THE EFFECT OF SOCIAL INTERACTIONS ON TADPOLE ACTIVITY AND GROWTH IN THE BRITISH ANURAN AMPHIBIANS (BUFO-BUFO, B-CALAMITA, AND RANA-TEMPORARIA)

Tadpoles of different species of frogs and toads display different ten dencies to aggregate. We investigated some of the costs and benefits o f aggregating in three British species by examining their behavioural responses to the presence of conspecifics, and by monitoring the perfo rmance of tadpoles under different levels of social interaction with o ther individuals. The common toad (Bufo bufo), an aggregating species, displayed higher levels of activity than the natterjack toad (B. cala mita) and common frog (Rana temporaria), two species that form aggrega tions less frequently. Moreover, out of the three species, only B. buf o increased activity in the presence of conspecifics. In all three spe cies, increased interaction between individuals resulted in increased variation in size. However, average growth rate was affected only in B . bufo, which grew faster when raised in isolation and not interacting with other individuals. Under certain conditions intraspecific compet ition therefore seems to tie more important than social facilitation, but may lead to average size at metamorphosis being larger within the population. The consequences of intraspecific competition within aggre gations mag therefore be different for individuals and populations.