Establishing an open-source animal-tracking analysis platform for archival geolocators

• Eli S. Bridge
• Eldar Rakhimberdiev
• Nathaniel E. Seavy
• David W. Winkler

Abstract
Light-level geolocation data loggers (henceforth geologgers), are simple animal-tracking devices that record light-levels over short time intervals and allow for the inference of location based on the timing of sunrise and sunset. Although these devices have long been used to track marine vertebrates, they have only recently achieved a level of miniaturization sufficient for use on small (<50g) land birds. For centuries, we have lacked the capability to determine how small birds move between breeding and wintering sites, and the few recent studies that have used geologgers to reveal songbird migration paths mark a revolution in the fields of ornithology and terrestrial ecology. However, a missing link in fulfilling the promise of this tracking method is a data analysis package that can make the most of the limited information stored on a geologger. Although a number of solutions exist, they all fall short as being either very simplistic (i.e. there is no accounting for potential location error) or so sophisticated that very few potential users can execute an analysis. Because of these shortcomings, there is a general lack of transparency and standardization with regard to the analysis and presentation of location data from geologger studies. Here we propose a working group that will bring together both simple and complicated analyses techniques into an extensive package for the R computing platform. In addition we will generate a user-friendly graphical user interface (GUI) available via Movebank.org that can execute analyses for users with little or no familiarity with R. This analysis platform would allow users to load raw data, run filters to identify possible analysis problems, choose among analysis methods, quickly run "canned" analyses, and pursue more specialized analyses to test hypotheses regarding the timing, direction, and speed of migratory movements. In pursuit of this goal, we propose to hold two meetings. The first will convene five biologists and statisticians working in the fields of marine biology and ornithology, who have pioneered new methods for obtaining animal tracking data using geologgers. This core group will work to refine and synthesize the analysis techniques that they and others have created. The second meeting will bring together a group of 15 scientists, including the core programming group as well as field biologists with geologger data sets that can be used to test the analysis platform. This second meeting will generate numerous examples of how to use the platform and will catalyze the implementation of the GUI.