Orca cares for a pilot whale calf. Scientists say this behavior has never been seen before.

It was on August 12, 2021, that a group of researchers from Iceland and Canada, while traveling along the Icelandic west coast to study the behavior of killer whales (Orcinus orca) from this region, encountered what Elizabeth Zwamborn, one of the team’s scientists, describes as “extremely interesting” behavior.

A group of three killer whales, consisting of two females and one male, were swimming off the Snæfellsnes peninsula, accompanied by a baby pilot whale (globicephala melas). The researchers, who revealed the discovery in an article published in February in the Canadian Journal of Zoology, say the observation of this unprecedented behavior lasted 21 minutes and there were no other cetaceans in the area.

It is not uncommon to record interactions between orcas and pilot whales, but these encounters are limited to confrontations between groups of the two species. What makes this sighting unusual is the fact that, according to the researchers, it appears that the tiny calf was adopted by the killer whales. This is because the calf was seen swimming with a female killer whale known as Sædís, a behavior commonly seen between mothers and calves of the same species.

As such, the authors say this is the first recorded case of an orca caring for a calf of another species, establishing a case of allopaternity (in which parental care is provided to young by individuals other than their parents). ).

The female killer whale, named Sædís, swims next to a pilot whale calf. This behavior, the scientists say, was never seen before and required a large expenditure of energy on the part of the “stepmother”, revealing a large investment in protecting the offspring.
Photo: Marie-Thérèse Mrusczok and Sara Rodríguez Ramallo (article co-authors)

“Never before have killer whales been seen caring for calves of another species,” Elizabeth Zwamborn points out, explaining that these two cetaceans “have very similar parent-calf relationships” and very close body dimensions, so “a pilot whale makes a good substitute for a orca calf’.

However, this behavior raised more questions than it answered, as researchers are unsure whether the calf was “abducted” from its pod of pilot whales during one of the conflicts between the two species, was orphaned, or was abandoned by the mother.

But they believe it is more likely she was adopted than forcibly removed from her original group, and say the female Sædís was never seen with one of her offspring during the time the scientists were in the field, between 2011 and 2022.

“It’s possible that she can’t bear young or can’t care for them,” Zwamborn explains, adding that this makes this female killer whale better able to care for a calf of another species.

However, a year after this unusual sighting, when the scientists returned to the Snæfellsnes peninsula, the orca Sædís was no longer accompanied by the young pilot whale, not knowing what might have happened to the calf, which, when seen for the first time, he showed signs of malnutrition.

With all these mysteries, the authors write that more scientific research is needed to unravel the strange relationship between orcas and pilot whales and to understand how a calf of one species could be adopted by a group of others.

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