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Do dolphins have “fingerprints”?


For over three decades photo-identification is being used for the study of population size and trends of small cetacean species. Photo-identification is a method used in “Capture-Recapture” species population sampling studies, which uses tags or the special markings on the body of an animal to distinguish it from other individuals.

For dolphins, scars and marks, such as nicks and notches especially on the trailing edge of the dorsal fin, tooth-rake marks, scratches and skin lesions on the dorsal fin and back are being used to distinguish between individuals. Those attributes on each individual’s body and dorsal fin are unique for each animal, just like fingerprints are for humans.

Observations and photographs of dolphins may be taken from a variety of platforms, such as coasts, boats and airplanes. In MOm’s Northern Aegean Dolphin Project we have incorporated our 13m research vessel, which has been accommodating the organisation’s research activities for the past 25 years. With the help of our supporters, we conduct daily surveys at sea in order to spot groups of dolphins in the area of the National Marine Park of Alonissos Northern Sporades (Greece).

During the surveys, the minimum number of people on-board is not less than three; one observing the front part of the boat and the other two, focusing on the left and right side. Upon encountering a group of dolphins the teams record the time, coordinates, distance from boat, species, group size and age differences. Then the ultimate goal is to parallel the group of dolphins and take as clear and perpendicular photos of dorsal fins of all the individuals comprising the group.

Back in the computer lab, the research team has to match photos of dorsal fins to individual dolphins, create and then update a photo-identification catalogue of the species (initial cataloguing of an identified individual is called the “capturing process”, and later resightings are defined as the recaptured events) and keep a record on the recapture history of each individual. This information along with data taken on board, such as environmental covariates, expressed behavior, group size, are incorporated in specific models in order to asses population size, survival rates, recruitment numbers, movements etc.

Research focusing on the local dolphin populations, including identification of important dolphin-congregation or passage areas and the compilation of a photo-identification catalogue of individuals, will become an invaluable asset, providing both in-depth knowledge on the vulnerable ecosystem dynamics within the park and a baseline to design and implement effective conservation strategies.

If you are interested in joining our efforts for the conservation of the dolphin species, and the marine environment as a whole, in the NMPANS join the Northern Aegean Dolphin Project!

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