Mysterious Beaked Whales around the South Shetlands
Cetacean surveys by helicopter turned out to be a particularly efficient technique to identify the poorly known beaked whales and therefore extend our knowledge of their geographical distribution in Antarctica.
Have you ever heard of "Ziphiids"? This term refers to the cousins of dolphins which belong to the most mysterious family of all cetaceans. This family, also known as beaked whales, is one of the biggest among cetaceans. In the Southern Ocean, their size varies from five meters for the smallest to twice as long for the Arnoux’s Beaked Whale. Despite their enormous size, these 20 species are still very poorly known. Some of them have never been seen alive, and most of the information about their biology has been gained by investigating stranded specimens. Beaked whales live in small and elusive family units often in deep waters. They feed on squid which they swiftly suck into their mouth during deep and long-lasting dives.
Beaked whales are notoriously difficult to identify from a ship. They spend a large proportion of their time under water and thus are hardly ever seen at the surface. To make things even more difficult the 20 species look very similar to each other. Some are only distinguishable by a pair of front teeth visible in adult males!
For the last two months, Dr Meike Scheidat and Linn Lehnert from the "Research and Technology Centre Westcoast", Büsum, Germany have been conducting aerial surveys of cetaceans and pinnipeds (seals) from the German research vessel Polarstern.
"This technique proved to be particularly useful for beaked whales. As soon as a sighting was made and identified as a "beaked whale", the pilots slowed down and positioned themselves so that the animals could be seen beneath the water surface." explains Meike Scheidat.
The first beaked whale sighting was from the helicopter of a pod of Arnoux’s beaked whales, one of two species typically found around Antarctica. In addition to this observation a remarkable series of photographs has been taken of this rarely sighted species.
"The helicopter pilot has to act fast once we’ve spotted an animal because if they feel disturbed and decide to dive they are gone for good." adds Linn Lehnert.
The careful manoeuvring allows not only to record information on group size and behaviour but also to take high resolution digital photographs. Examination of distinct details visible on the picture, such as the front teeth, allows for the identification of the species.
"On the 25th December, while surveying deep waters along the shelf slope of Elephant Island, we came across three different beaked whale species on a single flight! This is when we started to believe in Santa Clause again." Meike Scheidat reports enthusiastically.
If they were not surprised enough to spot a pod of Southern Bottlenose Whales, the finding of Strap-toothed Whales (picture) and Gray’s Beaked Whales came as a real shock. Both species are very rarely identified at sea, and together with a few other unpublished data, these sightings were made at the Southern limit of their geographical distribution.
"This exceptional series of observations may be linked to a particularly suitable habitat. But I’m also convinced that we might have found a new method to study beaked whales for the future" concludes Meike Scheidat.
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