Well after its discovery a decade ago, the sleek swimmer called the Omura's whale remained an enigma. Reports of live animals were vague and unconvincing, leaving the whale's habits and even its markings a mystery.
Now, scientists are starting to piece together the secret life of the little-seen species.
Recent expeditions off Madagascar revealed the whales devouring tiny shrimp-like creatures, as well as guzzling large mouthfuls of “dirty water"—a phenomenon scientists can't yet explain.
“People see our photos and videos and say, ‘What are they feeding on? I don’t see anything there,’” says Salvatore Cerchio, a marine mammal biologist at the New England Aquarium and leader of the first team to document the whales’ lives.
“Well, I don’t know yet.” (Read about the Madagascar Omura's Whale Project.)
The whales’ seemingly invisible food supply only adds to the mystique of the Omura's whale, whose habitat, lifestyle, and social lives make them standouts in the whale world.
Even so, the Omura’s has avoided the limelight. It wasn’t until 2003 that Japanese researchers identified it as a species in its own right rather than a petite version of the similar-looking Bryde’s whale. Genetic data confirmed the whale as its own species in 2006.
It’s no surprise—at least to scientists—that a 35-foot (about 10-meter) long animal could elude detection, says Francine Kershaw, a marine mammal science fellow at the Natural Resources Defense Council.
Sea surveys are costly, says Kershaw, who wasn't involved in the new study. And the Omura’s keeps a relatively low profile compared to showboats like humpbacks, which make eye-catching leaps out of the water.
Even after it was unmasked in the scientific literature, the Omura’s was still known only from dead specimens, some hauled onto whaling ships, others stranded on coastlines.
Then came the Omura’s big moment.
Scouting for dolphins near Madagascar a few years ago, Cerchio spotted some medium-size whales. After the DNA analysis came back, on December 24, 2014, Cerchio learned he’d stumbled onto Omura’s whales—“a very nice Christmas gift,” says Cerchio, a National Geographic explorer.
With their striking dark-light patterns and super-streamlined profile, Omura’s whales are a combination of “grace and beauty,” says Cerchio, whose work was supported by the U.S. Marine Mammal Commission. “They are stunning animals.” (See National Geographic's amazing whale pictures.)
Cerchio’s team made 44 sightings of the whales off Madagascar during 2013 and 2014 and more than 80 sightings in 2015.
"Very Thin Soup"
The team’s first round of data, published in October 2015 in the journal Royal Society Open Science, suggest that these Omura’s at least are homebodies. The sightings also suggest the Omura's sticks to tropical and subtropical waters.
For a whale, that’s doubly unusual. Most whales migrate, often over long distances, and most spend at least some of the year in cooler waters closer to the poles, where food abounds. (See "Life in Antarctica Relies on Shrinking Supply of Krill.")
The tropics, on the other hand, provide slim pickings for baleen whales like Omura's, which filter small organisms through their mouths.
"We call it the very thin soup,” says marine-mammal biologist Matt Leslie of the Scripps Institution of Oceanography, who wasn't part of the new study. So “one of the big questions is how they make their living.”
Cerchio’s team, which observed the whales swallowing murky water as recently as late 2015, suspects the whales are filtering out food such as fish eggs or tiny plankton that are almost invisible to the human eye.
Edge of the Iceberg
The new observations also showed the Omura’s social habits are distinctive. It doesn’t form tight-knit pods like many other whale species, but it isn’t solitary either.
Instead the Omura’s was seen hanging out in loose groups of up to a half-dozen animals. Animals stay within hearing range of each other, but give each other plenty of personal space.
The whales sing a low, repetitive melody that they may repeat for an hour or more. Occasionally multiple whales raise their voices in an Omura’s chorus. Perhaps males are gathering around a female and fighting it out via song, says Cerchio. Or perhaps they’re wooing her with ballads.
Next, the team hopes to identify the mystery food in the whales’ gulps of seawater and to understand how oil and gas exploration planned for their habitat will affect them.
“As a species, we think … we know so much,” says the Scripps Institution's Leslie.
“But we don’t. We’re still scraping the edge of the iceberg in terms of what we know about oceans.”
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