Personality and plasticity: temporal behavioural reaction norms in a lizard, the Namibian rock agama

Behavioural traits are often plastic and can allow animals important flexibility when environmental conditions vary. However, studies of animal personality suggest that behaviour can be ‘constrained’ to certain behavioural types, leading to consistent differences between individuals. Few studies have investigated the interaction between personality traits and the need for flexibility in individuals over different, naturally occurring situations in the wild. We investigated whether free-living Namibian rock agamas, Agama planiceps, were constrained by personality types or showed behavioural plasticity when their environmental conditions changed dramatically between the dry and rainy seasons. We examined three key behaviours: risk taking as measured by flight initiation distance, time budgets focusing on time spent conspicuous and rates of signalling directed at conspecifics. Risk-taking behaviour of males showed stable between-individual differences, but no between-individual differences in plasticity, supporting previous evidence that antipredator behaviour is determined by personality in this species. Time spent conspicuous showed a response to season, and an interaction between the individual and season, suggesting that behavioural plasticity itself may be a personality trait. In contrast, signalling behaviour changed in response to season but did not vary consistently between individuals. We suggest that where there are reliable environmental cues, individual plasticity will be favoured over consistency in the relevant behaviours.