River otters

UD grad student researches river otters, 'class clowns' of the animal kingdom

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11:08 a.m., Dec. 20, 2011--If high school existed in the animal kingdom, the river otter would be voted “class clown.” These curious and playful creatures have been known to chase sticks, play hide-and-seek and roll around in the grass. They’re loud, too. While playing, they bark, whistle, squeal and growl.

“A few years ago, I went to Centennial Park in Milton one Saturday and saw three river otters splashing around. They kept diving into the water and popping back up,” recalls Jason Beale, manager of Abbott’s Mill Nature Center in Milford. “The otters were a lot of fun to watch and they didn’t care that people were around.”

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The North American river otter is native to Delaware and at one point was found throughout North America. But their range has been greatly reduced due to habitat loss and their sensitivity to environmental pollution.

University of Delaware graduate student Curtis Bennett is studying the river otter to better understand its habitat needs and how it’s impacted by urbanization. His field work takes place in New Jersey, in large part because he received a grant from that state’s Division of Fish and Wildlife. But the research results could have implications for monitoring and managing Delaware’s river otter population, too.

Otters are seen regularly throughout Delaware and are not considered rare at this point. However, it’s unclear whether the state’s otter population is stable, increasing or declining because there isn’t enough data, says Joe Rogerson, a game mammal biologist with the state Division of Fish and Wildlife.

Bennett is about to start his second season of field work. Last winter, he visited 60 southern Jersey locations at least six times each. Winter is a good time to see otters because they tend to be more active, in preparation for breeding season. Bennett looked for river otters as well as evidence of their habitation, such as scat, latrine sites, animal tracks and the slides that they create. 

Just like kids on a playground, otters enjoy a fast ride down a slide. Otters build these slides on muddy or snowy river embankments and then repeatedly hurtle themselves into the water below. This behavior has no known connection with eating, reproducing or defending territory, notes Chris Williams, UD associate professor of entomology and wildlife ecology who is overseeing Bennett’s research. “It’s done for fun,” says Williams.

To make sure he’s not missing any otter evidence, at most sites Bennett dons hip or chest waders, as well as a life jacket, and strides through the water, sometimes up to his chest. “It gets pretty cold; you learn to be prepared for anything,” he says. “I always have extra clothes and snacks with me.” 

The otters at these research sites are more elusive than the extroverts Beale witnessed at Centennial Park. “As a rule, river otters tend to be pretty secretive in nature,” says Bennett. “Plus, they’re most active at night.”

Otters make their home in burrows near water and can be found adjacent to rivers, lakes, swamps and estuaries. Fish are their favorite food, says Bennett, but they’ll also eat crayfish, turtles, frogs and toads. They’re equally at home in water as on land, thanks to webbed feet, water-repellant fur, and nostrils and ears that can close. Don’t hold your breath waiting for an otter to surface after it dives into the water – it can hold its breath underwater for up to eight minutes.

If you’d like to see a river otter you’ll probably have more luck in Kent and Sussex, though otters can be found in New Castle County “We know we have river otters in the marsh; we’ve seen their scat,” says Lesley Bensinger, an educator at the DuPont Environment Education Center in Wilmington. “We just haven’t seen the otters yet.”

Downstate locales where otters and otter tracks have been spotted include Bombay Hook and Prime Hook wildlife refuges and Abbott’s Mill Nature Center. And, if you’re fortunate, maybe those attention-getting extroverts will return to Centennial Park.

Article by Margo McDonough

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