Sex-based divergence in tidal, lunar and seasonal cycles of activity in the olive sea snake, Aipysurus laevis (Elapidae, Hydrophiinae)

Marine environments show strong cycles at daily (tidal), monthly (lunar) and seasonal timeframes, and the behavioural responses of marine organisms to such cycles may depend upon ecological and behavioural traits that differ between the sexes. Underwater observations of free-ranging olive sea snakes (Aipysurus laevis, Hydrophiinae, Elapidae) at a site on the southern Great Barrier Reef revealed sex-based divergences in the effects of abiotic cycles on snake activity. Female snakes were active primarily on high and rising tides that allowed access to shallow-water sites for foraging. In contrast, male snakes were active primarily on low and falling tides, especially near the time of the full moon (when tidal range is highest), conditions that may restrict a female snake’s ability to evade a courting male. Males were common on the coral-reef site during winter (the mating season), but were rarely seen during summer, whereas females remained on the reef year-round. This highly sexually dimorphic species shows strong temporal separations between the sexes in patterns of activity.