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Curious Nature: Beavers are even busier in fall

Jeanine Junell
Special to the Daily

As our days grow shorter and the chill of fall begins to set in, some of us dream of those frozen days to come, when we can spend the day in a winter wonderland, sliding or gliding over the ice and snow. The animals of our valley are thinking of those coming days as well, but unlike us, they will not have access to grocery stores, warmed buildings, ice corers or snow shovels. They have to plan ahead for winter even more than we do.

For many animals, this is a busy time of year, spent putting on layers of fat and preparing themselves to survive the winter months. This might be found in a winter sleep, a trip far away, or staying awake and relying on the preparations that they make now.

The North American beaver is one native animal that can’t afford to take chances on food supply, since it is likely to be stuck under a thick sheet of ice for most of the winter while remaining active in its pond, den and lodge. Beavers are strict vegetarians and eat a variety of water and land plants as well as the leaves, branches and bark of trees, mostly aspen, cottonwood, willow and alder. However, since the entrances to their lodges and dens are underwater (to protect them from predators), when the pond freezes, they are many times restricted to the food supply within the pond.



Winter survival takes planning, and beavers don’t get labeled “busy” for nothing. During the fall, they collect food that will keep their large family fed during the winter. They stash leafy branches and sections of edible trees underwater, wedged under rocks or tree roots or stuck in the mud. They also construct “rafts” of inedible or unfavorable branches and then put more favored foods underneath. The raft becomes waterlogged, which pushes the food supply under the level of ice. And just like many of us who are more careful in our actions when we have more time, beavers are pickier in the foods that they cache at the beginning of the season than in the weeks just prior to the onset of freezing. When the pond is frozen, a beaver need only enter the water from its lodge or den, grab a stick or two with its water-sealed mouth or grasping front legs, and return to its home to eat.

During this time of preparation, beaver bodies are also readying themselves for the cold. Throughout the summer and fall, beavers store fat in their tails and under their fur for warmth and energy reserves. The fall also brings the re-growth of guard hairs that will be fully grown by January and will cover their dense fur coat. These guard hairs, groomed with specialized oil, make the beaver’s coat waterproof. (This waterproofing oil is different from castoreum, a scent-marking oil produced by beavers, which many confuse with the plant-derived castor oil.)



So, as you start to put away your summer clothes and think about the snowy days to come this winter, take a moment to think of the busy beaver, who is even busier this time of year, making sure that her home, her body and her family’s food supply are ready for the long, frozen winter.

Jeanine Junell is the lead naturalist for Walking Mountains (formerly Gore Range Natural Science School). She enjoys sharing information about the natural world with whoever will listen and can often be found watching and photographing birds and wildflowers wherever they are found.


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