The Omura's whale is a creature so elusive that its existence was confirmed only in 2003. Thirteen years on, only a very small number of documented sightings exist on record – but we can now add one more to that list. One of the world's least-known whales just showed up on the Great Barrier Reef!

This is the first time an Omura's whale has been seen in these waters. "It's amazing news!" Great Barrier Reef Marine Park staff wrote on Facebook. 

For years, Omura's whales (Balaenoptera omurai) were misidentified as Bryde's whales due to their similar appearance. Both species are baleen (filter-feeding) whales that possess a similar "stumpy" dorsal fin. But unlike their more common doppelgängers, Omura's whales sport a signature two-toned jaw: white on the right side and black on the left. And at 33 to 38 feet in length, they're also slightly smaller.

Late last week, tourists in Queensland's Port Douglas reported a possible Omura's whale sighting, so the likely explanation is that we're looking at the same individual. If this is confirmed, the whale (shown here near Mission Beach) has made a 200-kilometre journey in the past several days. 

There's no doubt that the whale's Australian visit is exciting – but it's also not entirely surprising. The 1,400-mile Great Barrier Reef sits along the South Pacific's Coral Sea, and nearby regions of the West Pacific are known territory for Omura's whales. Still, each encounter represents an important pin on the whales' largely blank range map.

There's sill a lot we don't know about these animals, including just how many are out there, but it's possible that the mysterious leviathans aren't as rare as we once thought. Some 40 groups have been spotted off Madagascar, and back in August, researchers from the Pontifical Catholic University of Rio Grande do Sul published the first study on an Omura's whale in the South Atlantic.

That whale had washed up dead in Brazil, and while it could simply have been passing through when it died, something about the sighting didn't add up for the team: the whale was a youngster. Another juvenile, a neonate, was found stranded in Mauritania in 2013, leading the team to speculate that parts of the Atlantic could serve as breeding grounds for Omura's whales.

The Omura's whale, a female calf, that washed up dead in Brazil. Image: Cypriano-Souza et al. 2016

We'll need more than just two specimens to know for sure, but with each encounter, we're slowly learning about the secretive lives of these animals. Confused for their Bryde's whale lookalikes, they've cruised under researchers' radar for too long, and we've yet to figure out how much this case of mistaken identity has affected their populations.

Bryde's whales have long been targeted by whalers, and despite some current protections, Japan continues to hunt the species as part of its controversial scientific whaling programme. If the global numbers of Omura's whales are indeed low, it's possible that accidental takes could have a serious impact on the health of their populations. 

For those looking to spot these elusive giants, Madagascar is the best place for it. In fact, marine biologist and Earth Touch contributor Dr Simon J Pierce recently encountered one on a dive near Nosy Be, an island off Madagascar's northwest coast. New England Aquarium's Salvatore Cerchio, one of the world's leading Omura's whale researchers, was delighted by the sighting."Fantastic!" he said in response to the image. "So happy they are up in Nosy Be now, they are apparently feeding away!" 

The Omura's whale spotted near Nosy Be, Madagascar. Image: Simon Pierce/Facebook


Top header image: Salvatore Cerchio et al. / Royal Society Open Science