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A female Cuvier鈥檚 beaked whale has been observed swimming around her dead calf, touching her head against his and trying to lift his body in an apparent show of grief. This is the first time such grieving behaviour has been documented in a beaked whale.

The pair was spotted by a tour group on board a whale-watching boat 21 kilometres off the coast of Bermeo in the Bay of Biscay in the north of Spain.

鈥淚t was very sad to see,鈥� says Gorka Ocio, a guide on the boat, which is operated by tour company Verballenas. 鈥淭he ship was silent. We were very aware that we were seeing something unique.鈥�

The 2.5-metre-long deceased calf, which was identified as male by observing his genitals, was floating on the surface of the water while his mother, who was about 5 metres long, repeatedly swam circles around him. His condition suggested he had died less than two days earlier.

In one instance, the female swam a few metres from her dead calf and then turned back to make head-to-head contact with him. She was also seen carrying him for a few metres on her back, as well as diving underneath him and trying to lift his body with her head while blowing vigorously.

Ocio says he believes the mother may have been unable to accept that her calf was dead and was lifting him to encourage him to breathe. 鈥淲e know that in other cetacean species, mothers lift their newborn calves with their bodies to help them take their first breath,鈥� he says.

at the College of William & Mary in Virginia, who has written a book about animal grief, says it is hard to know whether the mother was 鈥済rieving鈥� over her dead calf or simply 鈥渁ssessing her son鈥檚 state, perhaps trying to help him breathe, just in case he might still be living鈥�.

However, the fact that mothers from other cetacean species have been seen tending to dead calves in similar ways 鈥渟trengthens the possibility of grief behaviour鈥�, she says.

For example, a female orca named Tahlequah captured headlines in 2018 when she carried her dead calf for 17 days. And in 2007, a female bottlenose dolphin was seen repeatedly trying to lift her dead calf out of the water as if trying to help it breathe.

The female Cuvier鈥檚 beaked whale (Ziphius cavirostris) sighted by Ocio鈥檚 group was very thin, with her ribs showing. 鈥淚t seemed that she had not eaten for a long time and that her labour might have been hard on her as well,鈥� he says. It is unclear whether her calf鈥檚 death was related to her poor health, he says.

鈥淕iven the mother鈥檚 weakened condition, it鈥檚 very moving to learn that she expended energy to repeatedly swim near and contact the body of her son,鈥� says King.

Ocio says the observation provides new insights into the behaviour of beaked whales, which are among the least understood marine mammals because they typically live far offshore and spend most of their time diving deep underwater.