Back to Batting

Spring is finally here. As warmer temperatures return we are seeing an increase in activity by all types of critters in the Chicago area, including our flying mammals!

As winter winds down, bats begin to emerge from their hibernacula (structures where animals hibernate, such as caves), and those that leave Chicago during the winter make their way back to the Windy City. As part of our long-term study monitoring bat populations in Chicago, we eagerly await the return of spring so we can get back to the field—and back to learning about bats!

To study bats in Chicago, we use acoustic detectors (see photo below) to record ultrasonic echolocation calls produced by bats as they navigate the environment and forage for food. These detectors are placed at 25 sites around the Chicago area for one week during spring, summer, and fall. The visual depiction of the recorded calls (spectrograms) are generally identifiable to species, and thus we can begin to learn about where bats are, where they are not, and how the surrounding features of the landscape predict their presence or absence.

As bats are facing many threats (such as white-nose syndrome and wind energy development), we also are monitoring for any changes to the population. Cities may provide refuge from some of these threats, or some species may actually benefit from the decline of others. As the climate warms, some species may be expanding or contracting their ranges. These are just a few of the questions we are poised to ask with our long-term, systematic study design.

A bat monitor setup at a new location for 2018: Columbus Park in the Austin neighborhood of Chicago.

This has been an exciting year for the bat project! Our first manuscript based on this dataset was published in the journal Conservation Biology (Gallo et. al 2017), in which we examined how habitat at different scales influences the presence of bats at various sites in Chicago. For example, if we recorded a species at a particular location, was it because that site itself had a lot of tree cover, or was it because there was a lot of tree cover at that site and within the surrounding area? From these results, we were able to make predictions of areas of potential “bat hotspots” in the region, which could be used to identify and restore habitat for bats.

As we have now completed five years of data collection comparing bats in urban (Cook County) and rural (Kane County) locations, we have decided to shift our data collection to more urban sites, including city parks, urban cemeteries, golf courses, and even rooftops! By collecting data at more urban sites, we will be able to get more information as to how bats are using the city.

A spectrogram of a call produced by an evening bat (Nycticeius humeralis) recorded at Columbus Park. Note the feeding buzz at the end of this spectrogram (beginning around 180 msec on the x-axis), which is when a bat emits call pulses very quickly to gain more spatial information and hone in on a prey item (for example, a moth).

Finally, as part of our involvement in a region-wide effort to increase our understanding of bats in the Chicago area, we are piloting a citizen science bat-monitoring project. Volunteers at four Chicago sites will be walking transects (paths along which ecological data are collected) using handheld ultrasonic microphones and iPads that record the calls and automatically identify any bats that happen to fly by as they are walking. We are thrilled to be piloting this study and excited to not only broaden our data collection to more sites, but to provide volunteers with an opportunity to learn more about bats and participate in a scientific study! Stay tuned for more information about this project as we roll it out more broadly in 2019.

Liza Lehrer, M.S.
Assistant Director, Urban Wildlife Institute

PS. Did you hear the news? The little brown bat is now the official mammal of the city of Chicago! Learn more.