The scent of a hatchling: intra-species variation in the use of chemosensory cues by neonate freshwater turtles

Abstract

Chemosensory cues transmit information about the sender's species, sex, reproductive status, health, and genetic relatedness, moderating social behaviour. Adaptations for chemosensory communication and social interactions are well studied in some vertebrate taxa but have been historically discounted in others. For example, chemosensory communication in Testudines was only recently documented, and these studies are largely limited to adults. In the present study, we test the hypothesis that hatchling freshwater turtles can identify conspecific hatchlings and close kin through chemosensory cues and we also investigate potential variation in the use of chemosensory cues among species with different habitat preferences. Hatchling of semi-aquatic species (Emydoidea blandingii and Graptemys geographica) showed no significant preference for conspecific-scented water over unscented water. However, hatchlings of a strictly aquatic species (Apalone spinifera) preferred water scented by conspecific hatchlings to unscented water, and preferred water scented by distantly-related conspecifics to water scented by close kin. Hatchlings of aquatic species may rely more on water-borne chemosensory cues than hatchlings of semi-aquatic species. This is the first evidence of kin recognition in Testudines, and provides an intriguing example of the avoidance of close kin. Increasing the chemical pollution of wetland habitats may impact the ‘chemoscape’ of turtles and other aquatic species, and this potential threat merits further investigation.