Eight different species of whales and dolphins live in the Pelagos Sanctuary in the north-western Mediterranean

Striped dolphins, sperm whales, fin whales and bottlenose dolphins are the most common marine mammals

sperm whale (Physeter macrocephalus)

Sperm whale (Physeter catodon)

The spermwhale is the largest of the toothed whales. It has a disproportionately large head and typically wrinkled skin. Individuals in the Sanctuary are almost exclusively males, females and calves living further south in the Mediterranean.

In our study area they are mostly sighted over the continental slope, i.e. 5-10 nautical miles off the coast. They perform very long dives, up to 2 hours, and can easily be acoustically detected by means of a hydrophone.

fin whale (Balaenoptera physalus)

Fin whale (Balaenoptera physalus)

The fin whale is the only mysticete living in the Mediterranean, and the second largest species on the planet, right after the blue whale. Females are up to 24 meter long, males somewhat smaller.

In the Ligurian Sea they are almost exclusively sighted over deep waters. Being rich in krill (Meganyctiphanes norvegica), the Sanctuary is the only known fin whales’ summer feeding ground in the Mediterranean.

Risso's dolphins (Grampus griseus)

Risso’s Dolphin (Grampus griseus)

Risso’s dolphins are usually sighted a few miles from the coast in small to medium sized groups. They have slightly bulging foreheads and distinctive scratches and scars over their bodies. Therefore body colour tends to lighten with age. Lenght of adults is around 3,5 meters.

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striped dolphin (Stenella coeruleoalba)

Striped dolphins (Stenella coeruleoalba)

Striped dolphins are the most commonly sighted cetaceans in the study area. Apparently they like bowriding in front of the boat and usually they travel in medium to large groups. Adults are about 2 meters long.

pilot whale (Globicephala melas)

Long-finned pilot whales (Globicephala melas)

Pilot whales are large dolphins and are unmistakable because of their large rounded, black forehead and their low, broad-based dorsal fin. They typically live over high seas in large pods, but they are relatively rare in the study area.

Cuvier's beaked whale (Ziphius cavirostris)

Cuvier’s beaked whales (Ziphius cavirostris)

Also rather rare, and shy, Cuvier’s beaked whales are deep divers, up to 6 meters long. Individuals vary in colour, from white to reddish, often with scars over their body. They are usually spotted alone or in small groups.

bottlenose dolphin (Tursiops truncatus)

Bottlenose dolphins (Tursiops truncatus)

Common bottlenose dolphins are somewhat larger than striped dolphins (3-4 meters), grey, with a robust head and body. Although an offshore form exists, in the Sanctuary they are encountered mostly inshore, like near Corsica or in the eastern part of the area.

Common dolphin (Delphinus delphis)

Common dolphins (Delphinus delphis)

Short-beaked common dolphins were once actually common in the Mediterranean, but are now very rare. In the Sanctuary they are sometimes spotted together with striped dolphins. In respect to the latter they can be told apart by the distinctive hourglass pattern of white, grey and yellow on thier sides. Size is similar to striped dolphins’.

The research methods

The complexity and variety of the questions investigated by this study require a multidisciplinary approach, thus entailing the use of a wide range of techniques.

  • Visual and acoustic surveys are conducted on a daily basis. Position, movements of whales and dolphins, as well as their group size and composition are recorded during the sightings. Large marine animals other than cetaceans, including sea turtles, tunas, devil rays, swordfish and seabirds, are also monitored. All data regarding the navigation and the environment are recorded on a regular basis.

  • Human activities which are a possible threat to whales and dolphins are also monitored, especially counting watercraft and fishing gear detected from the ship. Although the acoustic pollution is recorded by means of a towed hydrophone array.

  • Photo-identification enables researchers to recognize individual animals by taking pictures of their natural, long-lasting morphological features like the shape of the dorsal fin or scars on their body. This technique provides population estimates and crucial information on cetaceans’ distribution, habitat use, social structure, seasonal presence, movements and association patterns.

  • Vocalizations and acoustic data are used to detect and follow the animals by means of a towed hydrophone array. Recordings of the cetaceans’ sounds are regularly collected. These data can be used to improve  knowledge of behaviour, ecology, abundance and distribution. The simultaneous collection of behavioural data is aimed at assessing the functional meaning of the animals’ sounds.

  • Behavioural studies and respiration patterns, collected according to a dedicated protocol, enable researchers to gain important information about different aspects of the animals’ biology and about their interactions with human activities.

  • Skin swabbing:  cells  are collected from some dolphins by touching them with a special sponge on top of a pole. By subsequently analyzing DNA, genetic variability of the population, individual gender, population inbreeding, kinship patterns, and social structure can  be assessed. Skin and blubber samples have been remotely collected in the past from fin whales. Blubber samples were used to determine concentrations of man-made contaminants, like polychlorobiphenils (PCBs).

  • Photogrammetry: sperm whales’ length can be estimated in the wild through a photogrammetric technique. It entails taking an identification photograph of the fluke while simultaneously measuring the distance to the animal through a laser range-finder. The animals’ length is then calculated from the proportion of the fluke span to the body length.

  • Faecal sampling is occasionally performed at the water-surface with the aim to investigate feeding habits of the species. The analysis of fin whale faeces showed the almost exclusive presence of a small planktonic crustacean, the main prey species of fin whales in the Ligurian Sea; the analysis of sperm whale faeces provided the first insight into the diet for sperm whales in the Mediterranean Sea.