Dolphins May Use Tools
Bottlenose dolphins may now be capable of using tools to protect their most sensitive of body parts. A study performed by Michael Krützen of the University of Zurich in Switzerland has found that dolphins may cover their beaks with sponges to protect them from damage while foraging. The sponge-using dolphins reside off the coast of Australia in Shark Bay, and are believed to descend from a single maternal lineage.
The researchers believe that this is a passing along of a learned behavior from mother to offspring. The first sighting of this behavior was in 1986 when a passerby boat caught a glimpse of a dolphin, which appeared to have a “tumor” on its beak. In 1997, it was then that researchers took action and found a population of dolphins that exhibit this practice which is now known as sponging. This behavior is the first recorded instance of tool use among dolphins.
The study of these dolphins has been difficult according to the researchers for the reason of large shark populations also residing within the bay. However, DNA was studied from this dolphin population of one-hundred and eighty-five, with 12 female spongers and only one male. The rest of the dolphins were non-carriers. The dolphins in ten scenarios of inheritance produced unsuccessful results in a genetic explanation to the female-bias of sponging. The exact cause how certain dolphins exhibit this behavior is unknown because of failed genetic trials and spongers and non-spongers coexsiting together.
Because a genetic solution is doubtful, these researchers believe that cultural transmission, or the learning of a taught behavior, is the best possible explanation. Further observation will be needed to determine the exact methods on how bottlenose dolphins obtain this behavior.
Posted by BRW (6)
4 Comments:
Your post is well written and very interesting. This is an important study for better understanding the evolution of animal behavior as it relates to higher learning outside of humans. As far as the actual behavior of the dolphin, I am part of a bottlenose survey based out of this campus headed by Prof. Maldini, and ironically have read this article. One hypothesis of this behavior is that male bottlenose dolphins usually form close bonds with other males. These alliances aren’t really suited to seabed foraging which is usually a solitary act, and thus may be a reason why it is passed to the females. Sorry this was long, but good post. Here is just a link to the survey as mentioned above: http://scientistlog.blogspot.com/
Posted by MPC
Two questions- did it appear that only those 13 spongers were of maternal decent or is the entire population related, and are you sure that the beaks are their most sensitive body part? I seem to remember from Zoobooks as a kid that dolphins use their snouts to ram shark fins for defense. All in all a facinating example of social learning, well presented and informative post.
A. McCandless
It does not surprise me to see that some pods of dolphins have adopted the ingenious use of tools, making them the second marine creature to perform such a task (otters being the other). Yet the article raises a pertinent question on why it is only certain individuals that use tools. Dolphins in Australia of course are negociating the Great Barrier Reef, an obvious mass of coral where fish use for cover. It could be that only some of the smaller dolphins like females, are able to navigate in such a tight area, while other males hunt in the open waters. Also other dolphins of different locations never have to contend with the quantity of reefs in Australia, and are perfectly suited to fishing the abundant schools of sardines, etc. that perform their migratory cycles. I think further clarifying tests might be to take dolphins of different areas and transplant them in Australia, and analyze their behavior, and/or genetics.
Posted by TSK (6)
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