A black Lab mix named Tucker sits on a motorboat. As the boat travels around Washington's San Juan Islands, researchers watch Tucker. When he wags his tail and leans over the side of the boat, the researchers know that Tucker smells orca scat, or poop.

Tucker is one of three dogs in the world trained to track the scent of orca scat. It's a big job, says Samuel Wasser. He is the director of the Center for Conservation Biology at the University of Washington.

The center's group Conservation Canines trained Tucker. At Conservation Canines, Tucker and other dogs take part in programs that help endangered species around the world.

A Moving Target

Orcas are also known as killer whales. Orcas are not endangered. But those that live near the San Juan Islands are endangered.

Studying what comes out of the whales helps scientists understand what could be harming the animals. But orca scat is not easy to find. It smells like salmon and is often the color of the water.

Tucker must signal the boat's pilot where to go while the scat is floating in the water. "It's a moving target," says Wasser, "but Tucker still gets it."

When Tucker finds the scat, he gets to play with a ball as a reward. By collecting frequent samples from the orcas, researchers have learned that the whales' biggest problem is a lack of fish to eat. "We couldn't do this without Tucker," says Wasser. And for that, Tucker deserves a special treat.

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