The Mediterranean sperm whale
Sperm whale Physeter macrocephalus in the Ligurian Sea. Photos © Tethys Research Institute.
No estimate of population size exists for the region, but the total number of sperm whales in the Mediterranean is more likely in the hundreds than the thousands.
Genetic and other data suggest that sperm whales in the Mediterranean constitute a separate population. No evidence exists of population fragmentation across the region.
Mediterranean sperm whales seem to have a particular repertoire of codas, the stereotyped patterns of clicks that sperm whales use for communication. Repertoire differences among populations have been interpreted as indicative of cultural differences. Although more than 25 coda types have been recorded in the Mediterranean, the coda repertoire is dominated by a "3+1" pattern that is not common in adjacent Atlantic waters.
There is evidence that sperm whales were formerly common in portions of the Mediterranean, such as in the Strait of Messina and the waters adjacent to the Eolian Islands, at least until the 1950s. Bolognari reported the frequent occurrence of large "aggregations" or "clusters" consisting of as many as 30 individuals, in the area of the Strait of Messina during winter in the late 1940s and early 1950s. Such large groups have not been recorded in more recent times in that area or anywhere else in the Mediterranean. When data on sperm whale encounter rates started to become available in the mid-1990s, they were very low compared to the impression given by the historical records.
Sperm whales have declined considerably in the stranding records of France and Italy in the last decade, in spite of the fact that efficiency of discovery and reporting of strandings has greatly improved over time. The abrupt decline in the number of records has been interpreted as a possible sign of decline.
Experts participating in a regional Red List workshop organized in 2006 agreed that Mediterranean sperm whales qualify as ’Endangered’ according to the IUCN Red List criteria.
The most likely cause of recent decline of sperm whales in the Mediterranean is entanglement in high-seas swordfish driftnets, which has caused considerable mortality since the mid-1980s. Such mortality is ongoing.
Despite international and national regulations banning driftnets from the Mediterranean, illegal or quasi-legal driftnetting continues in sperm whale habitat, not only in the western Mediterranean (e.g., in France, Italy, and Morocco) but recently also in the eastern basin (e.g., Greece and Turkey), thereby continuing to threaten the species' survival in the region.
Although the continuation of driftnet fishing by non-EU Mediterranean fleets and illegal EU operations represent the most important ongoing threat to sperm whales in the Mediterranean Sea, the disturbance from intense marine traffic and collisions with vessels may be serious as well. Underwater noise from mineral prospecting (seismic airguns), military operations, and illegal dynamite fishing are other sources of concern.
For more information on Mediterranean sperm whales see:
Notarbartolo di Sciara G., Frantzis A., Bearzi G., Reeves R.R. 2006. Sperm whale (Physeter macrocephalus), Mediterranean subpopulation. Pp. 48-56 in: R. Reeves and G. Notarbartolo di Sciara (compilers and editors). The status and distribution of cetaceans in the Black Sea and Mediterranean Sea. IUCN Centre for Mediterranean Cooperation, Malaga, Spain. 143 pp. (whole report: 2,752 Kb)