Rare Omura’s whales, the least-known whale species, documented in wild for first time

So little is known about Omura’s whales that researchers are unsure how many exist and just how rare they are. They are often mistaken for Bryde’s whales.

For the first time, confirmed sightings of Omura's whales have been made. Researchers observed them off Madagascar. Photo: Salvatore Cerchio

For the first time, confirmed sightings of Omura’s whales have been made. Researchers observed them off Madagascar. Photo: Salvatore Cerchio

Omura's whales, the least known among whale species and often misidentified, have been observed in the field for the first time by an international team of biologists off the coast of Madagascar.

The study published in the Royal Society Open Science journal is the first definitive evidence and detailed descriptions of Omura's whales in the wild and the findings are thrilling for biologists, considering how little is known about this whale species.

Scientists are unsure how many Omura's whales exist, so they don't really know just how rare they are, according to the Woods Hole Oceanographic Institution.

"Over the years, there have been a small handful of possible sightings of Omura’s whales, but nothing that was confirmed," said lead author and researcher Salvatore Cerchio of the Wildlife Conservation Society, New England Aquarium (NEAQ) and Woods Hole Oceanographic Institution (WHOI).

"They appear to occur in remote regions and are difficult to find at sea because they are small--they range in length from approximately 33 to 38 feet--and do not put up a prominent blow.

"What little we knew about these whales previously came primarily from eight specimens of Omura’s whales taken in Japanese scientific whaling off the Solomon and Keeling Islands and a couple strandings of dead animals in Japan."

Omura's whales observed off Madagascar were first believed to be Bryde's whales because of the similarities between to the two whale species.

Omura’s whales observed off Madagascar were first believed to be Bryde’s whales because of the similarities between to the two whale species. Photo: Salvatore Cerchio

More from Woods Hole Oceanographic Institution:

For many years, these marine mammals were misidentified as Bryde’s whales due to their similar appearance--both are small tropical baleen whales with comparable dorsal fins, though Omura’s are slightly smaller in size and have unique markings with a lower jaw that is white on the right side and dark on the left.

In 2003, using genetic data from samples obtained from old whaling expeditions and a few strandings in the western tropical Pacific, scientists determined Omura’s whales were actually a distinct species. But there had been no confirmed records of sightings in the wild and little else has been known about the elusive species until now.

Cerchio and his team have been conducting field research on marine mammals off the northwest coast of Madagascar since 2007, and first spotted Omura's whales in the area in 2011. They originally believed they were Bryde's whales.

After changing study areas and sightings of these whales became more frequent, the team, in 2013, was led to believe the whales might be Omura's whales.

The Omura's whales study area.

The Omura’s whales study area. Graphic: Salvatore Cerchio

"At first, we thought they were Bryde's whales, an understandable mistake because of the similar size and habitat, but then with good photographs and underwater video, we noticed they more closely resembled the description of Omura's whales," Cerchio told WJMN.

"When we clearly saw that the right jaw was white, and the left jaw was black, we knew we were on to something very special. The only problem was that Omura's whales were not supposed to be in this part of the Indian Ocean. Rather, they should be in the west Pacific, near Thailand and the Phillipines."

Over the next two years, the research team observed 44 groups of Omura's whales and managed to collect skin biopsies from 18 adults. DNA confirmed they were Omura's whales.

The team hopes to produce the first population estimate for Omura's whales. Thus far, 25 individual Omura's whales have been catalogued through photographic identifications.

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