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Carcasses reveal movement, feeding patterns of Sowerby's beaked whales

Carcasses reveal movement, feeding patterns of Sowerby's beaked whales
Sowerby's beaked whales are extremely elusive, making them hard to study and protect, according to researchers. Photo by Pj.vanderlinde/Wikimedia Commons

May 25 (UPI) -- Marine biologists have gained fresh insights into the movement and feeding patterns of Sowerby's beaked whales after analyzing skin, muscle and bone tissue from stranded carcasses -- they move around less than previously thought.

The analysis, detailed Tuesday in the journal Frontiers in Conservation Science, showed Sowerby's beaked whales hold both short- and long-term habitat fidelity.

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By plotting differences in isotopic ratios, researchers confirmed the presence of at least two subpopulations that move around and feed within a historically stable range.

Beaked whales, a group of toothed whales, account for roughly a quarter of all surviving cetaceans -- the marine mammal order that includes dolphins, porpoises and whales.

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Despite their prevalence, beaked whales are especially elusive and remain poorly understood.

The lack of data on the ecology and biology of beaked whale species makes conservation planning especially difficult.

"Beaked whales are really cool, but most people haven't heard of them because they are so enigmatic," lead study author Kerri Smith said in a press release.

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"Whales are generally large and charismatic -- we can go on whale watching trips and see them in the wild, yet there are entire groups of whale species we know almost nothing about," said Smith, a researcher at the University of Texas El Paso and the Smithsonian National Museum of Natural History.

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The Sowerby's beaked whale, Mesoplodon bidens, was first identified nearly two centuries ago, but 200 years later scientists still know relatively little about the species.

Though its range is thought to extend across the North Atlantic, researchers aren't sure if the species consists of a handful of distinct subpopulations or a single, highly mobile population.

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To get a better sense of how these whales organize themselves, researchers measured ratios of carbon and nitrogen isotopes in skin, muscle and bone tissue collected from bycaught animals -- those unintentionally caught by fishermen -- museum specimens and stranded carcasses from both the east and west Atlantic.

The data showed the species is divided between at least two distinct subpopulations, one loyal to the eastern half of the North Atlantic and another native to the western half.

"[The study] provides some of the first data about Sowerby's beaked whale long-term distribution and population structure, something that would be nearly impossible to learn by studying living whales in their habitat," Smith said. "We can learn a lot about beaked whale ecology from specimens of opportunity."

Scientists said they hope followup genetic surveys can highlight the ecological differences between the two populations, as well as provide insights into what those differences might mean for conservation efforts.

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"A key action to take going forward is generating more fundamental data through studies like this one -- successful conservation action requires a strong foundation of reliable data, and there is still so much we do not know about beaked whales and many other marine species," Smith said.

"As we learn more about them and their habitats, we may need to set aside important habitats as marine protected areas. Additional research to identify the potential influence of fishing activities and naval sonar on critical beaked whale habitats is also needed," Smith said.

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