An international team of marine biologists has found genetic evidence of a previously unknown species of beaked whale (Berardius sp.nov.) that ranges from northern Japan across the Pacific Ocean to Alaska’s Aleutian Islands.
Berardius sp.nov. Image credit: Uko Gorter.
Beaked whales (Ziphiidae) are the second most diverse family of cetaceans but remain poorly understood. There are currently 22 recognized species, comprising 24 percent of all cetacean species.
These whales are typically found at very low density and in deep offshore or deep basin waters, and observing them is complicated by their medium-to-small size (10-43 feet, or 3–13 m), deep diving behavior that keeps them below the surface for up to an hour, and low surface profile that makes them difficult to spot in rougher sea-state conditions.
The largest and one of the most common beaked whale species is the Baird’s beaked whale (Berardius bairdii).
It occurs throughout the temperate North Pacific, from the southern Gulf of California in the east, to the Bering, Okhotsk and Japanese Seas in the west.
In Japan, whalers have traditionally recognized two forms of Baird’s beaked whales: the common ‘slate-gray’ form and a smaller, rare ‘black’ form. They call the enigmatic black form ‘karasu,’ the Japanese word for raven.
“Japanese whalers have known about the black form but didn’t consider it a separate species,” said team member Dr. Erich Hoyt, from Whale and Dolphin Conservation, UK.
Dr. Hoyt and his colleagues carried out a DNA analysis of 178 beaked whales from around the Pacific Rim and found eight examples of this extremely rare form.
The eight included specimens from the Smithsonian Institution and Los Angeles County Museum of Natural History, a skeleton on display in an Alaska high school, and another that puzzled scientists trying to identify it when it washed up on an island in the Bering Sea.
“The challenge in documenting the species was simply locating enough specimens to provide convincing evidence,” said team leader Dr. Phillip Morin, of NOAA Fisheries’ Southwest Fisheries Science Center.
“Clearly this species is very rare, and reminds us how much we have to learn about the ocean and even some of its largest inhabitants.”
The newly-identified species closely resembles the Baird’s beaked whale, but is about two-thirds the size – about 25 feet (7.6 m) full grown – and darker in color.
This species and the Baird’s beaked whale are each more closely related to the Arnoux’s beaked whale (Berardius arnuxii) from the Southern Hemisphere than they are to each other.
The eight known examples cluster around northern Japan and the Aleutian Islands and Bering Sea. That suggests that the species has a smaller range than the Baird’s beaked whale.
Scars from the cookie-cutter-like bites of tropical sharks suggest that, like other beaked whales, the species may migrate to tropical waters.
“As much as we know about the genetic heritage of this animal, we still do not know very much about the animal itself,” Dr. Morin said.
“We can draw some indications from what we know about other beaked whales in terms of its range and behavior, but we still have many more questions than answers.”
The team’s results were published online this week in the journal Marine Mammal Science.
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Phillip A. Morin et al. Genetic structure of the beaked whale genus Berardius in the North Pacific, with genetic evidence for a new species. Marine Mammal Science, published online July 26, 2016; doi: 10.1111/mms.12345
