Survival and growth of brown frog juveniles in their dispersal away from breeding pond

摘要

The survival and growth of juveniles in Rana tempraria and R. arvalis were investigated for two years (1989-1990) using the group marking of individuals immediately after metamorphosos and their recapture within two transects of 700 m long each from a spawning pond. In 1989, the juveniles were smaller and their density was higher near the pond, while their mortality within the first 200 m from the pond was higher than in 1990. A higher survival of frogs was noted in the remaing 500 m of transects. The individuals, larger in size and leaving the pond earlier, survived better, but only at a distance of no more than 200 m from the pond on 1990 (in 1989 their density was greater). Among the juveniles leaving the pond at later dates, the larger individuals had an advantage with respect to survival for both years under investigation. The Rana arvalis juveniles who survived in 1989 were of larger size at a greater distance from the pond than those born in 1990. This compensated the smaller initial (just after completing metamorphosis) size of juveniles. The comparison of all the groups of juveniles revealeda correlation between the initial size of juveniles and the time of leaving the breeding pond and the size achieved by juveniles by the end of summer, the earlier small juveniles were equal in size to the later large ones and to medium later juveniles. As compared to Rana arvalis, the growth rates in Rana temporaria juveniles are higher which compensates their initially smaller size.