Whale Way: a fine Physeter m. audiovisual survey

The population of sperm whales, Physeter macrocephalus, classified as “Endangered” in the Mediterranean Sea by the IUCN, is threatened by human activities, even in the Pelagos sanctuary dedicated to them. Marine traffic, the densest in the world, is one of the main threats both by: 

- noise pollution which profoundly disrupts echolocation and communication, essential to the life of this large cetacean;

- collisions, the primary source of unnatural mortality for large cetaceans: 15% of the sperm whales we observed are injured by collisions (see photo).

 

In order to reduce the threats weighing on this very small population (a few hundred individuals), the Longitude 181 association has been carrying out, since 2022, jointly with CIAN, a study program (Whaleway expeditions) aimed at determining, both the preferred areas of presence, and the impact in these areas of anthropogenic noise on sperm whale activity. The method is based on a catalog of visual and acoustic (IPI) identity cards which allows the regular recapture of identified individuals, and on 3D acoustic recordings which allow the sperm whale to be positioned in the water mass, “click by click”, during hunting dives, with a precision never before achieved to date. Not only does this study open up a better understanding of social interactions in the night of the abyss (concerted hunting), but these daily (up to 4 consecutive days), monthly and annual recaptures allow us to draw up a detailed map of individual movements (see map) and relative area fidelity. Cross-referencing with other available catalogs reveals a mean recapture rate of around 2.5.

As a result, it is possible to compare this mapping to the movements of ships, thanks to their AIS, and to measure very finely the adaptation and disturbance caused by these anthropogenic aggressions. Ultimately, the aim is to make zoning proposals in the Pelagos sanctuary to request measures to preserve sperm whales.

Ref: H. Glotin et al, (2024): Bilan d’une décennie d’observations des grands cétacés en milieu anthropisé Nord Pelagos: BOMBYX, KM3Env, et antennes mobiles JASON. Programme de recherche triennal Pelagos 2021 – 2024 CIAN - DYNI LIS CNRS - Université de Toulon. 150.

Rendell L, Frantzis A. (2016): Mediterranean Sperm Whales, Physeter macrocephalus: The Precarious State of a Lost Tribe. In: Notarbartolo Di Sciara G, Podestà M and Curry BE, editors. Mediterranean Marine Mammals Ecology and Conservation. Advances in Marine Biology, Vol 75. Oxford: Academic Press; 2016. p. 37–74.

Frantzis A, et al (2019): Shipping routes through core habitat of endangered sperm whales along the Hellenic Trench, Greece: Can we reduce collision risks? PLoS ONE 14(2): e0212016. https://doi.org/10.1371/journal.pone.0212016