Tuesday, December 27, 2005

Dolphin daughters sponge for knowledge

Decade by decade, year by year, we find that we have underestimated animals.

From Discover Magazine:
Dolphins' Daughters Sponge for Knowledge

Scientists tracking dolphin behavior reported in June that the mothers pass tool use on to their female offspring.

Researchers found that bottlenose dolphins share knowledge of how to use marine sponges for foraging, reflecting a combination of tool use and social learning.

The dolphins wear the conical tools on their nose, or rostrum, although no one knows yet how this helps them feed, says Michael Krützen, an evolutionary geneticist who coauthored the study. ... he and his colleagues found that sponge users in Western Australia have a different diet from their pod mates. That suggests the tools let them gain access to a new food source, perhaps by protecting their rostrums as they sift the seafloor for bottom dwellers.

The technique is not genetically imprinted, like nest building, and probably originated with one innovative "sponging Eve," Krützen says. "If there is a prime candidate for social learning, the dolphin is a good animal," he adds. They are skilled imitators, and female dolphins spend a long time with their mothers. So far, the researchers have seen only one male sponge wearer.

The findings come in a year that saw gorillas added to the list of tool-using animals. The primates were observed using sticks to test water depth and branches as a makeshift bridge.

Finding species that both use tools and pass down learning is much rarer, though. Until this year, only chimpanzees and orangutans were known to be capable of transmitting a material culture. Dolphins are the first nonprimates to join the club. —Elise Kleeman

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