Evaluation of gps-sized expandable radiocollars designed for white-tailed deer fawns

During May 2018–July 2019, we tested fit and function of 3 Global Positioning System (GPS)sized expandable collar mock-up designs on newborn white-tailed deer (Odocoileus virginianus) fawns. We fitted 26 captive fawns with ear tags and collars (20 Vectronic Vertex, 3 Telonics TGW, 3 Telonics Recon) and ear-tagged 5 captive control fawns without collars. We collected neck measurements from fawns at birth and at approximately 6, 9, and 12 months of age. Additionally, we conducted observations of fawns to evaluate the potential effects of collars on behavior. The folds of all 6 Telonics mock-ups expanded prematurely by 75.8 ± 27.9 (SD) days resulting in extremely loose collars. Upon expansion, fawns were able to step through collars with their forelimbs resulting in collars positioned around the chest or waist. We observed one example in which premature expansion led to a dropped collar at just 80 days. On fawns ≥11 months of age, only 3 Vectronic Vertex mock-up collars dropped and none exhibited premature expansion. Neck measurements indicated newborn fawns would benefit from a smaller band circumference. For fawns through ≥10 months of age, we did not observe any collars being restrictive. Notable effects on fawn behavior included high-stepping during locomotion and erratic jumping, particularly when fawns were ≤1 month of age. Our results suggest that the GPS-sized expandable collars tested in this study would benefit from modifications before being deployed in the field. We recommend modifications to each design, such as an improved stitching patterns, alternative thread and elastic materials that facilitate a more gradual elastic expansion, decreased battery housing size and weight, and improved weight distribution of the electronic components.