Where are they over the winter?


“A sight for sore eyes” and “music to our ears” may be overused phrases, but they sum up the pleasures that warming temperatures deliver to lovers of backyard wildlife. They signal that winter has given way to spring, and our yards become filled with activity. Aside from the visual feast of greening plants and flowers beginning to bloom, we begin to see birds in courting plumage, frogs in the pond and butterflies nectaring. And, the sounds! Birds singing, frogs croaking and insects buzzing, chirping, trilling.

Eventually, it comes to a stop. It’s subtle, we hardly notice the transition from a yard filled with such wildlife-style busyness to one that’s gone dormant, until it has done. There comes a moment when we become aware that birds aren’t calling or crickets have gone silent or the lily pads are gone, and so are the frogs. Whatever triggers that for you, it’s the signal that summer has ended. Just as wildlife seemed to appear as if by magic, they disappear the same way. Have you ever wondered what becomes of all those animals? Or where they go? Here are the answers.

Mammals are still around, but they spend most winter days and nights sleeping in their dens, conserving energy, trying to stay warm and surviving off the extra body fat they packed on in the fall.

Skunks stay in their dens for weeks at a time. Several females often share the same den. Raccoons also sleep for weeks or months on end. Den sites for skunks and raccoons include such places as abandoned buildings, rock crevices, the abandoned burrows of other animals, and for the raccoon, tree hollows.    All about the Striped Skunk   All about the Northern Raccoon

Northern Opossums have naked tails and toes. (Normanack / Flickr; cc by 2.0)

Brrr! Northern Opossums have a thin coat and a bare tail and toes. (Normanack / Flickr; cc by 2.0)

Winter is hardest on opossums, as they lack a thick insulating coat of hair and their tail and toes are bare. They’re susceptible to frostbite, especially at the tip of their tail. They sleep in their dens in bad weather and forage for food when the weather warms up. To help insulate themselves, they line their dens with dry grass and leaves.   All about the Virginia Opossum

Tree squirrels may be seen out in winter, but they spend a lot of time sleeping in their nests, especially when it’s very cold. If the temperature isn’t too low, they venture out to find food, particularly the nuts they buried in the fall. In really bad weather, they may stay in their nests for several days at a time.   When snow covers the ground   All about Fox Squirrels and Gray Squirrels

Bats spend the winter in hibernation. Most bats are insect-eaters and insects aren’t available in the winter, so they disappear into places like unused buildings, old tree hollows, house attics and caves. They awaken periodically through the winter.

In March, as the weather gets warmer, bats begin to emerge, little by little. By April, they’re mostly out of hibernation and flying at night. If the weather cools down, they become inactive again. By May, they’re fully active.   All about bats

Nearly everyone knows about Monarch Butterflies and their annual fall migration to Mexico, where it’s warm all winter. Less well-known is that around a million Monarchs hibernate in the United States, overwintering in and around Pacific Grove, California, where it’s also warm year-round. In the spring, the Monarchs hibernating in Mexico begin an amazing trip north, 2,500 miles long, and fan out across the northern U.S. and southern Canada, staying east of the Rocky Mountains. Flocks in California migrate north and east, but remain west of the Rockies. (Southern Florida has Monarchs that don’t migrate, they’re year-round residents.)

Painted Lady Butterflies (Vanessa cardui) also migrate. (Esin Üstün / Flickr; cc by 2.0)

Painted Lady Butterflies (Vanessa cardui) also migrate. (Esin Üstün / Flickr; cc by 2.0)

Monarchs migrate for two reasons: They can’t survive cold winters and the host plants their larvae feed on don’t grow in their hibernation areas. They must travel to where these vital plants (milkweeds, the only plants their larvae will feed on) are plentiful. (By the way, milkweed species everywhere are under siege from farming and logging operations and human development, a serious threat to Monarch survival. So, be sure to find a place in your yard for milkweed plants.) Monarchs begin their migration north in late-February and arrive at their northernmost summer areas in late-May and June.   Monarch life cycle in pictures

Monarchs may be the best-known migrating butterflies, but there are others, including Red Admirals, Cloudless Sulphurs, Gulf Fritillaries, and Common Buckeyes. The pretty Painted Lady Butterflies (Vanessa cardui) also migrate north and south, although not every year. One of the most widespread species, you probably see them in your butterfly garden every summer.

Isabella Tiger Moths  (Pyrrharctia isabella) hibernate as caterpillars known as Wooly Bears. (IronChris / EOL; cc by-sa 3.0)

Isabella Tiger Moths (Pyrrharctia isabella) hibernate as caterpillars known as Wooly Bears. (IronChris / EOL; cc by-sa 3.0)

Some species, such as tortoiseshell and anglewing butterflies, hibernate as adults. Most, however, spend the winter hibernating in a caterpillar or pupa stage, near their host plants. Chrysalises may be found tucked into crevices on tree trunks, attached to sturdy plant stems or even to the side of a building. Caterpillars bury themselves in leaf litter and debris or, with moths, loose soil.

Other insects
All insects are cold-blooded, meaning they’re unable to regulate their body temperature to stay warm, as mammals do. Freezing weather would kill them. So, depending on the species, they use various tactics for survival — put on fat to carry them through the winter, reduce the amount of moisture in their bodies, bury themselves, and more. Some, such as the Praying Mantis, hibernate as eggs.

Honeybees stay in their hives through the winter. They don’t hibernate in there — they cluster together and flutter their wings and shiver to stay warm. They feed on the honey they stored away through the previous summer. If a winter day reaches about 65 degrees F (18 C) or higher, honeybees may leave the hive to forage for any nectar that can be found. All about honeybees

Hibernating ladybird beetles. (Doctor Popular / Flickr; cc by-sa 2.0)

Hibernating ladybird beetles. (Doctor Popular / Flickr; cc by-sa 2.0)

Many other insects also hibernate as adults. Ladybird beetles (ladybugs) pass the winter hibernating in huge, tight clusters in hollow logs, crevices, under leaf litter, and sometimes inside houses or attics. Ants hibernate underground. Some flies remain active through the winter, but the ones we notice most, the bigger ones, hibernate in cracks and crannies.

Most insects in the winter are hibernating in an immature stage — as an egg, larva, nymph or pupa of parents who have already died. Very hard to spot, they’re all around us — in the ground, in rock piles, woodpiles, under tree bark, attached to plants, under the lips of flowerpots, under the eaves of our homes, in sheds, under tarps, or any other place that offers some protection.

Some spiders are indoor spiders who are there year-round, even when we don’t see them. Outdoor spiders don’t come indoors, except by accident. The beautiful Golden Orb-weavers and other spiders die, but they leave behind sacs filled with eggs that defy frigid temperatures.

Orb-weaver egg sac. (L Church / Flickr; cc by 2.0)

Orb-weaver egg sac. (L Church / Flickr; cc by 2.0)

Other species spend winter as young spiderlings who hatched before winter, but remain clustered together in their communal egg sac until spring. Some wolf spiders spend the winter as nymphs and become adults in the spring. Still others, such as tarantulas and fishing spiders, hibernate as adults under the bark of trees, in cellars or any other place they’ll be protected. They’ll sometimes awaken and roam around on warm winter days in search of hibernating insects to eat.   All about spiders

Frogs, toads
They spend the winter hibernating in protected places, such as caverns, abandoned burrows, a crevice in a log, under a rock or leaf litter, or anywhere else they feel safe. Some hibernate up to eight months. Aquatic frogs hibernate underwater, lying on top of the mud at the bottom or partially buried. Wood frogs are known for their ability to freeze hard as a rock in frigid weather and still re-animate when temperatures warm up.   Watch frozen wood frog awaken   All about frogs and toads

It may be surprising to think of earthworms as migrators, but some are! Like insects, earthworms can’t regulate their body temperature and won’t survive freezing weather. So, they go “south,” so to speak, in the winter and “north” in mid-spring. That is, if you think of south as “down” and north as “up.” They move down below the frost line to avoid freezing and upward when the soil becomes warmer. Some species of earthworms always stay close to the surface and, therefore, die in the winter. However, they leave eggs which will hatch in the spring. The eggs are encased in tiny cocoons, which protect them from freezing and drying out.   Watch earthworms hatching

Nightcrawlers are the largest of the migrating earthworms. They remain fairly inactive in cold soil and become active as the soil warms up. They’re most active when soil temperature rises to 50 to 60 degrees F (10 to 15 C) You might see them in the winter during unseasonably warm weather, but they move back down when the soil turns too cold, again.   All about earthworms   Attract earthworms to your yard

Many species hibernate in winter. They tuck themselves into crevices, under rocks, under leaf-litter or other places where they’ll be safe from freezing temperatures. They then seal the opening of their shell with mucus to keep them moist (drying out will kill them). Their heart slows from about 36 beats per minute to only three or four and oxygen use is reduced to 1/50th of normal. Often, several snails hibernate together. They sometimes emerge on very mild winter days.   All about land snails

Common Poorwill. (Gavin Keefe Schaefer / Wiki; cc by 2.0)

Common Poorwill. (Gavin Keefe Schaefer / Wiki; cc by 2.0)

Birds are the year-round constant in our yards, although the species may vary. Northern Cardinals, Downy Woodpeckers and chickadees, for example, are year-round residents, but many others have migrated in for the winter. Half of North America’s 650 breeding species of birds migrate. Some move just short distances, from higher to lower elevations. Some move just a state or two away. But, more than half move to Central and South America.

The Common Poorwill (Phalaenoptilus nuttallii) is a distinctively unusual bird, being the only species that’s inactive in the winter. Tucked into piles of rocks, they remain there for extended periods — from weeks to months — in a state of “torpor,” which is a sleep that’s not quite as deep as true hibernation. Their cryptic coloration hides them well.   All about birds

Top image: clockwise, from upper/left: J JCadiz, Neil McIntosh, MrLebies, Bob Ireton, Skeeze, John Flannery, sparkielyle; CC