WASHINGTON • A grieving orca whale has released the body of her dead calf after carrying it for at least 17 days through the Pacific Ocean in an unprecedented act of mourning, according to researchers.

Last Saturday, Tahlequah, as the mother has come to be called, was observed swimming without the body of her calf, according to Centre for Whale Research founder Ken Balcomb.

"Her tour of grief is now over and her behaviour is remarkably frisky," read an update on the research centre's website.

The orca gave birth on July 25.

As Ms Allyson Chiu wrote for The Washington Post, the pod of killer whales roaming between Vancouver and San Juan Island has dwindled to 75 members over the decades. The cause is no mystery: Humans have netted up the whales' salmon, driven ships through their hunting lanes and polluted their waters, to the point that researchers fear Tahlequah's generation may be the last of her family.

The 180kg, orange-tinted baby was the first live birth in the pod since 2015, Ms Chiu wrote. It lived for about half an hour.

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.

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

The act itself was not unprecedented, but researchers said it was rare to see a mother carry her dead offspring for so long. She carried her calf for about 1,600km during the mourning.

WASHINGTON POST