Have you ever noticed less wildlife in the area from October through April? While we can choose to stay inside bundled up by the fire when the weather turns bad, our wild valley animals must find different ways of enduring our cold winters.
There are three primary ways animals endure chilly temperatures: Hibernation, Migration and Transformation.
According to the Merriman-Webster definition, to hibernate is “to pass the winter in a torpid or resting state.”
Hibernating animals need to conserve energy when food is not readily available. To achieve this energy saving, warm-blooded animals decrease their metabolic rate and body temperatures. This may last days, weeks, or months—depending on the species, temperature, time of year, and the individual’s body condition.
The first thing we all learn about bears is that they hibernate in winter. In the past several years, the talk has been that bears are not “true” hibernators. Not entirely understanding what that meant, I decided to talk to my wildlife biologist friend Daryl Ratajczak to see if he could explain. Our conversation went something like this….
Me: “Are bears hibernators?”
Me: “Are bears true hibernators?”
Daryl: “No. Not if you’re into nerdy biological terms.”
Me: “Then bears aren’t hibernators.”
Daryl: “Incorrect. They are hibernators.”
Me: “Wait. What?”
It felt a little like an Abbott & Costello reading of “Who’s on First,” and I was thoroughly confused. It seems that to differentiate between the different ways animals hibernate; the smart folks made the information less understandable to us regular folks.
Ratajczak explained that even though some say bears do not hibernate, they go into ‘torpor,’ and it’s all still hibernation. The term hibernation can be considered an umbrella term for many different kinds of dormancy practiced by a wide variety of animals.
Hey, smart people! We, regular folks, think true vs. false and get ALL confused. Maybe go for deep, medium and light hibernation instead of true hibernation.
So yes, Virginia, bears do hibernate. Western Washington Black Bears typically den from October to April after a fall feeding frenzy to put on fat called hyperphagia. Denning black bears enter a state of torpor, a drowsy condition that allows them to defend themselves (and their cubs) more effectively should a predator visit the den.
Bears do not need to eliminate their waste during this time but recycle it into proteins and other nutrients. By not defecating, bears keep their dens essentially scent-free, protecting them from potential predators.
Food availability, aka garbage, can cause extreme anthropogenic food supplementation and eliminate or drastically shorten the amount of time a bear would typically den. So, keep those garbage cans put away!
For an animal to be considered a true hibernator, there are three particular requirements: reduced metabolism, slower heart rate, and lowered body temperature. So, one example of a true (aka deep) hibernator in the valley would be Bats.
The Big Brown Bat and Little Brown Bat in Western Washington hibernate alone or in groups and enter hibernation sites in late September or October. According to the Washington Department of Fish & Wildlife (WDFW), most bats use a hibernation site called a hibernaculum to cope with winter conditions. Hibernation sites include cavities in large trees, caves, mine shafts, tunnels, old wells, and attics.
The hibernaculum protects bats from predators, light, noise, and other disturbances. Temperatures must be cool enough to allow bats to maintain a low body temperature but not freeze; humidity must be high and constant enough to prevent dehydration.
Cold-blooded animals have their own way of coping with winter called Brumation. Because of physiological differences, such as the inability to store fat and regulate body temperature, this process is not technically included under the hibernation umbrella but is similar.
Like bats, snakes will use a hibernaculum and brumate in groups. Brumation begins in late fall and is triggered by a lack of heat and a decrease in daylight hours in winter. A brumating animal will wake up to drink water, return to their dormant state and can go for months without food. Other cold-blooded animals will bury themselves underground or use rock dens.
Worth mentioning but not occurring in Western Washington is Aestivation. This state of dormancy, like hibernation, occurs in the summer rather than the winter. It is characterized by inactivity and a lowered metabolic rate and is a response to high temperatures and dry conditions.
Animal migration is the seasonal movement from one habitat to another in search of food, better conditions, or reproductive needs.
According to King County, of the 164 species of birds breeding in the county, 50 are here only during the spring and summer breeding months and spend winters south of us. Many of these birds are our South and Central America Migrants.
According to All About Birds, migration can be triggered by a combination of changes in day length, lower temperatures, changes in food supplies, and genetic predisposition. Different species of birds and even segments of the population within the same species may follow different migratory patterns.
Turkey Vultures can be seen in the Snoqualmie Valley, but when the weather grows colder in October, they leave for California and South America until March.
Many high-country birds, warblers, bluebirds, and swallows, spend the winter south along with shorebirds, raptors and local songbirds, including Lincoln’s Sparrow, Yellow Warbler and Bullock’s Oriole.
The Varied Thrush is a local example of a short-distance migrant making a small journey from a higher to a lower elevation.
So, what about the beasts who stick around through the cold and nasty months? The animals who stay and remain active undergo physical, behavioral and diet changes that help them cope with the changing weather.
Many mammals have fur with soft, dense undercoats that grow thicker in the wintertime serving as insulation against the elements. If you spot a particularly large-looking rabbit, raccoon, bobcat, cougar or coyote, it’s not likely bigger, just furrier. Overcoats are made up of guard hairs that can shed snow and absorb heat from our rarely-seen sun.
Our local elk range in color from light brown in winter to reddish-tan in summer and have buff-colored rear ends. In winter, a dark brown, shaggy mane hangs from the neck to the chest. They, too, grow a thicker coat of hair in the fall for insulation in the winter. That coat is shed, partially by rubbing up against trees by early summer.
Some local wild things drastically change their behavior in the wintertime. Skunks and rabbits don’t hibernate, but they do spend more time in cozy leaf-lined dens sleeping. Douglas squirrels also spend more time in their dens with the added benefit of lots of cached food to help them survive. Corvids and nutcrackers who don’t migrate hide seeds and can remember as many as 20,000 different locations to keep eating good during lean times.
Lastly, diet changes are necessary for both elk and deer. Browsing (eating high-growing vegetation) deer must switch from leafy to woody browse. While elk turn from their spring and summer grazing (eating vegetation near the ground) habits to fall and winter browsers.
Even though life can be difficult for our wild ones in the winter, the WDFW “generally discourages citizens from feeding deer, elk and other wildlife species because of the potential for harm.” Human food can be hard for wildlife to digest, and the wrong thing at the wrong time can cause digestive issues at best and death at worst.
The best thing we can all do is avoid disturbing winter routines to allow our animal friends to conserve energy and return strong when spring arrives.