Researchers surprised by the deep-sea fishing strategy of the unusually fast-beaked whale

Swerby’s beaked whale. Credit: NOAA Fisheries

An international team of biologists has successfully used biologists to reveal insights into the lifestyle and hunting behavior of an unknown species of the beaked Soerbie whale. The team’s first results show that these whales (which are similar to dolphins) have a surprisingly different lifestyle and are much faster than related species. The research was led by Fleur Visser of the University of Amsterdam (UvA) and the Royal Netherlands Institute for Ocean Research (NIOZ). The results were published on May 12, 2022, at Journal of Experimental Biology.

Beaked whales include a number of marine mammals that can perform standard diving. They routinely visit depths of several kilometers during hour-long fishing expeditions to search for squid and deep-sea fish. Because of their elusive nature and limited presence on the surface, little is known about their behavior.

With 16 species, the so-called Mesoplodont whales make up the largest genus of cetaceans. The genus includes some of the lesser known marine mammals—so much so that three new species of these rhinoceros-sized whales have been discovered in just the past 30 years. Most species are very similar physically and they are all presumed to be specialized deep-sea predators. Moreover, they often occur in the same areas and forage at similar depths. This raises the question of how they can avoid competing with each other for the same prey.

Sowerby’s beaked whales (Mesoplodon bidens) floating in the waters off Terceira Island, Azores. Credit: MG OudejansKelp Marine Research

biology

For a few beaked whale species, biomarkers, attached to their backs with suction cups, revealed that they had a low-energy lifestyle: they could perform extremely deep dives through slow-swimming, energy-conserving methods and hunting strategies. . But Swerby’s beaked whales have never been flagged before. However, after years of effort, the research team was able to publish biological markers on two Sowerby’s beaked whales. The tags recorded detailed information about the diving, locomotion and echolocation strategies of these extremely timid animals, providing the first opportunity to investigate foraging behaviour. This allowed a direct comparison of their hunting strategies with those of their relative, the slow-moving, beaked Plainville whale.

Sowerby's beaked whale (Mesoplodon Bidens)

Sowerby’s beaked whale (Mesoplodon bidens) floating in the waters off Terceira Island, Azores. The long beak characteristic of this type of water protrudes during the surface. Credit: Kelp Marine Research

Surprise

To the researchers’ surprise, Swerby’s beaked whales differ sharply from other species of Mizolodon in their swimming and hunting strategies. While targeting a similar forage depth (800-1300 m / 2600-4300 ft), they swim consistently faster, perform shorter deep dives, and echo-locate at a faster rate, with higher frequency clicks. This first record of a ‘fast’ beak whale indicates that Mesoblodon whales exploit a wider variety of deep-sea niches than previously thought. The deep sea is a rich and diverse hunting ground for predatory marine mammals, which have clearly evolved a wide range of specialized strategies to be able to exploit them from what was previously known. The observed deviation of Sowerby’s beaked whales from the typically slower behavior of other beaked whales also has potential implications for their response to human-made sounds, which appear to be strongly driven by behavior in other species.

Reference: “Swerby’s beaked whale motility and biostrategy indicate deep-sea foraging locus differentiation in mesoblodont whales” by Fleur Visser, Mitchell J. Degans, Ono A. Keeler, Peter T. Madsen, and Mark Johnson, 12 May 2022, Available here. Journal of Experimental Biology.
doi: 10.1242/jp.243728

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