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.