Orca seen foster parenting a pilot whale calf for first time

The first documented case of cross-species parental behaviour among whales has led researchers to wonder whether a long-finned pilot whale calf was adopted or abducted by an orca.

A long-finned pilot whale calf has been documented swimming behind the flipper of a female orca – in “echelon”, or the mother-and-calf position – for the first time. How the inter-species pair came together is unknown, leading researchers to wonder whether the calf was adopted or abducted.

Saedís, an orca, with a long-finned pilot whale calf at her side

In August 2021, a whale-watching tour near Snaefellsnes peninsula in West Iceland spotted a pod of three orcas with a surprise guest. Marie-Thérèse Mrusczok at the West Iceland Nature Research Centre, who was on board, saw a young whale drafting off the wake of a female orca named Saedís, but the calf was too small to be an orca (Orcinus orca).

The youngster looked like a long-finned pilot whale (Globicephala melas), which puzzled Mrusczok, as no pilot whales were swimming through the area that afternoon. “I knew what I was seeing – and I also saw it in the pictures – but my mind was just saying this cannot be. This is really, really weird,” says Mrusczok. When she and her colleagues reviewed images and video footage later, they confirmed their suspicion: this was the first documented case of an orca showing parenting behaviour to a calf of a different species.

The bond appeared to be exclusive to Saedís and the calf. In the 21 minutes that Mrusczok observed the pod, the other two orcas didn’t interact with the young whale. The pilot whale’s visibly low body fat suggested it wasn’t nursing and was in poor health. Its still-wrinkled skin, called fetal folds, indicated that it was a newborn. When researchers saw Saedís the following summer, the calf was no longer with her, having probably succumbed to malnutrition, they say.

Both pilot whale and orca calves are used to being “babysat” for short periods while their parents hunt, says Mrusczok, which could increase the likelihood that they could latch onto a non-mother caretaker.

But calling this cross-species relationship parenting may be going too far, says Filipa Samarra at the University of Iceland, who wasn’t involved in the work. The young pilot whale may have been swimming near Saedís to draft off her wake and make swimming easier. “It could be that the female is just tolerating the presence of this calf,” says Samarra.

Over the decade that researchers have been watching Saedís, she has never had a calf of her own, and it is possible that she may have adopted the pilot whale calf as a substitute. “One theory is that it was an orphaned calf that they found and took into the pod,” says Mrusczok. There could also be a more sinister explanation: this may be a case of calf-snatching.

When the two species cross paths in Icelandic waters each summer, pilot whales occasionally charge toward orcas to shoo them away. But in July 2022, a year after Saedís was seen with the calf, Mrusczok saw groups of both species make repeated advances toward each other in a way never before documented. This time, the orcas appeared to be the aggressors, charging a pod of pilot whales with multiple young calves. “There is a possibility that the female [orca] that had the pilot whale calf before was trying to obtain another,” says Mrusczok.

Whatever the cross-species custody arrangement is, it seems to be a trend. Samarra’s research team made a similar sighting in 2022. A different female orca in southern Iceland was swimming with a long-finned pilot whale at her side, which also looked malnourished.

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