It has been known for a long time that whales and dolphins are incredibly intelligent animals but it’s not often we see that intelligence so impressively displayed as when orcas (often called killer whales) hunt. Orcas can actually be divided into several different ‘types’ which are found in different areas of the world and often specialise in hunting different prey. Some, such as those around Norway and Greenland, are particularly adept at hunting herring and follow the fishes migration path. Others, such as those in the north-east Pacific are skilled salmon hunters, and some have even learnt to strip tuna fish from fisherman’s lines. There is one group however that outclasses them all, the orcas of the Antarctic peninsula have become specialised at taking seals from floating ice and the way they do it is simply breathtaking. Ingrid Visser and her colleagues were lucky enough to observe the attack in 2006 and described it like this
…one killer whale remained in position with its rostrum against the ice floe while four killer whales moved away from the ice floe with the seal on it. These four killer whales reappeared simultaneously, approximately 20 seconds later in line-abreast with all submerged just under the surface. All four were coordinated-swimming, with their left sides orientated towards the surface. A trail of bubbles emanated from each of the animals blowholes as they accelerated and passed directly under the ice floe, two on each side of the stationary killer whale. This generated a large wave, which tipped the ice floe initially towards the wave, then as the wave poured over and crested under the ice, it pivoted and tilted the ice in the other direction where the attacking whales were now waiting. The breaking wave washed the seal into the water…
This same hunting technique, sometimes termed “wave-washing”, was later filmed by the BBC for the series Frozen Planet (highly recommended if you haven’t yet seen it).
As someone who has worked with seals a lot over the last few years I have mixed feelings about this. On the one hand the seal is clearly distressed and is tormented for a very long time before it is finally killed, but on the other I can’t fail to be impressed by the skill and intelligence of the orcas that is required to pull off an attack like this. For this hunting strategy to be succesful there must be forward planning, and a high level of communication and coordination between individual orcas. These characteristics are not often associated with animals.
What is really interesting is that in the case described by Visser and her colleagues the seal was caught after around 15 minutes but then released and allowed back onto the ice. It then had to endure a second wave-washing attack before being finally killed almost 15 minutes later. Why did the orcas not kill and eat the seal immediately? The answer is not known, it could simply be play behaviour or, more interestingly, it may be that the adults are training their young to hunt. We clearly have a lot more to learn from these amazing animals and I expect there will be many more discoveries in the future.
For a detailed description of this behaviour see:
Visser I.N., Smith T.G., Bullock I.D., Green G.D., Carlsson O.G.L. & Imberti S. (2008). Antarctic peninsula killer whales (Orcinus orca) hunt seals and a penguin on floating ice, Marine Mammal Science, 24 (1) 225-234. DOI: 10.1111/j.1748-7692.2007.00163.x
Ecologica 
Thanks for the pingback, Sam, and this is a fascinating story – I wasn’t aware that their hunting behaviour was so co-ordinated. It’s pretty clear that there’s organisation there, which definitely implies intelligence.
And I’m a bit of a softie, so the idea of the poor seal suffering for so long is distressing for me too. But this is the way family groups of mammals hunt, I think, because the young need to be taught how to hunt. Cats are much the same.
But the implications of this method of hunting are quite staggering – it means that not only are they capable of planning and organising the attacke, they’ve also clearly learned through experience about the physics needed to tip a small floe and get a seal into the water, and passed that learning into the collected knowledge of their pod.
It’s a pretty strong argument that they’re not just animals…
Hi Alison, thanks for your comment. I completely agree, what really amazes me here is how well coordinated these attacks are. The orcas must me to communicate and plan as a group, then work together as a team to pull it off. I’m not aware of any other examples of behaviour as complex of this other than in humans.
Dude, that is so (for lack of a better word) cool! I had seen wave-washing once before, how long it took, and only thought about the possibility of play behaviour.
Hi Ria, It is very cool! This is probably my favourite example of highly intelligent behaviour by animals in the wild. No one really knows why they take so long to kill their prey but play is certainly a possibility. I’ve seen another case in which a group of orcas caught a sea lion pup but rather than just eat it they spent a long time throwing it in the air and passing it around the group. It’s very hard to understand but totally fascinating!