The Risso Project, started in 2000, studies the social organisation and social behaviour of Risso’s dolphin (Grampus griseus, Cuvier 1812).

The Risso’s dolphin is a poorly known species of the family of the Delphinidae. The diet of the species is mainly composed of deep water cephalopods, resulting in a distribution in deep,
offshore waters (350 - >1000 m) or over the continental shelf edge. Therefore, despite its presence world-wide in tropical and temperate waters, social structure and behavioural patterns have not yet been determined.

Reported group size ranges from 1 to several hundreds of individuals, with a mean of 10-30 animals. Some evidence of summer inshore movements and site-fidelity of individuals has been reported.

Recent research, comparing genetic material from Risso’s dolphins in UK waters and the Mediterranean Sea, has shown no evidence of exchange between these two populations, indicating little long-range dispersal between them.

The deep waters and steep slopes of the Azores form an exception to the preference for off-shore waters of Grampus griseus: the Risso’s dolphin here also inhabits the
coastal waters. Near Pico, one of the islands of the Central group, the species is usually found within 2 km from the coast and can be studied very well from both land and sea.

The Azores pose an important area for Risso’s dolphin: the species is present year-round and displays all behavioural types of the behavioural spectrum. Moreover, all age-classes are represented in the Azorean waters (newborn – old age). Photo-identification data have reveiled a minimum population size of 1028 Risso’s dolphins, sighted in the waters of Pico island alone.