VOLUNTEER NATURALIST CONDUCTS GROUNDBREAKING BAT RESEARCH

BY SUSANA RINDERLE

Often misunderstood or feared, bats are actually invaluable members of the global animal kingdom. While in some places, they pollinate many nightblooming plants and cacti, at Anza-Borrego Desert State Park (ABDSP), they mostly provide natural insect control, eliminating the need for harmful pesticides. Stable bat populations are also important indicators of an ecosystem’s overall health, and leading indicators of negative environmental trends.

On January 18, 2020, a human caused fire at Borrego Palm Canyon's First Grove burned a majority of the mature California fan palms known to provide roost habitat for bats, particularly western yellow bats.

The press reported a fatal impact on resident bats, but since there were no prior baseline data on the bats' presence or activity, district scientists had no way to assess the validity of these reports or the fire's impact on the bat population.

In partnership with the Colorado Desert District of the California State Parks, volunteer naturalist Don Endicott set out to establish that baseline. He positioned an ultrasonic microphone and battery-powered acoustic recorder near the center of First Grove, where bat calls triggered digital recordings. Every month for 14 consecutive nights, Don conducted acoustic sampling of the recordings starting 30 minutes before sunset and ending 30 minutes after sunrise. He analyzed the recordings with Wildlife Acoustics Kaleidoscope Pro software, utilizing batch processing methods, species-specific reference calls, and auto-identification functionality with manual spot checks to verify auto-identifications and rare species. Results were then organized, tallied, and entered into a spreadsheet to show daily and monthly activity trends.

The good news? Despite the fire, First Grove supports a diverse variety of bat species, including western yellow bats, at seasonally appropriate activity levels. In fact, drought, extreme temperatures, and lower availability of insect prey are probably more harmful to bat populations than localized fire damage!

In addition, he established a baseline for bat species activity and continues to monitor weekly, monthly, and year-to-year trends, which show higher May-through-June activity in years two and three compared to the first year. All told,15 different species of native bats have been detected, with over 80,000 acoustically triggered echolocation calls annually for each of the first three years. Canyon bats, Western small-footed myotis, Pallid bats and Big brown bats were the most active in terms of the number of acoustic detections, while infrequent detections of Western mastiff bats and California leaf-nosed bats suggest these were likely transients. Western yellow bats, the focus species, were seasonally abundant and active.

A retired civilian research engineer and executive in the Navy Communications and Network Technologies field in San Diego, Don is a long-time hiker and explorer who discovered a second career as a volunteer naturalist. He's been interested in bats for some time, partly because they are a good indicator of the ecological health of a natural area. He is a National Association of Interpretation (NAI) Certified Interpretive Guide who trained in ABDSP. He received The Anza-Borrego Foundation's second annual ABF Achievement Award in 2015 and was recognized as the Park's Volunteer Naturalist of the Year in 2018.

"This research effort establishes baseline data to help guide future Park land management and serves as a prototype for expanded bat monitoring throughout the Park," he says. "In fact, during the third year of the study and based on its methodology and findings, Colorado Desert District environmental scientists pursued equipment acquisitions to deploy and replicate similar efforts in other sectors of ABDSP."

This research is unpublished, but Don has presented the findings to Colorado Desert District environmental scientists, San Diego Natural History Museum research staff, and at the "Anza-Borrego: In Focus" lecture series last May.

If you would like to reach Don, please get in touch with him at dlejr@yahoo.com.

“To be whole. To be complete. Wildness reminds us what it means to be human, what we are connected to rather than what we are separate from.”― Terry Tempest Williams