Dolphins that hunt by beaching themselves

Here is a paper in the Canadian Journal of Zoology which documents learned hunting behaviour among Tursiops truncatus, the bottlenose dolphin, in Western Australia.

Specialization and development of beach hunting, a rare foraging behavior, by wild bottlenose dolphins (Tursiops sp.)

B. L. Sargeant, J. Mann, P. Berggren, and M. Krützen

Abstract: Foraging behaviors of bottlenose dolphins vary within and among populations, but few studies attempt to address the causes of individual variation in foraging behavior. We examined how ecological, social, and developmental factors relate to the use of a rare foraging tactic by wild bottlenose dolphins (Tursiops sp. Gervais, 1855) in Shark Bay, Western Australia. Beach hunting involves partial and nearly complete stranding on beach shores. Over 10 years of observation, only four adults and their calves were observed beach hunting in more than 1 year. Of two adult beach hunters observed in detail, one was more specialized in beach hunting than the other, indicating substantial flexibility in degree of use. Only calves born to beach hunters developed the tactic, although complete stranding was not observed at least up to 5 years of age. Beach hunters used shallow, inshore habitats significantly more than others and were more likely to hunt during incoming tide. Mitochondrial DNA haplotypes were not consistent with strict matrilineal transmission. Thus, beach hunting likely involves vertical social learning by calves, while individual, horizontal, and (or) oblique learning may occur among individuals who frequent coastal habitats.

What's interesting is that younger dolphins learn this socially. The notion of "vertical", "horizontal" or "oblique" transmission comes from the excellent work of Peter Richerson and Robert Boyd, who have produced a mathematical and comprehensive view of social evolution. Vertical evolution is learned from parent to child, while horizontal is between age cohorts, and oblique is from the older generation.

There is increasing evidence that animals apart from humans learn by imitation, ranging from birds learning bird song from their parents and flock, to monkeys learning how to wash potatoes, as this excellent post by Evil Monkey at Neurotopia, which debunks the myth of the Hundredth Monkey and replaces it with good old cultural transmission (in this case mediated by swimming).

The study of animal culture is useful because it reduces the variables that confound such investgation among humans, who have multiple lines of transmission including symbolic transmission through language, writing, and artifacts. As we get a handle on how culture evolves in what are relatively simple cases, we can then use that as a baseline to study human cultural dynamics without being sidetracked by the folk sociology that is based on "common sense", or, as Einstein put it, the set of prejudices we acquire by age 16.

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This reminds me of something very similar. Recently, in Science News I think, there was discussion of cultural transmission of hunting behavior down matrilineal lines among dolphins in a bay in western Australia.

The hunting behavior was the retrieval and use of a sponge to protect the beak as dolphins probed the sandy bottom acoustically. If I remember the explanation correctly, they hold the sponges in their mouths, then with their beaks right on the bottom, move about, trying to ping-up prey. As here, a small percentage of dolphins in the bay do this, all relatives. There were photos of the behavior.

Any connections to this. Researchers, location, etc.?

And of course, this pops up the video in my mind of the seal-pup-on-the-beach hunting Orcas, Patagonia I think.

By SkookumPlanet (not verified) on 25 Jun 2006 #permalink

Please expand the definitions. Interspecies cultural transmission also occurs. Humans learn behaviors such as termiting from chimps, mockingbirds learn sound patterns from us, and my cat has learned to open doors simply by observing me - a behavior I find annoying and would not willingly have taught her. I do not doubt that any method of obtaining food or avoiding danger that would be easy to adopt by another reasonably post-limbic (dare we say cortical?) species *will* be adopted, whether that requires crossing species boundaries or not.

Cultural transmission of behavior in dolphins is well-known as a phenomenon. This study properly discusses how they were going about studying the mechanism of this sort of transmission. Ob. disclosure: Janet Mann is a co-author on a submitted manuscript.