SPERM WHALE

 

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Sperm whale is the largest of the toothed whales, with males attaining an average length of 16m and females of 11m. Recent global population estimate is approximately 360,000; sperm whales inhabit all of the world's oceans, in general only mature males are found in the higher latitude cold waters, whilst the females and the young are limited to tropical and temperate seas.

In Mediterranean Sea, sperm whale has been reported throughout the basin, but due to the lack of knowledge or data, it is not possible to assess the conservation status of the species in this region.

 

 

 

Sperm whales are among the deepest and longest diving marine mammals, they perform prolonged and deep dives in search for food. Sperm whales appear to feed year round and throughout the day and their diet consists mainly of species of cephalopods (usually squids). No data on stomachs contents from adult sperm whales have been published for the Mediterranean Sea, so there is no documented evidence concerning sperm whale dietary habits in this region.

During the deep feed dive, the sperm whale emits an almost continuous sequence of loud impulsive clicks, which are thought to be used for echolocation. In these long sequences, clicks are emitted at a fairly regular rate and are generally referred as 'regular clicks'.

 

 

In our study area sperm whales were detected mainly acoustically, they seems to be more abundant in the month of October. Since 2002, a consistent number of social group of this species were monitored in the waters of Ischia. Sperm whales routes were mainly pelagic and located in the central part of the canyon (range 320-850 m). The animals were slow traveling (2,5/3 knots) or socialising at the surface.

 

 

 

 

Social groups, composed by females and juveniles, are very rare in the Mediterranean Sea, and the observation of their behavioral activities it is a special occasion.

Although females and immature sperm whales spent most of their time diving, members of the group clustered at the surface for periods of an hour or more. During these phases a number of different activities were seen from above the water surface.

 

 

 

 

Reports of vessel collisions with sperm whales are common in the Mediterranean: in 2003 summer we found a single adult male which showed traces of collision on its back in form of parallel cuts, caused by a propeller. In Mediterranean whales are also threatened by continuous by catch in driftnetting fisheries, now illegal and uncontrolled.