Mysterious whale reveals a secret

At least 24 species of beaked whales live in the world's oceans and biologists are still discovering new species: these marine mammals live in some of the least explored regions of the oceans and repeatedly spend long periods of time in the deep sea. As a result, relatively little is known about these animals. However, a group of Baird's beaked whales (Berardius bairdii) surprised a team led by Olga Filatova from the University of Southern Denmark: This school of whales could be observed regularly in shallower waters around the Russian Commander Islands in the North Pacific between 2008 and 2019 (Covid-19 and the attack on Ukraine subsequently prevented further research trips). The working group reports on its findings in the journal "Animal Behaviour".

Originally, Filatova and Co. wanted to study humpback and killer whales in the region, but then they noticed that several dozen beaked whales regularly visited this area off the islands. After several years, they concluded that this was a localised population forming a common group consisting of at least 79 animals. Over the years, the researchers also observed a further 107 individuals that were travelling through and mostly spent only a short time off the islands.

61 of the animals also interacted with the local beaked whales and seven even followed them into the shallower coastal waters that they normally avoid. According to Filatova and Co, this indicates a personal development and the exchange of cultural traditions between the beaked whales. "The transients are not as familiar with the local conditions as the locals and therefore normally search for food at the usual depths for their species," says the biologist: "However, we actually observed some transients in the shallows. These were individuals that had some form of social contact with the inhabitants. This contact must have familiarised them with the shallow water and its advantages." They therefore copy and learn the behaviour of their conspecifics - as we know from other whale species such as orcas.

What exactly they are looking for in the shallower waters is still unknown, but it is probably related to feeding grounds. The team found the highest number of Baird's beaked whales in shallow waters in an area where the shelf edge recedes from the coast and becomes less steep. This provides a suitable habitat for demersal fish and invertebrates at relatively shallow depths, but beyond the shelf edge, which Baird's beaked whales almost never visit. This allows the resident whales to feed at relatively shallow depths and expend less energy diving - ultimately providing an evolutionary advantage and benefiting this tradition. It is then preserved through transmission within the local Baird's beaked whale community.

A related species, the Cuvier's beaked whale (Ziphius cavirostris), holds several records among marine mammals: No other whale has ever been able to demonstrate a deeper (almost 3000 metres) and longer (222 minutes) dive.

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