'Extinct' Omura's whales spotted: How rare are they?

A whale species that marine conservationists feared was extinct is living off the coast of Madagascar, say scientists.

For many years, Omura's whales, named for Japanese whale expert Hideo Omura, were misidentified as Bryde’s whales, another small baleen whale, until genetic testing in 2003 revealed that Omura’s are a distinct species. 

For two years, Dr. Salvatore Cerchio – a guest investigator with the Woods Hole Oceanographic Institution, and a staff member at the New England Aquarium – and his team have investigated these little-known whales.

"Over the years, there have been a small handful of possible sightings of Omura's whales, but nothing that was confirmed," Dr. Cerchio said in a WHOI press release. "This is the first definitive evidence and detailed [description] of Omura's whales in the wild and part of what makes this work particularly exciting."

Because their numbers are low and their habitat overlaps with Bryde’s whales, scientists have struggled to identify and investigate them, say the researchers in a recent study in the journal Royal Society Open Science. The International Union for the Conservation of Nature (IUCN) has no classification for the species because there is not enough data.

In fact, during the initial stages of the study, the researchers themselves mistook the Omura’s whale for Bryde’s whales, due to the similarity in their shape and size: both species have elongated heads, although Omura’s whales have asymmetrical coloration and a distinctive ridge on the top of their heads.   

"The species is a tropical whale without segregation of feeding and breeding habitat, and is probably non-migratory," wrote the scientists. "Our data extend the range of this poorly studied whale into the western Indian Ocean."

Because Omura’s whales don't migrate, commercial whaling operations and by-catch threaten their survival. According to the IUCN, Omura’s whales "might have been harvested commercially in the past (probably identified as Bryde's Whale), and [are] still subject to some local level harvesting."

The research team also observed four mothers with young calves and frequent lunge-feeding, and they recorded song-like vocalizations that may play a role in mating.

Cerchio plans to return in November to continue studying the whales' songs, behavior, and population characteristics, and to look for them them in other parts of their range.

Omura's whales "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," he said.