SOUTHERN FOURTOOTH WHALE

The genus Berardius contains two species of beaked whale, Baird's Beaked Whale and Arnoux's Beaked Whale. The two species are so similar that some scientists regard their separation into distinct species as an historical anomaly. The two species are the largest of all beaked whales and collectively they are sometimes referred to as the giant beaked whales.

Physical description
The two species have very similar features and would be indistinguishable at sea if they did not exist in disjoint locations. Arnoux's is generally shorter. Estimated lengths of live Arnoux's at sea have been up to 12m. The Baird's on the other hand have been confirmed to grow to 12-13m.
Both whales have a very long prominent beak, even by beaked whale standards. The lower jaw is longer than the upper and the front teeth are visible even when the mouth is fully close. The melon is particularly bulbous. The body shape is slender - the girth is only 50% of length. The body is uniformly coloured and a particular individual's colour may anything from light grey through to black. The flippers are small, rounded and set towards the front of the body. The dorsal fin similarly is small and rounded and set about three-quarters of the way along the back. Both species pick up numerous white scars all over the body as they age and may be a rough indicator of age. There is little sexual dimorphism in either species.

Population and distribution
The two species ranges do not overlap and this perhaps the most significant reason why historically they have been treated as separate species.
Arnoux's inhabit great tracts of the Southern Ocean. Beachings in New Zealand and Argentina indicate that the whale is relatively common in the areas south of those countries down to Antarctica. It has also been spotted close to South Georgia and South Africa.

Behaviour
The whales normally move in close-knit groups of about 3-10, with groups of 50 observed in exceptional circumstances. Considering the extent of whaling of the species, the pod structure is not well known. One interesting curiousity is that two-thirds of all whales caught have been male, despite the fact that females are somewhat larger than males and thus would be the preferred targets for whalers, if they were as easy to catch.
Conservation
Arnoux's Beaked Whale has never been exploited and although no abudance estimates are available, the population is not believed to be endangered.