Breeding Ecology of Annandale's Tree Frog Chirixalus Simus (Anura: Rhacophoridae) Near Kolkata, West Bengal

6 Pages·2001·3.8 MB·

by  Kaushik Deuti

1
BREEDING ECOLOGY OF ANNANDALE’S TREE FROG CHIRIXALUSSIMUS
(ANURA: RHACOPHORIDAE)NEARKOLKATA,WESTBENGAL
1
KaushikDeuti2
(With oneplate)
Key words: Amphibia, Chirixalussimus arboreal foam-nest, breedingecology,insolation, desiccation
,
ThebreedingecologyoftheAnnandale’streefrog(Chirixalussimus)wasstudied in a340sq. m
marsh at Rajpur, West Bengal. Theresults showed thatthe species is an earlybreeder, breeding
in thefirstmonth ofmonsoon. Mostfoam-nests are constructed on grass, in the firsttwo weeks,
6-58 cmabove standingwaterand contain 153-234 eggs. The sizeofthe foam-nestsdependson
theirposition on thegrasswherethefrogsmate. Thenestsare located 10-807cmawayfromdry
land. It has been speculated that different species ofthe genus show apreference for land over
water for constructing foam-nests.
Introduction MaterialandMethods
Chirixalus is agenus ofsmallto medium- Thestudysitewaslocatedinamarshyarea
sized Old World tree frogs (Anura: Family at Rajpur (22° 20' N, 88° 35' E), South 24
Rhacophoridae) widely distributed from Japan Parganas district, West Bengal, 6 km south of
toIndiaandisknownfromninenominalspecies Kolkata in September, 1999 (Deuti etal. 2000).
(Frost 1985). Although there are some accounts Aplotof340 sq. m(20x 17 m) wasmarked off.
on the morphology of the genus, not much is Theplothas awaterholeof24 sq. m(6x4m) in
known about the reproductive biology. Most onecomerwithgrass(Saccharumspontaneum),
Chirixalus species are believed to construct banana (Musa paradisiaca) plantations on two
arboreal foam-nests, from which tadpoles drop sides, a village road on the third and a high
into ponds and ditches soon after hatching. concreteboundarywall ofaresidentialbuilding
ChirixalusnongkhorensisofThailandandChina onthe fourth. Theplot, including the waterhole,
constructs foam-nests on the surface of pond driesupcompletelyduringsummer,andthegrass
water(DuellmanandTrueb 1986). C. idiootocus is cropped short by grazing cattle. With the
of Taiwan lays eggs on land, near the edge of advent ofmonsoon, the plot gets waterlogged,
m
water without making a foam-nest. Hatching is thegrassgrowsupto2 andflowers.Thefrogs,
apparentlystimulatedbyrainandtadpolesspend which hide in the sheaths ofthe banana plants
a typical aquatic life in ponds or rain pools during summer, arrive at the plot to feed and
(Kuramoto andWang 1987). Ecological dataon breed on the grass, constructing foam-nests.
the breeding habits of the genus Chirixalus is Throughout the monsoon, from mid-June
lacking. In this paper, I report the breeding to mid-September, the plot was visited twice a
ecology of Chirixalus simus during June to week and the number of foam-nests, their
September 2000, at a site near Kolkata, West measurements, distance from dry land, height
Bengal, India. above ground and water-level, and maximum
depth ofwater in the plotwere measured. Daily
‘AcceptedJuly,2001 atmospheric temperature, relative humidity and
25Z3o5o,lMog-iBclaolcSku,rNveeywoAflIinpdoirae,,PKraonlikaVtiagy7a0n0B0h5a3,van, rainfall data were obtained from the Alipore
WestBengal,India. meteorological station, Kolkata, andthe data on
JOURNAL, BOMBAYNATURAL HISTORYSOCIETY, 98(3), DEC.200 341
BREEDINGECOLOGYOFANNANDALE’STREEFROGCHIRIXALUSSIMUS
number offoam-nests and depth ofwater in the maculatus arrivedattheplotandstartedcalling,
plotwere tabulatedwiththe weatherparameters but no females were sighted. The first week of
(Table 1). The mating calls were recorded and July was dry, without any precipitation. From
photographs of breeding pairs and foam-nests July 9, it rained daily and by July 11, it was
taken. Theplotwas sampledeverythree daysto apparent that the monsoon had finally set in.
allow the foam-nests counted earlierto dissolve WaterstartedaccumulatingintheplotfromJuly
and let the tadpoles escape into the water. This 12. By July 14 there was 5 cm ofwater in the
preventedre-countingandmeasuringofthesame plot and the first males ofChirixalus simus had
foam-nests. Some foam-nests were collected arrived and started calling. The first females
during different times ofthe breeding season to arrived only on July 16.
determine the clutch-size. On July 17, four pendulous foam-nests
were observedonthe grass (Table 1). When the
Results waterlevelattheplotincreasedto 11 cmonJuly
22,duetosubstantialraineveryday,thebreeding
In 2000, the monsoon commenced a little activity of the frogs peaked to 34 foam-nests,
late in southern West Bengal. There was gradually decreasingtononebyAugust 18. Due
negligible rain from mid-June to mid-July, the to heavy precipitation each day, the water level
plotremaineddryandtherewas verylittle water increasedfurtherto42 cmand58 cmonJuly24
in the waterhole. Only a few individuals of and July 26 respectively. However, the number
Hoplobatrachus tigerinus were heard calling at offoam-nestsdecreasedto 11 and6,respectively.
the plot on June 22, when there was a sudden As the water level at the plot decreased during
cloud burst, producing 69 mm ofrain, but they the next two weeks to 26 cmby August 13, the
couldnotbreedas the rainwaterquickly seeped frogs constructed fewernumbers offoam-nests.
intotheground. OnJuly7,2-3 malePolypedates Afterthatas the water-leveldecreasedfurtherto
Table1
BREEDINGPATTERNOFCHIRIXALUSSIMUSATTHESTUDYPLOT
DateofObservation Maxdepth Numberof Rainfallon Max&Min.temp, Max&MinR.H.
ofwater foam-nests previousday onpreviousday onpreviousday
(cm) (mm) (°C) (%)
14.07.2000(firstfrogarrived) 5 0 16.0 32.2-25.9 97-75
17.07.2000 6 4 11.1 32.8-27.0 97-73
19.07.2000 8 9 34.6 27.1-24.9 98-74
22.07.2000 11 34 25.7 27.0-26.4 98-85
24.07.2000 42 11 62.8 27.4-24.9 98-76
26.07.2000 58 6 12.4 29.9-25.4 97-76
29.07.2000 39 3 7.0 32.3-26.0 98-69
02.08.2000 33 2 13.0 32.5-25.2 97-75
07.08.2000 28 1 31.7 34.3-27.9 97-72
10.08.2000 30 1 11.3 32.4-27.5 94-73
13.08.2000 26 1 29.9 28.3-26.3 98-92
18.08.2000 23 0 56.3 32.9-26.2 98-79
25.08.2000(frogletsseenongrass) 15 0 0.2 34.0-27.2 94-67
30.08.2000 0 0 0.4 32.4-27.5 95-75
02.09.2000 22 0 20.5 31.8-25.3 98-70
08.09.2000 38 0 11.2 30.0-26.1 98-87
14.09.2000 13 0 0.2 32.4-26.2 97-71
342 JOURNAL, BOMBAYNATURAL HISTORYSOCIETY, 98(3), DEC 2001
BREEDINGECOLOGYOFANNANDALE'STREEFROGCHIRIXALUS SIMUS
Deuti, Kaushik: Chirixalus simus Plate 1
Fig. 2: Chirixalus simus at Rajpur, WestBengal
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BREEDINGECOLOGYOFANNANDALE'STREEFROGCHIRIXALUSSIMUS
0 cm (no standing water at all) on August 30, water (4-46 cm) at the base of the grass for
there were no more foam-nests. Tiny froglets constructionofthefoam-nests.Itwasobservedthat
(snout-ventlength: 9mm)wereseenclambering temperaturesof25-33 °Candrelativehumidityof
on to the grass on August 25, tadpoles of the 73-98% are required for breeding. The
first foam-nests had metamorphosed. In measurements ofthe foam-nests depend on then-
September, there was some more rain and the positiononthegrasswherethefrogsmateandlay
water level at the plot increased to 38 cm on eggs. The clutchsizevariedfrom 153-234 eggs.
September 8, but though other atmospheric Foam-nest construction has evolved
conditions were suitable for breeding, no more independently in five anuran families:
foam-nests were constructed. The breeding was Leptodactylidae,Myobatrachidae,Rhacophoridae,
over by mid-August, though some males were Hylidae (in a few species) and Hyperolidae (in a
still calling in the plot till mid-September. singlespecies,Opisthothylaximmaculatus).Foam
Ofthe 72 foam-nests observed, 22 were nesting species have evolved from aquatic to
measured. Lengthofthe foam-nestsvariedfrom terrestrialenvironments.Thisroutemayhavebeen
5.2-7.3 cm(X=6.06, SE=±0.15),breadthfrom throughtheevolutionofafoam-nest(Heyer 1969)
1.9-3.6 cm(X= 2.77, SE=±0.10) and thickness whosemainfunctionseemstobethatofprotecting
from 1.6-2.8 cm (X= 2.27, SE= ±0.08). The eggs and larvae againstdesiccation (Hodl 1986),
foam-nestswere constructedongrass, 17-89 cm and thermal damage as white foam reflects heat
above the land (X=48.61,_SE=±4.87) and 5-64 (Gorzula 1977). Inthe light ofthis information, I
cm above the waterlevel (X= 31.5, SE=±3.91). speculate that the construction of foam-nests in
The depth ofthe water in the plot ranged from Chirixalus has evolved mainly for protection
4-46cm(X= 17.11, SE=±2.76).Thefoam-nests against desiccation and insolation of eggs and
wereconstructed 10-807cmfromthenearestdry embryos. The route from aquatic to terrestrial
land (X= 231.9, SE= ±35.81). Six foam-nests habitats in the different species of the genus
collectedcontained 192, 164, 212, 234, 216 and Chirixalus has progressed from
153 (X= 195) eggs. C. nongkhorensis ofThailand which constructs
foam-nests on the surface of water, through
Discussion C. simus and C. dudhwaensis of India, which
construct foam-nests hanging from grass over
Fromthese observations, it is apparent that temporary water to C. vittatus ofMyanmar and
Chirixalus simus is an early breeder. Breeding Thailand,whichconstructsgelatinousfoam-nests
activity startswiththe arrivalofthemonsoonand onthesurfaceofgrassbladesgrowingattheedge
continues for about one month, but most ofthe ofwater, ultimately to C. idiootocus ofTaiwan,
breedingandfoam-nestconstructionoccurswithin which lays eggs on land near water without
thefirsttwoweeks.Thereafter, 1-2foam-nestsmay forming a foam-nest.
be constructed. The frogs exhibit sporadic rain
linkedbreeding (i.e. theybreedsporadically after Acknowledgements
heavyrains). Anurans intropicalareasbreedonly
whentherainfallissufficienttoprovideoviposition I thank Ananda Banerjee and Sayantan
sites (Duellman and Trueb 1986). In C. simus Biswas forhelp during field work, Sushil Dutta
,
some rain (11-63 mm) is required to initiate for suggestions, Indraneil Das and Pranjalendu
breeding activity, as there mustbe some standing Ray for comments on the manuscript.
JOURNAL, BOMBAYNATURAL HISTORYSOCIETY, 98(3), DEC2001 345
BREEDINGECOLOGYOFANNANDALE'STREEFROGCHIRIXALUSSIMUS
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