The seal that lived

A Weddell seal, surrounded and trapped on an ice floe by a group of killer whales, caught the attention of research biologists Robert L. Pitman and John W. Durban – along with the attention of a pair of large humpbacks – in Antarctica. To get their catch, the killer whales implemented their infamous hunting trick – forming powerful waves to wash the seal off of the floe in an attempt to expose the animal to a lethal attack in open water – and it worked. With death a high chance, the seal swam frantically toward its last remaining hope, the pair of incoming humpbacks. 

In a make or break moment for the seal, something incredible happened. Just as it reached the closest humpback, the whale rolled over onto its back – and the seal was swept up onto the huge chest between the massive flippers. Then, as the killer whales moved in closer, the humpback arched its chest, lifting the seal out of the water. Even when the water that was rushing off of the whale’s belly almost washed the seal into the sea, the humpback gently nudged the seal with its flipper to place it back in the middle of its chest. Moments later, as the orcas gave up their pursuit, the seal scrambled off and swam to the safety of a nearby floe.

"Even when the water that was rushing off of the whale’s belly almost washed the seal into the sea, the humpback gently nudged the seal with its flipper to place it back to the middle of its chest." © Robert Pitman

“Even when the water that was rushing off of the whale’s belly almost washed the seal into the sea, the humpback gently nudged the seal with its flipper to place it back in the middle of its chest.” © Robert Pitman

A full-blown cetacean war?

“The first time I knew unequivocally that humpbacks were protecting other species from attacking killer whales was when I saw [that] humpback in Antarctica roll over on its back and lift [the] Weddell seal out of the water as it was being attacked by killer whales. I was shocked, but then immediately curious: Animals don’t help other animals unless there is something in it for themselves,” recounts Pitman, who works at the Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, in California.

To many, the above story might seem a one-off act of kindness from a solitary cetacean. But for the two biologists, only a week before had they witnessed a similar situation, when another helpless Weddell seal was saved from a pod of 10 killer whales by a different pair of humpbacks. As Pitman began to look into this phenomenon, he realised that all over the world, from Antarctica to the North Pacific, these humpback rescue missions were being reported. Interestingly, it’s more than just the mammals and humpback calves that are being saved, with reports of humpbacks also attempting to thwart an orca attack on the ever-strange Mola mola.

This apparent full-blown cetacean war is not only between humpbacks and killer whales; there have also been indications of humpbacks driving off attacks from false killer whales and pilot whales – as well as one observation of a humpback escort (a male that accompanies a humpback cow-calf pair) driving off a white shark in Western Australia.

But it’s difficult to determine why the humpbacks are attempting to frustrate these attacks, especially those carried out by killer whales.

“Ultimately, as in all animals, self-interest is the driver,” suggests Pitman. “If humpbacks interfere when killer whales are attacking a humpback calf, they might end up saving a related individual (offspring, sibling, distant cousin, etc.). Their behavioural response may be general enough that they end up protecting other species at times, but if the net effect is that they project more of their genes into future generations, then the behaviour will persist. We referred to it as ‘inadvertent altruism’.”

Pitman hints that personal motive could drive them to respond to hunts: “We say in [our] paper that the response of the humpbacks seemed to vary among individuals and that that could reflect a number of factors, including personal history with killer whales. A humpback that was attacked as a calf may have learned from its mother to respond aggressively to killer whale attack vocalisations, regardless of the species being attacked.”

A calf being torn to shreds by a pack of orcas. "A humpback that was attacked as a calf may have learned from its mother to respond aggressively to killer whale attack vocalisations, regardless of the species being attacked.” Video © J. Totterdell

A calf being torn to shreds by a pack of orcas. “A humpback that was attacked as a calf may have learned from its mother to respond aggressively to killer whale attack vocalisations, regardless of the species being attacked.” Video © J. Totterdell

So it appears to be a case more of self-interest than selflessness on the humpback’s part. From the outside, rescuing a small seal from the jaws of killer whales could be described as compassion, but ultimately it is most probably a survival strategy for humpbacks. It’s a widely spread notion among scientists to intensely scrutinise anything that could be regarded as compassion in animals.

Pitman says: “I think if humpbacks were cleverer they wouldn’t spend their time and efforts intervening when other species are at risk from a killer whale attack. They are as smart as they need to be, but no more!”

How to save a life

How the rescue mission is identified and takes place appears to alter through different observations. In 89 percent of the recorded incidents, the humpbacks intervene only as the killer whales begin their hunt, or when they are already engaged in a hunt.

“We suggest in the paper that they cue in on killer whale attack vocalisations – mammal-eating killer whales are mostly silent when they hunt because their prey has acute hearing. But once they start an attack and especially after they have made a kill, they get quite vocal. It is only at these times that we have seen humpbacks aggressively approach killer whales.”

More often than not, the humpbacks thwart the attack in pairs. The reason for this, as Pitman points out, is that humpbacks often travel in pairs. Sometimes cows with calves or sometimes cows with escorts, or a male that hopes to mate with the female that he accompanies. Travelling together is mainly a strategy for reproduction, but also works for predator defence: If a cow has an escort with her, he will also help defend the calf.

A young calf humpback that was being attacked by a group of killer whales off Western Australia is being lifted out of the water by the head of its mother. Coming in from the side is an escort, to help defend the mother and calf. © Liss Ballance

A young calf humpback that was being attacked by a group of killer whales off Western Australia is being lifted out of the water by the head of its mother. Coming in from the side is an escort, to help defend the mother and calf. © Li
ss Ballance

As orcas are renowned for being top-of-the-trade group hunters, it seems odd that they cannot do anything about this irritant. Mature humpbacks are just too large and too formidable to be hunted by them, but their calves are vulnerable. As mainly adolescent humpbacks – who have also been the subject of orca attacks – are known not to back down from an orca fight, this behaviour could also be a way of humpbacks displaying dominance to the orcas.

Whale behaviour still remains little understood. Mainly due to commercial whaling in the 20th century slapping whale meat onto the dinner table, and changing ocean ecosystems depleting prey, huge gaps in whale knowledge has been left. But as their populations continue to recover, even more information about the behaviour and impact of these massive animals will be on show for researchers to scrutinise.