Dam It All: the Beaver’s DIY Guide to Winter Survival
Dam, dam, dam!
This is the mantra that fills a beaver’s mind when the autumn air starts to chill and the days start to shorten. For the beaver’s adaptation to winter, survival is not, like most, to hibernate or migrate. No, the industrious beaver’s solution is to engineer the ultimate winter shelter and, you guessed it, it involves a dam.
In this, the third of our winter wildlife series, we bring you the beaver’s DIY guide to winter survival in 5 easy steps.
Step 1: Buy the necessary tools
Well, if you’re a beaver, you can skip this step. Lucky for them, they are born with all the tools necessary to build the ultimate winter shelter - their bare hands and their teeth! Beavers' paws are especially adapted for building and swimming. Their forepaws are dexterous like a raccoon's and can carry logs and stones and are great at packing mud. Their back paws are webbed like a platypus’ and are excellent for swimming. This is especially important because it’s much easier to pull logs through the water than to drag them across land. Beavers’ teeth have a distinctive orange coloring that comes from extra iron in their enamel. This makes their teeth super strong -- strong enough to gnaw through tree trunks!
Step 2: Choose your site
When choosing a site for their winter shelter, beavers are looking for the perfect pond where the water will be deep enough and still enough to protect them from predators. They have no natural predators in the water, so they build a fortress of water to protect themselves. When the water’s not deep enough, they build dams to back up water and create the necessary depths.
Step 3: Gather your building materials
When we’re in need of lumber, we sing, “Heigh ho, heigh ho, it’s off to Home Depot we go.” Not so for the beaver. They are lumberjacks set up with their own mobile saw mill. An adult male can cut through a 6-inch tree trunk in under an hour. They take down large trees, mill them into smaller pieces of the necessary lengths and then they transport them via the water to their building site. They also use rocks and mud, which they collect from the bottom of the river or stream. In addition to building up the dam, dredging mud from the river bottom also deepens their pond. Now that’s an efficient contractor!
Step 4: Build the dam and lodge
Beavers have been around for approximately 20 million years, and in that time, they have perfected their building techniques. Their dams are built strategically with a base layer that is then weighed down with rocks and covered with interlocking larger logs and sealed with mud. They can easily add height just by piling on more logs. Their lodges are constructed over a burrow, often in the river bank. To keep warm and cozy through the winter months, even with subzero temperatures outside, they pile up insulating materials, which can be 2 feet thick. Inside the lodge they have different levels, kind of like rooms, for eating and sleeping. They also leave an opening in the roof, like a chimney, to allow for fresh air exchange. And most important of all, the entrance is underwater. It’s the perfect security system with no locks, keys, or cameras required.
Step 5: Stock the fridge
Once their dam and lodge are built, the last step for a beaver’s winter survival is to stockpile food. Beavers are vegetarians; they eat leaves and the sugary plant tissue that lies under the bark of trees and shrubs. In order to survive the winter, when their food is covered in snow, they have to fill up their fridge. And what, you might ask, does a beaver fridge look like? Well, it’s their pond. Beavers cut down fresh branches in the fall and pull them down into their pond. The pond's cold water preserves the branches and keeps them fresh under the layer of ice that forms on the top. Whenever the beaver wants a winter snack, it just swims out of the lodge, grabs a branch from the bottom of the pond and pulls it up into their kitchen.
Why Beavers Matter
Now that you have the down-low on beaver winter survival know-how, we thought we'd take a moment to discuss why beavers matter. Beavers are often thought of as pests that cause property damage, but they are important keystone species in riparian zones of the Western United States. Their dams create wetlands, which retain water for longer time periods, and provide vital habitat for many plants and animals in the arid western states. While once abundant, their numbers have been greatly reduced due to hunting and habitat loss. Lucky for us, the Truckee River Watershed still has a healthy beaver population, and you can see their handiwork first hand at Oxbow Nature Study Area in Reno. Plan a visit and talk to Nevada Department of Wildlife staff to learn more about these important members of our watershed.
Sources
McGill Office of Science and Society
Nature's Engineers The Dam Beaver National Geographic Nature Documentary HD 2013
How Beavers Build Dams | Leave it to Beavers | PBS
Wild Mammals of North America: Biology, Management,and Conservation. Second Edition.