Research News
Crabeater seals vociferate in particular during the mating season between October and December. Photo: Ilse van Opzeeland, Alfred Wegener Institute
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Listening to Life Underneath the Ice
Listening to what happens underneath the Antarctic ice shelf via internet livestream: For over five years already, this is made possible by the Alfred Wegener Institute's underwater acoustic observatory PALAOA. The world-wide longest civilian acoustic collection of data allows for insights into distribution areas and migration of marine mammals which otherwise are difficult to observe. Comparisons between different research years give rise to the assumption that the procreative period is linked to certain types of ice on which the animals give birth to their young. "Some species of seals indeed begin with their mating chants in exactly the same calendar week every year", Dr Ilse van Opzeeland describes the surprisingly exact timing of the animals. The observatory likewise recorded the chants of blue whales and thus refuted the assumption that these largest animals living on earth avoided the ice-covered sea. Even 50 years after the cessation of commercial whaling in the Antarctic only very little is known about these nearly extinct rorquals. Traditional counts based on sightings often register only very few animals during a journey of several months duration. By contrast, the PALAOA data contain blue whale vocalisations almost every day, for the calls of these animals have a high distance range of several hundred kilometres. Such information is extremely important in evaluating the mode of living and population size of rorquals, which continue to be endangered in a multitude of ways. The loudest sounds recorded by PALAOA come from collisions of icebergs: Approximately once a year, giants of up to the size of Berlin collide with each other or with the edge of the shelf ice within hearing of the station and create quite a din in the offices of the ocean acousticians at Bremerhaven, who conduct their everyday work to the accompaniment of live sounds from the Antarctic.
