A couple of blogs posted in the past few weeks relating to whales reminded me of something I saw on Animal Planet about the hunting behavior of Orca whales, so I decided to do some research to see what has actually been learned about these fierce predators. As you may know, Orca whales are not actually whales at all, but are in the order Delphinidae, making them the largest of the dolphin family. They form matrilineal groups called pods, which can then be grouped into larger clans based on genetic and behavioral differences. It is also important to note that there are 3 distinct population types; the transient, residential, and offshore populations. Residential populations, while still nomadic, have a smaller home range than the other two population types, and also tend to have larger pod sizes, around 50 individuals. Transient populations are usually only made up of 6 to 8 individuals, and do not seem to have the same strong family bonds displayed by the residential populations, likely because of the amount of movement to follow food displayed in these individuals. Not much is known about the offshore populations, except that they are genetically distinct from the other two populations, and (you guessed it) tend to stay close to the shore.
Orca whales are also known to have 3 types of calls: whistles, pulses, and clicks (used for echolocation). As it turns out, all Orca whales, much like species of birds we have talked about in class, are known to have pod-specific dialects, likely formed due to the high level of social interactions displayed between members of the same pod in this species. Dr. John Ford was able to group pods together based on similarities in their dialects, to form larger clans.
It has been observed that the various calls used by these whales are partly innate and partly learned. Apparently, different pods with genetically related individuals have more similar calls than those without genetically related individuals, suggesting that it is partly innate. However, according to MERSEA (Marine Education and Research of South East Alaska, 2009), mothers teaching their calls to their young has been observed.
The high level of social interaction displayed by these mammals has also led to the development of a quite impressive skill of coordinated hunting; although, what has really surprised me is the incredible variety in communication and hunting strategies displayed by this species.
I found an article from BBC news that focuses on the transient populations of Orcas, which have been observed during bouts of hunting as actually being silent until they make their kill, likely because they mostly hunt marine mammals that could hear them communicating underwater. In this article, researchers hypothesize that these small groups rehearse a simple hunting strategy which they can then employ without having to make sound. Here's a link to that article: http://news.bbc.co.uk/earth/hi/earth_news/newsid_9409000/9409694.stm
Here's a link to the hunt that I was originally thinking of; a small pod led by the head matriarch of the group, using communication & cooperation to catch the seal stranded on an ice flow: http://www.youtube.com/watch?v=p3xmqbNsRSk
Here's a link to another interesting clip I found, and I was really surprised by the difference between this behavior and the behavior of the previous clip.. I'm not sure if it is because this is two males (as opposed to the matrilineal family group of the first clip) or if maybe these are clips from two different populations, causing them to employ different hunting behaviors. http://www.youtube.com/watch?v=DWsN63PRCW8
Either way, Orca whales seem to be highly intelligent, and I think there is still a lot to be learned from these marine mammals and their methods of communication and hunting, despite their bad reputation as ruthless killers.
References:
Dolphins-World.com. (2009). Killer Whale Communication. Killer Whales. Retrieved from: http://orca.dolphins-world.com/killer-whale-communication.html
MERSEA (Marine Education and Research of South East Alaska). (2000). ORCA - The Killer Whale: King of the Sea. Retrieved from: http://www.mersea.com/Orca%20Info.htm
OrcaLab. (2011). OrcaLab. Orca Communication. Retrieved from: http://www.orcalab.org/about-orcas/information/communication/index.htm
Victoria Gill. (March 2011). BBC News. Killer whales hunt in silent "stealth mode". Retrieved from: http://news.bbc.co.uk/earth/hi/earth_news/newsid_9409000/9409694.stm
Posted by Brianna Eddy (4)
My heart goes out to these seals! So gruesome! The range of hunting tactics is impressive, however, I have to admit. In reference to the last video, I can't even believe those huge orcas beach themselves to grab the sea lions! And then they play with them before eating them? This better serve some purpose other than entertainment, like preparation for future fights like the video suggested. I think I struggle with this action because if it is just on the whim of the orca, then I would have to believe that animals can have malicious, bad characteristics. Good and evil, if you will. I know that this area of research in animals, of their emotions, is widely controversial. I personally like to think that they do everything they do for purposes of survival and kinship.
ReplyDeletePosted by Chelsea Van Thof
There sure is a lot of information on orcas this week! What really surprised me about this one was the diversity of different methods that these whales use to hunt. Communicating during a hunt is one thing, but rehearsing a silent stealthy strike is in a whole other ballpark. The way that the hunting style varies between populations is also interesting. It seems like every pod will invent their own technique. I wonder what causes different pods to have such different methods?
ReplyDeleteRhys Ursuliak
As it turns out, the resident and transient populations tend to specialize in different prey, with the resident populations eating more fish, and the transient populations eating more marine mammals. This also reflects the tendency for the resident populations to be more vocal than the transient (so their largely marine mammal prey can't hear them during the hunt). As for the second video, I wonder how common of a behavior that is, since it's not advantageous for the orca to expend all that energy playing with its prey and not eat it in the end; but I found that there is very little information about play behavior in this species available.
ReplyDeletePosted by Brianna Eddy