An American mink spotted at LaBagh Woods. View Full Caption Jeff Skrentny

CHICAGO — In one of Chicago's wildest places, Jeff Skrentny was able to see one of city's hardest-to-spot animals.

Skrentny recently photographed a wild American mink along the Chicago River in LaBagh Woods on the Northwest Side.

Mink can be found in every Illinois county, according to the Illinois Department of Natural Resources, but they are far less common than they were 50-100 years ago because of "habitat loss caused by development, stream channelization and drainage of wetlands."

Skrentny said he saw a mink at LaBagh in 2015 that gave birth to three kits. He said the one he witnessed recently looked like "a nursing female."

"With luck we will have more kits again in 2017," he said. "Nothing stops me in my tracks more than when I see one of the mink at LaBagh. I can watch them for as long as they will let me, constantly amazed by their agility, movement and willingness to explore and play."

LaBagh Woods is a perfect habitat for minks because it contains the Chicago River, plus wetlands and shorelines with grass, brush, trees or aquatic vegetation.

The Department of Natural Resources notes that mink are extremely aggressive and "capable of attacking and killing animals much larger than itself." Mink eat frogs, mice, rats, fish, rabbits, crayfish, birds, squirrels and muskrats, the department said.

Because mink are mostly nocturnal — active from dusk to dawn, according to the department — they're extremely difficult to see in the Chicago wild.

Friends of the Chicago River said mink can be found throughout the river, and the mammals can grow up to 2 feet long. An oily coat on their fur keeps it waterproof, and mink can swim up to 100 feet below the water's surface. That's not an issue in Chicago as the Chicago River only reaches about 12 feet deep.

Mink are smaller than otters, which have been spotted recently in Cook County but not officially in Chicago waters.

LaBagh Woods is home to more than 190 bird species, plus snakes, turtles, deer, muskrat and a host of other animals and plants.