It is a rare treat to see river otters, but they are surprisingly abundant in Durham. They have been seen in RTP, Ellerbe Creek and nearby state parks.

Last winter two otters adopted the 23-acre lake on the NIEHS campus on T.W. Alexander Drive. EPA worker Pete Schubert saw an otter twice.

"The otters were seen most often in early morning, swimming across the lake and playing in the water and around the partially submerged boulder islands," he said.

"They were playful and unmistakable. [Their] tails were too long and broad and thick for beavers, which also inhabit the lake, or muskrat," he said.

The otters were different sizes, so they were probably mates. Females mate after giving birth early in the year, or possibly in the fall. Juveniles stay with their parents for about a year. Otters can live 12 to 15 years, and 20 years in captivity.

The NIEHS pair vanished in late January or early February 2009.

"Rumors abounded that they were killed on the roads, but there were no confirmed reports," he said.

A dead otter was reported on Davis Road south of Hopson, but he doubts it because it was far from water.

According to field guides, otters will travel over land between waterways. Schubert suspects the otters came from downstream on Burdens or Northeast creeks. If they ventured farther upstream, they could have been affected by toll road construction.

Otters have been seen at many nearby state parks, including Eno River, from Hillsborough through Durham, and downstream in Falls Lake. According to Diana Tetens of the Ellerbe Creek Watershed Association, there was a possible Ellerbe sighting downstream of the Costco on Northe Pointe Drive, and 15 years ago one was seen behind the Museum of Life and Science. Jordan Lake, Umstead, Weymouth Woods and Kerr Lake also have otters, but most sightings are years old.

A Jordan Lake ranger saw one early in the morning in October 2008, crossing Farrington Road near Martha's Chapel Road. Farther back, rangers saw one over three days in the beaver pond on the left at the gate of New Hope Overlook, usually early in the day. Rangers parked on the road watched it playing, swimming, and sitting on a favored log to eat its catch.

Fish are otters' staple food. They eat what is easiest to catch, such as bottom feeders. Pairs can cooperate to trap schools of fish in narrow spots. The best places to look are often the mouths of large creeks, such as New Hope Creek, and ponds.

Confluences and land crossings are also good places to find rolls, where otters haul out and mark their territory. Otters produce potent scents, like skunks and other weasels. A male might use 15 to 30 miles of waterway, while a female might need a single mile.

The rangers say otters are elusive, but not necessarily rare, like coyotes, which definitely live at Jordan Lake but are rarely seen alive.

Beavers are much more common, and there are also some muskrats. Mink are another large, water-loving weasel found in the Triangle, but they are smaller and have white throats. Mink are more nocturnal, solitary, and terrestrial than otters, and don't have fully webbed feet, but both species are very playful.

At Umstead State Park, there have been 10 otter reports, the last Jan. 9, 2004. They were along Crabtree Creek and Sycamore Lake. Ranger Dan Schewlakow says he saw possible tracks around Big Lake and a swimming otter two years ago, but he isn't certain. He says the Sycamore Trail is the best trail to try for otters.

It is hard to say how otters are doing in Durham. They have probably benefited from limits on trapping, but mercury from coal-fired power plants, PCBs, and other toxic pollutants bioaccumulate up the food chain and can reach debilitating levels in these apex predators. Otters also might not cross roads well.