Novel method for identifying individual cetaceans using facial features and symmetry: A test case using dolphins

Individual identification plays a major role in our understanding of the biology, ecology and behavior in cetaceans. Being able to tell individuals apart can provide invaluable insight into basic biological and scientific questions, but is also highly relevant to science-based conservation. Given the importance of individual identification, it appears vital to improve existing identification methods and find new ones. Here, we present a novel identification method of using facial information, with common bottlenose dolphins (Tursiops truncatus) as a case study. In dolphins, dorsal fins are typically used for identification, but not all individuals or species are sufficiently marked. We show that facial features in bottlenose dolphins are long-term and consistent across the left and right sides, and may enable calves (which tend to have unmarked fins) to be re-identified after weaning, thus increasing cross-generational knowledge. This novel method can complement dorsal fin identification by helping document mark changes over time and reduce false negative or positive errors. It also shows that current identification methods can still be improved. With increasing prevalence of digital photography and computer-aided matching, it may become more viable to use 'unconventional' means of identification. We encourage other researchers to explore their photographic records for similar discoveries.