Behavioral asymmetries of pectoral fin use during social interactions of bottlenose dolphins (Tursiops truncatus)

Abstract

The preference for utilizing certain appendages (handedness) has been explored in a variety of vertebrate species. Similar to primates, dolphins possess hemispheres that allow an individual to present behaviorally dominant features and appendages (i.e., pectoral fins) that are utilized both as social facilitators, as well as means to interact with objects. Thus, the possibility of handedness in a captive population of 27 bottlenose dolphins (Tursiops truncatus) was explored. Dolphins in a mother-offspring relationship made significantly more pectoral fin contacts than in the absence of this relationship. No significant difference was observed between maternal siblings and non-maternal siblings in overall pectoral fin contact. Handedness indexes were calculated for 26 individuals that initiated pectoral fin contact with both conspecifics and flora (i.e., seagrass) in their habitat. No significant differences were observed between the sexes in handedness indexes; however calves displayed a significant right-fin handedness compared to both sub-adults and adults. Both sub-adults and adults showed a left-fin handedness indexes, but no significant difference in the strength of this relationship among these two age classes was observed. Individual variation in handedness indexes was also noted. These results suggest that handedness may be present in Atlantic bottlenose dolphins with regards to social contact, and a larger and more diverse sample size may provide a better understanding in why handedness may change across development.