River Otters on the rise

PHOTO BY PETER B. BRACE Evidence of otters found near island ponds and wetlands Nantucket does not have any rivers or streams and until recently, none of the four-legged inhabitants typically found in these waterways that connect to the ocean.

Yet, last spring, tracks belonging to river otters, which live in both fresh and brackish waters near the ocean ends of rivers, were discovered near Madaquecham Valley by island naturalist and bird expert Edie Ray and on the west shores of Hummock Pond by another island naturalist.

Luanne Johnson, a doctoral candidate in environmental studies at Antioch University, who lives on Martha's Vineyard, and professional tracker Mark Elbroch, author of "Mammal Tracks & Sign: A Guide to North American Species" and "Peterson Field Guide to Animal Tracks," both confirmed that river otters made these tracks on Nantucket; however, the animals have yet to be spotted on the island.

Since otters are capable of swimming long distances and small numbers live on Martha's Vineyard, No Man's Land and the Elizabeth Islands, it is highly possible that the tracks were made by river otters that swam to Nantucket from those islands, said Dr. Bob Kennedy, director of Natural Science at the Maria Mitchell Association.

"People could have introduced them [to the island] because people keep them as pets," said Kennedy. "Other than that, they're river otters and they are capable of swimming great distances."

New species arrive on the island through human aid or under their own power, for instance, birds that expand their range depending on climate changes or food availability; fish that swim into the island's warmer summer waters from the Gulf Stream and squirrels believed to have traveled to the island in firewood shipments.

"I'm convinced they could easily swim this distance," said Kennedy. "If they got washed out of a river, they could easily swim here. This is how animals disperse; they either fly, swim or they run, and most are very good swimmers."

Active year-round, river otters typically feed at night and live secretive lives, so if there is a small population living on Nantucket, they are going to be difficult to detect, said Kennedy.

But their believed existence on Nantucket works because river otters thrive on the small fish and crabs found in the island's great salt ponds, in the ocean and in its harbors. I