Summer wildlife disappear in winter, but where to?


Spring and summer abound with the sights and sounds of wildlife. Birds are singing, frogs are croaking, insects buzz, chirp, trill. Tadpoles are swimming in the pond, earthworms are revealed as we work our garden soil, and ants march across nearly every surface. Butterflies and honeybees dance around the flowers in colorful bloom. Every day, we’re witness to the active lives being lived out there.

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 of awareness that the birds aren’t calling or that crickets have gone silent, or the lily pads are gone, and the frogs are, too. Whatever triggers that for you, it’s the signal that the warm season is gone and winter is here. Just as wildlife began to appear in the spring as if by magic, they disappear the same way.

Have you ever wondered…where do they go?

Mammals are still around us, but they spend more time 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

Virginia Opossum standing on snow, showing bare toes and tail.

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

Winter is hardest on Virginia 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 stay in their dens in miserable weather and forage for food once it 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 frigid. If the temperature isn’t too low, they venture out to find food, mainly the nuts they buried in the fall. In nasty weather, they may stay in their nests for several days at a time. Ground squirrels hibernate in their den through the winter.
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 bat colonies disappear into places like unused buildings, old tree hollows, house attics, and caves. They awaken periodically through the winter to relieve themselves but don’t leave their shelter. 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

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 go only a state or two away. But, more than half migrate to Central and South America.

Common Poorwill, Phalaenoptilus nuttallii, lying on the ground.

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

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

Most butterflies and moths hibernate in a caterpillar or pupa stage near their host plants. They tuck into crevices on tree trunks or attach themselves to sturdy plant stems or even to the side of a building. Many are in leaf litter, debris or soil. Some species, such as tortoiseshell and anglewing butterflies, hibernate in their adult stage.

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. 

Monarchs migrate for two reasons: They can’t survive cold winters. And the only host plants their larvae will eat — milkweeds — don’t grow in their hibernation areas. So, they must travel to where these important plants are plentiful. (By the way, milkweed species everywhere are under siege from farming and logging operations and human development, a severe threat to Monarch survival. So, be sure to find a place in your yard for milkweed plants.)
Monarchs begin their spring migration northward in late-February and arrive at their northernmost summer areas in late-May and June. Flocks in California migrate to the north and east but remain west of the Rockies. (Southern Florida has Monarchs, too, but they’re year-round residents.) Monarchs that hibernated in Mexico begin an incredible trip north, 2,500 miles long. Successive generations of them fan out across the northern U.S. and southern Canada, staying east of the Rocky Mountains.  Monarch life cycle in pictures
Painted Lady Butterfly (Vanessa cardui), a species that migrates periodically.

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

Monarchs are the best-known migrating butterflies, but there are others, including Red Admirals, Cloudless Sulphurs, Gulf Fritillaries, and Common Buckeyes. The pretty Painted Lady Butterflies migrate, too, but not every year — they’re one of the most widespread species, you probably see them in your butterfly garden every summer.

Isabella Tiger Moth (Pyrrharctia isabella), which hibernates as a caterpillar known as a Wooly Bear.

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

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. They 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 there 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 they can find.  All about honeybees

Large cluster of hibernating ladybird beetles, unidentified species.

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 in the summer, 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.

Frogs and 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 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 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, as a result, 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 relatively inactive in cold soil and become active as the soil warms up. They’re most active once 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 snail 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 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 will hibernate together. Snails sometimes emerge on very mild winter days.   All about land snails

Some spiders are indoor spiders that are there year-round, even though we don’t notice 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.

Egg sac of an orb-weaver spider.

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

Other species spend the winter as young spiderlings that hatched before winter, but they 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 that protects them. They’ll sometimes awaken and roam around on warm winter days in search of hibernating insects to eat.    All about spiders

* Composite image at top of the page is composed from Creative Commons photos by these photographers — clockwise, from top/left: J JCadiz, Neil McIntosh, MrLebies, Bob Ireton, Skeeze, John Flannery, sparkielyle

More reading:

Cover provides safety, shelter for wildlife    
Basics of a backyard wildlife habitat