Aerial Photo-Identification of Sperm Whales (Physeter macrocephalus)

Photo-identification is a staple tool used in cetacean conservation studies since the 1970s to monitor individuals on a regional and ocean basin-wide scale to infer critical information about habitat use, suitability, and shifts. This technique has been extensively used on sperm whales globally since it was developed in 1982, initially using the tail fluke from deep diving whales and the dorsal fin when appropriate. From the mid 2010s onwards, the emergence of domestically available unoccupied aerial systems (drones) has reshaped how whale research can be conducted. Herein, we describe the suitability of aerial images to determine the identity of individual sperm whales (Physeter macrocephalus) using all available identifiable markings along their dorsal side to complement the use of fluke notches and dorsal fin scars photographed from the surface of the sea from boat-based platforms for photo-identification and to maximize opportunities to identify and monitor sperm whales. Drone data were gathered while flying over sperm whales in Andenes, Norway; Shetland, Scotland; Dursey Island, Ireland; and Faial and São Miguel Islands, Azores, Portugal, between 2017 and 2024, which enabled the entire dorsal surface of sperm whales to be captured and assessed. Aerial photographs and videos were used to differentiate between 336 individual sperm whales using physical characteristics. We identified the main features of sperm whales through aerial drone images, as well as their prevalence in Atlantic high latitude foraging grounds and lower latitude nursery grounds. We discuss the advantages of using aerial drone photographs to identify sperm whales in addition to traditional boat-based photo-identification.