Effects of age and group size on habitat selection and activity level in rana pip jens tadpoles

Amphibian lar . va� may use both intrinsic cues such as their own age, size or developmental stage and extrms1c cues such as chemical cues and group size to make behav ioural decisions. We performed a laboratory experiment to study habitat selection and activity level of Rana pipiens tadpoles at different ages and in groups of d ifferent sizes. Two ages of tadpoles were used: early (2 weeks after hatching; Gasner stage 25) and late (8 weeks after hatching; Gasner stages 36-38). Three group sizes were used : one, two and six. Tadpoles in pairs or groups tended to be more active and to occur in the open water column more than lone tadpoles. Younger tadpoles tended to use the open water column less and to be less active than older tadpoles, but there was no effect on the use of the vegetated habitat. Our results indicate that the determinants of amphi . bian larval behaviour include responses to both intrinsic (body size, age) and extrinsic (group size) cues.