We’ve long been anticipating the reappearance of river otters (Lontra canadensis) in our Arboretum. Historically, unregulated hunting and habitat loss had driven river otters to local extinction in southern Minnesota. The population has been gradually recovering southwards by itself and also through reintroduction by the Department of Natural Resources.

Over the past years, Arb staff and students have noticed signs of the reappearance of river otters, including the characteristic otter “sliding tracks” and many large half-eaten fish left on the ice.

A few weeks ago, a Carleton student Mathew Zappa spotted two otters on the ice along the Cannon River but could not take a clear picture due to the darkness at night. On Monday, February 3, a photograph clear enough to identify the animal was finally taken in the Upper Arb by a Northfield resident.

“I was walking with our two dogs along the trail heading south from the Druids rocks [circle] when the dogs stopped and looked intensely into the brush to the east. I have learned to take this action seriously because they often spot something that I don’t see. I soon saw the otter to the east of the trail walking along about 20 feet away from us moving in and out of hiding behind the brush,” said Alan Kraus, conservation program manager for the Cannon River Watershed Partnership, who took the clear photo. Kraus also reported that it was the second time he saw an otter in the Upper Arb. His first spotting was down on the bank of Spring Creek about 50 yards south of the foot bridge.

This is certainly happy news. Because of river otters’ sensitivity to pollution and requirements for a rich and diverse base of prey species, their reappearance indicates a healthy wetland ecosystem.