First reported observation of an apparent reproductive bottlenose x Risso’s dolphin hybrid

Abstract

1. Bottlenose dolphin photo-identification data were compiled from western Scotland to identify individuals and ultimately investigate population size, demographic parameters, spatio-temporal distribution, and movement patterns. 2. Opportunistic citizen science photographs revealed what appeared to be an adult bottlenose × Risso’s dolphin hybrid along with an apparent second-generation hybrid or back-cross calf. Both had atypically short rostra and the dorsal fin of the adult was noticeably taller than is normal for bottlenose dolphins. 3. Based on these characteristics, this case may represent a congenital rostral abnormality or the first intergeneric calf reported for this species combination, either in captivity or in the wild. 4. The previously reported presence of several putative hybrids and mixed-species sightings in the area, in combination with the tall dorsal fin, provide support for the second possibility, i.e. intergeneric hybrids. 5. Although rare, hybridization may have disproportionate conservation consequences, with population-level impacts in very small coastal populations of long-lived, slow-breeding animals.