Some scientists spend careers studying animal scat. Like archaeologists excavating kitchen middens, they pick apart what has been left behind in a search for clues about an animal’s history, environment and status.

A river otter.
A North American River Otter at Pelican Island National Wildlife Refuge. Scientists are studying the scat of river otters to study the animals’ health and the relationships between predator and prey. (Keenan Adams, U.S. Fish and Wildlife Service)

On the western shore of Chesapeake Bay, just south of Annapolis, scientists at the Smithsonian Environmental Research Center (SERC) are studying the excretions of river otters. What they are learning may help us save these remarkable creatures.

River otters, Lontra canadensis, inhabit waterways and marshes all over the world, including around the Chesapeake Bay. Related to weasels, they’re as long as a baseball bat (their strong, tapered tails make up half their length), and about the same weight as a West Highland Terrier. Their thick, waterproof brown fur — the densest in the animal kingdom — has around a million hairs per square inch. Long white sensory whiskers, known as vibrissae, sprout from their broad, round faces. Their webbed feet are as adept on land as in the water. 

Otters are trending these days. That’s not just because they’re cute; people also love their playful, energetic behavior. Perhaps you’ve watched them sliding and gliding down steep banks, burrowing in snow, frolicking in the water, or otherwise engaged in the business of otter life. They’re such good swimmers that they can dive to more than fifty feet and remain underwater for up to eight minutes. They mate in early Spring; otherwise, mature males and females don’t mingle. It may take a year for kits to be born because of a delay in the implantation of fertilized eggs in the uterus.

As with other animals, most otter activity involves food. To fuel their vigorous activity, they must eat 15-20 percent of their body weight every day. They mainly eat fish. They’re so good at fishing, using their sensitive vibrissae to detect prey, that Bangladeshis have trained them to herd fish into nets. Otters also consume shellfish, amphibians, turtles and other aquatic species. They’ll sometimes take small mammals and birds. In Scotland’s Shetland Islands, they hunt rabbits.

All that eating has the obvious outcome. For most animals, defecation is a solitary activity. Not so, for river otters. These animals use communal “latrines,” where relieving themselves becomes a social activity, an opportunity to build and strengthen bonds, exchange information and even groom one another. As the SERC’s Katrina Lohan and Karen McDonald put it, “River otters take party pooping to a new level.” And the redolent odor of otter ordure has an unexpected benefit — it may discourage predators.

That brings us to the SERC’s scat studies.

Knowledge of what otters eat can not only help scientists better understand the animals’ health and welfare, but also the status of an entire ecosystem. River otters are “apex predators,” meaning that they are at the top of a watershed’s complex food web. That makes them vulnerable to pollutants concentrated in their prey items. Because otters are what they eat, they’re also a “sentinel species” for Chesapeake Bay, giving warning of systemwide environmental problems.

That’s where the scat comes in. By scrutinizing dung collected from otter latrines, SERC researchers can learn about parasites, toxins and contaminants throughout the Bay. They can also decipher clues about predator-prey relationships and otter social behavior. The scat also includes “anal jelly,” a gooey excretion chock full of otter DNA, with encoded information about the population’s history, health and status.

You, too, could be an otter scat hunter. Even though Chesapeake Bay’s otter populations are important, we know too little about them. To close the knowledge gap, the SERC has established the Chesapeake Bay Otter Alliance, an affiliation of researchers and private citizens that seeks to map otter sightings, monitor behavior, study scat and educate the public.

Interested? Pick up the phone or send off an email. You can reach SERC here: Contact Us | Smithsonian Environmental Research Center ( or 443.482.2200.

Henry S. Parker is an adjunct associate professor at Georgetown University. He can be contacted at [email protected]

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Henry S. Parker is an adjunct associate professor at Georgetown University. He can be contacted at [email protected]