Otter Poop Helps Scientists Track Pollution at a Superfund Site

By Deirdre Lockwood

The Duwamish River, which winds through Seattle, contains a lot of unpleasant stuff. In one industrially contaminated stretch, which has been designated a Superfund site, levels of many pollutants exceed state health standards. The compounds, which include notorious chemicals such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), settle in river sediments and make fish and shellfish unsafe to eat.

Swimming amidst this pollution is a population of river otters. Now researchers are proposing to use otter poop to help monitor a 17-year-long plan to clean the river, recently approved by the U.S. Environmental Protection Agency. Biologist Michelle Wainstein, from Seattle’s Woodland Park Zoo, says the charismatic mammals are top predators who mainly eat fish and crabs but also dine on frogs, birds and small mammals. All these river denizens take in pollutants and pass them along to otters. The otters, in turn, use communal latrines on shore to defecate, making it easy and noninvasive to sample their scat for pollutants. “They like to get together and have poop parties,” Wainstein says.

This kind of sampling can give scientists a much better idea of what is getting into a body than simply analyzing water or river sediment. Picking up scat to determine pollutant levels also is preferable to trapping otters, because handling the creatures “can be extremely stressful for animals,” says Elizabeth Peterson, a postdoctoral researcher at Colorado State University–Pueblo. And cleaning the river is important. In mammals including humans PCBs disrupt reproduction and the endocrine and neurological systems, and are carcinogens. Many PAHs are also probable human carcinogens. In the otters, scientists suspect PCBs may harm reproduction but do not yet have direct evidence.

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