Events

Date: 8 October 2025   Time: 14:00 - 15:00

Location: Online talk, via the Teams link below

Abstract: Anomalous diffusion, characterized by a nonlinear dependence of the mean-squared displacement on measurement time, is prevalent in nature, ranging from molecular motion at microscopic scales to the large-scale trajectories of migrating birds. Using empirical datasets spanning many orders of magnitude in length and time, we employ methods that identify the underlying origins of anomalous transport and show how such decomposition yields behavioral insights. At the ecological scale, analyses of rich datasets on avian predators reveal distinctive movement characteristics, including weak ergodicity breaking of local searches. In ecological terms, we show that there are many ways to hunt within a patch, but only a limited number of ways to commute between distant patches. A continuous-time random walk framework captures the behavioral switch between local exploration and long-range movement between patches.
We next demonstrate the limitations of analyses restricted to the mean and mean-squared displacement, which correspond to only specific displacement moments. High-resolution tracking data from over 70 million localizations of free-ranging Barn Owls (Tyto alba) reveal strong anomalous diffusion, expressed in the nonlinear growth of higher-order displacement moments. The moment spectrum function λt(q) -- defined by 〈|????(t)|q〉∼tλt(q) -- displays piecewise linearity in q, with a critical moment marking a crossover between scaling regimes, and points to ecological drivers associated with age and temporospatial context. Using stochastic models—a bounded Lévy walk and a multi-mode behavioral model—we reproduce the observed phenomena, relating behavioral states to environmental constraints and showing how Lévy walk-like statistics may arise from underlying structure.
Taken together, this progression from diffusion to anomalous and ultimately to strong anomalous diffusion advances a unifying framework for characterizing ecological movement, and suggests that such dynamics may be widespread in animal behavior.

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