Behavioural repertoire of high-shore littorinid snails reveals novel adaptations to an extreme environment

Species that inhabit high-shore environments on rocky shores survive prolonged periods of emersion and thermal stress. Using two Hong Kong high-shore littorinids (Echinolittorina malaccana and E. radiata) as models, we examined their behavioural repertoire to survive these variable and extreme conditions. Environmental temperatures ranged from 4 ℃ in the cool season to 55.5 ℃ in the hot season, with strong seasonal and daily fluctuations. In the hot season, both species allocated >35 % of their activity budgets to stress-mitigating thermoregulatory behaviours (e.g. standing, towering) and relatively small proportions to foraging (<20%) and reproduction (<10%). In the assumedly benign cool season, greater proportions (>70%) of activity budgets were allocated to stress mitigation behaviours (crevice occupation, aggregation formation). Both species exhibited multifunctional behaviours that optimised time use during their tidally-constrained activity window in the hot season. Fe...