The Olympic Worthy River Otter

Feb 15, 2018

The winter Olympics are going on now, not only in South Korea but also right here in Wisconsin’s Northwoods. In this episode of Wildlife Matters, the Masked Biologist highlights the athletic river otter.

Right now, with the Olympics in full swing, I had the idea to try to find examples in the animal kingdom of wildlife that would compete in wintertime games. It didn’t work out very well. Wildlife activity changes in winter, especially in this kind of winter (the cold and snowy kind) and activity is often reduced to matters of life and death. There was only one exception that kept coming to mind—the otter.

The reason otters come to mind in winter sports is because of their unique mode of overland travel; they use a combination of lunging hops and belly slides. In wintertime, these slides can be up to 60 feet long. These slides are so large and visible that we use them as indicators of otter numbers; wildlife management staff fly over rivers and streams and count the number of otter slides they see. I haven’t seen a good explanation for why otters travel this way, but I could give an educated guess.

First of all, they are basically a semi-aquatic mammal. They spend a lot of time swimming in the water, and they have thick, dense, shiny fur that helps them move easily through the water. So, their fur and muscles are developed and adapted for swimming. Otters are one of the mustelids, a group of related animals like weasels, mink, badger, and fisher. These animals have long bodies compared to relatively short legs. Many of them have a kind of lunging gait, which makes their footprint pattern very easy to identify in the snow. The way it looks to me, this kind of “walking” is a lot of work, so getting some momentum up, flopping in the snow and sliding doesn’t seem like a bad way to go.

Historically, we had otters across a good portion of Wisconsin. In the late nineteenth and early twentieth century, otter numbers dwindled; they were given protection as a managed species around 1915. Careful management brought otter numbers back, and today it is not uncommon to see otters in Northwoods lakes and rivers. Our last otter flight survey indicated a slight otter population decline in northern Wisconsin, and an estimated statewide population of just over 10,000 otters coming into this winter.

The main reason for harvesting otter is for its fur. It is considered one of Wisconsin’s sturdiest and best wearing furs. Going back to the early 1800s, before Wisconsin was even a state, an otter pelt at the Green Bay fur depot was worth twice that of a beaver pelt, which means they could be worth up to $5. That was a lot of money back then. In recent years, otter pelts were very valuable, especially overseas where their otter numbers have declined. Four years ago, the average price of an otter pelt paid by fur buyers was $85. The current fur market is more in the $20 to $30 range, definitely not a great way to make a lot of money.

There is a perception that otters eat prized game fish, especially trout, and for this they are despised by many fishermen. The studies I have seen indicate that they do eat fish, some of which are game fish, but they eat a variety of other aquatic menu items as well. One study from Michigan examined the stomach contents of 95 otters, and found the largest amount of material in their stomachs was forage fish (like chubs and suckers). Next highest was amphibians like frogs and salamanders. They also love to feed on mussels or clams. All told, about 23% of their diet was game fish. Otters also eat aquatic insects and a good number of crayfish.

I don’t know if I could choose a sport that best describes otter movement. At first, I was thinking snowboarding, but their travels are not strictly downhill; many are cross country. It would probably be a combination of sports. If we created a new winter Olympic sport that included skiing, running, and swimming long distances beneath the ice, perhaps we could call it the otter triathalon.

Striving to make new things familiar and familiar things new, this is the Masked Biologist coming to you from the heart of Wisconsin’s great Northwoods.