This article was originally published by the Chesapeake Bay Journal, an award-winning nonprofit news organization that has been covering environmental issues in the Bay region for more than 30 years.
Four decades ago, populations of the river otter, a playful, whiskered member of the weasel family, were so depleted that most states in the Chesapeake Bay region considered them endangered.
Today, the species known for its fondness of clean water is turning up throughout the Bay watershed, including seemingly unlikely places.
They inhabit a floating wetland constructed in Baltimore’s Inner Harbor.
They’ve been spotted munching on fish in downtown Norfolk and in all branches of the Elizabeth River.
And they’re seen in and around the District of Columbia, including Rock Creek and the Anacostia River.
Biologists once thought such urban areas were mostly off-limits to the semi-aquatic mammals, which are often associated with more pristine conditions. Their recovery in Baltimore Harbor and the Elizabeth and Anacostia rivers is especially notable because those areas were once considered the most “toxic hot spots” in the Bay region.
“We have a major conservation success story in terms of restoring a predatory animal that had declined significantly,” said Tom Serfass, a river otter expert at Frostburg State University in Maryland.
“It’s a good example that some of the water quality regulations have worked,” Serfass said. “It also demonstrates the otter is a bit more tolerant if we give it a little protection.”
Serfass spearheaded otter reintroduction efforts in Pennsylvania, starting as a graduate student in the 1980s. Back then, otters had vanished from the state except for a remnant population in its northeast corner.
While populations survived in many coastal areas like the Eastern Shore, where there was ample marsh for protection, they disappeared from much of the continental United States and Canada. The less dense populations strung out along river shorelines were vulnerable to trapping, shoreline disturbances caused by deforestation, and water pollution.
Serfass’ work restored otter populations in nearly all major river basins in Pennsylvania, while Maryland, Virginia, West Virginia and New York undertook their own reintroduction efforts.
Today, otters appear to be expanding both from those efforts and from coastal areas where populations had survived.
Serfass has been surprised at the scope of the comeback. In a project funded by the National Park Service, he placed wildlife cameras every two miles along the Chesapeake and Ohio Canal towpath from Cumberland, MD, to just outside the District of Columbia. Otters have been seen crossing the towpath along the canal’s entire length — an area with no otters only a few decades ago, he said.
Today, they’re being touted as “clean water ambassadors” to highlight improving conditions and spur citizen science efforts to help monitor their abundance.
They are top-of-the-food-chain predators, which means they are essentially absorbing everything that’s accumulated in the things they eat. That can reveal a lot about the local environment.
“You can’t have otters in a body of water unless there’s a healthy enough ecosystem to support them,” said Victoria Dunch, resilience research manager with the Elizabeth River Project in Virginia.
The Elizabeth River, which runs between Norfolk and Portsmouth, was once considered nearly “dead” because of pollution. Scientists didn’t even bother to conduct fish surveys there.
But that started to change as recovery efforts took hold — the Elizabeth River Project now gives the river a “C” on its report card. And the otters are weighing in, too: “People have been telling us about their otter sightings for probably well over a decade,” Dunch said.
To better quantify that recovery, the nonprofit organization two years ago teamed up with the San Francisco-based River Otter Ecology Project to create a website that allowed people to report otter sightings.
So far, the site has logged about 150 observations from more than 90 people in the broader Hampton Roads area. They have been seen chowing down on fish in downtown Norfolk and denning in culverts.
Dunch said the organization incorporates otters into educational programs. “Otters for Water,” for example, encourages people to take actions, such as reducing fertilizer use, to protect local waterways.
That appreciation is quite a change from when Serfass started his work. At that point, the idea of returning river otters to places they had disappeared raised alarm among some, especially angers who worried they’d eat too many trout. Buoyed by research showing that otters eat a wide range of species and relatively few trout, he gradually won their support.
“Negative predator attitudes have been with us since the inception of our wildlife management system in the late 1800s early 1900s,” he said. “So you need public support.”
As in the Elizabeth River region, otters today are gaining public attention around the watershed.
Fredericksburg, VA, has embraced their “otter-ly amazing” return as a sign of recovery in the Rappahannock River and local waterways. Even if people don’t see wild otters, which are often elusive, they can search for seven bronze otters created by local artists that are scattered throughout the downtown area to celebrate their recovery.
In Pennsylvania, an otter is featured on the state’s wildlife conservation license plates.
In Baltimore, the National Aquarium began constructing an 8,000-square-foot “floating wetland” in the adjacent harbor in October 2023. Before it was completed, aquarium staff were often asked about what types of animals might eventually use it. They would run through the litany of possibilities: blue heron, eels, fish, cormorants. Maybe, eventually, they would say, even an otter.
In fact, the otters didn’t wait for the wetland to be completed. A night watchman spotted otters in the wetland in June the following year, two months before it was slated to open. By November, the staff was seeing regular visits on their trail cameras in the wetland.
“It’s just wild how quickly they showed up,” said Taylor Long, of the aquarium’s field conservation department. “We’re still very surprised about it.”
The aquarium has incorporated otters into education programs, too. For example, students can examine otter poop through microscopes and try to identify fish scales that indicate what the otters have been eating.
There’s plenty of poop to be found: Otters use the aquarium’s wetland as a latrine.
The poop is also used for scientific work. The aquarium participates in the Chesapeake Bay Otter Alliance, created by the Smithsonian Environmental Research Center (SERC) in Edgewater, MD, as a regional network of organizations, parks and agencies working to map the presence of otters and collect their poop for analysis.
By analyzing the poop, the project’s aim is to better determine the health of the ecosystem, in part by understanding the diversity of fish and other things in the otters’ diets. More diversity should indicate a healthier system.
Eventually, they hope to look for contaminants and pollutants that could impact otters — and humans — using the rivers.
“I think using a top predator to assess, [and] kind of looking backwards down a food web, to try to figure out what’s going on in an ecosystem, is kind of a cost effective approach,” said Katrina Lohan, a senior scientist at SERC who oversees the project.
Trying to survey otters is difficult, though. Although otters are known for their playful antics, such as sliding down muddy or snow-covered riverbanks into the water, actually spotting the largely nocturnal animals isn’t easy.
“I’ve been studying them for six years, and I’ve never seen one in the wild,” Lohan said.
But their latrines, which can be used by generations of otters and also serve as a social gathering point, can more easily be located along shorelines using one’s nose.
“Otter latrines are really stinky,” said Callie Wise, a SERC field technician who works with Lohan. “They eat so many fish that usually an active latrine is just covered in otter scat, which is full of fish scales and just stink of fish.”
But their latrines are common along streams on public lands and parks, confirming their regional comeback. “I found them almost everywhere,” Wise said.