Ask the Master Naturalist: Otters a common sight throughout northern Minnesota – Brainerd Dispatch

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Question: We were walking through Rotary Riverside Park in Brainerd and saw three animals cross the trail. They were too large to be muskrats, but didn’t look like beavers. Could they have been otters?
Answer: Yes, it’s likely. River otters (lontra canadensis) live near lakes, ponds, streams and rivers throughout Minnesota. Adult river otters can be over 4 feet long, including their tail, and weigh up to 30 pounds (but usually under 20 pounds). Their fur is dark brown, short and very dense. Otters, unlike beavers and muskrats, are usually in groups. If this sounds like what you saw, you probably saw river otters.
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Question: What do otters eat?
Answer: The river otter is Minnesota’s largest aquatic carnivore, eating fish, crayfish, clams, turtles, frogs, birds’ eggs, and even muskrats. They will also eat aquatic plants when necessary, as otters have a high metabolic rate — which you can tell because they rarely stop moving. Otters may eat up to 20% of their body weight every day, meaning 4 pounds for an adult otter.
To get all this food, otters are very effective predators. They can remain underwater for more than four minutes, dive to 60 feet, and swim fast for short distances, using their short legs, webbed feet, and long tail to propel themselves through the water. In murky water, they use their whiskers to detect fish and prey movement. On land, they also catch small mammals such as mice, chipmunks, and even young rabbits, as they can run as fast as 15 miles per hour!
Question: Does the river otter have any predators?
Answer: In Minnesota, coyotes, wolves and eagles will sometimes attack otters on land. In the water, otters are generally safe, with few predators. Historically, humans have been their biggest predator. Otters were trapped for their fur going back to the early 1800s, when there were no bag limits or seasons. Unlimited trapping, along with wetland drainage and habitat destruction, caused otters to become extirpated (locally extinct) in southwestern Minnesota by the late 1800s.
Question: Are there more otters today?
Answer: Otters are now common in all of northern Minnesota and are becoming more common in southern parts of the state. The DNR estimates there are about 12,000 otters in Minnesota. The state now carefully controls the harvest, and trappers must register every otter pelt with the DNR. Their presence is a sign of good water quality and a healthy ecosystem, as otters need good populations of food or else they will quickly move to a better location.
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The DNR restored otters to southwestern Minnesota thanks to your voluntary tax checkoff for the Minnesota Nongame Wildlife Program. As one of their first projects in 1980, the Nongame Program enlisted local trappers to trap otters in central and northern Minnesota, including trapper Wayne Retka of Fort Ripley. Starting in November 1980, and continuing through the spring of 1982, the trappers caught 22 otters, which were released at the Lac qui Parle and the Big Stone National Wildlife Refuges on the western edge of Minnesota. After this introduction, the first reported sighting of a wild otter was from a spearer on Lac qui Parle Lake. While he hunched over his hole, an otter climbed out, looked at the shocked spearer, and then disappeared back into the water!
From the reintroduction at the Minnesota River headwaters, these 22 otters and their progeny dispersed along the Minnesota River toward Mankato and traveled up tributaries like the Pomme de Terre, Yellow Medicine, Lac qui Parle, Redwood, Cottonwood and Chippewa rivers.
In southeastern Minnesota, otters have also slowly come back on their own, dispersing from northern Minnesota along the Mississippi River. Otters can travel up to 25 miles per day, which has helped in their restoration.
Local efforts have also helped the otter population. In August 2023 and August 2024, Brainerd area Master Naturalist Scott Ransom helped staff from Garrison’s Wild & Free Wildlife Rehabilitation Center release orphaned river otter pups by the Mississippi River near his house. They chose the location as the Ransoms regularly saw another otter family in the area, and they hoped the orphaned pups (nicknamed Ollie and Ozzy) would be adopted by that family, helping the pups survive.
Question: How many pups do otters have every year?
Answer: Otters birth between one and three pups, which are blind and helpless when born, but they learn to swim after a couple of months. Otters, like other members of the family mustelidae, have a long period of delayed implantation. Soon after they have a litter of pups, they breed, but the embryos don’t start developing until eight months later! Then, after about 50 days, the pups are born and remain with their parents until the next spring. They can live eight to nine years in the wild but have lived up to 21 years in captivity.
Question: We saw what looked like two otters rolling around in the snow last winter. Were they fighting?
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Answer: They were probably just playing. River otters often wrestle with each other or engage in other play-like habits, like sliding down snowy stream banks. They have been seen pushing sticks across the water and dropping pebbles to the lake bottom and retrieving them. Though it appears to be just play, this behavior helps otters become the skilled predators that they are.
Do you have any questions about the natural world, such as birds, bugs, critters or native plants? Email me at BLAmasternaturalist@gmail.com and we will answer you in the column if space allows.

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