Adaptation and Orientation in Animals’ Movements: Random Walk, Kinesis, Taxis and Path-Integration

A first order correlated random walk model was developed to represent animals’ movements. This model makes it possible to formalize the stochastic concept of sinuosity of an animal’s search path and to determine some basic properties such as its diffusion. This model can be used to analyse actual animals’ movements, or to develop more complex movement models integrating cybernetic controls of the sinuosity and the velocity as a function of environmental stimulations. Models of this kind show how animals can orient themselves in a stimulation gradient field or exploit patchy environments using simple klino- and ortho-kinetic mechanisms which have been reformulated. When movement regulation depends on the local value of the field potential (absolute mode), klinokinesis and orthokinesis can both be seen to be elementary space-use mechanisms, allowing the animal to adapt its movements to the environmental conditions. When movement regulation depends on variations in the field potential (differential mode), klinokinesis can be seen to be an elementary spatial orientation mechanism, whereas orthokinesis seems to have no biological relevance. Contrary to differential klinokinesis, taxis is an orientation mechanism based on the determination of the gradient direction. The properties of differential kinesis and taxis are compared and statistical tools for distinguishing between them by means of path analysis are proposed. Finally, the first order correlated random walk model was used to quantify navigational errors involved in path-integration as a function of the type and the magnitude of estimation errors about route-based information.