Tracking Tiny Animals: Assessing the Strengths and Limitations of Proximity Loggers in Deer Mice

While the bio-logging revolution has provided a wealth of data on animal movement and survival, small rodents have typically been excluded due to the challenges of creating small transmitters relative to animal body weight and short battery life.Very rarely do bio-logging studies track the actual impact of attaching transmitters to wild animals on their behavior and survival, which can lead to biased estimates of population health and dynamics.We studied contacts between deer mice (Peromyscus maniculatus) in experimental enclosures as part of study on Sin Nombre Virus transmission, an endemic disease in deer mice.To track mouse interactions, we tested a novel proximity sensor system called Dulog, which uses a tiny miniature Bluetooth transmitter weighing only 1.1 grams; this is the smallest transmitter of its kind available.This technology has never been used on North American rodents before and represents an potentially important step forward for tracking small mammals and understanding disease transmission and social behavior.We discovered that while the transmitters did capture contact events, deer mice are not a suitable species for this technology at this time due to additional weight from protective casing required to prevent conspecifics chewing on the transmitters. We investigated changes in body weight and leukocyte profiles to assess the impact of the transmitters on the mice. We also recorded novel methods for animal handling and transmitter attachment, including systematic testing of materials and placement.Our research includes both the best practices and unintended consequences of bio-logging for cryptic small mammals, in hopes that our transparent discussion of the impacts of tracking technology will be followed by other researchers.