. 368 JOURNAL, BOMBAYNATURAL HISTORYSOCIETY, 97(3) DEC. 2000 FOODHABITSANDACTIVITYPATTERNOFTHECOMMONOTTER Acknowledgements Dr. Ajith Kumar, Salim Ali Centre for Ornithology and Natural History, Coimbatore, I am grateful to Prof. G. Durairaj, for going through an earlierversion ofthe draft Department of Zoology, University of Madras and the Tamil Nadu State Forest Department for guidance and encouragement. I thank for financial assistance. ReferENCES Altmann, J. (1974): Observational study ofbehaviour: NatureConservation,London,96pp. samplingmethods.Behaviour49:227-267. Krishnan, M. (1977): Indian Wildlife. Department of Foster-Turley, P., S. Macdonald & C. Mason (Eds.) Tourism,GovernmentofIndia. (1990):Otters.Actionplanfortheirconservation. Kruuk, H., J.W.H. Conroy & A. Moorhouse (1987): IUCN,Gland,Switzerland, 126pp. Seasonalreproductionmortalityandfoodofotters Hussain, S.A. (1992): The wild otters ofthe Chambal. (Lutralutra)inShetland.J.Proc.Zool.Soc.Lond. Sanctuary,Asia XII,No. 5:24-31. 58:263-278. Joint Otter Group (1997): Otters. 1977. Nature Macdonald,S.M.&C.F.Mason(1986):Otter: Ecology ConservancyCouncil/SocietyforthePromotionof andConservation,Camb.Univ.Press,Cambridge. JOURNAL, BOMBAYNATURAL HISTORYSOCIETY, 97(3), DEC 2000 369