Temperature-driven plasticity in boldness, its predictability and learning in the beadlet anemone, Actinia equina

Variation in ambient temperature is for poikilothermic animals a key driver of behavioural variation because of its multiplicative effects on metabolic rate. Apart from the fundamental environmental source of behavioural variation, understanding the effects of temperature is also important in the context of predicted climate change scenarios. In particular, behavioural responses to extreme temperature fluctuation could represent maladaptive responses to rapidly changing environments. However, behavioural responses to moderate temperature fluctuations, within ranges that are routinely experienced, likely represent adaptive plasticity. Recent studies have addressed this question within an animal personality framework, which can quantify the effects of temperature regime across a range of biological levels, spanning sample mean level effects, between-individual differences (repeatability) through within-individual variation in two senses: differences in reaction norm across a temperature gradient and the effect of temperature on behavioural predictability. In this study, the effect of a moderate temperature differential (4 °C), reflecting routine ambient temperature fluctuation, on the duration of startle responses following repeated disturbance in the beadlet sea anemone, Actinia equina, was investigated. Overall, startle responses were longer at 10 °C than at 14 °C, but this effect was moderated by the number of prior observations, indicating an interaction between the environment and the rate of simple habituation learning. Underlying this sample mean effect, we found that individuals varied in how their startle responses differed between the two temperatures and, on average, behaved less predictably at the higher temperature. These effects are similar to those that have been previously observed across a greater temperature differential, indicating that behavioural responses to temperature variation may reflect adaptive responses to temperature fluctuation in A. equina . • Ambient temperature influences risk-taking behaviour in animals. • Responses to extreme temperature gradients may be maladaptive. • Boldness in sea anemones is plastic across a moderate temperature difference. • This plasticity was seen at the sample mean, between- and within-individual levels. • The effects of moderate temperature variation may be adaptive responses.