BatRack: a remote sensing tool for bat detection and identification

Summary

Declines in bat populations are of increasing concern due to habitat loss, collisions with wind turbines, and white-nose syndrome. Gathering data on bat behavior and activity at roosts and maternity colonies is critical to understanding bat ecology and informing current and future conservation strategies to combat population declines.

Remote sensing technology offers a powerful tool to study secretive nocturnal animals such as bats. Gottwald et al. (2021) describes a remote sensing technology called BatRack to survey bat activity in small defined areas using a combination of acoustic, video, and radio telemetry sensors.

The BatRack system is run and configured with free open-source software, which can be downloaded from the project’s GitHub page. The BatRack system is also relatively inexpensive at approximately ~650€ without a power supply. Its modular design allows it to be assembled quickly and customized depending on the goals of the study.

The novel aspect of the BatRack system is that video recording can be triggered by bat detections from the acoustic and telemetry sensors. This triggering feature improves analysis efficiency and reduces data storage requirements, rather than a time-based only video recording schedule. This triggering configuration is an optional feature of the system.

The radio telemetry receiver also allows researchers to identify individual bats if they are tagged with a radio transmitter. The ability to identify individual bats has the added cost of having to mist net and tag individuals, but this is useful for observing behavior in the field while knowing exact species and physical characteristics of individuals. Observing the behavior of specific individuals is normally only possible in a laboratory setting. One limitation of BatRack’s ability to observer individual bats is that it is difficult to distinguish among multiple tagged bats in the video that are recorded at the same time.

Another limitation of BatRack involves the amount of area where data can be collected. BatRack is limited to small targeted areas such as bat roosts and maternity colonies where sensors will be able to sample the area adequately. This is particularly important if radio tagging is being used to identify individuals; one is much less likely to detect specific individuals as the distance from roosts or maternity colonies to BatRack sensors increases.

Commentary

Remote bat detection systems have existed for some time in the form of radio telemetry and acoustic sensors. The novel aspect of BatRack is that visual, acoustic, and telemetry devices work in tandem to detect bats and provide unique information from each sensor. As the viewshed of the video system is limited, the applicability of this system will be limited to small, defined areas where bat activity and behavior are of interest.

In Figure 2 there is a reference to motion detection acting as a trigger for the other sensors; however, this is not described in the text. It’s unclear to what extent motion sensors are used as part of BatRack.

References

Gottwald, J., P. Lampe, J. Höchst, N. Friess, J. Maier, L. Leister, B. Neumann, T. Richter, B. Freisleben, and T. Nauss. 2021. BatRack: An open-source multi-sensor device for wildlife research. Methods in Ecology and Evolution 12:1867–1874. <https://onlinelibrary.wiley.com/doi/abs/10.1111/2041-210X.13672>. Accessed 14 Feb 2022.

There is also a website for the project that describes how to build and set up a BatRack system.