Who is who? Photo-identifying cetaceans in the AHAB Project
The AHAB Project: Deep Diving Cetaceans and other species in the northern sector of the Mediterranean Cetacean Migration Corridor, with the support of the Fundación Biodiversidad, the Ministry for the Ecological Transition and the Demographic Challenge, enters the final stretch.
The main objective of this study is to obtain data that help to better understand the deep-diving cetacean species that can be found in the submarine canyons of the north of the Levantine-Balearic marine demarcation. This area is located on the northern limit of the Marine Protected Area “Mediterranean Cetacean Migration Corridor” and is adjacent to the Natura 2000 area – SCI “ESZZ16001-Western Submarine Canyons System of the Gulf of León”. Among others, the AHAB project wants to confirm the area as a relevant area for feeding and for the connectivity of these cetaceans in the corridor area with the population of the northeast of the Balearic Islands. It is hoped that the information obtained will help to carry out adequate management of these protected areas and reinforce the value of the area ” Mediterranean Cetacean Migration Corridor ” as an area of importance for cetacean species. After carrying out the maritime campaign during the months of June and July of this year in the Cap de Creus and Palamós canyons, we are now working on the analysis of the data obtained.
With around 700 kilometres travelled, and more than 140 acoustic and visual detections of cetaceans, in total 5 of the 8 species of cetaceans that can be observed in the Western Mediterranean have been recorded.
Once the data is obtained, now it is time to analyse them. Among other analyses, we are working on the photo-identification of the different observed individuals of sperm whales (Physeter macrocephalus), Risso’s dolphin (Grampus griseus), long-finned pilot whales (Globicephala melas) and Cuvier’s beaked whales (Ziphius cavirostris).
Photo-identification of cetaceans
Most species of cetaceans have natural and/or anthropogenic marks, such as scars, as well as pigmentation patterns that allow individual recognition. The photo-identification technique is a non-invasive tool for the study of cetaceans, which consists of taking photographs of different parts of the animal’s body, such as the dorsal fin, the caudal fin or other parts of the body to analyse their shape, pigmentation and the presence of these natural or anthropogenic marks and thus be able to identify the different individuals of the same species.
Thanks to this methodology we can obtain information, for example, about social structure, habitat use, demographics (survival rate, longevity, etc.) and movement patterns. It also allows making abundance estimates to know the size of the population and its trend.
The photographs to be taken are different depending on the species to be studied. In the case of dolphins, pilot whales and beaked whales, photographs are taken as perpendicular (90º) to the axis of the body as possible, since the objective is to obtain the side of the body and the dorsal fin. The silhouette, the marks and the different notches that can be observed in the dorsal fins of the individuals of these species will help us to identify the different animals.
For those species that take the tail fin or tail out of the water before submerging, such as the sperm whale, in addition to the photographs of the sides, tail photos will be taken to analyse the shape, profile, notches and other characteristics of this body part.
Once the best photographs of each individual have been selected, a catalogue is created for each species with all the identified individuals, which will be used later to compare with other animals of the same species observed on other dates or in other areas.
At this time, we have managed to photo-identify around a dozen individuals of sperm whales in the study area of the AHAB Project, and we will soon begin to compare our catalogue with the catalogue of sperm whales from other areas of the Mediterranean to study the movements of this species in our waters.
Will we find the same fin in another area? We will soon find out and we can’t wait to find out.