Modeling Animal Movement Using the Argos Satellite Telemetry Location Error Ellipse

• Activity Number: 675
• Type: Topic Contributed
• Date/Time: Thursday, August 13, 2015 : 10:30 AM to 12:20 PM
• Sponsor: Section on Statistics and the Environment
• Author(s): Brett McClintock*
• Keywords: animal location data ; hierarchical model ; measurement error ; movement ecology ; state-space model ; monitoring

Abstract

The Argos satellite telemetry system is popular for tracking marine animals. However, inaccurate locations are common, and Argos now provides an estimated location error ellipse that has yet to be incorporated into analyses of animal movement or space use. We present an observation model utilizing the Argos error ellipse and demonstrate how it can be combined with a simple three-dimensional movement model to infer activity budgets and movement characteristics for two species of seal. These datasets are of variable quality and represent species that differ in both space use and latitudinal range relative to the polar orbits of Argos satellites. We found the theoretical bivariate normal distribution corresponding to the error ellipse often failed to adequately explain the most extreme location outliers. In practice, we support the Argos recommendation that practitioners wishing to more properly account for location measurement error utilize the error ellipse, but the presence of outliers suggests practitioners should consider using a fat-tailed distribution derived from the error ellipse (e.g. bivariate t-distribution) or filtering extreme outliers during data pre-processing.