The utilisation distribution describes the relative probability of use of a spatial unit by an
animal. It is natural to think of it as the long-term consequence of the animal's short-term
movement decisions: it is the accumulation of small displacements which, over time, gives
rise to global patterns of space use. However, most utilisation distribution models either
ignore the underlying movement, assuming the independence of observed locations, or are
based on simplistic Brownian motion movement rules.
We introduce a new continuous-time model of animal movement, based on the Langevin
diffusion. This stochastic process has an explicit stationary distribution, conceptually anal-
ogous to the idea of the utilisation distribution, and thus provides an intuitive framework to
integrate movement and space use.
We model the stationary (utilisation) distribution with a resource selection function to link
the movement to spatial covariates, and allow inference into habitat selection.
Standard approximation techniques can be used to derive the pseudo-likelihood of the Langevin
diffusion movement model, and thus to estimate habitat preference and movement parame-
ters from tracking data. We investigate the performance of the method on simulated data,
and discuss its sensitivity to the time scale of the sampling. We present an example of its
application to tracking data of Stellar sea lions (fEumetopias jubatusg).
Due to its continuous-time formulation, this method can be applied to irregular teleme-
try data. It provides a rigorous framework to estimate long-term habitat selection from
correlated movement data.
Joint work with Marie-Pierre Etienne (AgroCampus Ouest) and Theo Michelot (University of Shefield)