Evaluating GPS biologging technology for studying spatial ecology of large constricting snakes

Brian J Smith,Mathieu Basille,Kristen M Hart,Christina M Romagosa,Frank J Mazzotti

doi:10.1186/s40317-018-0145-3

Abstract

BackgroundGPS telemetry has revolutionized the study of animal spatial ecology in the last two decades. Until recently, it has mainly been deployed on large mammals and birds, but the technology is rapidly becoming miniaturized, and applications in diverse taxa are becoming possible. Large constricting snakes are top predators in their ecosystems, and accordingly they are often a management priority, whether their populations are threatened or invasive. Fine-scale GPS tracking datasets could greatly improve our ability to understand and manage these snakes, but the ability of this new technology to deliver high-quality data in this system is unproven. In order to evaluate GPS technology in large constrictors, we GPS-tagged 13 Burmese pythons (Python bivittatus) in Everglades National Park and deployed an additional 7 GPS tags on stationary platforms to evaluate habitat-driven biases in GPS locations. Both python and test platform GPS tags were programmed to attempt a GPS fix every 90 min.ResultsWhile overall fix rates for the tagged pythons were low (18.1%), we were still able to obtain an average of 14.5 locations/animal/week, a large improvement over once-weekly VHF tracking. We found overall accuracy and precision to be very good (mean accuracy = 7.3 m, mean precision = 12.9 m), but a very few imprecise locations were still recorded (0.2% of locations with precision > 1.0 km). We found that dense vegetation did decrease fix rate, but we concluded that the low observed fix rate was also due to python microhabitat selection underground or underwater. Half of our recovered pythons were either missing their tag or the tag had malfunctioned, resulting in no data being recovered.ConclusionsGPS biologging technology is a promising tool for obtaining frequent, accurate, and precise locations of large constricting snakes. We recommend future studies couple GPS telemetry with frequent VHF locations in order to reduce bias and limit the impact of catastrophic failures on data collection, and we recommend improvements to GPS tag design to lessen the frequency of these failures.

Highlights

GPS telemetry has revolutionized the study of animal spatial ecology in the last two decades
Aim We explored whether GPS technology could provide the data necessary to answer questions about large constrictor spatial ecology that we have been unable to answer with VHF telemetry
Due to the logistical difficulties of working in the vast Everglades landscape, VHF tracking has typically been limited to one location/animal/week, obtained during daylight hours, severely limiting the inferences that can be drawn about python spatial ecology

Summary

Introduction

GPS telemetry has revolutionized the study of animal spatial ecology in the last two decades. While GPS does represent a major technological advancement, it still comes with potential drawbacks, including larger tag size (compared with a VHF transmitter), high cost (and a trade-off with low sample size of individuals), low positional precision (compared to direct observation, superior to many alternative technologies), and habitat-driven location bias [7,8,9]. Given these potential hurdles, deciding whether or not GPS is the right tool for tackling relevant ecological or management questions is an important consideration [10]. Compared with VHF tracking, GPS tracking is generally a superior choice for biological questions that require more locations per animal (as opposed to more animals in the population) or for biological questions focused on temporally fine-scale movements [4]

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