June 6, 2005 (Discovery News) — The use of sponges as tools among some dolphins could be the first documented case of a material culture in a marine mammal species.
The behavior, called sponging, involves a dolphin affixing a marine sponge over its snout to protect itself while it pokes and prods for fish on the sea floor. Researchers believe the use of this sponge tool is a fishing technique that mother dolphins teach to their children.
The study is published in this week's Proceedings of the National Academy of Sciences.
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Dolphin mums teach daughters to sponge
Judy Skatssoon
ABC Science Online
Researchers have seen dolphins using tools for the first time, and they say the practice seems to be passed down from mother to daughter.
Dolphins use a piece of sponge to coax fish out from under the sea floor, the first time material culture, or the use of tools, has been seen in cetaceans.
The international research is published today in the Proceedings of the National Academy of Sciences.
"It seems highly likely that sponging is culturally transmitted mainly within a matriline, ie, daughters learn this behaviour from their mothers," reports lead author Dr Michael Krützen, who did the work while studying for his PhD at Australia's University of New South Wales.
Male dolphins have the same opportunity as their sisters to learn the trick, but apparently have better things to do, he suggests.
Krützen, who is now based at the University of Zurich, and colleagues, observed sponging among a group of wild bottlenose dolphins at Shark Bay, off the West Australian coast, between 1988 and 2002.
Some 500 of Shark Bay's 3000 dolphins are well known to researchers, and many of them have devised ingenious ways of catching fish, such as chasing them ashore.
Researchers have seen about 25 dolphins sponging, which involves breaking off a cup-shaped piece of sea sponge and putting it over their rostrum, or nose, while they forage for food.
The team studied 13 spongers, all apparently related, which included only one male.
Culture versus genes?
University of New South Wales geneticist Associate Professor William Sherman worked with Krützen on the project.
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