Wisconsin Bat Roost Monitoring Program


Summer roost monitoring is a crucial
component of the Wisconsin bat monitoring program. Roost monitoring volunteers provide the
program with valuable information that increases
our understanding of Wisconsin bats. In addition to lacking information about
basic biology, phenology, and population levels in
Wisconsin, bats in North America are threatened by the disease white-nose
syndrome. White-nose syndrome is a fungal disease that fatally affects bats during
hibernation. The disease has mortality rates up to 95 percent at affected sites and has the possibility
to cause regional extinction of common bat species. The roost monitoring project helps the
bat program gather baseline data before white nose occurs in the state
and increases our understanding of bat populations throughout the state. The survey is conducted by counting the
bat as they emerge from the roost. The species you will see during a roost count are either little brown bats or big brown bats, both of which are
susceptible to white-nose syndrome. Female little brown and big brown bats
congregate in structures such as buildings and bat houses in spring and summer to give birth and
rear their young. Bats give birth to pups from June 1st to July 1st; this is known as the pre-volant period. At three to four weeks after birth the
pups are ready to forage and fly. This stage when the young began to fly
is known as the post-volant period. Ideally surveys are conducted during
both the pre-volant and post-volant period; however, all levels
of commitment are welcome. Colonies of bats can often be found in
buildings such as old houses, churches, barns and of course in bat
houses. If you know of a roost on private
property be sure to seek landowner permission before accessing the property. After finding a suitable roost determine
where bats are exiting before the first survey. To find the primary exits, look for
discolored areas in and around chimneys, eaves, and soffits. Guano will likely be found below these exits. If all exits cannot be viewed from a single
location, it may be necessary to enlist the help
of family and friends to ensure an accurate count. Surveys should be conducted when starting temperatures are above 60 degrees. Wind speed should be less than twelve
miles per hour, and it should not be raining. To conduct a survey arrive 30 minutes
before sunset. Situate yourself so that you can see the
bats silhouetted against the night sky as they exit. Count
the bats as they exit the roost. It may be helpful
to tally the number that exit on a piece of paper or to
use a clicker counter. Some may re-enter the roost, especially when their pups
inside. Be sure to note re-entries as they may affect your final count. If an overwhelming number of bats exit
at once, estimate, counting by 10’s as they emerge. Do not shine a light into the roost as this may disturb the
bats and is not an accurate way of counting. If no bats have exited for a period of
five minutes the survey is complete. Remember to fill
out the datasheet completely.

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