TITLE: “An updated movement path randomization method to distinguish social and spatial drivers of animal interactions.”
ABSTRACT: Studying the spatial-social interface requires tools that distinguish between social and spatial drivers of interactions. Testing hypotheses regarding the factors determining animal interactions often involves comparing observed interactions with reference or ’null’ models. One approach to constructing reference models that account for spatial drivers of social interactions is randomizing animal movement paths to decouple their spatial and social phenotypes while maintaining environmental effects on movements. Here we propose a new randomization approach. Using agent-based simulations, we explore the utility of the new approach for different types of animal movements and compare its performance to existing approaches. We show that our method provides reference models that are more similar to the original tracking data, while still distinguishing between social and spatial drivers. Furthermore, the new approach results in fewer false-positives than other approaches, especially when animals do not return to the same place each night but change movement foci, either locally or directionally. Finally, we show that interactions among GPStracked griffon vultures (Gyps fulvus) emerge from social attraction rather than from their movement patterns alone. We conclude by highlighting the biological situations in which the new method might be most suitable for testing hypotheses about the underlying causes of social interactions.