Abstract
Animals follow specific movement patterns and search strategies to maximize encounters with essential resources (e.g. prey, favourable habitat) while minimizing exposures to suboptimal conditions (e.g. competitors, predators). While describing spatiotemporal patterns in animal movement from tracking data is common, understanding the associated search strategies employed continues to be a key challenge in ecology. Moreover, studies in marine ecology commonly focus on singular aspects of species' movements, however using multiple analytical approaches can further enable researchers to identify ecological phenomena and resolve fundamental ecological questions relating to movement. Here, we used a set of statistical physics‐based methods to analyze satellite tracking data from three co‐occurring apex predators (tiger, great hammerhead and bull sharks) that predominantly inhabit productive coastal regions of the northwest Atlantic Ocean and Gulf of Mexico. We analyzed data from 96 sharks and calculated a range of metrics, including each species' displacements, turning angles, dispersion, space‐use and community‐wide movement patterns to characterize each species' movements and identify potential search strategies. Our comprehensive approach revealed high interspecific variability in shark movement patterns and search strategies. Tiger sharks displayed near‐random movements consistent with a Brownian strategy commonly associated with movements through resource‐rich habitats. Great hammerheads showed a mixed‐movement strategy including Brownian and resident‐type movements, suggesting adaptation to widespread and localized high resource availability. Bull sharks followed a resident movement strategy with restricted movements indicating localized high resource availability. We hypothesize that the species‐specific search strategies identified here may help foster the co‐existence of these sympatric apex predators. Following this comprehensive approach provided novel insights into spatial ecology and assisted with identifying unique movement and search strategies. Similar future studies of animal movement will help characterize movement patterns and also enable the identification of search strategies to help elucidate the ecological drivers of movement and to understand species' responses to environmental change.
Highlights
Animals use specific movement strategies to meet their essential biological and ecological requirements such as finding prey, favourable habitat, avoiding risk or seeking shelter (Nathan et al 2008, Hussey et al 2015, Kays et al 2015)
Plotting the average number of grid cells visited by the reshuffled trajectories against those visited by the original trajectories resulted in slopes of 1.05, 1.21 and 1.35 for tiger, great hammerhead and bull sharks, respectively (Fig. 3C–E and Supporting information), indicating that slightly more grid cells were visited in the reshuffled trajectories than in the original trajectories
Using a combination of analytical methods derived from statistical physics, we identified the search strategies and comprehensively described the movements of three sympatric apex predators in productive coastal habitats
Summary
Animals use specific movement strategies to meet their essential biological and ecological requirements such as finding prey, favourable habitat, avoiding risk or seeking shelter (Nathan et al 2008, Hussey et al 2015, Kays et al 2015). For migratory species, these strategies are often complex and composed of multifaceted movements. These strategies are often complex and composed of multifaceted movements While understanding these complex strategies continues to be a key challenge in ecology (Hays et al 2016), a range of advanced analytical methods are available to investigate various aspects of movement. By using a combination of methods ecologists can comprehensively analyze species’ movement strategies, identify ecological phenomena and resolve fundamental ecological questions relating to species movement behaviour (Sutherland et al 2013, Hays et al 2016)
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