Nesting in close quarters: causes and benefits of high density nesting in painted turtles

Abstract

Nesting is a costly time for female turtles, both energetically and from threat of predation. Females must ensure maximum survival of offspring for population stability and individual fitness. I observed signs of communal nesting in female Painted Turtles (Chrysemys picta). My goals were to determine; are females choosing to nest at high nest-densities, what cues do they use to select nest sites, are offspring benefitted. Using ArcGIS, I found that females nested in clusters, the location of clusters varied among years, and that nest site selection was not strongly determined by environmental characteristics. When female turtle models were placed on the nesting embankment females nested most often with the highest density of models. In ~25% of cases, nests were so clustered that eggs were deposited directly into existing nests or directly beside existing nests. Survival of clustered nests (49%) was higher than that of solitary nests (39%). In incubators, older clutches had faster incubation times, suggesting embryonic communication as a mechanism promoting hatching synchrony. We strongly suggest that female Painted Turtles choose to nest in close proximity to conspecifics, and that this clustering results in a fitness benefit.