Why are humpback whales rescuing seals?

humpback

Robert Pitman is a marine ecologist with the National Oceanic and Atmospheric Administration in La Jolla, California. His paper on humpback whale behaviour appears in Marine Mammal Science (DOI: 10.1111/mms.12343)

 

You first saw humpback whales behaving strangely in 2009. What happened?

We were doing killer whale research in Antarctica and had the BBC on board filming Frozen Planet. We saw some killer whales interacting with some humpbacks and thought it could be an attack. We went over to have a look and the humpbacks were a little agitated, but it wasn’t a full-on attack and the killer whales ended up going away. We weren’t quite sure what was going on, but when we looked at the BBC footage, we saw there was a Weddell seal between the two humpbacks. So we thought maybe the seal was trying to escape and found refuge.

We followed the killer whales and soon they started attacking a crabeater seal on an ice floe, creating waves to try to wash it off. A few minutes later, the two humpbacks we had left behind came charging in and chased after the killer whales, slapping their flippers and making a nuisance of themselves. This was different because the humpbacks were on the offensive. But we figured it was just mobbing behaviour, like when garden birds mob a predator to try to get rid of it.

When did you realise the whales were doing more than just driving a predator away?

Well, a couple of days later we saw some killer whales attacking a Weddell seal on an ice floe and there were a couple of humpbacks in the vicinity. We could tell they were agitated because we could hear them bellowing – it’s an impressive sound. The killer whales washed the seal off the ice and it started swimming into open water. Then, suddenly, one of the humpbacks comes to meet the seal and, just as it gets to the seal, rolls over on its back and the water washes the seal onto its chest. The whale lifts its chest up out of the water with the seal on it.

That sounds like pretty unusual behaviour for a whale…

Yeah – we were amazed to see it. But we immediately thought maybe the whale didn’t know the seal was there, maybe this was all just coincidence. Then we looked at the BBC footage, and we saw that at one point the seal had started to slip off the whale’s chest. The humpback used a 5-metre-long, 1-tonne flipper to gently nudge the seal back up onto its chest. Once we saw that, we knew it was no accident and something was going on.

What did you think was happening between the humpbacks and the seal?

It looked like altruism – as if the whales were acting out of concern for the smaller animal. But we are not talking about humans here, and when animals do something that appears to be altruism, I try to come up with rational explanations for it. But the reason wasn’t obvious because, as best we know, animals always act in their own self-interest. “This needs an explanation,” I thought.

What about other cetaceans — does their behaviour offer clues as to what was going on?

There are lots of anecdotes about dolphins helping other animals in distress, including humans. But that’s different from the humpbacks: they were going in to help an animal being attacked by an apex predator.

 

Read the rest of this interview at newscientist.com here.

Photo credit: Antartica Bound, flickr