The orca gave birth on July 25 in what should have been a happy milestone for her long-suffering clan.

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The pod that roams between Vancouver and San Juan Island has dwindled to 75 over the decades. The cause is no mystery: humans have netted the orcas' salmon, driven ships through their hunting lanes and polluted their water to the point that researchers fear Tahlequah's generation may be the last of her family.

The orange-tinted baby that wriggled out of her that morning was the first live birth in the pod since 2015. It lived for about half an hour.

People love to anthropomorphise animals, but studies have found that orcas - also known as killer whales - really do possess high levels of intelligence and empathy, and emotions that may not be totally alien to our own.

So, when Tahlequah did not let her emaciated calf sink to the bottom of the Pacific, but rather balanced it on her head and pushed it along as she followed her pod, researchers thought they understood what was happening.

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"You cannot interpret it any other way," said Deborah Giles, a killer whale biologist with the University of Washington. "This is an animal that is grieving for its dead baby, and she doesn't want to let it go. She's not ready."

That was the beginning of a long funeral procession.

"The hours turned into days," Allyson Chiu wrote in The Washington Post two days after the death. "And on Thursday she was still seen pushing her baby to the water's surface."

And still the next day, and through the weekend, and into the next week and next month.

The act itself was not unprecedented, but researchers said it was rare to see a mother carry her dead for so long. It couldn't have been easy for her. Tahlequah's pod travels dozens of kilometres a day, and she pushed her baby every inch of the way. She was forever picking up the body as it sank, hoisting it out of the water to take a breath, and repeating.

Researchers with the Canadian and US governments and other organisations tracked her all the while, hoping to capture the calf once Tahlequah finally let go, and discover why it had died – as nearly all the babies in this pod seemed to.

But Tahlequah would not let go. Eventually, researchers stopped calling what they were witnessing "rare" and began using the word "unprecedented".

And the phenomenon was no longer of purely scientific interest.

People wrote poems about Tahlequah and drew pictures. People lost sleep thinking about the whale. A scientist cried thinking of her. Tahlequah inspired politicians and essayists – and a sense of interspecies kinship in some mothers who had also lost children.

And still, Tahlequah carried her child. The world's interest in her feat finally grew to encompass her whole family.

Last week, The New York Times reported that biologists and government officials were working on a plan to save the youngest living member of Talhequah's pod – a three-year-old orca that appears to be on the brink of starvation. They are tracking the young whale, dubbed Scarlet, in an attempt to feed her antibiotic-laced salmon.

In that sense, maybe, Tahlequah's doomed calf did bring new hope to the pod, which had previously swam and struggled in near-anonymity.

At the same time, the mother's obsession had become gravely concerning to researchers. They worried that the effort of pushing her calf – for about 1600 kilometres – would make Tahlequah weak and keep her from finding enough food. Fortunately, that doesn't appear to have been the case.

The Centre for Whale Research said Tahlequah "vigorously chased a school of salmon with her pod-mates" when researchers spotted her on Saturday.

The Washington Post