Bats Get Ready for Winter

During this week, the eight species of bats in Wisconsin begin preparing for winter in different ways. Big and little brown bats are gathering together in abandoned mines and caves and getting ready to hibernate. They are full hibernators and will keep their body temperatures just high enough to keep them alive. These bats will lose 1/4 -1/2 of their weight over the course of the winter. Even while hibernating the bats must briefly wake to urinate and drink moisture from cave walls. Hibernation sites are crucial to the bats' survival. If disturbed often while hibernating, a bat may not retain enough energy to make it through the rest of the winter.

Not all Wisconsin bats will hibernate here. Red, silver-haired, and hoary bats will journey to southern states in search of warmer places in which to hibernate. Sometimes these bats are found migrating along with flocks of small birds.

Did you know? When bats hang upside-down their toes lock in place with special tendons so that they don't have to use any energy to stay put. And...

Big brown bats sometimes hibernate in our attics and walls, because their bodies are able to withstand sub-zero temperatures. The oldest bat on record was a 33 year old little brown bat. Bats are in a family called chiroptera which means "hand wing" in Greek. This refers to the thin membrane of skin stretched across a bat's finger bones which lets them fly. 

Learn more: Bat Conservation of Wisconsin

For pictures of bat skulls go to: Animal Diversity Web

Woolly Bear Caterpillars Abound

Keep an eye out for woolly bear caterpillars at this time of year. They are the larvae of the Isabella tiger moth. According to folklore, the longer the caterpillar's reddish brown bands the shorter and milder the coming winter will be. Unfortunately, the myth isn't true. As woolly bears grow and molt their old tight skin, their new skin has more brown and less black fuzz.

After a season of feeding on dandelions, asters, birches, clovers, and maples, woolly bears begin to search for overwintering sites under bark, rocks, and logs. Caterpillars hibernate there in often sub-freezing temperatures. When spring arrives, the woolly bears awaken and create fuzzy cocoons in which to transform into moths.

Did you know? Woolly bear caterpillars have a wonderful defense mechanism. The tiny, sharp hairs that cover the caterpillar's body can detach and cause irritation. This works especially well when a predator has already put the caterpillar into its mouth-ouch! Some people are also sensitive to the woolly bear's hairs, so be careful when handling them.

Learn more: Enature

Bald-faced Hornets Prepare for Winter

Bald-faced hornets create the paper nests that we see hanging from trees at CWES. These nests were made by many female workers who chewed up wood fibers and then added a secret ingredient- their own spit -to stick things together. With the first frost these workers die, leaving behind a paper nest that won’t be used again.

Just before her workers die, the queen hornet lays eggs containing new queens and drones (males). After these hornets mate, the new queens hide from the approaching cold in crevices and under tree bark. The only surviving members of their colony, they will hibernate through the winter. Come spring, they will begin to build new nests and lay their first eggs. These will hatch into sterile females that will continue building the nest and care for new eggs. These colonies may hold as many as 400 hornets which mainly eat other insects.

Did you know? Paper wasps create the small honeycombed nests that hang underneath the eaves of buildings. They have a very similar lifecyle to the bald-faced hornet. Bees, however, have a very different winter routine from both hornets and wasps. Bee hives remain active through the winter, using honey stores for fuel. The worker bees surround the queen and shiver to generate enough heat for survival.

Learn more: Harvard University

Turkey Vultures Migrate

These amazing birds are beginning to stretch out their 6 foot wingspans and head south. You can tell a soaring vulture from other birds by the way that they hold their wings in a strong V-shape and tend to rock in flight. Bald eagles hold their wings level with their bodies when they fly. If the wind is right, a vulture can soar for 6 hours without flapping its wings. Look for them high above Sunset or Minister Lake.

Vultures eat mostly carrion (dead animals) and some plant material. They play an important role in cleaning up waste that might otherwise spread disease. To help them locate their pungent meals, these birds have an excellent sense of smell. They also have very strong stomach acid that kills the bacteria and viruses often found in their food.

Though the vulture doesn't have many natural predators, it does have some pretty clever (and gross) defenses. If a turkey vulture has been feeding on carrion and is approached by a predator, it will vomit as a defense strategy! The smelly substance deters the predator and can even sting its eyes, plus the vulture has lightened its load and may take off more quickly.

The vulture has another cool adaptation-literally! On hot days, vultures will urinate on their legs to cool them off. The strong acid in their urine also kills bacteria on their legs and feet, and helps keep them healthy.

Did You Know? According to DNA evidence, vultures are actually a member of the stork family. Their weak feet aren't built for grasping and piercing prey like those of the raptors. Also, a vulture is not actually a buzzard. Buzzard is the British word for hawk.

Learn more: Cornell Lab of Ornithology