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Acoustic Bat Monitoring

Tom Malloy and Trevor Hebert (JRBP)
Myotis californicus - photo by Merlin D. Tuttle

Summary

Long-term studies of organisms and the environment may help detect threats to both individual species and ecosystems as a whole. Monitoring bats can provide early warning of potentially negative changes in our local ecosystem such as habitat fragmentation and loss of habitat. Bats provide essential ecosystem services by consuming vast numbers of insects and healthy bat populations and species diversity are an indicator of a healthy landscape with intact bat roosting habitat and natural food supplies.

The current acoustic bat monitoring effort was established in May 2013 with financial support from the Henry T. Mudd, Jr. Exempt Trust and Deborah Stipek. In 2001 Tom Mudd set up Jasper Ridge's first acoustic bat monitoring station and operated it until he passed away in 2007. Tom's pioneering efforts provided the foundation and inspiration for the current bat monitoring project.

The monitoring array consists of four Binary Acoustic Technology FR125-EXT full-spectrum audio recorders with hemispherical ultrasonic microphones which are able to record the echolocation calls of bats as they fly and feed nearby. The recorders are solar-powered and are connected to the Jasper Ridge wireless mesh network which allows automatic uploading and archiving of the bat echolocation recordings (.wav files) to a server at the Sun Field Station. Once they are on the server, batch scripts automate organizing and processing of the recordings with  Sonobat, a software application designed specifically for identifying bat species from echolocation calls. Sonobat recognizes 17 species of bats in the Western US and California and has indicated the presence of up to 14 of those species at Jasper Ridge.

To date the project has collected over 15 Terabytes of .wav recordings and is being used in research projects related to bats and the environment. Myotis californicus photo above by Merlin D. Tuttle.

Echolocation call of Yuma myotis bat displayed in Sonobat
Ultrasonic bat microphone by Searsville Reservoir
Total bat calls by station - all species (2013-2015)