The Omura's whale is a big enigma, both literally and figuratively. It can grow as long as a bus, yet scientists know almost nothing about its behavior or biology. It was only recognized as a unique species in 2003, and wasn't caught on video until 2015.

Now, however, the scientists behind that video have announced an even bigger discovery. Led by Salvatore Cerchio of the New England Aquarium (NEA), they returned to the same waters off Madagascar in November 2015, just weeks after releasing the initial video. Not only did they see more Omura's whales — they found 80 of the elusive leviathans in one month, and even caught several on video.

That's the largest aggregation of Omura's ever seen, and it's also nearly double the 44 previous sightings in the entire research record. It was a "whale jackpot," according to the NEA, offering a bonanza of important scientific insights. The 80 whales included five calves with their mothers, for example, as well as some individuals seen in the area before, suggesting this may be a resident population.

If so, it would be a major breakthrough in our efforts to understand — and protect — these mysterious mammals. Here's the new video, which was released March 3:

Omura's whales were long lumped in with Bryde's whales, which look similar, until a 2003 study revealed they're a distinct species (now named after late Japanese ecologist Hideo Omura). Yet the whale was still known only from dead specimens, notes National Geographic's Traci Watson, leaving it cloaked in mystery.

Finally, in 2013, a team of biologists led by Cerchio saw strange baleen whales near Nosy Be, an island off the coast of Madagascar. "When we found them, we thought they were Bryde's in part because they weren't supposed to be in this area," Cerchio tells Michael Casey of Fox News. "The known range of Omura's whales at that point was the western Pacific and the far eastern Indian Ocean off of Australia."

After a few more sightings, however, the researchers started to figure out the true significance of what they'd found. "Once we realized they were Omura's whales, it was mind-boggling because, first of all, no one had studied these animals," Cerchio adds. "No one had seen them or documented them in the wild."

This was a big deal for a few reasons. It meant scientists finally had live Omura's whales to study, and that the species' range is larger than anyone knew. Plus, they were seen feeding in tropical waters, where food is typically too sparse to support such hefty whales. (Omura's are relatively small by baleen standards, but they're still big, growing up to 38 feet long). Many baleen species do visit the tropics for breeding, but don't eat until they migrate back to colder regions with lots of zooplankton.

Nosy Be beachIn addition to Omura's whales, the warm waters of Nosy Be are also popular with human tourists. (Photo: Shutterstock)

Cerchio's research suggests these Omura's whales are year-round residents of Nosy Be, or at least regular seasonal visitors. And since he has recorded them gulping mouthfuls of seawater — which baleen whales normally do in cooler water to filter out tiny animals — it begs the question: What are they eating?

When Cerchio arrived on his latest trip to Nosy Be, locals told him about high levels of "tiny shrimp" offshore. Those zooplankton turned out to be tropical krill known as euphausiids, and they also turned out to be on the menu for Omura's whales.

"Lots of food anywhere in the animal kingdom usually attracts lots of animals," the NEA notes, "and consequently the Omura's whales were seen in record numbers."

Omura's whale feedingAn Omura's whale feeds on euphausiids near Nosy Be in 2015. (Photo: Cerchio et al./Royal Society Open Science)

This is still "a nearly unknown whale species," the NEA adds, so seeing 80 individuals in a month — and a record five calves — was a historic moment. The team ended up with a trove of data to help demystify the species, including observations of feeding behavior, distinct markings around the head and two weeks of continuous acoustic data from remote recorders, some of which caught "dense choruses" of Omura's songs that Cerchio describes as "very simple but interesting."

Cerchio will make another trip to Nosy Be in several weeks, hoping to learn more about the size, range and stability of this whale population. Until we have a clearer context, he explains to Casey, we can't know how much danger the whales face from human activities like plastic pollution, ghost fishing, or oil and gas exploration.

"Whenever you have a small population like this, they tend to be more vulnerable to any local threats," he says. "The small resident populations tend to have low genetic diversity and also be subject to any environmental pressures."