Monday, October 21, 2013

Readers Write In: Endangered Bats Roosting by my House?

Hello Dr. Steen,

I have had these little bats roosting in my pavilion for the past several weeks and am wondering if they are the common Brown Bat or the endangered Indiana Bat. I know that these two species are often confused and this unfortunately was the best picture I could get of them without disturbing. Thanks for any possible info, the previous owner of our property says these little guys come back every year. I live in central Pennsylvania about an hour north of Harrisburg.

Thank You,

John K. @wildlifesnap

    A good old fashioned bat question just in time for Halloween. Pennsylvania is home to nine different species of bats. The good news is that John has narrowed the nine potentials down to two species. The bad news is that these two species are very difficult to tell apart.

    First off, the Little Brown Bat (Myotis lucifugus) is a very common species. In the eastern United States, the little bats that you see flying around above your yards in the evening dusks of summer are almost always Little Brown Bats. They are also usually the species that makes their way inside of houses. Hopefully these little bats will stay common despite the white-nose syndrome that is decimating bat colonies across the northeastern United States.

   Indiana Bats (Myotis sodalis), on the other hand, are a federally endangered species that are known to spend the winter in only a handful of spots in Pennsylvania, and they have never been documented in the vicinity of Harrisburg. So, just by playing the odds, I will bet that these are Little Brown Bats.

    The two species look very similar though, and it's hard to tell them apart with certainty without looking at subtle differences in their morphology. Making things even trickier is that sometimes the species will roost together. But, Indiana Bat faces are generally a little pinkish and I don't see that here. Unfortunately, we can't look at the membranes on the tails of these bats or look at the hairs on their feet, this would allow us to confidently determine the species.

  So, in all likelihood these are Little Brown Bats but I'm hoping that some of you with more bat experience can chime in and confirm (or deny) my identification (Update: be careful what you wish for! Make sure to read the Comments to find out why I am probably wrong).

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