EGG SIZE VERSUS CLUTCH SIZE: VARIATION AND TRADE-OFF IN REPRODUCTIVE OUTPUT OF Rana dalmatina AND R. temporaria IN A POND NEAR BONN (GERMANY)

The common frog (R. temporaria) is a widespread and abundant species of woodland and agricultural landscapes in Europe and north-west Asia. In contrast, the distribution of the agile frog (R. dalmatina) is rather scattered and re- stricted mainly to deciduous and mixed forests in western, central and south-eastern Europe. Within their overlapping range, both species often breed in the same ponds. Al- though ecology of these brown frog species is well known in parts, many aspects of their biology possibly explaining niche differentiation and large and small scale distribution remain uncertain. Interspecific variation in reproductive output may be one key factor explaining local differences in their abundance and dispersal ability. Our study com- pares the reproductive output of both species in a single pond near Bonn (Germany) using data on egg size (dia- meter, egg mass), clutch size, body size, age, and body condition.