Fractal reorientation clocks: Linking animal behavior to statistical patterns of search

Abstract

The movement ecology framework depicts animal movement as the result of the combined effects of internal and external constraints on animal navigation and motion capacities. Nevertheless, there are still fundamental problems to understand how these modulations take place and how they might be translated into observed statistical properties of animal trajectories. Of particular interest, here, is the general idea of intermittence in animal movement. Intermittent locomotion assumes that animal movement is, in essence, discrete. The existence of abrupt interruptions in an otherwise continuous flow of movement allows for the possibility of reorientations, that is, to break down previous directional memories of the trajectory. In this study, we explore the potential links between intermittent locomotion, reorientation behavior, and search efficiency. By means of simulations we show that the incorporation of Lé vy intermittence in an otherwise nonintermittent search strongly modifies encounter rates. The result is robust to different types of landscapes (i.e., target density and spatial distribution), and spatial dimensions (i.e., 2D, 3D). We propose that Lé vy intermittence may come from reorientation mechanisms capable of organizing directional persistence on time (i.e., fractal reorientation clocks), and we rationalize that the explicit distinction between scanning and reorientation mechanisms is essential to make accurate statistical inferences from animal search behavior. Finally, we provide a statistical tool to judge the existence of episodic and strong reorientation behaviors capable of modifying relevant properties of stochastic searches, ultimately controlling the chances of finding unknown located items.animal movement ͉ intermittent locomotion ͉ Lé vy walks ͉ random walks ͉ search strategies T he movement ecology framework explicitly recognizes animal movement as the result of a constant ''dialogue'' between environment (external factors) and animal internal states. This dialogue affects organisms' motion and/or navigation capacities to finally produce the actual movement (1). Beyond phenomenological descriptions of movement, the random paradigm (1) should seek to understand how interactions between the four components of the movement ecology framework (i.e., internal states, external forces, motion, and navigation capacities) might be translated into observed statistical patterns of movement (2, 3). In the present work, we suggest that a major advance in bridging the gap between animal behavior (mechanistic approach) and the statistical properties of search strategies involves a statistical reinterpretation of the idea of intermittent locomotion (4-6).The biological principle of intermittent locomotion assumes that animal behavior unavoidably produces observable punctuations in the movement (e.g., stops, strong changes in speed). Thus, the forces generating movement operate discontinuously, producing pauses and speeding patterns on the move. Intermittent locomotion (also known as stop-and-go movement, pau...

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