Tuesday, February 10, 2009

Tool-use and innovation in wild bottlenose dolphins

Last month, I saw this article about wild bottlenose dolphins in Spencer Gulf, South Australia, preparing cuttlefish to eat by deboning and ridding them of ink. Last night, thanks to CANZ and STIA, I had the pleasure of hearing a presentation by Georgetown University professor Janet Mann, who described what she and her students have observed in the wild bottlenose dolphins in Shark Bay, Western Australia. Several dozen of the dolphins she has been studying demonstrate a behavior she calls "sponging." They carry sponges in their beaks to scare up a certain kind of fish from the sandy floor of the bay. She and her team have identified sponging as the first clear case of tool use by wild dolphins, whose brains are proportionally three times as big as chimpanzees. The have also determined that sponging is socially learned behavior, passed down from the mother, and that sponging dolphins spend more of their time (17%) foraging for food than their non-sponging counterparts. "It turns out the brainiacs of the marine world can also be tool-using workaholics, spending more time hunting with tools than any nonhuman animal,” Mann says. The Ruler Lady has been aware of this unique research opportunity in Australia because she has checked and accepted the dissertations of several of Mann's doctoral advisees. Listed below are the three most recent:
Dr. Mann and her fellow researchers track birth and death rates, relatedness (genetics), and shark attacks. They also monitor where dolphins range, how long they nurse (which can be up to 8 years!), their hunting techniques, and their courtship behavior. “Over the years we’ve collected data on about 1,500 different dolphins,” she says, “but we’ll actually see between 400 and 600 in any given year.” Dr. Mann has been carrying out a longitudinal study about dolphin mothers and calves since she first came to Shark Bay as a graduate student in 1988.

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