The Keweenaw is dotted with remnants left behind from its mining past. Among its towering
rock piles, industrial buildings, and surface infrastructure, are abandoned mine shafts,
connected to miles of underground tunnels. When mining operations ceased, shafts were
frequently left open at the surface. The open shafts provided access to stopes and drifts
near the surface, whose cave like feature provided critical wintering habitat for great
lakes bat populations. However, these open mine shafts posed a safety hazard.
Beginning in the 1960's and 70's, many of these openings were sealed with concrete caps.
In doing so, thousands of hibernating bats were unintentionally entombed in mines throughout
the Keweenaw. Starting in 1993, the North American Bats
and Mines project began an effort to retrofit mine caps with bat-friendly gates. These gates
were designed and constructed to have openings large enough for bats to fly through, but
small enough to keep people and predators out. Thanks to these efforts, mines are again
home to tens of thousands of bats. The two primary species found in Keweenaw
mines are the North American Little Brown Bat and the North American Big Brown Bat.
As winter settles in, and hibernation begins, bats drop their body temperature and heart
rate to as low as ten beats per minute. Hibernation can last more than six months, and by the
time spring arrives, the bat will often lose half of its body weight.
During the spring, these bats will migrate from the Keweenaw to surrounding states and
Canada. In summer, they hunt insects to build up fat reserves, which they use during the
fall to return to their winter home in the Keweenaw.
Bats are important, both ecologically and economically. A recent study estimates that
bats provide a 23 billion dollar a year benefit to farmers in the U.S. by controlling insects.
Yet the future for bats is uncertain. White nose syndrome has killed millions of bats
since its discovery in a New York cave in 2006. This white fungus disturbs a hibernating
bat, causing it to awaken and prematurely deplete its viable fat stores. Mortality rates
of 100% are reported at some sites. Bats across North America are at impending risk, unless
a solution is found. Researchers have been able to pinpoint the fungus, and are working
on how to treat a bat without disturbing it. For the most current information about white
nose syndrome, and to learn what you can do to help, please visit this website.