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Journalism of Courage
When marine biologists first spotted bottlenose dolphins cavorting off the coast of Australia wearing sea sponges on their snouts, they didn8217;t know what to make of the odd behaviour. Now, an international team of researchers has produced evidence that the animals8217; antics represent a form of culture, which would add the dolphins to an elite group of species that pass traditions down through generations without being compelled by their genes.
8216;8216;We define culture as a behaviour that is acquired and passed on in a population,8217;8217; said Michael Krutzen, of the University of Zurich in Switzerland, who led the research. 8216;8216;We think this behavior is an example of that. It8217;s very exciting.8217;8217; Krutzen and his colleagues believe the dolphins, which live in Shark Bay off the west coast of Australia, wear the sponges while foraging for small fish, crustaceans and other food along channels in the sea floor to protect themselves against sharp coral and stinging stonefish. It8217;s a trick that appears to be almost exclusively passed on from mothers to daughters.
8216;8216;They wear them like a glove,8217;8217; Krutzen said. 8216;8216;When they go down to the sea floor to probe for prey, there are lots of noxious animals down there. By using the sponge, it protects them.8217;8217;
Many species use tools to perform tasks. Crows, for example, fashion tools out of leaves and twigs to forage for food. And many animals learn behaviour by mimicking their elders8212;that8217;s how birds develop their songs.
But those abilities stem from instincts that are inherited through genes. Aside from humans, the only other creatures known to transmit behaviour purely by interacting with one another are primates. Unrelated chimps pass on techniques for using sticks to fish ants out of nests; different groups of orangutans display eating habits, bedtime rituals and other behaviour that researchers believe is example of socially transmitted culture.
The bottlenose dolphins would be the first marine mammal shown to exhibit similar behaviour, indicating that complex social conduct may be more common than had been thought. 8216;8216;The boundaries between humans and animals are becoming less and less clear,8217;8217; he said.
The genetic analysis indicated that the behavior probably originated from a single ancestral female at some undermined point in the past. 8216;8216;All the animals that are spongers have the same maternal gene, which shows that all the animals are descended from the same female,8217;8217; Krutzen said. 8216;8216;We call her the Sponging Eve. 8217;8217;
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