Creatures of the Cave

Crystal Cave is home to three types of bats: Eastern Pipistrelle, Little Brown Myotis (commonly called the little brown bat), and Northern Myotis. The little brown bat is about 9 cm long with a 25 cm wingspan, glossy brown fur, and a grayish-brown belly. It weighs about 7 grams. The Northern Myotis looks similar to the little brown bat but the Northern Myotis has duller and less glossy hair and narrower, longer ears. The Eastern Pipistrelle is the smallest bat of Wisconsin, at around 1.5 cm long. It usually has a wingspan of less than 18 cm, weighs around 5 grams, and has yellowish brown fur with darker coloring on the back.

The bats inhabit trees, bat houses, and buildings during the summer, forming colonies of hundreds or thousands. One bat can eat up to 3000 bugs in one night. They breed in the fall and the young (pups) are born between May and July. One pup is born to each mother bat. They live to be 20 to 25 years old because they hibernate which lowers their metabolism and stress levels.

The bats hibernate for six to seven months in the winter, from around October to March or April. Some bats fly several hundred miles to reach their hibernation site, which must be cool but the temperatures must stay above freezing. The site also needs to be relatively free of human disturbance; if a bat is awakened from hibernation too often, it will use its fat reserves too quickly to survive the winter. The bats wake about once every two weeks and may fly out on warm nights but do not feed.

Little browns are the most common bats in North America (BCM, 2005).	The Northern Myotis can be mistaken for little brown bats at a distance (BCM, 2005).	The Eastern Pipistrelle is the smallest bat found in Wisconsin (BCM, 2005).

Bats in Crystal Cave on November 7, 2005 hanging in the Ballroom.

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