http://www.nytimes.com/2005/12/11/magazine/11ideas1-14.html?_r=0
By AARON RETICA
New York Times, Published: December 11, 2005

Sometimes, when a dolphin in Shark Bay, off the coast of Western Australia, prepares to forage, she drops to the sea floor, rips a fat conical chunk of sea sponge out of it, covers her beak with the sponge cone and sets to work. After she finds the fish she wants, she drops the sponge. “Sponging," as the scientists at the Shark Bay Dolphin Research Project call this behavior, is an unusual instance of an animal using another animal as a tool, but that is not what makes the sponging interesting to biologists. It’s that dolphins learn to use the sponges – to probe deeply for food while protecting their beaks – from their mothers.

In “Cultural Transmission of Tool Use in Bottlenose Dolphins," a paper published this spring in the Proceedings of the National Academy of Sciences, Michael Krützen, Janet Mann and several other researchers argue that they have demonstrated “the first case of an existing material culture in a marine mammal species." Genetic explanations for the behavior, they write, are “extremely unlikely." And there are dolphins in Shark Bay that don’t use the sponges but forage in the same deep-water channels as those that do – so sponging can’t be only habitat-driven either.

The sponging dolphins “see what Mom does and do it," Mann says. One-tenth of the mothers sponge. Many of their offspring have been seen sponging, too, and there is at least one documented case of sponging by a grandmother, a mother and a granddaughter. Nearly all of the mature spongers are female. Quite a few juvenile males try sponging, but they don’t keep it up. Krützen and his colleagues speculate that the solitary nature of sponging may be incompatible with the intense social requirements that characterize mature male dolphin life.

All but one of the genetically-tested sponging dolphins share “recent co-ancestry" with an animal the researchers call a “Sponging Eve," the first dolphin to discover the technique and pass it on. In other words, they’re related to one another. “It’s a little sponge club," Mann explains. But the genetic markers they share don’t seem to correspond to anything that has to do with their ability to sponge.

To discover dolphins, with their incredibly efficient bodies, using tools is startling because “they’re streamlined not to use tools," Mann says. “That’s why the mechanism of how they do it is very interesting."

From Wikipedia: (part)

Dolphins

Dolphins are social and live in groups known as “pods." Pods can contain up to a dozen dolphins. In places with an abundance of food, pods can merge temporarily, forming a “superpod." Such groupings may exceed 1,000 dolphins. Dolphins communicate using a variety of clicks and whistle-like sounds. Membership in pods is not rigid. However, dolphins can establish strong social bonds. For example, they will stay with injured or ill dolphins, even helping them to breathe by bringing them to the surface if needed. This altruism does not appear to be limited to their own species. A dolphin in New Zealand has been observed guiding a female Pygmy Sperm Whale together with her calf out of shallow water where they had stranded several times. They have also been seen protecting swimmers from sharks by swimming circles around the swimmers or charging the sharks to make them go away.

Dolphins also display culture, something long believed to be unique to humans, and possibly other primate species. In May 2005, a discovery in Australia found bottlenose dolphins teaching their young to use tools. They cover their snouts with sponges to protect them while foraging. This knowledge is mostly transferred by mothers to daughters, unlike primates, where knowledge is generally passed on to both sexes. Using sponges as mouth protection is a learned behavior. Another learned behavior was discovered among river dolphins in Brazil, where some male dolphins use weeds and sticks as part of a mating display.

Dolphins also engage in acts of aggression towards each other. The older a male dolphin is, the more likely his body is to be covered with bite scars. Male dolphins engage in such acts of aggression apparently for the same reasons as humans: disputes between companions and competition for females. Acts of aggression can become so intense that targeted dolphins sometimes go into exile as a result of losing a fight.