SREL Reprint #3393

Environmental conditions and animal behavior influence performance of solar-powered GPS-GSM transmitters

Michael E. Byrne1, Amanda E. Holland1,2, A. Lawrence Bryan1, and James C. Beasley1,2

1Savannah River Ecology Laboratory, University of Georgia, Aiken, South Carolina, USA
2Warnell School of Forestry and Natural Resources, University of Georgia, Athens, Georgia, USA

Abstract: Solar-powered GPS transmitters linked to the GSM cellular transmission system are a powerful new tool for avian research. Data collection can be researcher programmed or use dynamic fix (DF) rates that are automatically adjusted in accordance with battery charge. Lack of prior knowledge of fix (location) collection rates represents an obstacle to designing studies with transmitters that use DF rates. We assessed the quantity and quality of data collected by a commercially available DF transmitter. To assess fix collection rates, factors influencing fix collection rates, GPS accuracy, and the ability of transmitters to differentiate movement from nonmovement, we used a combination of controlled static tests at known locations, deployments on free-ranging Black Vultures (Coragyps atratus) and Turkey Vultures (Cathartes aura), and motion tests. During static testing, transmitters often collected upwards of 500 fixes per day in open habitats with little cloud cover. Hourly fix rates varied, commonly reaching 1 fix min-1 at midday but dropping to 1 fix hr-1 at night. The numbers of daylight fixes collected during vulture deployments were greater on days with little cloud cover, positively correlated with increasing daily movement rates, and positively correlated with available daylight hours, likely due in part to increased solar radiation near the summer solstice. Mean horizontal GPS error was 7.8 m (± 12.2 m SD). Mean vertical error was 4.5 m (± 142 m) above true elevation. Speed records >0 km hr-1 were reliable indicators of movement provided a 3D fix was obtained. Overall, the transmitters that we evaluated provided large volumes of data, but the inability to control data collection schedules may prove problematic for some applications. DF solar-powered transmitters appear best suited for use with active species in open habitats, and least suitable for use with species that inhabit high latitudes year-round or spend considerable time under forest cover.

Keywords: animal location data, animal movement, Cathartes aura, Coragyps atratus, fix rate, GPS accuracy, telemetry

SREL Reprint #3393

Byrne, M. E., A. E. Holland, A. L. Bryan Jr., and J. C. Beasley. 2017. Environmental conditions and animal behavior influence performance of solar-powered GPS-GSM transmitters. The Condor/Ornithological Applications 119(3):389-404.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).