I've read that Orca whales hunt together as a unit. It's very interesting and I want to know more about the dynamics of their hunting strategy and how they make sure that even the younger members of the pod have a role in acquiring their prey.
Dear Patrícia
Orcas do have several predatory strategies and some are very well documented: http://www.aquaticbiosystems.org/content/8/1/3
Also check here: http://www.nancyblacklegaldefense.org/Nancys_orca_research.htm
and read this attached paper.
Of course you know that the most studied predatory behaviour of orcas is in Peninsula Valdéz and there are lots of good literature on this (I made some intersting diving there and felt big orcas catching Arctocephalus australis right next to me). Pay also attention to orca predation on penguins and subadult elephant seals in the Kerguelen islands.
Best of luck,
Cheers,
JP
Hi Patricia,
in the following article they describe a strategy of orcas to prey on herring in Norway. This is really interesting and something different from the strategies on other mammals. It's amazing how those tactics vary, depending on the prey.
Nøttestad L, Fernö A, Axelsen BE (2002) Digging in the deep: Killer whales' advanced hunting tactic. Polar Biology 25:939-941
Patricia, if you look at my list of articles you will find a recent article called "Prey switching by killer whales in the north-east Atlantic: observational evidence and experimental insights", where you'll find several references to hunting strategies among orcas in the North Atlantic. The strategy described by Nøttestad in 2002, was first described by Similä and Ugarte in 1993, and they called in "carousel feeding", in which a group of whales surround a small patch of herring by showing them their white bellies, and then swim through the patch and stun single herring with their tail slaps. Tail slaps produce cavitation in the water, releasing enough energy to stun the fish. Nøttestad found by use of sonar equipment, that they also used this technique at depth. You can also see several clips on Youtube (http://www.youtube.com/watch?v=AwbNRNCxhFg), showing how groups of orcas hunt seals on ice floes in Antarctica, where the group cooperates to produce waves that wash seals off ice floes.
I'm not sure if there are papers on it yet, but orca in New Zealand feed very heavily on stingrays. They, and possibly some other orca groups, have learned that holding elasmobranchs upside down induces a tonic state, rendering the prey immobile and non-harmful to the whale. In NZ, orcas that have located a stingray appear to turn upside down, descend, grab the stingray often by the tail, and then when they right themselves the ray is flipped over and tonic is induced. There are a couple youtube videos which show this (featuring NZ orca research Ingrid Visser). One also shows a male orca passing half of a stingray to a juvenile for it to eat.
Have a look at this paper.
Article The diving behaviour of mammal-eating killer whales (Orcinus...
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