Upper Peninsula (Michigan) Bats

Bats are  an important part of the Lake Superior and inland lakes because they are efficient mosquito eliminators. A little brown bat (Myotis lucifugus), the most common species in the Keweenaw and Upper Peninsula and can consume up to 1,000 flying insects in an hour and over half its body weight in insects in a night. The Keweenaw is home to seven bat species. Three Keweenaw bat species are seasonal residents who migrate: the red bat, the hoary bat, and the silver bat. Four species hibernate in caves and old mine shafts: the little brown bat, the big brown bat, the northern long- eared bat, and the tri-colored bat (formerly pipistrelle). 90% of Michigan’s hibernating bats winter in the UP, mostly in old mines located in the western portion of the UP. Some of these hibernation locations - called hibernacula - house just a few bats, some house tens of thousands.

Conservation staff say at least 200 northern long-eared bats hibernate in the mine near Iron Mountain, Michigan each winter. A steel gate was installed on an exposed 50-foot-deep hole, more than 20 feet wide, that connects to 400 feet of mining tunnel. A smaller hole was also gated   to let the bats come and go, but they were also designed so people can't fit through them. A hatch in the gates allows DNR staff entry to work on research.   The region also has little brown bats, tri-colored bats and big brown bats. 

 

Dangers to Bats - Foolish people and White-nose syndrome

The northern long-eared bat is a little critter with brown fur and ears are longer than average. In winter, it hangs out in mines and caves in the Upper Peninsula.   The really alarming fact concerning bats is that hibernating bats are rapidly being wiped out by the aggressive fungal parasite, Geomyces destructans or "White-nose syndrome". This cold loving fungus grows on bat skin membranes and forms a fuzzy white growth on their muzzles. White Nose fungus, which arrived in the United States from Europe, is a constant irritant that causes bats to be repeatedly awakened from their hibernating torpor. Hibernating bats don’t eat for many months, so any disturbance depletes precious stored fat resources endangers them. Starving, infected bats may become confused and leave the hibernacula in mid-winter in search of food which is non-existent at that time.

More than 90% of bats infected by the fungus starve to death and this is causing strong concern among scientists.. Along the East Coast of the U.S. whole bat populations are being wiped out. Michigan now holds the distinction of being one of the last Midwest outposts with many hibernacula (hibernating roosts) free of the deadly White Nose fungus as it continues to spread west from the east coast. Experts fear this fungus may push the little brown bat, now the most common bat in the Keweenaw, to extinction in the lower 48 states in 15 years! Bats are very social creatures, so the fungus is easily transmitted easily from bat to bat. White Nose fungus is a disease specific to bats and not harmful to people or other animals. However, the fungus can travel on the clothing, shoes, and equipment of people who visit or work in caves and mines, and can also be transmitted to bats in this way. Effort is being made to find ways to stop the transmission of the disease by people to these beneficial bats through research. 

This is not helped when people disrupt research in this area.  Officials are looking for vandals who broke into an abandoned iron mine in the Upper Peninsula where scientists are studying hibernating bats threatened by this deadly illness. The Department of Natural Resources says the intruders disturbed the bats, stole cameras and no-trespassing signs, built a bonfire and damaged a gate that allowed the bats to enter and exit.  This kind of idiocy, along with  pockets of white-nose syndrome is responsible for many of the bat die offs in northern Michigan.  Michigan counties where white-nose syndrome has been found include Alger, Alpena, Clare, Delta, Dickinson, Houghton, Keweenaw, Mackinac, Manistee, Marquette, and Ontonagon. The DNR and Eastern Michigan University are monitoring bats populations this winter and anticipate finding infected bats at most caves and mines where bats spend the winter.

Prior to  white-nose syndrome,  bats were hibernating in 82 of 119 abandoned mines in northern Michigan. Unoccupied sites typically were short and/or experienced chimney-effect airflow, which led to temperatures near or below freezing.  The occupied sites were more structurally complex, longer, and warmer than unoccupied mines. Number of bats varied from 1 to  55,000,  the median being around 115 per hibercacula. . Perimyotis subflavus (Eastern Pipistrelle) and Eptesicus fuscus (Big Brown Bat) accounted for only 0.5% of the total of 244,341 bats that were observed. Ninety percent of hibernating animals were Myotis lucifugus (Little Brown Bat), and almost 10% were M. septentrionalis (Northern Bat).  Little Brown Bats, Northern Bats were more common in the mines of the Upper Peninsula than in the East and Ohio River Valley. Maximum ambient temperature, presence of standing water, and water vapor pressure deficit were potential predictors of the number of Myotis that was present. Seventy-five percent of Northern Bats and 22% of Little Brown Bats roosted alone, rather than cluster with other bats. Little Brown Bats in Michigan were much more solitary than in the east.
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Links:

Bats of Pictured Rocks National Lakeshore

Millie Mine Bat Cave

 

Iron Mountain Bat Research

 

Bat Magazine