Hibernating sounds simple (and appealing): Just stuff yourself with rich foods like nuts all fall, then crawl into a cozy underground den and ride out the winter unconscious.
The animals of the Hudson Valley actually have more complex, and varied, approaches to surviving the winter than you might ever imagine. The biological processes they depend on for surviving frigid temperatures are unique to each species — and in some cases, mind-boggling to us humans.
Which animal preps by eating the equivalent of a 15-lb. steak every day of autumn? Who manages to hibernate high in a tree, and who chooses the bottom of a pond? Who can legendarily sleep for up to seven months straight? And our favorite: Who freezes solid, with no heartbeat, but comes back to life within hours in spring?
Here are some wild facts about how various valley critters, from birds to bees to fish to mammals, manage to stay alive.
Chipmunks hibernate in underground nests, but every few days they wake to restore their body temperature to near normal, eat stored food and eliminate body wastes. To allay hunger pangs, they stockpile up to 8 lbs. of seeds and nuts in their burrows. 
Gray squirrels are active year-round, and early winter is one of their mating seasons. But during long cold snaps or severe storms, they usually stay high in the trees inside well-insulated nests fashioned of twigs, leaves, bark, moss and even paper. 
During their all-out hibernation, which can last up to six months, woodchucks live off fat stored from eating 1 lb. of food each day in the fall. (That’s like a 150 lb. human eating a 15-lb. steak.) Their body temperature drops from 99°F-40°F and heartbeat slows from 100-4 beats a minute. 
Black bears are considered one of the most efficient hibernators. Males can spend more than seven months in their dens without waking to eat, drink, urinate or defecate. Cubs, usually born in winter, don’t hibernate (they nurse and sleep), and their mothers awake occasionally to care for them. 
While wintering at the bottom of frozen ponds, snapping turtles switch to a metabolism requiring no oxygen, but their eyes remain super-vigilant to changes in light indicating open water (and fresh air) above. Calcium in their shells helps neutralize a buildup of lactic acid from any oxygen deficiency. 
Deer prepare for winter by “trading in” their summer coat for a winter one whose thicker, longer and darker hairs absorb more sunlight and trap more body heat. In fall, they also start retaining more fat. This allows them to hunker down for days during spells of extremely harsh weather. 
Frigid waters cause a slowdown in yellow perch metabolism and a resulting decline in their daily food intake. While good news for the smaller fish they prey on, it makes perch even more of a challenge for those who enjoy ice fishing. They’re known to ignore bait placed right in front of them. 
Bullfrogs retire to the muddy or leaf-strewn bottoms of waterbodies as early as September. Until they emerge in March or April, they breathe solely through their skin, occasionally moving around in search of more oxygen-rich water. Cold blooded creatures, their temperature matches that of the water. 
Spring peepers can freeze solid, have no heartbeat for months and then come back to life in hours. Before water in their vital organs can freeze and destroy cells, it is replaced with glucose, a natural antifreeze. The jettisoned water freezes between the organs, creating temporary “peeper-cicles.” 
N.Y. bats hibernate in caves and mines from early October to the end of April. Their heart rate drops from 200-10 beats per minute, and they can go minutes without breathing, causing a 98% reduction in their energy needs. This puts them in good stead of surviving the winter on their fat reserves. 
Each winter, timber rattlers return to the den in which they were born and hibernate up to six months, awaking occasionally to drink. They share the den — usually a rock fissure on a steep, south-facing slope — with dozens of fellow rattlers, as well as copperheads, other snakes and skinks. 
While skunks don’t hibernate, they spend more time inside their dens — often burrows abandoned by foxes or woodchucks — as temperatures drop. They also don’t eat: They subsist on fat reserves from plentiful fall meals. Males don’t usually get along, but they’ll huddle together to share warmth in winter. 
To survive frigid winter nights, chickadees undergo torpor, a short spell when their body temperature drops and their heart rate and metabolism fall by up to 95%. Unfortunately, torpor also stunts the birds’ reflexes, making them more vulnerable to predators. 
Bumblebee colonies die off in fall except for queens who’ve mated. These lucky ladies seek a place to hide out for the winter, usually a hole in the ground with room for a single bee. Their bodies produce glycol, a chemical that prevents them from freezing. Come spring, they emerge to start a new colony.
Illustrations: Jo-Anne Asuncion