Minnesota Department of Transportation

511 Travel Info

News Release

July 18, 2016

Orange barrels on a highway

Bat colony preservation work near I-90 Dresbach Bridge shows early success

ROCHESTER, Minn. – Little brown bats are inhabiting the new bat homes installed to preserve the colony on the north side of the new Interstate 90 bridge abutment at the Dresbach Bridge project, but bat experts say long-term study needs to continue to determine if the effort is a success.

The structures were installed in the fall of 2015 after the bats had migrated to hibernate for the winter. The installations were requested by the Wisconsin Department of Natural Resources, which determined a colony estimated at possibly 3,000 little brown bats were living in the old I-90 bridge. That old bridge is being demolished as the Minnesota and Wisconsin departments of transportation work to complete a new Mississippi River crossing on I-90 this fall.

“We’re excited about this initial count,” said Heather Kaarakka, a Wisconsin DNR conservation biologist and bat specialist. “There aren’t a lot of examples of this, so we’re hopeful that the colony will return and populate it.”

On a recent visit to the site near the new bridge, Kaarakka estimated that 400 to 500 bats are present in the homes with a mix of adults and their young pups. The hope is that the bats will continue to grow in numbers in these homes.

The aim is to preserve the colony by providing an option that replaces the bats’ previous living areas. The new home is a 4-foot-by-4-foot wooden structure mounted on posts 10 feet to 15 feet tall. An additional six bat bunkers were installed in the area as well. This new roosting area is north of the construction limits in the Mississippi River backwaters area on the Wisconsin side near the bats’ old roosting grounds.

The Wisconsin DNR has been making an effort to preserve existing colonies, such as the I-90 bridge colony, because white-nose syndrome, a deadly disease for bats, has been found in Wisconsin. MnDOT, WisDOT and the project contractor Ames Construction have worked with the Wisconsin DNR since the start of the project to ensure that the new homes and bunkers are in compliance with the Wisconsin DNR’s optimal bat habitat factors.

The $187.5 million river bridge project is a cooperative effort between the Minnesota and Wisconsin departments of transportation and will continue through 2016. The project includes constructing a new I-90 crossing over the Mississippi River and reconstructing Highway 61/14 and the I-90 interchange. MnDOT urges motorists to always be attentive, drive with caution, slow down in work zones and never enter a road blocked with barriers or cones. 

For more information about the Dresbach Bridge project and detour, visit www.mndot.gov /dresbachbridge or www.facebook.com/DresbachBridge.

For statewide travel information in Minnesota, visit www.511mn.org.

Little brown bats of the I-90 Bridge (1 of 1) (3)
Photo credit: Heather Kaarakka, Wisconsin DNR

A look up into one of the bat houses near the Interstate 90 Dresbach Bridge shows that bats and their pups inhabiting some of the new homes established after the demolition of the old bridge.
used I-90 boxes (1 of 1) (2)
Photo credit: Heather Kaarakka, Wisconsin DNR

Two of the bat houses that were established on the Wisconsin side of the Mississippi River to provide a place for the bats after their old home underneath the old Interstate 90 bridge was demolished.

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