Wasser has been called the “guru of doo-doo,” and it’s a title he wears with pride. In the 1980s, he pioneered the use of scat as a tool for studying wild animals by extracting hormones from their droppings. Then, in the 1990s, he became one of the first researchers to show that feces could be a source of DNA. “Scat is the most accessible animal product in the world,” Wasser told me. “And it contains a huge amount of information, from the DNA of the animal that left it, to the DNA of all the things the animal was eating, to the microbiome in its gut, to its reproductive hormones, to its stress and nutritional hormones, to toxins.”

Because scat contains so much information—and because so much is churned out daily—Wasser has been able to resolve questions that probably otherwise would have been unanswerable. When, for example, orcas off the San Juan Islands stopped having babies, no one was sure why. Some marine biologists blamed stress caused by boatfuls of whale-watching tourists; others proposed the cause was toxins, like PCBs, which accumulate up the food chain. By analyzing the orca poop from the open-bowed deck of a Grady-White powerboat, Wasser and his graduate students were able to determine that the orca whales were conceiving. The trouble was they were miscarrying 60 percent of their fetuses. Wasser’s team found the reason: a decline in the whales’ favorite food, Chinook salmon. As the orcas grew hungrier, their fat released toxins that ended their pregnancies. (The discovery has not yet led to any policy changes, to Wasser’s regret.)

Wasser began enlisting dogs in his research after he attended a conference on bears and heard a talk about hunting with hounds. He found a program run in a state prison that taught dogs how to sniff out narcotics, and the sergeant in charge invited him to attend two rounds of training. “They start the dogs on marijuana because it smells so much,” Wasser explained. “When they moved to heroin, we moved to poop.”

Read the full article in the Smithsonian.