Grief has long thought to be a human trait, but other animals – from killer whales to crows – also appear to suffer loss when a companion dies.

Last week, a female killer whale was spotted off the coast of Washington State pushing the body of her dead newborn calf. The orca, known as Tahlequah, was observed doing the same thing in 2018 after another of her calves died in infancy. On that occasion, Tahlequah pushed the body of her offspring for 17 days, continually retrieving it and preventing it from sinking – an incredible feat given the fact that killer whales can travel an average of 120km (75 miles) a day.

Whales are not the only species known to carry the bodies of their deceased young. In 2021, Edinburgh Zoo reported that one of their chimpanzees, Lianne, had given birth to a stillborn baby and was refusing to let go, carrying the infant around with her within the zoo enclosure. Other highly intelligent mammals, such as dolphins and monkeys, have also been observed behaving this way.

"It's hard to see this behaviour without thinking of it through the lens of grief, partly because, as humans, if we lose someone we want to cling on to that person in some sense," says Becky Millar, a researcher specialising in the philosophy of cognitive sciences at Cardiff University.

"It seems to be a very literal manifestation of that kind of urge to retain bonds with the dead loved one."

According to Millar, what's notable about these cases is that these animals don't treat the deceased infant in the same way that they would treat a merely immobile, but live infant. This suggests that it's not just a matter of them not understanding that their infant is dead.

"There is some sort of tension where the animal isn't quite able to let go," says Millar. "It's like they're trying to grapple with this new world that they're faced with and trying to come to understand that loss."

There are signs that both humans and animals undergo this readjustment period. For example, Millar points to the fact that animals often search for their companions after their death, while humans also engage in what are called search behaviours following a bereavement, where they scan the environment for any sign of the deceased person.

Sometimes this behaviour can continue long after the death. Famous examples include that of Greyfriars Bobby, a terrier who spent 14 years guarding his owner's grave in Edinburgh, Scotland, and Hachiko, an akita dog that continued to wait for its owner at a train station in Japan long after his death.

There are also anecdotal stories of animals displaying acute distress after the loss of a close companion. There are reports that upon seeing their babies eaten by killer whales, for example, sea lion mothers wail pitifully in apparent anguish.

There are other examples too. In her book How Animals Grieve, anthropologist Barbara King also describes accounts of cats, dogs and rabbits crying and searching for their companions, and horses gathering around the grave of a member of their........

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