Seal encounters at sea: A contemporary spatial approach using R-INLA

Acoustic telemetry is an active field of research integral to the study of marine life. The latest generation of acoustic tags is making available new types of data. As part of the Ocean Tracking Network (OTN) (www.oceantrackingnework.org) acoustic tags known as VEMCO Mobile Transceivers (VMTs) (www.vemco.com) are being deployed on Sable Island grey seals (Halichoerus grypus) in order to record instances of proximity to each other (as well as any other acoustically tagged animals). The seals essentially become bioprobes yielding data exhibiting both spatial and temporal variation. Fortunately, recent developments in the field of spatial statistics have greatly facilitated the fitting of complex spatial and spatio-temporal models. Here we specifically propose a hierarchical spatio-temporal model framework and fit it to these data using both Stochastic Partial Differential Equations (SPDE) and Integrated Nested Laplace Approximations (INLA) through R-INLA (www.r-inla.org). In so doing we demonstrate the effectiveness and advantages of these techniques. These methods readily extend to spatially explicit data collected by any sort of mobile receiving platform (e.g. wave gliders, remotely operated underwater vehicles).