Environmental effects on the ontogenesis of tadpole personality

Abstract

Behaviours are highly plastic phenotypic traits whose variation depends on the short-term response to external stimuli (contextual plasticity) and on the long-term response to past experiences (developmental plasticity). Despite this great flexibility, behaviours often show individual differences that are consistent across time and context (i.e. ‘animal personality’). By adopting a behavioural-reaction-norm (BRN) approach, we used a factorial common garden experiment to investigate the effects of contextual and developmental plasticity on the antipredator behaviour of treefrog tadpoles, Hyla intermedia . We raised 96 tadpoles from eight half sib–full sib families under different biotic (predation risk) and abiotic (shading) environmental conditions and described their activity and spatial behaviour in experimental arenas with either a caged predator, a caged conspecific or an empty cage. Tadpoles raised with predator cues were always less active and stayed further away from caged predators than their predator-naïve siblings. Tadpoles raised in the shade were less active than those raised in the sun. Not only was the raising environment responsible for among-individual variation but it also acted at the within-individual level by affecting behavioural repeatability, which was higher in predator-naïve than in predator-experienced tadpoles. Besides the important role of the environment, this study also shows consistent variation in BRNs with body size and time: tadpoles became more active as they got larger and their activity increased with time in the presence of caged predators, decreased in the presence of empty cages and did not change with caged conspecifics. These results suggest that the effects of past and present experiences on tadpole behaviour vary with time as a consequence of growth and development. • We investigate the environmental effects on the development of tadpole behaviour. • Tadpoles were raised under different predation risk and shady conditions. • The ontogenetic environment has strong effects on tadpole personality. • Stressful environments reduce variation in personality. • Independent of the environment, personality changes during growth and development.