Crystal Cave is home to four species of bats.  They can generally be seen in the cave throughout the year but are most common during the winter months.  Bats are gentle, intelligent creatures that rarely interact with humans. 

Bats are mammals.  They are the only true flying mammal in the world.  The wing of the bat is composed of the forearm and extended “fingers” of the hand.  The third, fourth and fifth fingers support most the very thin wing membrane, a piece of delicate skin laced with veins.  The thumb is seen as a tiny hook on top of the wing.   The wing membrane connects with the body, hind limbs and, in most bats, encloses the tail.

There are over 900 species of bats found throughout the world.  Wisconsin and Minnesota are home to seven species, all insect eaters.  Three species spend only summer months in our area.  The remaining four species are cave bats, are the most common, and remain here throughout the year. These bats are the little brown bat, big brown bat, eastern pipistrelle, and northern myotis.  They are found in caves, abandoned mines, and buildings.

Cave bats range in size from three to five inches in length with wingspans of eight to thirteen inches.  They weigh very little, from a tenth of an ounce to one-half an ounce.  Bats can live to be twenty to thirty years old and usually have only one young, called a pup, each year.  Because they are mammals, the baby bat is born alive and fed milk by the mother. The mother bat will nurse for about six weeks or until the pup can fly and catch insects on its own.  Bats found in Crystal Cave give birth in late May and early June.  The female bats gather together in large groups called maternity colonies.  These colonies generally occupy an attic or old abandoned building where temperatures will be warm enough to protect the hairless newborns.  All pups are born about the same time and can be found clinging to the ceilings.  Each female can locate her infant among thousands of others by sound and smell.  Immature pups that fall from the ceiling cannot be rescued by the adults and usually die soon after.

Cave bats feed at night, catching insects such as moths, flying beetles, and mosquitoes.  They use ultrasonic sound, called echolocation, to locate their food.  This echolocation involves emitting a high frequency sound which bounces off obstacles.  Bats are able to hear these echoes and locate, identify, and capture moving prey while flying through the dark.  The large ears on bats aid them in hearing these echoes.  Contrary to popular belief, bats are not blind.  They see as well as humans and, if flying in the presence of light, will use their eyes rather than the echolocation.

Many people think bats are dirty, disease-carrying creatures.  Again, this is largely based on false information.  Bats are actually clean, relatively disease-free.  People are most concerned with bats and rabies.  This falsehood began more than forty years ago when erroneous testing procedures resulted in all bats testing positive for rabies.  After additional testing, it was discovered that the bat carries a harmless virus that caused the same reaction as the rabies virus.  Unfortunately, the damage was already done and this peaceful little creature was labeled as a menace to society.  We must understand that because bats are mammals, there is the possibility of contracting the disease, but in this part of the United States, rabid bats are very rare.  In any case, if a bat is on the ground you should assume it is sick.  It should only be handled by a professional and sent to a lab to be examined for any diseases.

Bats are not an animal of which to be frightened.  They will eat up to 500 insects each hour they feed in an evening, ridding us of real unwanted pests.  You should never disturb bats when you find them sleeping in caves or mines.   Unless they become a nuisance, consider them as welcome guests!  But remember, they are wild animals so never try to pet them or catch them for fun.  They will bite in self-defense.  If a bat happens to get into your house remain calm.  Allow the bat to land, then take a heavy towel, gently cover the bat, and remove bat and towel to the outside. 

The big brown bat is approximately 4-5 inches long.  It has a wingspan of about 12-13 inches and weighs 0.4-0.5 ounces.  The bat’s fir is usually dark brown with the face, ears, and wing membranes a blackish color.  Big brown bats can be found in the city or country.  They like to roost in attics, barns, behind doors and shutters, and in hollow trees.  Big brown bats fly at dusk and generally feed in the same area each night.  They fly in a nearly straight line and quite often, you will hear them “chatter” while swooping for food.  These are the last bats to enter hibernation usually in late October or mid-November but they may wait until December.  They emerge from hibernation in late March or early April to begin feeding on bugs.  Big brown bats give birth to two pups in June.  They may live to be as old as twenty years.

The most common bat in Wisconsin is the little brown bat.  This bat is about 3-3.5 inches long with a wingspan of 8.5-10.5 inches.  They will weigh about 0.25-0.35 ounces with the females slightly heavier than the males.  Little brown bats can be found with a wide range of colors from almost black to a pale brown-gray.  Often, a dark spot can be seen on the shoulder of the bat.
Little brown bats eat a wide variety of flying insects including night-flying moths, bugs, beetles, flies, and mosquitoes.   Insects are caught with the wing or tail membrane and “flipped” into the mouth of the flying bat.  Little brown bats usually begin to feed just at dusk, after locating and taking a drink of water.
Little brown bats begin hibernation in mid-October.  They gather together in clusters on the cool cave ceiling to conserve body heat.  The bats will wake from hibernation in late April or early May.  Little brown bats return every year to the same cave or building to hibernate.  Pups are born in mid-May or very early June in maternity or nursery colonies.  Little brown bats give birth to one pup each year.  The young pups grow rapidly and are able to fly in about four weeks.  Little brown bats may live as long as twenty-five years.

The eastern pipistrelle, fondly called the pip, is Wisconsin’s smallest bat, only about 2.5 to 3 inches long.  The pip weighs only 0.14-0.25 ounces and has a wingspan of 8-10 inches.  Pips are yellowish brown to silvery-brown.  A unique color feature is the “orange” arm bone of the pip which helps to separate it from the little brown bat.  Pips feed in the early evening looking for flies and grain moths.  They spend summers in open woods, near water, cliff crevices, buildings and caves.  Pipistrelles hibernate from September through May in caves with temperatures around 50 degrees.  The pip is an extremely sound sleeper, seldom moving during the winter.  It is a solitary hibernator, preferring to be along rather than in clusters.
Pipistrelles give birth to one or two pups in June.  The littlest bats in Wisconsin live an average of 4-8 years but can live to be 15 years old.  In Michigan, pips are considered a species of concern.

The northern myotis closely resembles the little brown bat in coloring, size, facial features and habitat.  In most instances the only way to identify the northern myotis is by closely checking ear length.  The ears of a northern myotis will be 0.55-0.75 inches long compared to only 0.43-0.63 inches for a little brown bat.