Scientific Name: Orcinus orca
The killer whale, also known as the orca (Orcinus orca) is a marine mammal classified under the family of Delphinidae (dolphins) and included with the group of toothed whales (the other main group are the baleen whales: Mysticetes, which do not have teeth) or Odontocetes (which possess teeth). Orcas are widely distributed around the world, being found in many polar and tropic regions and both in open and coastal waters. In the Mediterranean Sea, these marine mammals are regularly distributed in the Strait of Gibraltar. Nevertheless, the killer
whale is only considered as a visitor to the western Mediterranean (obviously coming in from
the Atlantic) and vagrant to the eastern side.
Killer whales are black and white in colour, and usually everyone is quite accustomed to identify such species with a grey patch on the patch that is called the saddle and they generally travel in pods. The size of each killer whale generally depends on the gender. Male orcas are relatively large and they can grow up to approximately 9.8m in length. On the other hand, the female orca is relatively smaller with the largest female size ever recorded of approximately 8.5m. The body shape of an orca is roughly cylindrical and tapering at both ends. This shape is
very efficient for these marine species as they are able to swim with less opposing drag force.
It is important to point out that the dorsal fin differs amongst gender. Male orcas tend to have long, triangular dorsal fins, whereas females generally have a short one curving backwards. Like all whales they contain blubber, which is a thick layer of fat (approximately 7.6 to 10m) exactly under the dermis of their smooth skin. The blubber has many functions, mainly:
o Maintaining the body heat of the orca;
o Storing energy as fat in the event of food shortage; and
o Contributing to the killer whale’s streamline fat
The presence of such a thick layer of blubber makes it more adaptable to live in cooler regions. However as stated earlier there are records which state that killer whales were spotted in the Straits of Gibraltar (Notarbartolo di Sciara & Birkun, 2010). The presence of these killer whales might have been due to the large amounts of blue fin tuna, which are the primary prey of such cetaceans in the Mediterranean. The killer whales found in the vicinity of the strait of Gibraltar are reported to be threatened mainly due to sea pollution, fishing practices and prey depletion.