Cues for communal egg-laying in lizards (Bassiana duperreyi, Scincidae)

Animals may aggregate either because the presence of conspecifics provides information about habitat suitability, or because the presence of conspecifics directly enhances individual viability. For a female lizard, the advantage of laying her eggs in a communal nest may entail either information transfer (hatched eggshells show that the site has been successful in previous seasons) or direct physiological benefits (recently-laid eggs can enhance water availability to other eggs). We tested the relative importance of these two mechanisms in the three-lined alpine skink (Bassiana duperreyi Gray, 1838) by offering gravid females a choice between sites with hatched eggshells versus freshly-laid eggs. Females selectively oviposited beside fresh eggs. In this species, early-nesting females use information transfer (i.e. the presence of old eggshells) as a nest-site criterion, whereas later nesters switch to a reliance on direct benefits of conspecific presence (i.e. the presence of freshly-laid eggs).