Wildlife in the Winter

Nov 28, 2017
While we're staying warm and snug in our toasty homes, what do wildlife do to survive the winter?

By Jen Zalewski

It’s happened again—the days are getting shorter and colder. Here in Central Oregon, you may have found yourself remarking to a neighbor or co-worker, “Wow, I can’t believe how early the sun is setting!” This is a common reaction, even though it should be no surprise by now; most of us have lived through decades of seasons. But we should give ourselves a break; after all, most of us humans have adapted so thoroughly to the changing of the seasons that we hardly need to see it coming. Perhaps we should buy a roof rake (I’m putting that on my list right now), gather up our leaves before they do something terrible to the lawn, and cover the patio furniture. Done. Ready for snowpocalypse. But what about the rest of the creatures that inhabit our local forests, rivers, and skies? Without home furnaces controlled by smartphones and Subarus with remote start buttons, they must rely on their hardwired routines and adaptations to get them through the cold, dark days of winter.

I thought I would shed some light on how a few of our local creatures get through the winter so the next time my kid asks me “Where do bees go in winter?” I don’t have to try to sound convincing when I say, “Well, to their condo in Florida, of course.”

So let’s start there.

 

Honeybees and Bumblebees: Forgive me while I generalize here, for there are many species within these categories.

Honeybees spend the warmer months preparing for the winter. They produce and store honey that sustains them in the hive when the temperature drops into the 50s. Cool temperatures drive the queen deep into the hive where the worker bees (all female) cluster around her. The workers flutter their wings and shiver to create heat to insulate the queen while feasting on the stored honey for energy. This shuddering hive can create a Florida condo microclimate of 80 degrees! Male bees (drones) never even make it to winter. The goal of their short lives is to attempt to mate with virgin queen bees in the warm season, after which they die. If mating doesn’t do them in, they are expelled from the hive before winter and succumb to exposure; such is the life of an individual in a species that reproduces as a colony. Honeybee queens can live for a while, surviving up to five seasons, while their colonies are perennial, surviving indefinitely.

A snowy forest. Photo: Amanda Egertson.
A snowy forest. Photo: Amanda Egertson.
Bumblebees have a different strategy. Their colonies have an annual cycle. They do not store food externally as honeybees do. Without stored sustenance, the current year’s bumblebee queen, the males, and workers all succumb to starvation when the temperature drops. In the meantime, a new fertilized queen has emerged from the colony. The new queen has stored energy (aka fat) inside her body, having feasted heavily on pollen and nectar before winter. She then finds a sheltered place, typically in the ground, where she hibernates alone. Her suppressed metabolism slowly utilizes her fat stores and, if she survives the winter, she will emerge the following spring to start a new colony.

It is important to note that honeybees, although commercially important pollinators, are not native to North America. The introduction of honeybees may be partially responsible for the decline of our native bumblebees; however, both honeybee and bumblebee species are declining due to habitat loss and fragmentation, pesticide use, disease, and climate change.

 

Sockeye: Historically, the Metolius Preserve was home to one of two sockeye salmon runs in the state! Young sockeye would spend 1-2 years in Suttle Lake growing before they migrated in the spring via Lake Creek and the Metolius River to the ocean. After 2-3 years, they returned home in the summer/fall to spawn and die. In the 1960’s, dams on the Deschutes River blocked passage for sockeye and other salmon. Today, a massive partnership is underway to return these fish to their historic range. While 2017 returning sockeye numbers were small, 2016 was a banner year that has given us all hope for the species. In winter, sockeye salmon do one of two things: any adults that have returned have spawned and are now fertilizer, returning nutrients to the earth. Young sockeye spend winter in their rearing grounds at Suttle Lake where they are biding their time until they leave on their journey to the ocean. Lake Creek is essentially a sockeye ghost town in the winter.

Learn more on sockeye salmon in the Deschutes River system and reintroduction efforts.

 

A river otter at night. Photo: Land Trust.
A river otter at night. Photo: Land Trust.
River Otters: It’s pretty much business as usual for river otters in the winter. River otters are semi-aquatic carnivores that hunt and fish all year. They do not hibernate and are well adapted to cold weather. Their fur is incredibly thick and they have special oil glands they use to oil and waterproof their fur. Their warm coat and a layer of fat underneath allows them to spend more time in the water than on land where the air temperature is often cooler than the water temperature. Oh, and they go sledding, of course (and then go sledding some more).

 

Black Bears: During winter, bears den up and sleep the days away because food is scarce. They do not eat and therefore do not urinate or defecate. Very efficient hibernators, their respiration and heart rate drop significantly, but their body temperature stays near normal. Female bears (like all mamas) remain busy during the winter. Assuming they mated the previous spring, female bears have a cool adaptation called delayed implantation. This adaptation allows the egg that was fertilized last spring to go into suspended animation and delay a pregnancy until fall when the bear has enough fat stored up to sustain gestation. Only them does the egg implant. Female bears spend their winter growing and then birthing baby bears, which emerge in the spring weighing 10 pounds and ready to climb a tree.

 

A pygmy nuthatch. Photo: Kris Kristovich.
A pygmy nuthatch. Photo: Kris Kristovich.
Pygmy Nuthatch: Birds have a variety of ways to survive the cold of winter. Many migrate to the tropics where food is plentiful or move regionally to lower elevations where temperatures are milder. Others decide to stay put and stick it out. Among these is the pygmy nuthatch. If you are not a birder, you need to know they are all kinds of adorable. High on the list of their adorable behaviors is their preference to roost in groups at night; dozens, or even a hundred individuals might be found huddled together—all in a single nest cavity! Along with this sheltered huddling activity, they let their body temperature drop to save energy—an adaptation called torpor. Pygmy nuthatches are the only North American birds that employ these three strategies (cavity sheltering, huddling, and torpor) to survive a cold night. How does this tiny bird, or any bird for that matter, go around in bare feet all winter? A close association between the veins and arteries in their legs and feet regulates the temperature of the blood between their lower limbs and their heart, ensuring they do not lose too much warmth through their feet, yet keep their feet warm enough not to freeze.

 

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