Choice of oviposition site by nicobar frog, hylarana nicobariensis (amphibia: anura)

Observation on the choice of oviposition site of Nicobar frog, Hylarana nicobariensis was conducted under both natural and laboratory conditions. It was found that H. nicobariensis is the stream breeder, and the breeding season co-incides with winter season (October – February) in Mizoram where the water became shallow and slow flowing, and the peak period of abundance is December when the water become very shallow with the minimum velocity as well as temperature. The eggs are laid in one clutch, which remains submerged and attached to a suitable substratum in water about 5 cm – 10 cm in depth, such as rocks, boulders, pebbles, aquatic plants, dead logs, even among other laid egg clutches, etc., this ensure that the eggs are not washed away by the water currents as there is no parental care in this species. Communal egg masses were observed in the same oviposition site along the rivers or streams and it is suggested that this may confer advantages because the eggs become warmer, the risk of predation is decreased and closely positioned egg masses often adhere to each other as the jelly coat absorbs water or as the water level of the pool decreases. To test the oviposition site choice trials in 23 amplecting pairs in the laboratory, the point bi-serial correlation coefficient was calculated for the successfulness of mating and the temperature under observation for the 11 pairs kept in the terrarium without any substrata. The result revealed highly negative correlation (rpbis = -.84) with the statistically probability (p>.001). It is also suggested that the availability of substratum with low temperature provided the ambient condition for laying the eggs in the terrarium.