Mediterranean cetaceans constitute a unique assemblage of species found in the virtually closed basin of the Mediterranean Sea. This assemblage differs from those found in the North Atlantic or the Red Sea. In the Mediterranean, cetaceans are represented by around twenty species, but only eight of these are considered common: the Short-beaked dolphin, Common dolphin, Bottlenose dolphin, Risso's dolphin, Long-finned pilot whale, Cuvier's beaked whale, Sperm whale and Fin whale. Their distribution varies greatly from region to region, and their abundance and diversity seem to be greatest in the Corso-Liguro-Provençal basin, where cetaceans have been protected by the Pelagos Sanctuary since 2002.
Renowned for their intelligence, which in some respects is similar to that of humans, cetaceans are the focus of protection measures that are all the more important given that their slow life cycle makes them vulnerable to the many threats that affect them in the Mediterranean. Indeed, the density of human settlement and traffic in the Mediterranean basin exposes marine species, and particularly large marine mammals such as cetaceans, to numerous threats that require specific conservation measures.
Situation
Geography
The Mediterranean Sea is a quasi-enclosed sea, divided into four main basins: the Western Basin, the Adriatic Sea, the Central Mediterranean and the Eastern or Levantine Basin – each in turn subdivided into secondary seas. The Mediterranean is known as a very oligotrophic sea, i.e., low in nutrients (and even more so in the eastern basin): only two major rivers flow into it (the Rhone and the Nile), and its weak current limits the circulation of nutrients, particularly nitrates and phosphates. As a result, phytoplankton levels are low, and the pelagic ecosystem is less dense than in other oceanic regions. This explains why cetaceans, and whales in particular, are mainly found near rivers and outlets (Alboran Sea, Aegean Sea) and in areas where deep currents resurface, such as the Ligurian Sea.
Bordered by 23 Mediterranean countries with a coastal population of 150 million, the Mediterranean is the world's leading tourist destination and one of the planet's main commercial shipping lanes, handling a quarter of the world's commercial traffic and a third of its oil traffic. As a result, pollution and nuisance are high, and collisions between ships and cetaceans are commonplace.
History Cetaceans, and dolphins in particular, have been familiar to Mediterranean populations since antiquity. They are depicted in bestiaries, as well as in mythology, and appear as early as the 2nd millennium BC on the frescoes of the Minoan palace at Knossos, Crete. The philosopher Aristotle, in the 4th century B.C., devoted lengthy studies to cetaceans, establishing that they are indeed air-breathing mammals that incubate their young with a placenta before nursing them. Several other naturalists, such as Pliny the Elder, have provided very detailed descriptions and numerous anecdotes concerning these animals, attesting to their assiduous frequentation and mutual curiosity.
In particular, dolphins enjoyed a very positive image in seafaring civilizations such as the Greeks and Romans: a constellation was named after them, they were seen as cheerful companions of sailors, and it is said that they sometimes rescued shipwrecked sailors, as did the poet Arion of Methymne.
Whales, on the other hand, are less familiar to sailors and more intimidating, inspiring fear above all on account of their oversized mouths, and most mentions of them in ancient literature tell stories of devouring by the terrifying monster ketos/cetus (like Jonah in the Bible or Lucian of Samosata in his True Stories), a theme much taken up in both the Middle Ages and the Classical period and which we encounter right up to the 19th century with the story of Pinocchio.
Some archaeological data suggest that cetaceans may have been hunted and consumed during the Roman period, but this seems to have remained fairly localized, and there is no historical record of significant fishing of these animals in the Mediterranean (unlike the Atlantic, where the Basques, for example, hunted cetaceans intensively as early as the Middle Ages). Mediterranean whales are essentially rorquals ("skinny" whales): during the most intense period of industrial whaling (late 19th and early 20th centuries), right whales (cold-water whales, for their blubber) were the main target, so this activity had less impact on the Mediterranean basin. However, several species disappeared from the Mediterranean during historic times (notably the harbour porpoise and the grey whale), and it is still difficult to determine the exact causes and mechanisms leading to these disappearances.
List of species Cetaceans, from their scientific name Cetacea (from ancient Greek κῆτος / kêtos, "cetacean"), form an infra-order of aquatic mammals, classified in the order Artiodactyla, where their closest cousins are the hippopotamuses: like all mammals, they breathe air and nurse their young, despite their exclusive adaptation to the marine environment, which has notably caused them to lose most of their hair and their hind limbs. In 2020, some 86 cetacean species were known worldwide, a number of which are endemic to freshwater or polar waters. These highly charismatic mammals are reputed to have remarkable intelligence, which contributes to their popular success and hence to the desire to protect them.
Twenty cetacean species have been officially recorded in the Mediterranean (and as many as twenty-four counting old or doubtful records), but only eighteen are part of the stable population, of which only eight are considered common: Striped dolphin (Stenella coeruleoalba), Short-beaked common dolphin (Delphinus delphis), Bottlenose dolphin (Tursiops truncatus), Risso's dolphin (Grampus griseus), pilot whale (Globicephala melas), Cuvier's beaked whale (Ziphius cavirostris), sperm whale (Physeter macrocephalus) and fin whale (Balaenoptera physalus). Their distribution is highly heterogeneous from region to region, depending in particular on nutrient load and depth, with, for example, cetaceans that are rare in the Adriatic and abundant in the Ligurian and Alboran Seas.
Today's Mediterranean cetacean population is the result of a constantly evolving history. Some species, such as the harbour porpoise, disappeared in historical times due to human influence, while others, such as the Indian Ocean humpback dolphin (Sousa plumbea), could colonize the area thanks to the Suez Canal. On larger time scales, many other species that are now extinct or exiled have inhabited this basin, with significant changes in response to geological changes such as the Messinian salinity crisis.
Mysticetes (baleen whales)
Fin whale (Balaenoptera physalus)
The fin whale (Balaenoptera physalus) is the only baleen whale species with a significant resident population in the Mediterranean, mainly located in the northern half of the western basin, between Spain, France and Italy. It is the second largest animal on our planet after the Blue whale (B. musculus), reaching 22 m in length and weighing 70 tonnes. In the Mediterranean, it feeds almost exclusively on Meganyctiphanes norvegica, the Mediterranean krill.
They are found singly or in small groups, mainly offshore and especially in the western Mediterranean, where they do not go beyond Crete. A large proportion of individuals migrate to the Ligurian Sea in summer and return south and east in winter. The Mediterranean population is estimated at between 1,500 and 2,000 individuals, including 650 in the Pelagos Sanctuary, and appears to be only weakly connected to the Atlantic population.
The fin whale is classified as "vulnerable" on the IUCN Red List.
Minke whale (Balaenoptera acutorostrata)
The Minke whale (Balaenoptera acutorostrata), also known as the Minke Whale, is a small whale (7 to 9 m) with a pointed, keeled snout. It's a curious species that likes to spend its time on the coast.
This species is rare in the Mediterranean (mainly reported in the western half, very sporadically), and its presence may be largely due to incursions of specimens from the Atlantic, where it is abundant. However, it seems to be observed at least once a year on average in the Mediterranean, and particularly in France east of the Rhône, and especially in the Pelagos Sanctuary.
Sei whale (Balaenoptera borealis) The sei whale, or Rudolph's whale (Balaenoptera borealis), lives mainly in the North Atlantic and avoids enclosed seas, but occasionally makes incursions into the Mediterranean, although this is considered exceptional and restricted to Spain and France.
The sei whale is classified as "endangered" on the IUCN Red List.
Humpback whale (Megaptera novaeangliae) The humpback whale (Megaptera novaeangliae), also known as the Jubarte or Megaptera, is a migratory whale related to the rorquals, considered very rare in the Mediterranean, where its presence is probably due to occasional incursions of Atlantic specimens, mainly in the north of the western basin. However, it seems to be observed at least once a year on average, and this figure may be rising.
Grey whale (Eschrichtius robustus) The gray whale (Eschrichtius robustus) is a species of whale related to the rorqual whales that has been eradicated from the Atlantic by fishing, and now survives only in the North Pacific. Nevertheless, adventurous or stray individuals occasionally reach the Atlantic Ocean, and some have been observed as far south as the Mediterranean, where conditions do not seem to allow their survival. However, this remains exceptional and generally concerns disoriented, sick or dying individuals, of whom only two have been identified with any certainty in the 21st century (in 2010 and in 2021).
Archaeological evidence suggests that the Spanish and Catalan coasts of the Mediterranean were home to a resident population of grey whales in Roman times.
Odontocetes (dolphins, killer whales and toothed whales)
Delphinidae (dolphins and orcas)
Blue and white (striped) dolphin (Stenella coeruleoalba) The Striped dolphin (Stenella coeruleoalba) is one of the most common dolphin species in the Mediterranean: ships encounter an average of one every 4 km (or rather a group of ten every 39 km).
It's a small dolphin, measuring around 2 m and weighing 80 to 100 kg, and feeds on fish and squid. They tend to live offshore (45 km from the coast on average), in groups of ten to thirty individuals, sometimes more, throughout most of the Mediterranean basin, with the exception of the Aegean Sea. They often like to be "pushed" by the bows of boats, which is one of the most frequent modes of encounter. This dolphin is absent from the Black Sea.
Short-beaked common dolphin (Delphinus delphis)
The short-beaked common dolphin (Delphinus delphis) is a small species, no more than 2 m long. It can be recognized by its hourglass lateral pattern, with a buffy-beige, almost yellow anterior zone and a bluish-gray posterior zone; the back is dark gray and the belly light. The rostrum is tapered, with a narrow melon, and the dorsal fin is high. It is found in medium-sized bands (ten to fifty individuals), both offshore and inshore. Its diet is varied and opportunistic, with a preference for small oily fish such as anchovies and sardines. It's a very sociable dolphin, enjoying the company of boats, especially sailboats.
Its distribution is very uneven: it is rare in the western basin (virtually absent from the French-Mediterranean coast),) and more common in the southern and eastern Mediterranean, particularly in Greece; it is particularly abundant in the Black Sea, where it replaces the Blue and White Dolphin (no doubt due to the relative absence of squid) and is sometimes considered a subspecies (Delphinus delphis ponticus).
Bottlenose dolphin (Tursiops truncatus)