We propose that changes in movement behavior may be a proximate mechanism that influences the accumulation of animals at habitat edges. We tested this idea with a combination of empirical and simulation experiments in a resource-free landscape. The movements of individual flour beetles, Tribolium confusum, were tracked across a paper arena edged with invisible tape until beetles crossed the edge. Movement behavior (step lengths and turn angles) and cumulative occupancy were analyzed according to distance from the edge. We found that beetles took smaller steps with larger turn angles near edges than in the center of the arena and that beetle distribution was highly biased towards the edge of the arena. We then tested two agent-based simulation models for each beetle: an edge-independent model and an edge-dependent model. Both models predicted less time spent at the edge than was observed. The proportion of time spent at edges depended on the propensity to cross the edge, which could not be explained by beetle body size or energetic condition. The distribution of animals with respect to habitat edges depends on many factors, but we suggest that proximate mechanisms such as movement behavior should be explicitly considered when interpreting animal distributions. 1. Introduction Movement of individuals is a critical factor for the population ecology of most organisms, affecting energy flow, distribution, and the genetic and demographic structure of populations [1–4]. Knowledge of the causes of movement behavior may be key in developing a full understanding of the spatial structure and dynamics of populations [1, 5–10]. For example, an increasingly large body of research finds that organisms generally move quickly and directly through low-quality habitats (e.g., [4, 11, 12]). This in turn predicts there will be fewer individuals in resource-poor than in resource-rich environments [5, 13], and many studies have found such a correspondence between movement behavior and population density (e.g., [14–18]). In addition to habitat quality, another key factor affecting the movement of organisms is the degree of permeability of the interface between habitats [16, 19–21]. Permeability is the tendency of the edge to inhibit or enhance organisms’ movement across it [19, 21–23] and it directly affects the degree to which organisms leave a particular habitat [12, 15, 19]. Borders that are readily crossed by dispersing individuals are considered to be soft or semipermeable edges, while those that are unlikely to be crossed are known as hard or impermeable. This
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