Which cetaceans live in the Mediterranean all year round?

The Mediterranean is often seen as a place of passage for large marine animals on migration. That picture is incomplete: it is also a genuine permanent home for several cetacean populations. These are resident populations, genetically distinct from their Atlantic relatives and finely adapted to the very particular conditions of this semi-enclosed basin. Seven main species live there all year round.

The seven permanent residents

The Mediterranean holds, as year-round residents, seven main species: the common bottlenose dolphin, the fin whale, the sperm whale, the striped dolphin, Risso’s dolphin, the long-finned pilot whale and Cuvier’s beaked whale (the ziphius). They are the mainstays of the basin’s cetacean fauna, each occupying a particular ecological niche.

Beyond these resident species, rarer visitors may occasionally be encountered: humpback whales in transit (very exceptional cases), killer whales passing through the Strait of Gibraltar, and even common minke whales. But these are rare sightings, whereas the seven residents can be seen all year round by sailors, by ferries and by whale watching operators.

The common bottlenose dolphin, coastal and sedentary

The common bottlenose dolphin (Tursiops truncatus) is the most visible resident. Highly sedentary, it lives in small groups along the coasts throughout the Mediterranean. Its movements are limited, generally within a radius of 80 km around its preferred area, and several clearly distinct communities have been identified by photo-identification, in particular around Corsica, the Bouches-du-Rhône, the Gulf of Lion, and around the Greek islands.

It is on the continental shelf, where the depth stays moderate, that it is most often seen. It hunts fish (sea bass, mullet, sardines) and cephalopods (squid, octopus), and sometimes takes advantage of trawler discards. Its closeness to the coast makes it particularly vulnerable to human activities: shipping traffic, pollution, bycatch in fishing gear.

The fin whale, giant of Ligurian waters

The second largest animal on the planet after the blue whale, the fin whale (Balaenoptera physalus) is the emblem of the Pelagos Sanctuary, a vast marine protected area created in 2002 by France, Italy and Monaco. At 20 to 25 metres, it frequents the deep waters of the north-western Mediterranean all year round, where it feeds mainly on krill (Meganyctiphanes norvegica).

The Mediterranean population of fin whales is genetically distinct from that of the Atlantic. Estimated at 1,500-3,000 individuals, it is isolated and particularly vulnerable. Ship strikes (fast ferries in particular) are one of its main causes of mortality, which has led to the introduction of managed shipping lanes in the Pelagos Sanctuary.

The sperm whale, diver of the canyons

A resident subpopulation of sperm whales lives in the Mediterranean, genetically separate from the Atlantic populations. It frequents the submarine canyons of the north-western Mediterranean (the Hérault canyon, the Stoechades canyon and others), where it hunts cephalopods on deep dives. Its size is estimated at fewer than 2,500 individuals, which gives it “Endangered” status on the IUCN Red List.

As with their Atlantic relatives, the females and the young stay in family groups in the central and eastern waters, while solitary males move north (Liguria, the Tyrrhenian Sea) to feed. Contamination by microplastics and PCBs is of particular concern for this isolated population.

The deep-water delphinids

The striped dolphin (Stenella coeruleoalba) is probably the most abundant cetacean in the Mediterranean, with several hundred thousand individuals. It is met in large groups (50 to 200 individuals, sometimes more) in the open sea, often near the large rorquals. It is the species seen most frequently on offshore watching trips.

Risso’s dolphin (Grampus griseus), recognisable by its grey body studded with white scars, frequents the flanks of the continental slope where it hunts cephalopods on moderately deep dives. The long-finned pilot whale (Globicephala melas), a large stocky black dolphin, lives in very stable small social units, another notable case of matrilineal society among cetaceans.

The elusive Cuvier’s beaked whale

Cuvier’s beaked whale (Ziphius cavirostris), also called the ziphius, is one of the most discreet and fascinating cetaceans of the Mediterranean. The outright champion of mammalian diving, with a record of more than 2,990 metres and breath-holds of 222 minutes, it lives in areas of great depth and remains hard to observe from the surface.

Its presence is regular in several deep Mediterranean areas: Liguria, south of the Balearics, the Tyrrhenian Sea, the Alboran Sea. It is also the species most vulnerable to military sonar; several mass strandings have been documented in the Alboran Sea and in the Canary Islands, which has led to exclusion protocols during naval exercises.

These seven species make the Mediterranean one of the richest cetacean basins in the world, a unique biological heritage, but also an extremely fragile one in the face of the human pressures accumulating on this small enclosed sea.

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