As Old Man Winter makes his way into the forest, both animals and plants prepare for his arrival by battening down the hatches.

Minus 5 degrees, icy winds, a layer of snow more than 3 feet thick, and hardly anything to eat—in winter both animals and plants face extreme hardship. But foxes, deer, and even trees have developed ingenious survival tricks to make do in this winter wond

No more berries to be found, frozen ground, and an icy wind whipping through bare branches at 25 miles per hour: Now the dainty European robin will have to fight for its survival. Winter poses the ultimate challenge to these teeny birds, which weigh in at just over half an ounce. But the bird resorts to an ingenious trick: It starts tracking a group of wild boar. How does that help it? Even during the coldest days of the winter, these robust forest dwellers are always digging up the ground—and in the process turning up small items the robin considers delicacies, such as worms, insects, and buried seeds. Like the robins, many other animals have special strategies for surviving months of subfreezing temperatures. But what about the flora? After all, winter is also a tough time for trees, shrubs, and other plants. They too need effective tactics to see them through winter’s harsh conditions.

Their strategies can border on the brilliant, as seen, for example, in the quaking aspen (Populus tremula). When the days get shorter and the temperatures drop, aspens undergo a process that resembles something that might be seen in a high-tech chemistry laboratory. Scientists at the National Center for Atmospheric Research in Colorado (NCAR) found that aspen trees warn one another of the impending winter by releasing messenger substances from their roots and leaves: methyl salicylate, for example, an aspirin-like natural organic compound. When subjected to stresses like frost or fluctuating temperatures, they’re able to release 0.0076 mg of methyl salicylate per hour per square foot. When other aspen trees detect the presence of the substance, they too go on high alert and prepare for the hard times ahead. Methyl salicylate activates their system of immunity in a process called systemic acquired resistance. “Unlike humans, who’ll take aspirin as a fever suppressant, plants have the ability to produce their own mix of aspirin-like chemicals, triggering the formation of proteins that boost their biochemical defenses as well as reduce injury,” says Thomas Karl from NCAR. And methyl salicylate is pure poison to many of the pests that live on trees, such as insects and their maggots.

DO TREES MAKE THEIR OWN ANTIFREEZE? At the same time a tree is activating its system of immunity to prepare for winter, it is also reducing its energy consumption. When temperatures start to fall, for example, to 40°F, a quaking aspen, which can grow to be 100 feet tall, switches over to an energy-saving mode within four hours. The tree then begins exuding water from its leaves, and its sap will become increasingly viscous until it consists mostly of sugar and proteins. Resins and tree syrup will ultimately result from this reduction process. The modification will make the quaking aspen resistant to cold because the new composition of its sap doesn’t let the substance freeze unless the temperature plunges to below minus 40 degrees. And some tree species are able to withstand temperatures as low as minus 60.

If the temperature falls below that level, however, things can get dicey

for a tree: In the taiga, the coniferous forests of subpolar regions, nighttime temperatures can be as low as minus 85. Then things become volatile. The loud noise that sounds like a gunshot is actually the sound of a coniferous tree exploding! For even the strongest trees are pushed to their limits when the cold becomes this extreme: The small amount of fluid that remains in the trunk freezes and expands. If the pressure is too great, the entire trunk can blow apart—as though someone had deliberately blown up the tree. But trees growing at lower latitudes have nothing to fear: Their survival strategies enable them to withstand average temperatures as low as zero degrees without a problem. And the trees’ needles have strategies of their own: Abscisic acid, a plant hormone, induces stomatal closure, sealing off the needles and keeping the tree from drying out. To protect themselves from the cold, some trees also produce a resinous coating around their buds. This is extremely effective for keeping the buds warm and repelling water— even when it is in the form of snow. Given all of these survival strategies, which trees have spent 380 million years developing, it’s no wonder that forests thrive as winter habitats.

But some organisms prefer cooler weather: They spend the summer and autumn underground, just waiting for the weather to turn crisp and frosty. When the temperature drops below 50°F, it’s sprouting time for such fungi as the oyster mushroom (Pleurotus ostreatus), the herald of the winter (Hygrophorus hypothejus), and the wood ear mushroom (Auricularia auricula-judae), which can cope with ice and snow. Researchers believe

In order to get through the winter, a fox not only dons a warm winter coat, it also establishes dozens of food depots all across its territory. Thanks to an extremely keen sense of smell, a fox always knows the location of the nearest fridge. It also uses its magnetic sensing ability to dive headfirst into the snow and catch prey that are hidden beneath the surface.

As soon as the weather turns cold, deer switch over to an extreme energysaving mode. Their heart rate slows to half its normal speed and their body temperature drops to just below 90°F—a temperature that would be deadly for most other warm-blooded animals. In this diminished state they mostly just stand around, falling into a kind of torpor. Instinctively they know that the less they move, the less energy they’ll need. WORLD-CHAMPION ENERGY-SAVER

When winter blankets the ground with snow, things get tough for the barn owl (Tyto alba), which can still use its acute sense of hearing to detect mice and voles but cannot get at them. That’s one reason the big birds (with a wingspan of 4 feet) like to hang out near people— and their snow-plowing services— in the wintertime.

CLEVER COLLECTOR Thick fur, a perfectly insulated nest, and a knack for collecting—squirrels know how to prepare themselves for winter. As cold weather approaches, they even grow additional hair on the bottoms of their feet to provide them with an enhanced grip when the branches get icy.