LANCASTER, J.R.*; ESPINOZA, R.E.; California State Univ., Northridge: What good is grouping for geckos? Testing the benefits of aggregation in Coleonyx variegatus

Social aggregations have been studied in a variety of animals and found to have important social, ecological, and fitness implications. Several species of nocturnal geckos form diurnal aggregations; however, few studies have attempted to determine the benefits or mechanistic basis of these groupings. The objectives of my study were to identify why banded geckos (Coleonyx variegatus) aggregate during periods of inactivity, and test the potential benefits of aggregation. I tested two hypotheses proposed to explain why geckos aggregate�conspecific attraction and predator avoidance�by investigating the role of chemical cues in retreat-site selection. To assess the role of conspecifics in aggregation, groups of geckos were presented with a surplus of shelters to test whether diurnal aggregation is socially mediated or results from a rarity of suitable shelters. To investigate whether grouping provides a predator-avoidance benefit, groups of geckos were introduced to arenas with a surplus of retreats either with or without predator scent. Geckos may also benefit from grouping by reducing their effective surface-area-to-volume ratio, thus reducing evaporative water loss (EWL). I compared EWL rates of geckos when alone vs. in groups. Geckos exhibited no preference for shelters scented by conspecifics, but avoided predator-scented shelters. Geckos grouped with conspecifics in an unscented arena, but did not group when the arena contained predator scent. No difference was found in EWL rates of geckos alone vs. in groups. These results suggest that geckos do not group to avoid predators, but additional studies are needed to test the benefits of grouping on EWL and social interactions. Determining why geckos group may shed light on the evolution of sociality in other animals.