After every snowfall you may have noticed a series of odd, tube-shaped slides, wending mostly through Island woodlands but also over roads and even into downtown Oak Bluffs or Edgartown. The creatures that left these mysterious trails are less easy to spot, but recent research carried out by two Vineyard scientists suggests they are abundant. They are coastal river otters.

Luanne Johnson moves from skunks to otters. — Mark Alan Lovewell

For the past year wildlife biologists Luanne Johnson and Liz Baldwin have been ferreting out the secret lairs of these water weasels, analyzing and identifying sites where the animals groom, socialize and relieve themselves. To date Ms. Johnson said they have identified 61 otter latrine sites and five dens scattered at the edges of ponds throughout the Island.

And she has no doubt there are more. Now she is calling on the Island community to help connect the dots and uncover the many overland thoroughfares used by otters as they travel from pond to pond.

Last night Ms. Johnson spoke at the Chilmark library about her research, which is being funded by grants from the Sheriff’s Meadow, Edey and Dr. William and Nan Harris Family foundations, and aided by every Island conservation group. Ms. Johnson is inviting volunteers to help track the otters after the next snowfall, when their trails will be most evident.

Mapping Island’s otter thoroughfares for first time.

“A lot of people have studied otters out West but it was amazing to me that no one had done a diet study in this coastal area,” Ms. Johnson said in an interview this week. She said most of what is known about coastal river otters comes from research done in the wake of the Exxon Valdez oil spill. But local coastal otters have received scant academic attention — until now.

“Blue claw crabs aren’t really listed as part of their diet but of course they are a huge part of their diet,” Ms. Johnson said. She knows this because the work of a wildlife biologist often includes such thankless tasks as sifting through excrement to uncover fragments of fish scales and crab legs, a method that has revealed much about the local population. Her research shows that Island otters love their fish for dinner.

“They eat a lot of small fish like mummichogs, minnows and killifish. They’ll certainly eat things like yellow and white perch, and they’ll even eat striped bass and bluefish but typically they’re not eating huge fish,” Ms. Johnson said. “Then they also eat basically anything that moves . . . they’re a big weasel,” she added.

Fresh snow makes otter slides easier to see. — Courtesy Coastal Otter Research Project

To find their next meal otters often travel surprisingly long distances over land, on routes that sometimes bring them within close contact with humans. One overland route, particularly familiar to cross-country skiers in the Southern Woodlands in Oak Bluffs, takes the otters from the head of Lagoon Pond to Wiggy’s Pond and then on to Sengekontacket. A cursory survey of a map reveals that the otters journey across both Barnes and County Roads. Occasionally they will leave Lagoon Pond for Duarte’s Pond, an inland pond owned by the Martha’s Vineyard Land Bank behind the Island Alpaca Farm, and in doing so cross the even more congested Edgartown-Vineyard Haven Road. With some otters weighing up to 40 pounds and exhibiting their unmistakably goofy undulating gait, it’s a surprise that they are so difficult to find. Unfortunately though, Ms. Johnson said the famously elusive animals are not immune to human interaction.

“Up by the Aquinnah water testing lab we get them on the road all the time and they’ve been hit by cars there before,” she said.

Apart from scientific curiosity, this is one of the reasons Ms. Johnson hopes to map the otters’ routes. In the future she envisions building underpasses at particularly dangerous crossings or setting up motion-activated warnings for drivers when the dark-coated, nocturnal animals choose to brave busy Vineyard byways.

Caught on camera near Squibnocket. — Courtesy Coastal Otter Research Project

The otters have enjoyed somewhat of a resurgence of late, in part thanks to a trapping ban passed by Massachusetts in 1996. Now Ms. Johnson said the animals are showing up in surprising places, including Noman’s Land, where she said they “commute,” and even farther afield.

“These females we’ve studied on Edgartown and Tisbury Great Ponds are having two or three young a year so I said, ‘Where are they going? They have to go somewhere,’” she said. “Now there are river otters on Nantucket. Everybody always said they weren’t there so it seems as though they’re dispersing.”

Otter on a frozen Chilmark pond, about to eat a fish.

More study of the animals may also help us understand our own relationship with the environment, because toxins tend to accumulate in otters from human sources. Ms. Johnson said the Environmental Protection Agency is interested in monitoring a number of substances including triclosan from antibacterial soaps, furniture flame retardants and pharmaceuticals that leach into sediments, often through septic systems. In the future, and with the help of more grant money, Ms. Johnson hopes to capture some of the animals and test them for toxins. In addition she hopes to tag and videotape the otters to help gauge the size of their population on the Island, which she estimates at anywhere from 35 to 150.

In the short term though, as soon as the next snow falls Ms. Johnson will be trudging through the woods, likely with a GPS-trained pack of Boy Scouts recruited to help her map the otter wanderings.

“What has surprised me the most is how much otter activity there is around the Island,” she said. “Some people I don’t think even realize that they are there because they’re so nocturnal, but there really is a tremendous amount of activity on this Island if you know where to look.”