Prey Selection by Tigers Panthera Tigris (Linnaeus 1758) in the Sundarbans East Wildlife Sanctuary of Bangladesh

2008·4.9 MB·

by  M Monirul H Khan

Journal ofthe Bombay Natural HistorySociety, 105 (3), Sep-Dec 2008 255-263
PREY SELECTION BY TIGERS PANTHERA TIGRIS (LINNAEUS 1758)
IN THE SUNDARBANS EAST WILDLIFE SANCTUARY OF BANGLADESH
M. MonirulH. Khan1
'WildlifeResearchGroup,DepartmentofAnatomy,UniversityofCambridge,DowningStreet,CambridgeCB23DY,UK.
PresentAddress:DepartmentofZoology,JahangirnagarUniversity,Savar,Dhaka1342,Bangladesh.Email:[email protected]
This study was conducted to determine prey selection by Tigers Panthera tigris in the Sundarbans East Wildlife
SanctuaryofBangladesh.Atotalof145 scatswereanalysedand78killswerestudied.Thefrequencyofoccurrenceof
differentprey speciesin scatsandkillswassignificantlydifferent. On an average, the Spotted DeerAxisaxiswasthe
mostfrequent prey in scats and kills (78%). Most Spotted Deerkills were adult animals and were in good condition
before they were killed. The frequency ofoccurrence in scats was converted to the relative number ofkills, which
showedthattheSpottedDeerwasstill themostfrequentprey(29.9%). OtherthantheSpottedDeer,tigersalsopreyed
on Wild Boar Sus scrofa Rhesus Macaque Macaca mulatto and Lesser Adjutant Leptoptilosjavanicus. Soil and
, ,
sungrassbladeswerefoundinscats asnon-fooditems. Scats with soil were moreavailable in winterthan in summer.
Ingeneral, thetrendofpreyselectionappearedtofollowpreysizeandabundance,butWild BoarandLesserAdjutant
were two mosthigh-rankingprey species, because theirselectivity was higherin comparison totheirabundance.
Key words: mangroves, tigerfoodhabit, tigerkills, tigerscats, spotteddeer
INTRODUCTION MATERIAL AND METHODS
The acquisition offood is a fundamental component Study area
of every predator’s daily existence. Hence, knowledge of The study was conducted in a part ofthe Sundarbans.
food selection is critical to understanding life history The entire Sundarbans is an area ofabout 10,000 sq. km in
strategies and developing sound conservation the Ganges-BrahmaputradeltaofBangladesh and India, but
recommendations(Miquelleetal. 1996). Predatorystrategies roughly60%ofthisforestliesinthesouth-westofBangladesh
are shaped and refined by natural selection to maximise and the rest 40% is in the south-east of the Indian state of
nutrient intake within the bounds of a wide range of West Bengal. The monthly mean temperature and relative
biologically relevant ecological constraints (Clutton-Brock humidity normally varies from 23 °C (during December-
andHarvey 1983; SunquistandSunquist 1989). Carnivores January) to35 °C (during May-June) andfrom 70% to 80%,
often regulate or limit the numbers of their prey, thereby respectively. There are three wildlife sanctuaries in the
altering the structure and function of entire ecosystems BangladeshSundarbansthattogetherformaUNESCOWorld
(Schaller 1972; Smuts 1978; Berger et al. 2001; Terborgh HeritageSite.TheSundarbansEastWildlifeSanctuary(WS)
et al. 2002). The role Tigers Panthera tigris play as top (312 sq. km) is one of these three sanctuaries where this
predators is vital to regulating and perpetuating ecological research was concentrated (Fig. 1)- Geographically the area
processesandsystems(Sunquistetal. 1999;Terborgh 1999). is locatedbetween 21° 47'-22° 03' N and 89° 44’-89° 56' E.
The analysis of food habits provides practical and
immediately useful information for the management of a Scat analysis
particular species, and occasionally aids law enforcement The scat samples were collected from the field, on a
and management needs (Korschgen 1971). monthly basis, for 18 months (September 2001 to February
The general objective in this research is to identify 2003). Since the Tiger is the only large carnivore in the
whether Tigers in the Sundarbans have any preference for Sundarbans, Tiger scats could be identified without any
prey in terms of species, availability, age and health. The confusion. The samples were sun-dried whenever necessary,
specific questions are; 1) What are the proportions of preserved in a tagged polythene bag, and brought to the
different prey species in Tiger scats andkills? 2) DoTigers laboratory for analysis. At first, each of the dried scats was
sometimes ingestnon-food items? 3) Does prey abundance classified accordingtotherelative volume, weighedusing the
have any effect on prey selection? 4) What are the LarkJPT-2 (range: 0.1-200gm) beambalance(big scatswere
proportions of kills in different age and health classes? weighed in sections), and were classified according to their
5) Does the abundance of the Spotted Deer Axis axis in wejght.Theneachscatwasbrokenandcarefullysoakedinwater
different age classes have any effect on its selection? to separate prey remains, such as hair, bones, hooves, teeth.
PREY SELECTION BYTIGERS IN THE SUNDARBANS EASTWILDLIFE SANCTUARY
Fig. 1: The Sundarbans of Bangladesh and Indiashowing the Sundarbans EastWildlife Sanctuary
feathers. The separated items were studied with the unaided this study), the frequency of occurrence can considerably
eye and with a magnifying glass, as well as under a light distort the relative numbers ofdifferent prey species in the
microscope,ifnecessary,andwereidentifiedbycomparingwith diet (Panwar 1990; Karanth and Sunquist 1995). However,
areferencecollection (fromdifferentspeciesofkillsand from the frequency ofoccurrence ofdifferent prey species in the
captive animals) using features such as structure, colour, and scats of Tigers can be converted to relative numbers and
medullaryconfigurationtoidentifypreyspecies(Koppikarand biomass ofdifferent prey taken, which represents the actual
Sabnis 1976; Amerasinghe 1983; Kitsos et al. 1995; selectivity pattern (Floyd etal. 1978;Ackermanetal. 1984;
Ramakrishnanetal. 1999).Theremainsofonepreyspeciesin Karanth and Sunquist 1995). In the light of the previous
onescatwereconsideredasfrequencyone.Iftherewereremains approaches (Schaller 1967; Johnsingh 1983; Putman 1984;
oftwopreyspeciesinascat(whichwasararecase;foundonly Emmons 1987; Karanth and Sunquist 1995), the method
inafewscats),thefrequencywasdividedinto0.5foreachprey developed by Ackerman et al. (1984) for Puma Puma
species. The non-food items were recorded when the item concolor,toconvertthefrequenciesofoccurrenceintorelative
formed more than 50% of the scat volume (Schaller 1967; numbers and biomass of individuals killed, was used.
Johnsingh 1983),butthesewereexcludedwhileestimatingdiet Assumingthatthedigestivesystemandthedegreeofcarcass
compositionandthebiomassoffoodconsumed(Reynoldsand use of the Tiger is comparable to that of the Puma, the
Aebischer 1991).ReynoldsandAebischer(1991)definednon- following regression was used to relate live weight ofprey
food itemsin the scats asremains ofingestathathave little or killed (A) to the weightofthatpreyrepresentedinonefield-
-
nonutritivebenefit(i.e., soil andsungrass inthis study). collectableTigerscat (Y)
Todetermine whetherthe scat sample size issufficient,
the method was followed from Mukherjee etal. (1994), who Y= 1.980+0.035 X
studiedtheeffectofscatsamplesizeonfrequencyofoccurrence
in scats of a given prey species and identified the minimum The average number of collectable scats produced
reliablesamplesize(MRSS)asthatwhichdoesnotcauseany by a Tiger from an individual animal of each prey species
furtherchange in aprey with increase in sample size. (X. = X/Y),andtherelative numbersofeachpreykilledwere
Although the frequency ofoccurrence ofprey species computedfromthe aboveequations(Ackermanetal. 1984).
incarnivorescatsisacommonly-usedparameterinthestudy Therelativenumberswerethenconvertedtorelativebiomass
ofcarnivore food habits, ifprey size is highly variable (as in by multiplying with the minimumadult weight.
256 J. Bombay Nat. Hist. Soc., 105 (3), Sep-Dec 2008
;
PREY SELECTION BYTIGERS IN THE SUNDARBANS EASTWILDLIFE SANCTUARY
Preyselectivityindex SelectivityoftheTigerpredationforageclassesofthe
The selectivity index (S) (Sourd 1983; Julliot 1996), Spotted Deer was assessed by Ivlev’s selectivity index (D)
used to compare the abundance ofeach edible prey species (Okarmaetal. 1997; Khorozyan and Malkhasyan 2002)-
in the habitat and its proportion in the Tiger diet, was D = (ffi- fL)/(fE + fL - 2fEfL)
calculated by using the equation mentioned below - Here fE= fraction ofagiven age class among Spotted
Deer eaten by Tigers (adult = 0.765, yearling = 0.176 and
S = (PC -PA )/(PC + PA fawn = 0.059; ages identified on the basis of the eruption
' sp sp7 v sp sp')
ofthe teeth (Table 5), and fL is the fraction of a given age
Here PC = proportion ofone particularprey species class in the habitat (adult = 0.722, yearling = 0.205 and
sp
intheTigerdietasapercentageoftherelativenumberofthat fawn=0.073; Khan2004).Thepositiveornegativevalueof
prey speciesintheTigerdiet(SpottedDeerAxisaxis=43.4, D for a certain age class means that the individuals of that
Wild Boar Sus scrofa = 8.5, Rhesus Macaque Macaca ageclass were positively ornegatively selected.
mulatto =22.2,LesserAdjutantLeptoptilosjavanicus= 8.5,
RedJunglefowlGallusgallus- 17.4,WaterMonitorVaranus RESULTS
salvator=0; Table 3), and
PA =proportionofthesameprey speciesavailablein Scat volume and weight, and minimum sample size
the habitat as a percentage ofthe individual density ofthat In terms ofrelative volume, there were no significant
prey species in total prey population (Spotted Deer = 48.2, differenceinthefrequenciesofsmall,mediumandlargescats
Wild Boar = 1.1, Rhesus Macaque = 15.0, Lesser (yp — 0.68, df = 2, p - 0.713), but medium-sized scats
Adjutant= 1.4,RedJunglefowl= 16.1,WaterMonitor= 18.2; were the commonest (36.6%). On the other hand, classes
Khan 2004). based on dry weight show that there were significant
The species wasthenconsideredas: a) ahigh-ranking differencesinthefrequenciesofscatsinthreedifferentweight
species, when S > 0.3 (PC at least double than PA ); classes (y2 = 25.00, df = 2, p < 0.001), but relatively light
b) a middle-ranking species, when S lies between -0.3 and weight (<100 gm) scats were the commonest (51.0%)
0.3 (PCsp similar to PA ); c) a low-ranking species, when (Table 1). The mean weight of dried scats was 124.9 gm
S < -0.3 (vPCspat least half than PAsp7); and d)7 an uneaten (n = 145, range = 10.6-406.6 gm, sd = 94.8).
species, when S = -1 (PC = 0, non-used edible species). The results ofthe testforminimum sample size ofthe
p
scats, required for actual presentation ofthe proportion ofa
Killstudy prey species in the scats is illustrated in Fig. 2. It is evident
Crows and vultures are good advertisers ofTigerkills that even 34 samples are sufficient to represent adequately
in most of the Tiger ranges of the Indian subcontinent the occurrence ofthe Spotted Deer in the Tiger diet, which
(Schaller 1972;Johnsingh 1983;KaranthandSunquist 1995), stays virtually steady-state regardless of the larger sample
butthedensevegetation,andtherarityofcrowsandvultures size.
intheSundarbans,forcedmetodependmainlyonodourand
draggingsigns.Inadditiontothespeciesofpreykilled,ifthe Preyselection
killwasrelativelyintact,theageclassandhealthofthekilled The frequency ofoccurrence ofdifferent prey species
individual was recorded on the basis ofthe size, colour and inscatsandkills (Table2) showsthatexcludingzerovalues,
overallconditionoftheanimal.Wheneverpossible,thecolour the frequencies ofdifferent prey species were significantly
and texture offemur marrow fat were examined in order to different (in scats: yj = 545.71, df = 7, p < 0.001; in kills:
record the health condition of the kill more accurately yj- 316.15, df=6,p<0.001). On an average. SpottedDeer
(Schaller 1967;SinclairandDuncan 1972;Riney 1982).The
lowerjaws were collected wheneveravailable, and taken to
thelaboratorywherethetotallengthanddiastemalengthwere Table 1: Scat size oftheTigeron the basis
ofvolumeand weight
measured,andusedtoclassifythekillsintoagecategoriesas
adult, yearling/juvenile and fawn/young on the basis of Relativevolume Weight (gm)
eruptionandwearofpremolarandmolarteeth(Schaller 1967 % %
Riney 1982;vanLavieren 1983).Ialsotriedtodeterminethe Class No. Class No.
age of kills by counting tooth cement rings (Ashby and Small 46 31.7 <100 74 51.0
Santiapillai 1986; Ballard et al. 1995; Landon et al. 1998), Medium 53 36.6 100+to200 46 31.7
but no distinct annuli were found. Large 46 31.7 200+ 25 17.3
J. Bombay Nat. Hist. Soc., 105 (3), Sep-Dec 2008 257
PREYSELECTION BYTIGERS IN THE SUNDARBANS EASTWILDLIFE SANCTUARY
Unidentified
Fig. 2: Relationship betweenthe sample size ofTigerscatsand
percentage ofthefrequencyofoccurrence ofthe Spotted Deer
in scats in the Sundarbans EastWildlife Sanctuary
wasthemostfrequent(78%),butTigersalsoconsumedWild
Boar, Rhesus Macaque, Porcupine (Indian Crested Hystrix
indica or Brush-tailed Atherurus macrourus Leopard Cat
),
Prionailurus bengalensis Irrawaddy Dolphin Orcaella
,
brevirostris(diedinthe fishingnet, which was thrown away
andfloatedtothebank,andfinallyeatenbythetiger).Lesser
Adjutant,RedJunglefowl,MudCrabScyllaserrataandWater
Monitor Varanus salvator which together form the rest of
,
thefrequencypercentage(Table2).Sincethepreysizesvaried
considerably, the frequency ofoccurrence was converted to Fig.3: Proportionsoftherelativebiomassofdifferentpreyspecies
therelativenumbersofpreyanimalskilled, anditwasfound consumed byTigers in the Sundarbans EastWildlife Sanctuary
that Spotted Deer was still the most frequently consumed were also found in a number of scats, but only one scat
(29.9%) (Table 3). When relative numbers ofdifferent prey (collected in January 2002) had sungrass more than 50% of
animals consumed by Tigers were converted to the relative the volume. In almost all cases the soil was very hard in the
biomass,itshowsthattheSpottedDeerformsthebulkofthe scat, probably due to contraction in the intestine. The
diet(80%)andWildBoaristhesecond-mostconsumed(11%) occurrence of scat samples with more than 50% soil in
(Fig. 3). These are the two species on which Tigers in the different periods of the months was significantly different
Sundarbans are thriving. (yp = 27.19, df= 8,p = 0.001). More than 80% ofthe scats
with soilwerefound in winter/dry season (October-March),
Non-food items in scats with the peak in November-December (c. 15%), which
Other than the prey animal remains, 74 (51%) scat indicates a strong seasonality in soil ingestion by Tigers
samples had large quantities of soil (more than 50% ofthe (Fig. 4). Notably, the monthly total collection ofscats was
volume). Sungrass (Imperata sp.) blades, and rarely leaves. almostequallyproportionalindifferentseasons.Thepresence
Table 2: Occurrenceofdifferentprey species in scats and killsofTigers
% % %
Preyspecies Frequency in scats frequency in scats Frequencyin kills frequency in kills total frequency
in scatsand kills
Spotted Deer 108 74.5 66 84.6 78.0
Wild Boar 16 11.0 2 2.6 8.1
Rhesus Macaque 8 5.5 1 1.3 4.0
Porcupine 2 1.4 0 0.0 0.9
LeopardCat 1 0.7 0 0.0 0.5
IrrawaddyDolphin
(strandedcarcase) 0 0.0 1 1.3 0.5
LesserAdjutant 3 2.1 5 6.4 3.6
RedJunglefowl 1 0.7 1 1.3 0.9
Mud Crab 1 0.7 0 0.0 0.4
Water Monitor 0 0.0 2 2.5 0.9
Unidentified 5 3.4 0 0.0 2.2
258 J. Bombay Nat. Hist. Soc., 105 (3), Sep-Dec 2008
00
PREYSELECTION BYTIGERS IN THE SUNDARBANS EASTWILDLIFE SANCTUARY
Table3: Estimated average numberofcollectable scats producedfrom individual prey animalsand relative numbersofdifferent
preyspecies killed byTigers in the Sundarbans EastWildlife Sanctuary
Preyspecies Weight (kg) Frequencyof No. ofcollectable Total no. of animals Relative no. of
occurrence in scats scats produced/kill eaten to provide preyanimals killed (%)
collected-scats
Spotted Deer 47. 1 108 13.1 8.2 29.9
Wild Boar 32. 1 16 10.3 1.6 5.8
RhesusMacaque 4.0' 8 1.9 4.2 15.3
Porcupine 8.02 2 3.5 0.6 2.2
LeopardCat 3.03 1 1.4 0.7 2.6
LesserAdjutant 4.04 3 1.9 1.6 5.8
RedJunglefowl 0.6s 1 0.3 3.3 12.1
Mud Crab 0.36 1 0.2 5.0 18.3
Unidentified 5.07 5 2.3 2.2 8.0
N.B. Mainlythe minimum adultweightsofthe preyspecieswereconsidered.
'Source: Karanth & Sunquist(1992);2Source: Karanth & Sunquist (1995); 3Sourcei: Prater (1971); “Sources: www.ndngrd.com;
5Source: www.international.tamu.edu; 6Source: local crabcollectors; 7Source: arbitrarilyassumed, as in Karanth & Sunquist (1995)
of a large amount of soil proves that these were not lengths of these two specimens were 20.5 and 21.7 cm,
accidentallyingested. andthediastemalengthinbothcaseswas0.5cm.Mostofthe
kills were adult animals (based on freshkills-56.5%, based
Prey abundanceversus preyselection on eruption of teeth - 76.5%) (Table 5), and were in good
Theselectivityindex(S)forsixpotential preyspecies condition before they were killed (78.8%) (Table6).
shows that Wild Boar and Lesser Adjutant were high
ranked; SpottedDeer,RhesusMacaqueandRedJunglefowl AbundanceandselectionofSpottedDeerindifferentage
were middle ranked; and Water Monitor was a non-used classes
species (Table 4). It is notable that the two least-available Based on Ivlev’s selectivity index, the values of D
prey species were highest in the ranking, i.e., rates oftheir foradult, yearlingandfawn ageclassesofthe Spotted Deer
selectivity by Tigers were highest in comparison to their werecalculatedat0.112,-0.094and-0.113,respectively.Since
abundance. thevalueispositiveonly foradultageclassandnegativefor
yearling and fawn classes, it can be concluded thatthe adult
Age and health ofkills Spotted Deerwere positively selected, whereas the yearling
The mean lengths oflowerjaw bone and diastema of and fawn Spotted Deer were negatively selected. In other
theSpottedDeerwere 18.7cm(n=34,range= 12.0-21.7cm, words,thepredationwashigherthantheabundanceofadults,
sd = 2.1) and 5.0 cm (n = 34, range = 3.2-6.3 cm, but lowerthan the abundance ofyearling and fawn.
sd=0.8),respectively. Otherthanthe SpottedDeer,onlytwo
intact lowerjaws of Wild Boar were found. The lowerjaw DISCUSSION
Preyselection
14 The preference for large prey species (Spotted Deer),
as found in this study, supports the hypotheses related to
10 10
Q
foraging theory (Stephens and Krebs 1987), which suggest
Table4: Preyspecies ranking based on selectivity index
2 2
i LI U Preyspecies Selectivity index (S) Rankofthepreyspecies
S-0 N-D J-F M-A M-J J-A S-0 N-D J-F
2001 2002 2003 Spotted Deer -0.05 Middle
Collectionmonths Wild Boar 0.77 High
RhesusMacaque 0.19 Middle
LesserAdjutant 0.72 High
Fig. 4: Bi-monthlyoccurrenceofTigerscatswith soil consisting
of morethan 50% ofthe volume in the Sundarbans East RedJunglefowl 0.04 Middle
Water Monitor -1.00 Non-used
WildlifeSanctuary
J. Bombay Nat. Hist. Soc., 105 (3), Sep-Dec 2008 259
PREYSELECTION BYTIGERS INTHE SUNDARBANS EASTWILDLIFE SANCTUARY
that predators may select species containing the most (Koppikar and Sabnis 1979; Gogate and Chundawat 1997;
'profitable’ prey, as measured by the ratio ofenergy gain to Bagchietal. 2003).InHuaiKhaKheng,Thailand,theBarking
handlingtime(MacArthurandPianka 1966;Schoener 1971; Deer is the main prey species (Rabinowitz 1989). In the
Charnov 1976; Scheel 1993; Karanth and Sunquist 1995). Russian Far East, Elk Cervus elaphus and Wild Boar were
For large felids the mostprofitable prey type would seem to consistently the two key components of the Tiger diet
be the largest available prey that could be safely killed, but (Abramov 1962;Miquelleetal. 1996).KaranthandSunquist
the importance of search time, encounter rates, and the (1995) reported that in Nagarhole, India, the biomass ofthe
energeticcostsofcapture forvariousprey typesalsoneedto SpottedDeer,Sambar,GaurBosfrontalis.WildBoar,Barking
be considered (Sunquist and Sunquist 1989). Tiger and DeerandCommonLangurSemnopithecusentelluscomprised
Leopard Panthera pcirdus usually catch the kill when it is 97.6% of the biomass killed by Tigers. In contrast, I have
largeenoughtoaffordmorethanonemeal(Johnsingh 1983). foundthatthe SpottedDeeralonewas 80.1% ofthebiomass
It has been reported that Tigers prefer to hunt larger consumed by Tigers in the Sundarbans.
prey species (>176 kg), especially when there are other
carnivoreslikeLeopardsandAsiaticWildDogsCuonalpinus Non-food items in scats
in the same habitat (Schaller 1972; Karanth and Sunquist Otherthantypicalfooditems, soilandsungrassblades
1995, 2000; Bagchi et al. 2003). In the Sundarbans, Tigers have been reported in Tiger scat samples (Powell 1957;
mainlyhuntthelargestavailablepreyspecies,i.e.,theSpotted Schaller 1967; Johnsingh 1983; Reza et al. 2001). During
Deer, despite the fact that there is no Leopardoverthere. thisstudy, soil wasfoundinlargequantities(morethan 50%
%
Rezaetal. (2001) reported that in the Sundarbans East ofthevolume)in51 ofthescatsamples,whichisthehighest
WS
the average percentage by weight ofSpotted Deer, Wild proportion of soil-containing scats ever reported. Schaller
Boarand RhesusMacaquehair, and unidentifiedanimalparts (1967)reportedthatscatswithsoilandgrass(morethan50%
andsolublematerialwere69, 15,5,4and6,respectively.Their of the volume) represented 3.8% and 2.3% of all types of
methods were questionable, because the weight, size and items eaten byTigers in Kanha, India. He foundmost ofthe
densityofhairsofthesethreespecieswerenotuniform.Hence, soil-containing scats during October-December, i.e., early
therelative weights ofhairsamplesin scatsdonotaccurately winter, and suggested a seasonal incidence of soil-eating.
representeitherrelativebiomassorrelativenumbersofdifferent A similartrend was found in this study, in which more than
prey speciesconsumed.They have found the mean weightof 80% ofthe soil-containing (more than 50% ofthe volume)
scatas 122gmandtheSpottedDeerastheprincipalprey,which scats were found in winter (October-March), with the peak
wasgenerally the same as in thisstudy. inNovember-December(c. 15%).InBandipur,India,Johnsingh
AccordingtoTamang 1993), the principal prey ofthe (1983)foundthatoutof36scats,threecontained soilandtwo
(
TigerintheSundarbansareSpottedDeerandWildBoar,but contained grass (more than 50% of the volume). Reza et al.
Tigers are opportunist feeders and there are records of (2001) mentioned the occurrenceofan average 6% weightof
predation of Rhesus Macaque, Barking Deer Muntiacus scatscomposedofsoilintheSundarbans,butinthisstudy,soil
muntjak, otters, small carnivores, birds (mainly Red wasfoundtoconstitutemorethanhalfofthevolumeof51%of
Junglefowl),lizards(Varanusspp.),otherreptiles,frogs,fish, scat samples. This meansthat the percentage ofweightofsoil
crabs,andoccasionallyhumans. Myfindingsgenerallyagree was definitely much higher than 6%. Other than soil, I have
with this. found significant amount ofsungrass blades in one scat. The
In India, the SpottedDeeristhe main prey ofthe tiger ingestion ofsoil and sungrass blades byTigers is probably to
inKanha,BandipurandNagarhole(Schaller 1967;Johnsingh meetmineralrequirements,forbetterdigestionand/ortoscour
1983; Karanth and Sunquist 1995), but it is the second or thedigestivesystemforinternalparasites.InKanha,India,one
third main prey in Ranthambhore, Panna and Melghat grass-blade-richTigerscathadatapeworm(Schaller 1967).
Table 5: Age ofSpotted Deer kills based on observation of kills
and on the eruption ofteeth inthe lowerjaw Table 6: Condition of Spotted Deerkills
Age based on kills Age based on eruption ofteeth Condition
Class No. % Class No. % Class No. %
Adult 26 56.5 Adult 26 76.5 Good 52 78.8
Yearling 11 23.9 Yearling 6 17.6 Moderate 14 21.2
Fawn 9 19.6 Fawn 2 5.9 Bad 0 0
260 J. Bombay Nat. Hist. Soc., 105 (3), Sep-Dec 2008
PREY SELECTION BYTIGERS IN THE SUNDARBANS EASTWILDLIFE SANCTUARY
Prey abundanceversus prey selection Although the Water Monitor was common, it has been
In Nagarhole, India, Karanth and Sunquist (1995) identified as a non-used species (there was no trace of it in
studied prey selection by Tiger, Leopard and Asiatic Wild scats) probably because of its smaller size and aquatic
Dog. They concluded that all three predators selected prey habitation, and like most mammalian species. Tigers might
species non-randomly, which was mainly based on the prey be reluctant to hunt such areptile.
sizeandencounterprobability. IntheSundarbans,Ihavealso
foundthatTigersnon-randomlyselectedthepreyspeciesand Selectivityforageclasses
thelargestandcommonestavailableungulate(SpottedDeer) Predators may preferentially select substandard
forms the bulk ofthe diet. (juvenilesandyoung)animals,becausetheyarelessadapted
In Bandipur, India,Tiger scat and kill data reveal that toescape(Homocker 1970;Mech 1970;Schaller 1972;Curio
proportionately fewer Spotted Deer were killed than were 1976; Vitale 1989). Karanth and Sunquist (1995), and
present in the population (Johnsingh 1983, 1993). This can Miquelle et al. (1996) reported that although Tigers
be attributed to the anti-predator behaviour of the Spotted predominantlykilladultprey,theyoungorsubstandardprey
Deer,whichassembleinopenareastospendthenight,where is killed in relatively high proportions.
they are relatively less vulnerable to Tiger predation. The In mystudy mostoftheTigerkillswereadultanimals,
Spotted Deer was virtually the only large prey in the whichdonotagreewiththeabove-mentionedfindings.There
Sundarbans,soitisdifficulttocomparemyconclusionswith wasnotendencytopreferyoungorsubstandardprey,probably
thoseofJohnsingh(1983, 1993).Ingeneral,preysizetogether becauseitmaynotbe ‘profitable’ tohuntyoungSpottedDeer
with the abundance is the most important factordriving the instead ofthe adult because ofsize. The adult Spotted Deer
prey consumption. However, there are many other factors is not too big to pose any challenge to the Tiger and in the
that might be involved in Tiger predation, such as anti- Sundarbans there is enough cover for the Tiger to ambush.
predatorbehaviour, detectability, and ‘profitability’ in terms My findings from Tigerkills and theirjaws, however, could
ofenergy gain. be adult-biased, because young and juvenile animals are
Basedonpreyselectivityincomparisontoabundance, smaller and they are more commonly eaten completely by
theindexofselectivityofthesixpotentialpreyspeciesinthe predators (Schaller 1967; Sunquist 1981; Johnsingh et al.
WS
SundarbansEast identifiedWildBoarandLesserAdjutant 1991). Moreover, the kill detectability by the researcher is
as the two highest-ranking species. These two species, normally large-animal-biased (Ruggiero 1991).
however,contributelittleinbiomassabundanceandbiomass
ACKNOWLEDGEMENTS
consumed by Tigers in the Sundarbans, so highest-ranking
species should not be confused with commonly-preyed
species.SincebothWildBoarandLesserAdjutantarelargely I gratefully acknowledge Dr. David J. Chivers forthe
WWF
solitary, they are more vulnerable to Tiger predation. supervision, and Commonwealth Scholarship (UK),
Accordingto van Orsdol (1981), Lion Panthera leohunting Prince Bernhard Scholarship for Nature Conservation
successvaried withthe sizeofprey group; single andpaired (Switzerland), and Cambridge Commonwealth Trust (UK)
prey were more easily caught than those in larger groups. for the financial support, which made this study successful.
Moreover, Tigers probably preferred Wild Boar and Lesser Also, thanks to Bangladesh Forest Department for giving
Adjutant as a change in common prey item (Spotted Deer). permission and providing local support.
REFERENCES
Abramov, V.K. (1962): On the biology ofthe Amur Tiger, Panthera Bagchi,S.,S.P.Goyal&K. Sankar(2003): Preyabundanceandprey
tigris longipilis, Fitzinger, 1868. Acta Societatis Zoologicae selectionbyTigers(Pantheratigris)inasemi-arid,drydeciduous
Bohemoslovenicae26: 189-202. forestin westernIndia.JournalofZoology260(3): 285-290.
Ackerman,B.B.,F.GLindzey&T.RHemker(1984):Cougarfoodhabits Ballard, W.B., GM. Matson & PR. Krausman (1995): Comparison
in southern Utah. JournalofWildlifeManagement48: 147-155. oftwomethodstoagegraywolfteeth.Occasionalpublicationno.
Amerasinghe, F.R (1983): The structure and identification ofthe hair 35.Pp.455-460. In:Carbyn,L.N.,S.H.Fritts& D.R. Seip(Eds):
of the mammals of Sri Lanka. Ceylon Journal ofScience Ecology and Conservation of Wolves in a Changing World.
(BiologicalScience) 16: 76-125. Canadian Circumpolar Institute, Canada.
Ashby, K.R. & C. Santiapillai (1986): The life expectancy of wild Berger, J., B. Stacey-Peter, L. Bellis & M.P. Johnson (2001): A
artiodactyleherbivores.WaterBuffalo(Bubalusbubalis),Sambar mammalian predator-prey imbalance: grizzly bear and wolf
(Cervus unicolor). Spotted Deer (Axis axis), and Wild Pig (Sus extinction affect avian Neotropical migrants. Ecological
scrofa),inRuhunaNationalPark,SriLanka,andtheconsequences Applications 11: 947-960.
formanagement. Tigerpaper13(2): 1-7. Charnov, E.L. (1976): Optimal foraging: the marginalvaluetheorem.
J. Bombay Nat. Hist. Soc., 105 (3), Sep-Dec 2008 261
. .
PREYSELECTION BYTIGERS IN THE SUNDARBANS EASTWILDLIFE SANCTUARY
TheoreticalPopulation Biology9: 129-136. JournalofWildlifeManagement62: 674-682.
Clltton-Brock,T.H.&RH.Harvey(1983):Thefunctionalsignificance MacArthur,R.H.&E.R.Pianka(1966):Ontheoptimaluseofapatchy
of variation in body size among mammals. Special publication environment.AmericanNaturalist100: 603-609.
no. 7. Pp. 632-658. In: Eisenberg, J.F. & D.G. Kleiman (Eds): Mech,L.D.(1970):TheWolf:ecologyandbehaviourofanendangered
Advances in the Study of Mammalian Behaviour. American species. TheNatural HistoryPress,NewYork,USA.428pp.
SocietyofMammalogists, Kansas, USA. Miquelle, D.G., E.N. Smirnov, H.B. Quigley, M.G. Hornocker,
Curio, E. (1976): Ethology of Predation. Springer-Verlag, Berlin, I.GNikolaev&E.N.Matyushkin(1996):FoodhabitsofAmurTigers
Germany. inSikhote-AlinZapovednikandtheRussianFarEast,andimplications
Emmons, L.H. (1987): Comparative feeding ecology of felids in a forconservation.JournalofWildlifeResearch 1(2): 138-147.
Neotropicalrainforest.BehaviouralEcologyandSociobiology20: Mukherjee, S., S.P. Goyal & R. Chellam (1994): Standardisation of
271-283. scat analysis technique for Leopards (Panthera pardus) in Gir
Floyd,T.J.,L.D.Mech&PJ.Jordan(1978):Relatingwolfscatcontents National Park,Western India. Mammalia58: 139-143.
topreyconsumed.JournalofWildlifeManagement42: 528-532. Okarma, H., W. Jedrzejewski, K. Schmidt, R. Kowalczyk &
Gogate, N. & R.S. Chundawat(1997): Ecology ofTiger: to enable a B.Jedrzejewska(1997):PredationofEurasianLynxonRoeDeer
realistic projection of the requirements needed to maintain a and Red Deer in Bialowieza Primeval Forest, Poland. Acta
demographically viable population of tigers in India. Second Theriologica42: 203-224.
ProgressReportto-SaveTheTigerFund,Washington,DC,USA. Panwar, H.S. (1990): Tiger’s food in Kanha National Park. W1I
Hornocker,M.G.(1970):AnanalysisofMountainLionpredationupon Newsletter5(1): 12-15.
Mule Deer and Elk in the Idaho Primitive Area. Wildlife Powell,A. (1957): CalloftheTiger. London,UK. 199pp.
Monograph21: 1-29. Prater, S.H. (1971): The Book of Indian Animals. Bombay Natural
Johnsingh,A.J.T.(1983):Largemammalianprey-predatorsinBandipur. History Society and Oxford University Press, Bombay, India.
J. BombayNat. Hist. Soc. 80: 1-57. 324pp.
Johnsingh, A.J.T. (1993) Prey selection in three large sympatric Putman,R.J. (1984): Factsfromfaeces. MammalReview 14: 79-97
carnivoresin Bandipur. Mammalia56(4): 517-526. Rabinowitz,A.R. (1989): Thedensity andbehaviouroflargecatsin a
Johnsingh,A.J.T.,H.S. Panwar&W.A. Rodgers(1991): Ecologyand drytropicalforestmosaicinHuaiKhaKhaengWildlifeSanctuary,
conservationoflargefelidsinIndia.Pp. 160-166.In:Proceedings Thailand. Natural History Bulletin ofthe Siam Society 37(2):
of the International Symposium on Wildlife Conservation, 235-251.
21-25August 1990.TsukubaandYokohama,Japan. Ramakrishnan, U., R.G. Coss & N.W. Pelkey (1999): Tiger decline
Julliot, C. (1996): Fruit choice by Red Howler Monkeys (Alouatta caused by the reduction oflarge ungulate prey: evidence from a
seniculus) in a tropical rain forest. American Journal of studyofLeoparddietsinsouthernIndia.BiologicalConservation
Primatology40: 261-282. 89(2): 113-120.
Karanth,K.U.& M.E. Sunquist(1992): Populationstructure,density Reynolds,J.C.&N.J.Aebischer(1991):Comparisonandquantification
andbiomassoflargeherbivoresinthetropicalforestsofNagarhole, of carnivore diet by faecal analysis: a critique, with
India.JournalofTropicalEcology8: 21-35. recommendations, based on a study of the Fox Vulpes vulpes.
Karanth, K.U. & M.E. Sunquist (1995): Prey selection by Tiger, MammalReview21: 97-122.
LeopardandDholeintropicalforests.JournalofAnimalEcology Reza, A.H.M.A., M.M. Feeroz & M.A. Islam (2001): Food habits of
64: 439-450. the Bengal Tiger (Panthera tigris tigris) in the Sundarbans.
Karanth, K.U. & M.E. Sunquist (2000): Behavioural correlates of BangladeshJournalofZoology29(2): 173-179.
predationbyTiger(Panthera tigris), Leopard(Pantherapardus) Rlney,T.(1982):StudyandManagementofLargeMammals.JohnWiley
andDhole(Cuonalpinus)inNagarhole,India.JournalofZoology & SonsLtd,NewYork,USA.
London250: 255-265. Ruggiero. R.G. (1991): PreyselectionoftheLion(PantheraleoL.)in
Khan, M.M.H. (2004): Ecology andconservationofthe BengalTiger the Manavo-Gounda-St Floris National Park, Central African
in the Sundarbans mangrove forest of Bangladesh. Ph.D. Republic.Mammalia55: 24-33.
dissertation. UniversityofCambridge,Cambridge,UK. 297 pp. Schaller,G.B. (1967):TheDeerandtheTiger.UniversityofChicago
Khorozyan, I. & A. Malkhasyan (2002): Ecology of the Leopard Press,Chicago, USA. 370pp.
Pantherapardus)inKhosrovReserve,Armenia:implicationsfor Schaller, G.B. (1972): The Serengeti Lion: a study ofpredator-prey
(
conservation. Societa Zoologica ‘La Torbiera’, Italy. Scientific relations. UniversityofChicagoPress,Chicago,USA. 504pp.
report6: 1-41 Scheel, D. (1993): Profitability, encounter rates, and prey choice of
Kitsos, A.J., M.J. Hunter, J.H. Sabnis & A. Mehta (1995): A guide AfricanLions. BehaviouralEcology4: 90-97.
to the identificationofsome Indian mammal hairs. Pp. 125-130. Schoener,T.W.(1971):Theoryoffeedingstrategies.AnnualReviewof
In: Berwick, S.H. & V.B. Saharia (Eds): The Development of theEcologicalSystem2: 369-404.
International Principles and Practices ofWildlife Research and Sinclair,A.R.E.& P. Duncan(1972): Indicesofconditionsintropical
Management,AsianandAmericanApproaches.OxfordUniversity ruminants.EastAfrican WildlifeJournal 10: 143-149.
Press, New Delhi,India. Smuts, GL. (1978): Interrelations between predators, prey, and their
Koppikar, B.R. & J.H. Sabnis (1976): Identification ofhairs ofsome environment. BioScience28(5): 316-320.
Indian mammals.J. BombayNat. Hist. Soc. 73: 5-20, 74: 50-59. Sourd,C. (1983): Etudedes modesd’exploitationdesresourcesfruit-
Koppikar,B.R.&J.H.Sabnis(1979):Faecalhairremainsserveasevidence ieres par Cercopithecus cephus au cours d’un cycle annuel (in
for determination of food habit of Tiger. Paper presented at French).[StudyofexploitationoffoodresourcesforCercopithecus
InternationalSymposiumonTiger(ISOT),NewDelhi,India. 10pp. cephus]Thirdcyclethesis.University ofRennes,Rennes.
Korschgen, L.J. (1971): Procedures for food-habits analysis. Stephens, D.W. & J.R. Krebs (1987): Foraging Theory. Princeton
Pp. 233-258. In: Giles, R.H. (Ed.): Wildlife Management University Press, Princeton. 262 pp.
Technique, 3rdedn.TheWildlife Society, London, UK. Sunquist,M.E.(1981): SocialorganizationofTigers(Pantheratigris)
Landon, D.B., C.A. Waite, R.O. Peterson & L.D. Mech (1998): inRoyalChitwanNationalPark,Nepal.SmithsonianContribution
Evaluation of age determination techniques for gray wolves. toZoology336: 1-98.
262 J. Bombay Nat. Hist. Soc., 105 (3), Sep-Dec 2008
PREY SELECTION BYTIGERS IN THE SUNDARBANS EASTWILDLIFE SANCTUARY
Sunquist, M.E., K.U. Karanth & F.C. Sunquist (1999): Ecology, Terborgh,J.,L.Lopez,P.Nunez,M.Rao,G.Shahabudin,G.Orihuela,
behaviourandresilienceoftheTigeranditsconservationneeds. M.Riveros,R.Ascanio,G.H. Adler,T.D.Lambert&L.Balbas
Pp. 5-18. In: Seidensticker, J., S. Christie & P. Jackson (Eds): (2002): Ecological meltdown in predator-free forest fragments.
Riding the Tiger: tiger conservation in human-dominated Science 294: 1,923.
landscapes. CambridgeUniversity Press, Cambridge, UK. van Lavieren, L.P. (1983): Wildlife management in the Tropics
Sunquist, M.E. & F.C. Sunquist (1989): Ecological constraints on with special emphasis on South East Asia (report), part 2.
predationbylargefelids. Pp. 283-301.In: Gittleman,J.L. (Ed.): School of Environmental Conservation Management, Bogor.
CarnivoreBehaviour,EcologyandEvolution,CornellUniversity 75 pp.
Press, Ithaca. vanOrsdol, K.G. (1981): Lionpredationin RwenzoriNationalPark,
Tamang, K.M.(1993):WildlifemanagementplanfortheSundarbans Uganda.Ph.D.dissertation.UniversityofCambridge,Cambridge,
reservedforest. ReportoftheFAO/UNDPproject(no. BGD/84/ UK.
056), Dhaka, Bangladesh. 113 pp. Vitale, A.F. (1989): Changes in the anti-predator responses ofwild
Terborgh,J. (1999): RequiemforNature. Island Press,Washington, rabbits, Oryctolagus cuniculus (L.) with age and experience.
DC,USA. 246pp. Behaviour110: 47-61.
J. Bombay Nat. Hist. Soc., 105 (3), Sep-Dec 2008 263