Donning warm, cozy layers, winterizing gardens and swapping salads for soups — these are some of the things we humans do to prepare ourselves for winter. All over the world, species are also taking steps to prepare for the coming winter. From the extremely harsh conditions seen in polar regions to milder climates like the ones in the Pacific Northwest, we can see different species follow observable patterns to ensure their best chance of survival for the coming months. 

Dark-eyed junco

Dark-eyed junco
John Marzluff
Dark-eyed junco

School of Environmental and Forest SciencesJohn Marzluff kicks us off with the dark-eyed junco, who escapes the cold North by migrating south to the Gulf coast. Not all dark-eyed juncos stick together for the journey. Adult males migrate farthest south, leaving behind females and the young, while young males stay the farthest north for their migration to Indiana and Ohio. Adult and young females migrate to intermediate latitudes. For the juncos that call the more temperate Pacific coast home, some are seen traveling farther north or don’t migrate at all for the winter.

Flying from the northernmost to the southernmost parts of the United States takes a lot of energy, and the majority of that energy comes from fat, which yields twice as much energy and water as carbohydrates and protein. Much like how a runner will prepare for a marathon by “carb loading” the night prior, juncos will fatten rapidly before migration. Juncos will also feed and rest at stop-over sites during their journey. These sites are very important for birds flying over vast inhospitable areas like oceans, large lakes or deserts. 

The timing of these flights are also extremely important. Once juncos have the energy needed to start their journey, they also want to choose a departure date when atmospheric conditions generate the greatest wind assistance possible at both the departure and throughout the flight. In the fall, this occurs in the southward flow of dry polar air immediately following the passage of a cold front. Once airborne, juncos usually fly downwind regardless of wind direction.

This impressive journey proves that not only are dark-eyed juncos great long-distance athletes, they are also superb navigators who use learned and innate behaviors to reach their destination.

Polar bears

Kristin Laidre is seen with two polar bear cubs.
Kristin Laidre/University of Washington
Kristin Laidre is seen with two polar bear cubs.

Polar bears live year-round in some of the harshest winter conditions around the world, and School of Aquatic SciencesKristin Laidre has traveled to these regions to better understand polar animals.

Polar bears spend the springtime and the majority of the summertime fattening up and consuming as much prey as they can before fall. Pregnant polar bears will go into their maternity dens — dug into snow drifts, ridged ice or hillsides — around October or early November when they are fat enough, and stay in these dens until the following spring when they give birth and nurse their cubs. If the female polar bears don’t get enough to eat, they will lose their pregnancies. Polar bear activity starts dropping around the late fall, when sea ice is sparse and hunting gets harder. 

Unlike other bear species that go into a true hibernation – a physiological state of conservation prompted by dropping temperatures – polar bears that aren’t pregnant are still walking around and moving to different areas in winter, just at significantly lower rates than throughout the rest of the year. This strategy makes sense for bears that live in areas that see only a small amount of daylight throughout the winter time.

Many bears on land are waiting for the sea ice to form so they can get back to hunting. Recent studies have shown that polar bears in areas with multi year ice are actually seeing short-term benefits from the changing climate because more sunlight is able to reach the ocean surface, which makes the system more ecologically diverse. Hibernation for these polar bears look exactly like hibernation for other polar bears.

Narwhals

A pod of narwhals in Melville Bay, Greenland.
Kristin Laidre/University of Washington
A pod of narwhals in Melville Bay, Greenland.

Narwhals are some of the most elusive creatures in the ocean, so not much information is available on specific winter preparation techniques. Luckily, Laidre has spent multiple fieldwork seasons in the Arctic so we are able to provide some information on how the unicorns of the sea prepare for winter. These Arctic whales need oxygen to breathe, so when the ocean starts to freeze over in the fall, they head south to stay ahead of the forming sea ice. They will go offshore to deep waters in search of Arctic pack ice — ice that moves around and contains cracks and other openings that allow narwhals to breathe.

Winters are spent making dives more than a mile deep into the ocean, feeding on deep water fish like halibut. This period of intensive feeding provides narwhals with a lot of their nutrition, as opposed to the majority of Northern Hemisphere whales who do more feeding in summer than winter. Once ice in the south Arctic starts breaking up in the early spring, narwhals will migrate back north.

Hunkering down for winter takes preparation for all species, including us humans. Shrinking daylight hours across the globe and colder temperatures mark the changing of the seasons, and all species must adapt to survive and thrive through the winter. Which one of these techniques will you be deploying for this winter?