Salvatore Cerchio stunned the small world of whale science in 2015 when he found examples of a new species in the wild for the first time. Now, he’s mapped the habitat of that species, called Omura’s whale after Hideo Omura, a prominent Japanese whale biologist.
The surprise in the new study, published in Frontiers in Marine Science, is that Omura’s whales, though little seen, are widespread across the tropical world.
Dr. Cerchio, a researcher with the New England Aquarium in Boston, found a population off the northwest coast of Madagascar, where he works, and compiled reports of sightings from Japan, Australia, Brazil and off the coasts of Indonesia, among others. In total, from photographs, audio recordings, museums and documents, he identified 161 accounts of Omura’s whales in 95 locales.
Scientists said the finding is a reminder of how little we actually know about what goes on in the world’s oceans.
“To me, this is a beautiful example of how much we didn’t know and how much we can know,” said Christopher W. Clark, a retired senior scientist at Cornell University, who was not involved in the research.
Technological innovation in recording devices, advances in genetic analysis — and simply knowing what to look for — seem to have led to the new insights.
Dr. Clark, an expert in whale acoustics, said that for decades researchers simply dropped the equivalent of a cassette recorder off the side of a boat, recorded for as long as the tape lasted, and then pulled it back up. Today’s more sophisticated devices allow researchers to position recorders at the bottom of the sea for six to 12 months at a time. The devices also can detect a wider range of tones, enabling them to hear the low notes of Omura’s whales for the first time.
Dr. Clark said he plans to go back into his own recordings to search for the animal’s signature sounds. “I know there are places that I’ve recorded Omura’s whales in the last nine months,” he said.
They sing at such a low frequency, Dr. Cerchio said, that when he was diving in their habitat, he felt rather than heard their distinct, rhythmic patterns of song, and typically had to speed up the recordings to actually hear them.
Dr. Cerchio said many whale experts and amateurs thought they had seen Bryde’s whales, a slightly larger species of baleen whale, when they were really watching Omura’s whales. It’s like the difference between coyotes and wolves, if you didn’t know they were two species, he said.
Japanese researchers first identifiedOmura’s whales in 2003, based on a 1998 stranding in Japan and tissue from eight animals killed during Japanese scientific whaling operations in the 1970s. The Omura’s whales have relatively small bodies, distinct genetics and unusually shaped skulls, leading researchers to conclude that the new species had split off from its genetic cousins 17 million years earlier.
Omura’s whales are baleen whales, meaning they are filter feeders, and they can be identified by their asymmetric coloration. The right side of their jaws are white, with a swirling, smoky splash of light coloration and four bisecting dark stripes on the right side of their heads, and their backs are decorated with asymmetrical chevrons. They favor tropical environments more than than most whales and don’t migrate, Dr. Cerchio said.
After publishing his 2015 paper, in which he described more than 40 whales seen in the wild and expanded their range beyond the Indo-Pacific, Dr. Cerchio said people sent him pictures of similar looking whales.
“Little by little it became clear that there were a lot more out there that could be researched and tallied,” he said.
At the urging of Bob Brownell, the paper’s senior author, Dr. Cerchio counted images he received, those he’d stumbled across on the internet, as well as sound recordings and historical sightings dating back to a 1955 magazine article from Hong Kong University that misidentified an Omura’s whale as an immature fin whale.
Bob Pitman, a scientist with the National Oceanic and Atmospheric Administration who was not involved in this research, said he was surprised to learn the scope of the species’ habitat. “I think most of us whale scientists expected that it would have a small, relatively localized population,” he wrote.
As Mr. Pitman noted, “if new whales are still being described, it means we are probably also losing species of animals that we never even knew existed.