From A to B, randomly: a point-to-point random trajectory generator for animal movement

Abstract

For applications in animal movement, we propose a random trajectory generator (RTG) algorithm that combines the concepts of random walks, space-time prisms, and the Brownian bridge movement model and is capable of efficiently generating random trajectories between a given origin and a destination point, with the least directional bias possible. Since we provide both a planar and a spherical version of the algorithm, it is suitable for simulating trajectories ranging from the local scale up to the (inter-)continental scale, as exemplified by the movement of migrating birds. The algorithm accounts for physical limitations, including maximum speed and maximum movement time, and provides the user with either single or multiple trajectories as a result. Single trajectories generated by the RTG algorithm can be used as a null model to test hypotheses about movement stimuli, while the multiple trajectories can be used to create a probability density surface akin to Brownian bridges.

Keywords:

• movement simulation
• movement ecology
• random walk
• Brownian bridges
• space-time prisms

Acknowledgements

We are grateful to Andrea Flack of the Max Planck Institute for Ornithology, Radolfszell, Germany, for providing the data used in Section 6.2. The data can be found on the Movebank website: https://www.movebank.org. Funding by the Swiss State Secretariat for Education, Research and Innovation (SERI) through project CASIMO (C09.0167) is gratefully acknowledged.