A killer whale has been born in the Pacific Northwest, and so far, it looks happy and healthy.

It could be a lifeline. For years, no orca born into this group has survived.

The calf, known as L124, is part of a group of orcas known as the Southern Residents. The group has been shrinking for decades — it had nearly 100 orcas in the mid-90s, and now has 75 — in large part because of a depletion of its main food source, the Chinook salmon. Pollution and noisy boat traffic also appear to be hastening the group’s decline.

Since no calves born to the group since 2015 have survived to maturity, researchers are crossing their fingers for L124.

“I wish I could say that the odds are good, but unfortunately, the Southern Residents aren’t doing too well right now,” said Melisa Pinnow, a biologist with the Center for Whale Research, a nonprofit group in Washington state. “In the last three years, every calf that’s been born has died, and we’ve had miscarriages as well.”

Another calf from the same group made headlines around the world after it died last year and its mother, known as J35, carried its small body on her nose for 17 days in an unusually long show of grief.

The new calf was discovered last week. Pinnow was watching Seattle news coverage of the killer whales Thursday when she thought she saw a small addition to the extended family. Shortly after dawn the next morning, she and three other researchers set out in a boat to investigate. They found the baby swimming with its family in Admiralty Inlet, at the north end of Puget Sound.

“It looked like a normal calf, just kind of bebopping around between its mother and its uncle and its older sister,” Pinnow said, adding that it seemed to be at least three weeks old.

It is still unclear whether L124 is male or female, said David Ellifrit, another biologist on the trip. “Hopefully it’s a female, because we need more reproductive-age females,” he said. “And hopefully it will continue to grow and thrive.”

Orcas, one of the world’s most powerful predators, are found in all of the world’s oceans. Some groups are thriving, but others — especially those live near industrialized areas, like the Southern Residents — are suffering from pollution and environmental degradation. Polychlorinated biphenyls, a variety of biochemicals known as PCBs, have been found to linger in the blubber of killer whales, and mothers can pass those toxins onto their offspring.

The Southern Residents are divided into three pods — J, K and L — each with its own dialect of call sounds. The new calf is a member of the L pod, which now has 35 killer whales in all.

The groupings follow matrilineal lines; grandmothers live with their daughters and their daughters’ offspring. Older females go through menopause, just like humans, and after that they often help their daughters take care of the calves.

The orcas are social and can be playful, but only when they have time to play. These days, searching for food keeps them more busy than it used to.

But last week, some of them seemed to be in a happy mood; researchers saw members of the L pod doing spy hops, pec slaps and cartwheels. Later in the day, all three pods gathered together in the same space. That was a rare sight for the researchers, Pinnow said. But this party was a little dull — nothing like the more playful, interactive gatherings these orcas used to have decades ago.

Pinnow added that J35, the one carried her dead calf last year, appeared to be doing all right, even if she was perhaps a little mopey. J35 might soon lose her mother, J17, who is hungry and visibly weak.

In a group of mammals with such tight family bonds, the fertility problems could be distressing, Ellifrit said.

“It’d be like living in a tiny little town where nobody knows why all the kids are dying,” he said. “Everybody knows each other, but they’re just dealing with this kind of premature death, over and over and over.”

He called the birth of L124 “a bright spot, for sure.”

Saving this group of orcas from extinction would be a complex undertaking. Gov. Jay Inslee of Washington established a task force last year that reported on ways to increase the salmon population and fight noise and chemical contamination.

Pinnow recommended a range of things that people could do to help the Southern Residents, including supporting the breaching of nearby dams, banning net pens of farmed salmon and cutting back on salmon consumption overall.

“We don’t have too much longer to dillydally before they go extinct,” she said.

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