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New species of Wisconsin bat discovered in Rock County

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Xavier Ward
Thursday, September 15, 2016

TOWN OF AVON--Researchers from the Wisconsin Department of Natural Resources have discovered a new species of tree bat living in Rock County, bringing the official count for species of bats in Wisconsin to eight.

The species, called the evening bat, is the first new species of bat discovered in Wisconsin since 1954. The evening bat is frequently found in the southern United States and has been seen once in Minnesota, but Wisconsin is the first northern state to have a sustained evening bat population, said Owen Boyle, section chief of the DNR National Heritage Conservation branch.

Researchers found the bat living in hollow trees in the Avon Bottoms Wildlife Area in the southwestern corner of Rock County, Boyle said.

The researchers were searching for northern long-eared bats and eastern pipistrelle bats.

Bats are separated into two groups: tree bats and cave bats. Cave bats are easier to monitor because they hibernate but are susceptible to diseases such as white-nose disease. Tree bats, such as the evening bat, are migratory and thus much harder to monitor and track.

To monitor bat populations, researchers use GPS transmitters to track bats back to their maternity colonies. When researchers discovered the female evening bat, they tracked her back to the maternity colony, discovering 100 other evening bats.

The DNR has been conducting GPS tracking research on bats in Rock County for the past three summers. Researchers have also used acoustic monitoring to measure certain bat populations for the past six years.

Boyle called the evening bat discovery “a happy accident.” He said researchers were not searching for a new species.

Bats play an important role in the Wisconsin ecosystem, and a decline in bat populations could have serious ecological consequences, Boyle said.

The average bat eats its weight in insects every day, and areas with decreased bat populations see a spike in the number of pests. This can negatively affect other forms of plants and wildlife, Boyle said.

A existential threat for cave bats is white-nose disease. White-nose disease is a fungal infection that wakes cave bats from hibernation. The disturbance in their sleep causes them to use energy they had stored for the winter, and since there are no insects to eat, the mortality rate is 75 percent to 100 percent, according to the DNR website.

Prior to white-nose disease, Wisconsin had more than 1 million cave bats. That number has been steadily decreasing.

Of the species of bats in Wisconsin, four are susceptible to white-nose disease. The small brown bat, the large brown bat, the northern long-eared bat and the eastern pipistrelle bat are cave bats prone to the disease. Of the four, the eastern pipistrelle and northern long-ear are uncommon in Wisconsin.

Nationally, millions of bats have died since the appearance of white-nose disease in 2006. It is possible the appearance of the new species found in Rock County is related to the void created by the decline in the brown bat population, Boyle said.

Only time will tell the overall ecological effect of the evening bats' discovery, Boyle said. Perhaps it will help fill the void left by dead cave bats.



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