Happy Halloween: A Spooky Look at Bats and Housing Development

Understanding the Importance of Bat Surveys

Wendy Knight from Pacific Coast Ecology visited the Rosa Butron de Canet Adobe, the future site of Waterman Village, three times in the past month to look for bats. Due to the planned work on the adobe and the removal of some trees, the City of San Luis Obispo required a bat survey by a qualified biologist. We recently received the results of this survey, just in time for Halloween. I wanted to share this spooky behind-the-scenes look at what it takes to develop affordable housing on the site of a historic building.

The First Two Site Visits

During the first two site visits, Knight investigated both the interior and exterior of the adobe for signs of bats. In both the attic and the main interior, no bats were sighted, and it seemed this was not a space commonly used by bats for roosting. Bat feces, called guano, is a common method for determining whether bats frequent an area. Although there were some sightings of bat guano, there were no major accumulations. This led Knight to believe the adobe was not a regular roost site.

Identifying Bat Guano

Guano is crucial for determining the presence of bats in a survey location. To differentiate bat guano from the feces of other species, such as rodents, there are a few key differences to look for. As Knight explained, after smearing the guano, you should “look for its crumbly texture and shiny, iridescent flecks (from insect exoskeletons) when crushed. Unlike hard, smooth rodent droppings, guano will easily disintegrate into fine powder when touched or pressed.” Interestingly, guano is also great for plants, in case any gardeners are interested!

The Acoustic Survey

The third site visit was an acoustic survey. This survey included a passive monitoring method that used a bat detector microphone and Sonobat Acoustic Analysis Software to analyze different bat calls. During this three-hour survey, 164 recordings were collected. Knight was able to identify six different bat species responsible for making the recorded noises. In addition to these six species, two additional species were identified by Knight as likely to be present on site, although they were not detected in this recording.

Interview with Wendy Knight

We reached out to Knight after receiving her report and asked a few questions about the experience.

Q: How do you handle crawling around deserted buildings full of critters and their droppings in the middle of the night?

A: I did the survey during the daytime so that I would see roosting bats if they were using the attic. I wore a Tyvek suit and a face mask due to all the rodent scat in the attic. It was pretty gross, and the suit and mask were pretty hot. So, I made sure to do it first thing in the morning before the attic had a chance to warm up.

Q: What if you had found bats in the adobe?

A: Then we figure out a way to exclude the bat from returning if it is a solitary roosting bat. We wouldn’t disturb a maternity colony. We would wait until all the young were flying and then try to seal up the building after they left in September. However, we would need to get permission from CDFW to do this. Maternity colonies are protected by CEQA.

Q: Why do we care about bats on the WV site and other sites all over?

A: Great pest control! They eat scads of insects every night. Bats are good neighbors, and most people do not even know they are around!

Q: How can we all help the bat population thrive?

A: Be kind to bats. Just because they are roosting somewhere doesn’t mean they need to be evicted. We should try to coexist. We need to educate people that we want bats around. There are no vampire bats in California!

Conclusion: The Role of Bats in Our Ecosystem

Bats play a vital role in our ecosystem. They help control insect populations, which is beneficial for both agriculture and our daily lives. Understanding their habits and habitats is crucial for successful housing developments like Waterman Village.

We would like to extend a big thank you to Wendy Knight and Pacific Coast Ecology for conducting this bat survey. If you would like to read the full report, we have attached the file below.

Bat Survey Letter Report.pdf

Download PDF • 3.98MB