Nose guard.

Bottlenose dolphins in Australia's Shark Bay like to accessorize: They sport sponges (a type of sea organism that lacks a backbone) over their snouts. Scientists have recently discovered how dolphins acquired this odd behavior.

Why would Flipper wear a soft sponge on its rostrum? "The sponge acts as a glove to protect their sensitive beaks," explains Michael Krutzen, a geneticist at the University of Zurich in Switzerland. That way, when the dolphin pokes around on the seafloor for fish, its snout is safe from the bottom's jagged rocks.

Not all bottlenose dolphins use sponges in this way. So Krutzen and his colleagues wondered what led to the Shark Bay dolphins' behavior. To see if it was inherited, the researchers studied the dolphins' genes, or units of hereditary material. Result? It's unlikely that "sponging" dolphins carried a unique gene.

Instead, Krutzen's team believes that the dolphins learn the skill from their moms. One piece of evidence: Scientists had observed that female dolphins born to sponge-sporting moms start donning a nosepiece by the time they're 2 or 3 years old. But it turns out most males don't take up the behavior. Why not? Krutzen says that young males may be too busy trying to woo females to learn the skill from mom.