After a Century, Chicago-Area Otters Are Back—but They Aren’t the Same

These wetland predators are showing scientists a whole new side to otter behavior.

Otters in a Cook County Forest Preserve in Illinois

Credit: Peter Pekarek/Forest Preserve District of Cook County

Biologist Chris Anchor is fairly sure river otters are camping out by this Cook County pond. For the past few mornings, he’s heard the telltale tickings of telemetry signals coming from transmitters tucked inside the bodies of a couple of males. He has even seen some otters swimming around, but one can never be too sure whether the dark brown predators with pale, furry faces have moved on to another den. Sitting with Anchor beside the water in the shade of an oak tree, I’m waiting to see them too, despite his warnings that most people never do.

Anchor, who wears a beige and forest-green uniform and a baseball cap faded by the sun, spends most of his time in the field. For the past 36 years he has studied the wildlife within the Cook County Forest Preserve—69,000 acres of protected land that comprise roughly 11 percent of this county that surrounds and includes Chicago. Since he began monitoring the area’s fauna, more species have moved in, including perhaps a dozen river otters.

“Here you’ve got an apex predator that’s exploiting the uppermost trophic level of our wetlands,” says the fast-talking Anchor. “What could be better?” The presence of these sleek swimmers, he explains, proves food is plentiful and the local water quality is good. But Anchor hopes the animals can tell us even more—about how otters behave in semi-urban surroundings and how diseases travel between them and other species in the region.

River otters haven’t been around these parts since the early 1900s, due mostly to habitat loss and the fur trade. But in the early 1990s, biologists in Indiana, Missouri, Illinois, Iowa, Pennsylvania, Kentucky, and Tennessee had Louisiana trappers send them some otters to help bring the animals back. The release point closest to Cook County was 150 miles to the south, but as the state’s otter population ballooned, some of the animals made their way north. Last year Chicagoans reported seeing an otter in the Chicago River downtown.

Anchor trapped his first otter in 2015, brought it to Brookfield Zoo in suburban Chicago, where vets inserted a transmitter, and released the animal where he had caught it. A year later, he trapped two more and did the same. Now, whenever the otters are within a mile, Anchor can track their movements, study what they eat, and just see what they’re up to.

The otters we’re spying on today are proving elusive. The biologist holds up an antenna attached to a telemetry device and rotates through the channels. Suddenly we hear consistent clicks. Anchor puts his head down and laughs gently. “He’s out. He’s sitting right over there,” he says. “Now you don’t have to guess. You know he’s there.”

Anchor’s experience—and his enthusiasm to get his “ass in the grass”—are part of what makes his work so compelling to the scientific community. “I can’t tell you how many hours I’ve spent listening to static, praying to hear the beep of a tagged animal,” he says. The quality of his research has also helped keep his lab afloat (he’s one of about a dozen wildlife biologists left in the state, down from around 100 when he started).

Partnering with universities, zoos, and wildlife organizations, the biologist and his team publish about one study each year on the region’s various flora and fauna. They meticulously catalog tissue and blood samples taken annually from up to 1,200 animals—everything from raccoons to turtles. He has also trapped and collared timber wolves and bears in nearby states and conducted the only scientific study on how urban coyotes may affect populations of outdoor cats.

His department is probably best known for its ongoing, 17-year-long Cook County Coyote Project, a collaboration with the Max McGraw Wildlife Foundation, Ohio State University, and Cook County Animal and Rabies Control, which tracks thriving coyotes throughout Chicago’s urban metropolis. Most field studies last one to three years, Anchor says, but research over the longer term, like the coyote study, gives deeper insight into how wildlife behaves, transmits viruses, survives disease outbreaks, and adapts to various environments. People around the world know all about these coyotes, says Anchor, and he hopes to translate that success to the otters.

Here on the outskirts of Chicago, otters behave differently from their rural cousins. For one, urban otters seem to be more opportunistic, eating anything available instead of constantly making dashes for the next pit stop. That’s due, in part, to the fact that the city otters haven’t had much competition for food.

In one Cook County pond, Anchor inserted transmitters into every turtle he could find. Then the otters arrived and ate all the turtles they could get their little hands on. The only survivors were those too large for the 20-pound predators to consume. Anchor has also seen them eating fish, water beetles, crows, and even road-killed possums and raccoons. “I go to conferences and people say otters don’t scavenge. Mine do,” he says. And since otters eat muskrats and beavers—unusual prey for most predators in the area—the otters can contract and spread diseases like spotted liver and rabies.

I grab the binoculars. Something’s swimming near a fallen tree at the water’s edge. Through the lens I see a hooded merganser guiding her ducklings. We settle back into our camp cushions.

Anchor and other biologists didn’t think the otters would survive their first winter in Cook County. Oily runoff from nearby highways, they reasoned, would wash into the pond where the otters swam, coat their fur, and keep them from being able to warm up. Turns out they were wrong.

Runoff is still a problem, but to fully understand what affects these animals, Anchor says you have to “sleep with the otters; you have to live with them.” And with only a few years left before this 54-year-old retires, he’s trying to secure funding for another field scientist to do just that for years to come. An official otter study isn’t in the works right now, but if Anchor can drum up support, he’ll begin a long-term investigation and train a protégé to eventually take over.

We spend hours at the pond, watching blue herons and snowy egrets skim the surface and listening to chickadees and red-breasted grosbeaks call from the trees. But the otters never show themselves. Another biologist needs the truck, so we head back to the office. Anchor will return tomorrow (and probably the next day) to observe the otters slipping into the pond and voraciously eating whatever they can find there. What they do next—and what they’ll do once Anchor hangs up his uniform—could be anybody’s guess.

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