Acoustic monitoring for Iowa bats: preparing for White Nose Syndrome


Principal Investigator:

Julie A. Blanchong

Rebecca Christoffel

Student Investigator:



Daryl Howell


December 2013 to December 2014

Funding Source(s):

Iowa Department of Natural Resources (IDNR)

Goals and Objectives:

  • Conduct acoustic surveys along drive transects and in fixed-locations to monitor bat activity



White Nose Syndrome (WNS), a devastating disease associated with the mortality of millions of bats was first documented in New York during the winter of 2005-2006, and is now confirmed in numerous US states and Canadian provinces. The fungus that causes WNS was detected on a big brown bat hibernating in an Iowa cave in March 2012. The loss of large numbers of bats due to WNS is expected to have enormous economic impacts to agriculture. Knowledge of the abundance and distribution of bat species in Iowa is minimal, but is critically needed to understand the potential ramifications of WNS to Iowa.

We conducted acoustic surveys along 19 30-mile drive transects in eastern, central, and southern Iowa to document bat echolocation activity in order to gain a better assessment of bat abundance and distribution in Iowa. Each transect was surveyed twice between May 28 - July 30, 2014. To complement these mobile surveys, we will establish three fixed-location sites in urban parks that are difficult to survey by vehicle as well as three fixed-location sites in agricultural areas in central Iowa were monitored twice during summer 2014.

A final report was submitted to the Iowa Department of Natural Resources in November 2014.

Conclusions and Recommendations:

For drive transects, bat activity was higher in the Eastern region of Iowa than in the Central or Southern regions. This difference may be tied to differences in bat habitat in the three surveyed regions of Iowa. Qualitatively, the eastern counties appear to be more densely forested and less agricultural than the central or southern counties. Bat activity varied across farms while bat activity in the 3 parks was similar.

In the Central and Southern regions of Iowa, bats in the low frequency group, consisting of Big Brown, Hoary, and Silver-haired bats, were most commonly recorded. In the Eastern region, bats in the high frequency group, consisting of Eastern Red, Evening, Indiana, Little Brown, Northern Long-eared, and Tricolored bats, were most commonly recorded. The reason for this difference in the percentage of bats in these two frequency groups between eastern and central-southern regions of Iowa may be tied to habitat differences between the regions and warrants further exploration.

We had limited ability to identify bat calls to a single species. The Hoary bat was the bat most commonly identified to species and outnumbered call sequences identified to each of the other species that were able to be narrowed down to a single species. This greater identification of Hoary bats is likely attributable to the distinct nature of call sequences produced by this species, making it by far the easiest species to identify. Bats will vary their calls due to flight pattern, foraging phase, the presence of conspecifics, and the density of acoustic clutter in the environment. This variation increases the overlap in call characteristics among species making it difficult to identify individual species. In addition, Doppler shifts associated with drive transects can affect the characteristics of the call recording which can further complicate identifying a call. 


12/01/2013 to 12/01/2014