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Today’s automated echolocation analysis software programs have been developed to efficiently handle large data sets. Users expect that these products will make echolocation call analysis fast while providing highly confident results for species occupancy. Unfortunately, the reality is that none of the current automated classifier tools associated with these programs are as accurate or precise as we would like them to be, especially when their outputs have the potential to impact major land management or development decisions. Currently, the only way to obtain high levels of confidence on species level identification is to have expert, human review of the recordings in question to make accurate presence/absence determinations for the species-of-interest. Bat Survey Solutions, LLC is here to help stake-holders analyze, interpret, and apply results from acoustic surveys in a responsible ways using the best available science.
Bats typically use echolocation as a functional device, not as a unique identifier like most animal vocalizations. Therefore the analysis of pre-recorded bat sounds is confounded by the amount of overlap in typical echolocation calls employed by different species. Additionally, high-frequency sound used by bats is uniquely affected by atmospheric conditions, temperature, humidity, and mechanical effects, further reducing abilities of computer-assisted algorithms to return accurate results. The Bat Survey Solutions staff has decades of experience recording, viewing, measuring, interpreting, and analyzing North American bat calls with insights from the physical properties of high-frequency sounds. Therefore we are uniquely positioned to provide critical expert manual vetting services to confirm or reject computer-assisted classifications, and bring higher degrees of accuracy to acoustic surveys and their implications for bat management.
Automated bat identification software should be considered a tool to aid the researcher in sorting thru volumes of data. When a species of interest is found, it would be professionally negligent to rely solely on automated results, necessitating expert review and either conformation or rejection of the computer-generated suggestions.
The fast pace of advancement in bat detector technology and computer-assisted analysis and classification programs has outstripped many users abilities to appreciate and understand the equipment well enough to implement current acoustic survey protocols efficiently and effectively. The Bat Survey Solutions staff has been intimately involved in reviewing and revising many North American acoustic survey guidelines as they have been developed and brought on-line. We can provide critical commentary and review services for a full range of active, passive, and mobile acoustic surveys, including analysis of extremely large data-sets and interpretation of all major classification software outputs.
Recent changes to state and federal listings have prompted recent interest in the Indiana bat, Northern long-eared bat, and Eastern small-footed bat, among others. Recording echolocation calls from bats is more complex than merely deploying microphones across a habitat and allowing computers to analyze recordings. Our decades of in-field monitoring and interpretation has provided our staff with the unique experience and insight to collect high-quality recordings with greater potential for accurate analysis. To date we have conducted tens of thousands of monitoring hours. Our value-added experience with equipment, deployment, and analysis efforts brings unique efficiency to acoustic surveys. When results matter, especially during the relatively short window of summer bat activity, contact us for a full range of survey solutions and expertise for assistance in completing all types of bat compliance surveys.
Take a look at some of our recent work.
Nine different paired trials from Arizona, California, Kentucky, Pennsylvania, and Utah were conducted to test different microphone types (omnidirectional vs. directional), heights above ground level (agl), orientations (horizontal, 45-degree up, and vertical), and different weather-proofing schemes.
We found different microphone types returned significantly different results. Though omnidirectional microphones returned up to 3-times more recordings, directional microphones returned between 10-35% more quality recordings capable of being confidently identified to species.
Download a PDF Downloadwith the complete results of this survey here.
In 2014 nearly 200 passive bat detectors were deployed for a total of 6,000 monitoring hours across a 15-mile corridor containing 12 distinct rocky habitat features in order to survey for Myotis leibii, the eastern small-footed myotis. During this survey, over 18,000 recordings of bats were collected.Upon analysis, and manual vetting just one rocky habitat feature was determined to contain the bulk of the Myotis leibii activity, with over half of the activity documented at a single monitoring location. In this case, acoustics were effectively deployed for an efficient survey that would have been impossible to conduct using visual observation or video recording methods.
Every survey method is biased. Some bat species are more easily captured in mist nets, others are more easily captured in harp traps. There are some bats that are easy to detect acoustically and others that are more difficult. Additionally some bats are easier to identify acoustically, while others are more challenging.
By combining different capture and acoustic inventory techniques at a single inventory site, bat workers can active a more accurate picture of species diversity during a shorter period of time. During a single night survey in Arizona, 21 species of bats were documented with a combination of mist nets, harp traps, passive acoustic monitoring and active bat detector surveys. When survey methods were taken alone, each only documented between 12 and 15 species.