Echoes of the Forest | Insights from New Acoustic Bat Monitoring Research

Alexis setting up a bat monitor and downloading data, with a friendly helper. 

UC Berkeley PhD candidate Alexis Flores is leading new acoustic bat monitoring research to better understand bat diversity in East Bay urban ecosystems. They shared insights on their inspiration, methods, and what these findings tell us about local ecology and conservation.

FOSC: What inspired you to focus your research on acoustic bat monitoring?

Alexis: I was inspired to use noninvasive acoustic monitors to study bats for a couple of reasons! One reason is that bats are crepuscular, meaning they are most active from dusk to dawn, which makes studying and surveying them a bit more difficult than for day-dwelling organisms. Deploying these monitors allows for continuous data collection throughout the night without researchers needing to be present. We can put up the monitor and leave it to do the work!

FOSC: Could you give a brief overview of your monitoring project—how long it’s been running, how you collect data, and what your main goals are?

Alexis: This project has been years in the making and we were finally able to get monitors up and running in April 2025. March/April is when bats come out of hibernation or migrate back from the winter, and we plan on having the monitors collect data through December, when they return to hibernation or migrate away. Our goal is to investigate change in activity and species identification throughout the year and connect that with social-ecological patterns like urban light, noise, and impervious surface.

FOSC: What geographical range does your project focus on, and why did you select the redwood forest habitat in Fern Ravine as one of your sites?

Alexis: The range of this project is (for now) just in the East Bay, with 16 sites spanning Richmond, Berkeley, and Oakland. Because this is a project focused on urban ecosystems, the majority of our sites are in backyards and apartment balconies. However, we were interested in urban green spaces as well, so we have a few urban gardens as well as the Fern Ravine! This gives us a chance to see a range of our social-ecological variables: a lot of light to no light, a lot of noise to no noise, and a lot of impervious surface to no impervious surface.

Mexican free-tailed bat (Tadarida brasiliensis), the most abundant bat in the Bay Area, was identified at every site. Source: Bat Conservation International

FOSC: How many species did the monitor record in the redwood forest of Fern Ravine? Are you surprised by the results? Are there certain bats you expected to see, or others that came as a surprise?

Alexis: We identified 7 species at Fern Ravine– which was surprising given the fact that it was the site with the least amount of recordings (number of times the monitor was triggered and recorded ultrasonic noise)! These are also preliminary findings because we are still analyzing the data, but still very interesting! Some species use redwood trees as roosts and I assumed there would be more recordings considering this site has the least amount of urban disturbances (light, noise, and impervious surface) compared to all our other sites across the East Bay. However, after thinking about the ecology and life histories of some of these species, they may have everything they need within the Ravine so the species that were identified there don't need to travel far to forage. The same goes for species that may not be in the Ravine, those species may be in areas with more light/impervious surface which provides roosts and food for them to be successful and they don't need to leave.

FOSC: What can these findings tell us about bat diversity and the health of the local ecosystem? Are there broader conservation implications?

Alexis: I think one of the major takeaways from what we’ve collected so far is that bats, like humans, are resilient organisms! They can and will persist in many different ecosystems, even ones we think may not be ideal. In areas with both high and low levels of light and noise, they continue to roost and forage. Speaking to Fern Ravine specifically, when I have been there setting up monitors, the forest floor is quiet and the temperature drops significantly more than outside of the forest. This may be favorable to some species, while other species may like the heat and tight cavities of city-life. Once we have completed the data collection and are able to analyze the full April to December activity, these ideas may also change and there may be parts of the picture we don't see until their full life cycle is captured! In terms of conservation, one thing I want everyone to know is WE LOVE BATS! They provide an array of ecosystem services for humans, like insect suppression and nutrient redistribution across the landscape and help us maintain healthy ecosystems.

FOSC:  What is the next step for you as part of this research project?

Alexis: The next steps for this project are to continue recording data through December so we can have a full picture of what activity looks like from emergence to hibernation. After this, we will have over 100,000 recordings (an estimate) to analyze and hopefully publish our findings in the next calendar year! Next year, we plan to deploy monitors again in April at all new sites in the East Bay and into San Francisco.