Methods for measuring fine-scale social proximity in small mammals

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Abstract There are barriers to directly observing animals that are cryptic or live in environments inaccessible to humans. Biologgers, animal-attached devices designed to collect data on animals without a human researcher present, have become useful tools for studying species that cannot be directly observed. The use of biologgers has been size-limited until recent efforts to miniaturize the technology opened up the possibility of using them on small animals. In this study, we packaged and deployed proximity logging devices (“ProxLogs” model) for use on a small, socially monogamous, semifossorial mammal, the Prairie Vole (Microtus ochrogaster), as a means to collect high-resolution data on fine-scale spatial proximity between conspecifics. First, we evaluated multiple packaging options for the devices and found that UV-curing epoxy resin containing grit (sand) was the most durable packaging material. ProxLogs recorded voles when they were within 6 cm of each other. We compared the resolution of social proximity data collected by ProxLogs to patterns of social proximity collected through livetrapping and, as expected, found that the ProxLogs generated significantly higher-resolution data than livetrapping. We also found that social proximity data collected through livetrapping significantly predicted social proximity data collected by the ProxLogs. Our findings provide proof of concept that proximity loggers, packaged with UV-curing epoxy resin, are a reliable, high-resolution method to collect 24-h social proximity data on small mammals that are otherwise difficult to observe.