How Plants and Animals Survive the Brutal Cold of January

Field report

Freeze-tolerant frogs, antifreeze fish, and a full 'Wolf' Moon illuminate winter's hidden vitality.

A very happy New Year and welcome to 2023! January is typically pretty quiet on the conspicuous-wildlife front — and for those of us in parts of the Northern Hemisphere under a deep freeze, that's not necessarily a bad thing for the animals that hunker down. Luckily, the first month of this year is offering us a slate of ecological wonders ranging from freeze-tolerant wood frogs that literally ice solid to river otters sliding across snow with astonishing grace. Wishing you warm boots and sharp eyes!

Cold Snaps Create the Best Conditions for Spotting Wildlife Sign (All Month)

While plunging temperatures may not inspire motivation to get outside and look around, I'm going to recommend you drag yourself away from your warm fireplace and do it anyway. Why? Because a fresh snowfall is the best tracking surface nature ever invented. Every deer hoof-print, rabbit bound, and fox trot is recorded in white powder like handwriting on paper. Summer tracks, on the contrary, are often smudged by rain and obscured by leaf litter. Combine crisp snow with bare trees and long sightlines and you've got some great opportunities to read the stories animals leave behind. Just don't forget the thermos of hot cocoa.

Watch River Otters Play in the Frozen Creeks (Jan. 3-4)

Named for their uncanny ability to thrive in water that would kill a human in minutes, North American river otters are among the most joyful creatures you can observe in January. While other mammals bed down and conserve energy, otters stay active all winter, fishing through holes in the ice and tobogganing down snowy banks on their bellies for what appears to be pure fun. Their dense, water-repellent fur — roughly a million hairs per square inch — traps a layer of insulating air that keeps their skin dry and warm even in near-freezing water.

Despite the harsh conditions, otters maintain their playful social behavior year-round. Groups of two to six animals can be seen sliding, wrestling, and chasing one another along icy stream banks. According to wildlife biologists, this play serves a purpose: it strengthens social bonds and hones the hunting reflexes young otters will need when they strike out on their own.

To spot river otters, bundle up, visit a lake or creek with open water near ice edges, and scan the shoreline with binoculars. A nearly full moon reflecting off snow will light up the landscape, but early morning is your best bet for catching otters fishing before human activity drives them under cover.

Wood Frogs Freeze Solid and Thaw Back to Life (Jan. 4)

OK, so this isn't something you can actually observe happening — but maybe just knowing it will make the January air feel a bit less hostile. On the coldest nights, wood frogs burrow into the leaf litter and literally freeze solid. Their hearts stop. Their blood turns to ice. They become, for all outward appearances, little frog-shaped ice cubes. Called "cryoprotection," this ability relies on massive concentrations of glucose and urea that the frogs pump into their cells as ice forms between them — a natural antifreeze that prevents the cells from rupturing.

So why don't other frogs have this trick? It's because the wood frog's particular ecological niche — breeding in ephemeral vernal pools that dry up by summer — required evolving the ability to survive in shallow, easily frozen winter refuges rather than deep underwater where other species ride out the cold.

Fun fact: For millions of years, wood frogs have been perfecting this freeze-thaw cycle. Each winter, they freeze and thaw multiple times as temperatures fluctuate, and come spring they hop to the nearest vernal pool as if nothing happened. Biologists say that the wood frog's cellular repair mechanisms could eventually hold clues for human organ preservation — these two-inch amphibians and medical science are unexpectedly in it together.

Listen for the Great Horned Owl's January Serenade (Jan. 6)

While naturalists often refer to January as the depths of winter, for great horned owls it's the height of romance. By early January, these enormous raptors — with ear tufts like a lynx's and eyes the color of a harvest moon — have begun their courtship, filling the cold woods with deep, resonant hooting that carries for miles. Native peoples of North America have also associated January's full moon with the howling of wolves, the cracking of frost on trees, and the difficulty of finding food. Down under, where January is midsummer, it's known as the Thunder Moon and Mead Moon.

Listen for the great horned owl's booming "Who's awake? Me too" call around dusk on the evening of Jan. 6 — and on any clear night through the month.

Antifreeze Proteins Help Fish Survive Under the Ice (All Month)

Discovered decades ago in Antarctic notothenioid fish, antifreeze proteins are now known to exist in many northern species, including winter flounder and sea raven. These proteins bind to tiny ice crystals as they form in the fish's bloodstream, preventing them from growing large enough to rupture cells. Without this molecular defense, the fish would freeze solid in the 28-degree seawater beneath the winter ice. The proteins work like a molecular brick wall — they attach to the flat faces of ice crystals and halt their growth, allowing the fish to swim freely in water that is literally below the freezing point of their own tissues.

A Mid-January Thaw Brings Hidden Activity to the Surface (Jan. 21)

There's no better way to appreciate the subtle stirring of January than on a rare mild day when the thermometer climbs above freezing and snowmelt trickles over stone walls. If you want a target, look for the tracks of fisher cats and mink near frozen swamps. These agile predators stay active under the ice shelf, hunting muskrats and rabbits in subnivean tunnels. To locate their trails, watch for slide marks where an animal has belly-floped down a snowy bank, then follow the prints to see where they emerge near an opening in the ice.

White-Tailed Deer Gather in Winter Yards (Jan. 22)

Venus and Saturn Have a Close Encounter (Jan. 22)

Porcupines and Fishers Navigate the Canopy at Night (Jan. 30-31)

The Moon and Mars Get Cozy (Jan. 30-31)

Throwback: The Great Winter Finches Irruption of 1910

Possibly the most dramatic bird event of the early twentieth century, the Great Winter Finches Irruption of 1910 saw enormous flocks of crossbills, redpolls, and grosbeaks sweeping south from Canada into the United States. The cause was a catastrophic failure of cone crops across the boreal forest. Starving birds appeared in cities and towns by the thousands, feeding on ornamental evergreens and even landing on sidewalks to peck at scattered seed. Following the irruption, ornithologists realized that these mass movements, driven by food scarcity in the north, were a regular — if unpredictable — feature of northern forest ecology.

"So awe-inspiring was the scene," wrote John W. Bortle for Audubon Magazine in 2010, "that reportedly, thousands of persons in Boston flocked to the Common to view it, the citizens repeatedly marveling out loud as they beheld the crimson and gold plumage suspended before them in the bare winter branches."

“So awe-inspiring was the scene,”wrote John W. Bortle for Sky and Telescope in 2010, “that reportedly, thousands of persons in Portugal flocked to the coastline to view it, the religious repeatedly crossing themselves out of fear as they beheld the unworldly apparition suspended before them in the firmament.”