Winter Wildlife on the River
Patrick DiGiulian, Marketing and Online Communications Assistant
March 14, 2013
A guest blog from Communications Intern Johannes Dreisbach.
As we celebrate the last part of the winter season, we wanted to take a look at how different wildlife found in and around our rivers adapt to the unique season.
You'll see that these amazing animals each take on the cold temperatures, harsh weather, and limited food supplies in their own special way.
North American River Otter
North American river otters are semiaquatic mammals that do not hibernate when winter comes around. They are primarily nocturnal, but become more diurnal in winter, meaning they are active during the day and sleep at night. River otters use openings in the ice, and will sometimes even break through beaver dams, to gain access to rivers and other waters. They can also slide across the ice to get where they need to go. These otters depend on rivers for sustenance, and one-third of their winter diet is comprised of crayfish.
Check out this fun video of river otter winter playtime!
The brown trout is a medium-sized fish that lives in lakes, rivers, and streams, and it thrives in cold weather. During the winter, ice builds up and blocks light from penetrating into the water, food becomes less abundant, and the water holds less oxygen. Despite this, brown trout, as well as lake trout and whitefish, have adapted to allow themselves to remain active throughout the winter months. Though some fish become sluggish, brown trout face relatively few changes. Lower temperatures and higher oxygen levels actually make the waters more comfortable for them, allowing them to venture into habitats that are out of their range in the summer.
North American Beaver
The North American beaver is a large, semi-aquatic rodent. It makes its lodges in lakes, streams, and rivers, and those are typically made of sticks, twigs, rocks, and mud. Beavers do not hibernate, so to stay warm in the winter, they add mud to the outside of their lodges so it will freeze and help insulate their homes.
Because food is hard to find in the winter months, especially when the water is frozen over and hinders their travel, beavers stock up in the fall before the cold hits. They store branches of trees underwater, sticking the chewed bases into the mud next to their lodges, (check out a photo here). This allows them to easily access food even in the harshest of weather.
Grizzly bears live in northern North America, including Alaska, Washington, and Montana in the United States. They are very large mammals, weighing between 290 and 790 pounds. Grizzlies hibernate during the winter months, and in order to sustain themselves during this time, they need to eat a lot in the fall.
A primary food source for the bears is fish, and they spend a lot of time hunting salmon, trout, and bass. In order to survive the harsh northern winters, bears need to eat 90 pounds of salmon—or 25 fish—per day, so grizzlies, despite being solitary creatures, will often congregate around streams, lakes, rivers, and ponds during spawning season. Grizzly bears will generally wait until a snowstorm before entering their dens for the winter, so as to prevent predators from finding them, and they wake in the spring after sleeping for up to 7 months.
The Tundra Swan is a large, white waterfowl with a dark beak and dark legs that lives in North America. During the summer, the swans inhabit shallow ponds, lakes, and rivers in northern Canada. When winter comes, they migrate south into the United States and northern Mexico, living in grasslands and marshlands in the Northwest/Pacific, Northern Rockies, California, Southwest, Southeast, and Mid-Atlantic regions. Aquatic plants, mollusks, and arthropods help comprise the Tundra Swan’s diet, showing how much they rely on rivers, and with many migratory birds staying in the northern U.S., it is clear that they remain comfortable in cold winter weather.
What's your favorite animal during the winter? Do you know of any other wildlife that have interesting winter habits? Let us know in the comments below!