As Minnesotans pull fish houses off melting lakes, keep an eye peeled for one of the state's estimated 12,000 river otters. As ice thins, they scamper across it to find or make their own holes. Agile swimmers, they slip down into frigid water and, often within a few minutes, pop back up. They pull themselves onto the ice and eagerly chomp silvery fish wriggling from their jaws.

Observers might see evidence of where otters slide down snowbanks and riverbanks on their bellies. Otters romp with each other on land and in water and may engage in playful activities such as pushing around sticks or retrieving pebbles they drop into the water, according to the Minnesota Department of Natural Resources.

Playtime can hone skills that help Minnesota's largest aquatic carnivore capture clams, turtles, amphibians, mussels and muskrats as well as pursue chipmunks, young rabbits and mice on land. Otters can weigh 10 to 30 pounds and have webbed feet for swimming. Some have been tracked traveling up to 25 miles a day.

Female otters seek out a den sometime in March or April and will have about three pups, which typically leave the den and swim within two months.

If highly social otters want the local scuttlebutt, so to speak, they can pick up information through the scents fellow otters leave behind at communal latrines that a group of otters will create and use.

, Jim Buchta, The Minnesota Star Tribune
A river otter in the snow at Wild River State Park.

Otter populations, like many wildlife species, plummeted in the mid-20th century as loss of habitat, water pollution and hunting took their toll. Conservation efforts including wetland restorations and cleanups have helped them flourish in northern Minnesota again and move into the southern regions, as well, including the Mississippi National River and Recreation Area in the Twin Cities metro.

The National Park Service has been surveying otter populations in the metro area since 2009. A healthy otter population can be indicative of water quality and a healthy ecosystem.

Anyone spotting otters or signs of them in the metro (like tracks and slides) can contribute to the Minnesota Metro Otter Survey on the iNaturalist app, a citizen science project led by the Minnesota Wildlife Tracking Project and the National Park Service.