A newly developed wireless biologging network (WBN) enables high-resolution tracking of small animals, according to a study published April 2 in the open-access journal PLOS Biology by Simon Ripperger of the Leibniz Institute for Evolution and Biodiversity Science, and colleagues. As noted by the authors, WBNs could close an important gap in biologging: the fully automated tracking and proximity-sensing of small animals, even in closed habitats, at high spatial and temporal resolution.
Recent advances in animal tracking technology have ushered in a new era in biologging. By collecting data of unprecedented quantity and quality, automated methods have revolutionized numerous fields, including animal ecology, collective behavior, migration, and conservation biology.
However, satellite communication for localization or data access requires a lot of power, and heavy transmitters greatly limit the ability to track smaller vertebrate species. To address this problem, Ripperger and colleagues developed their WBN -- a system that enables high-resolution tracking of animals weighing as little as 20 grams. These smaller species make up a large proportion of birds and mammals, so WBNs will give researchers new capabilities to address a wide range of questions in animal behavior and ecology.
As reported in the study, WBN is a scalable, flexible system that offers a temporal resolution of seconds, allows automated recording of movement trajectories even in structurally complex habitats such as woodland, and is an ultra-low-power solution for remote data access over distances of several kilometers.
The researchers deployed WBN to study wild bats, creating social networks and flight trajectories of unprecedented quality. To do this, wireless localization nodes are placed in the area of study, and light-weight mobile nodes are attached to the animals. In one example, the authors planted 17 localization nodes in a 1.5-hectare area of German forest, and glued mobile nodes to the fur on the backs of 11 mouse-eared bats, allowing them to track their flights and interactions.
According to the authors, WBNs will greatly benefit biologging of small animal species that move over smaller and more predictable spatial scales, especially inside habitats where signal transmission is constrained. Such setups will allow studies on the effects of social network dynamics on phenomena such as transmission of social information and pathogens, and key ecosystem functions such as pollination and seed dispersal.
Ripperger adds: "Key to success in this project was the close collaboration among biologists, computer scientists, and electrical engineers. Thanks to the high level of miniaturization of the animal-borne tags, we can now collect data of unprecedented quantity and quality that allows us studying the behavior of small animals in much greater detail. For example, we learned from proximity sensing in the wild that noctule bat mothers guide their offspring to novel roosts and that social relationships in vampire bats that formed in the lab persist in the wild. In the future, we plan to expand our work to other taxonomic groups - a method that allows tracking bats is also likely to work for other small animals such as reptiles or songbirds."
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Citation: Ripperger SP, Carter GG, Page RA, Duda N, Koelpin A, Weigel R, et al. (2020) Thinking small: Next-generation sensor networks close the size gap in vertebrate biologging. PLoS Biol 18(4): e3000655. https://doi.org/10.1371/journal.pbio.3000655
Funding: This study was funded by grants of the Deutsche Forschungsgemeinschaft (FM, AK, RK, KMW, WSP, JT, JR, FD; https://www.dfg.de/) within the research unit FOR-1508, a Smithsonian Scholarly Studies Awards grant (RAP, GGC, SPR, FM; https://www.si.edu/), and a National Geographic Society Research Grant WW-057R-17 (GGC; https://www.nationalgeographic.com/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors declare that no competing interests exist.