Body size and temperature interact with time of day to shape the activity pattern of an ectothermic predator

Abstract

Changes in animal behaviour are often the first response to environmental change, reflecting a shift in the balance of energetic opportunities and constraints. However, few studies have considered how the ecological consequences of global change shape behavioural patterns across diel cycles in free-ranging aquatic ectotherms. We used activity data from acoustic accelerometers with a suite of models to determine the extent to which the behaviour of an ectothermic mesopredator, Common Snook (Centropomus undecimalis), is governed by interactive effects between time of day and body size, temperature and hydrology—predictors susceptible to global change (e.g. shifting size distributions, increased metabolic needs). Models that incorporated these interactions outperformed those that considered the singular or additive effects of each driver on activity. Snook of intermediate size were most active on average, while large individuals were more active during the day. Activity declined rapidly beyond 26°C, with evidence of diurnal–nocturnal switching at temperature extremes. Collectively, we show that animal activity patterns must be interpreted through the lens of diel variation. This work contributes to a growing understanding of how the diel behaviour of wild aquatic ectotherms responds to global change. Such knowledge will enhance our ability to incorporate animal behaviour into theoretical and conservation frameworks.