Behavior changes the thermal experience of ectothermic organisms, resulting in physiological costs or benefits. Animals moving at the speed of environmental shifts can optimize body temperature. Animals that are slow relative to environmental fluctuations may be able to use predictable patterns, such as the two-week tidal cycle, to thermoregulate. The marine snail Nucella ostrina is common to intertidal shores throughout the northeast Pacific Ocean. N. ostrina preys upon barnacles living high on shore in areas with extensive exposure to solar warming during low tides. Consuming prey takes this snail so long it almost certainly will be exposed to low tide conditions. We hypothesized that spatiotemporal patterns of snail foraging reduce thermal risk. We tracked snail behavior in lab aquaria, field mesocosms, and natural habitat. We estimated body temperatures of snails in various microhabitats by deploying physical thermal mimics. We translated temperature into performance values by evaluating righting behavior and survival following aerial exposure. We modeled a distribution of body temperatures for a stationary snail remaining in a sun-exposed feeding area and for a snail moving between feeding areas and thermal refuges such as cracks. We then simulated projected climate change scenarios by adding uniform increases in temperature.
Results/Conclusions
Snails foraged periodically and predictably—visiting sun-exposed high shore feeding areas on the days of the two-week tidal cycle that were reliably cool. This behavior can be generalized as 4 d of foraging in high shore areas on the days with the shortest durations of midday low tides, followed by 10 d of retreat into thermal refuges. This resulted in a disproportionate amount of time snails experienced cooler temperatures than expected at random. In performance assays, snails reattached to the substrate relatively quickly in treatments 30°C and under, but mortality was high once that temperature reached 35°C. Our model showed the number of risky days above 30°C was reduced by more than 60% by migratory foraging behavior. With projected temperature increases, the number of risky days above 30°C climbed rapidly for modeled stationary snails, yet the increase was very slight for modeled migrating snails. Migration reduced snail thermal risk and increased performance. An increase in lethal events with increasing global temperatures is unlikely for N. ostrina because it isn’t present when and where temperatures are highest. This behavior confers a thermal benefit regardless of causation and suggests that animals may thermoregulate on timescales unintuitive to humans.