Abundance and Breeding of the Common Skittering Frog(Euphlyctis cyanophlyctis)and Bull Frog(Hoplobatrachus tigerinus)at Rawal Lake,Islamabad,Pakistan

摘要

The population density and breeding of two frog species,i.e.,the Skittering Frog(Euphlyctis cyanophlyctis)and the Bull Frog(Hoplobatrachus tigerinus)were studied at Rawal Lake,Islamabad,Pakistan,by using visual encounter method from September 2009 to August 2010.Mean population density for the two frogs was 1.55±0.44frogs per ha,with that for the Skittering Frog being 1.09±0.33 frogs/ha and that of the Bull Frog 0.46±0.11 frog/ha,respectively.It is concluded that both frog species are explosive breeders,i.e.,their breeding activities were confi ned to the f irst showers of the monsoon season.The mean spawn weight of the Skittering Frog was 1.5 g with more than 1000eggs in each spawn,while that of the Bull Frog was 0.26 g with less than 1000 eggs in a spawn.The spawning sites of the two species were investigated in detail.Generally,no threat to their populations was observed.However,the opening of the spillway of Rawal Dam following the torrential rain destroyed the breeding sites of the frogs.It is maintained that the event did not produce any signif icant impact on their populations and breeding as the two species were quite common.