American Society of Naturalists

Quinn M. R. Webber, Michel P. Laforge, Maegwin Bonar, Alec L. Robitaille, Christopher Hart, Sana Zabihi, and Eric Vander Wal (July 2020)

Individuals display plasticity in movement strategies across a resource availability gradient

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Caribou adjust movement behavior based on the distribution of foraging habitat

How do animals use space to find the best food? Movement is the mechanism by which animals find and access profitable foraging habitat. Animal movement is therefore shaped by the environment an individual animal experiences. Because individual animals experience different environments, we might expect individuals to vary in their movement tactics, but these tactics are predicted to vary as a function of the distribution of food resources. Contemporary behavioral ecology preoccupies itself with understanding meaningful consistent variation among individuals to understand how individual behavioral variation, or animal personality, is likely to result in individuals being consistent in their movement strategies across contexts.

It is through the lens of animal plasticity and consistent differences that Webber, Laforge, and colleagues tested how free-ranging caribou on the island of Newfoundland, Canada, adjusted their movement patterns as a function of the distribution of profitable habitat, high-quality spring vegetation. Specifically, they tested the hypothesis that individuals that experience densely aggregated foraging habitats should move more slowly and intensively in a small localized area. By contrast, when foraging habitats are distributed more evenly across the landscape, individuals should move faster and more linearly throughout their range. As predicted, individuals adjust their movements as a function of resource distribution. In addition, individual caribou also display consistent differences in their movement behaviors, suggesting the fastest moving individuals in one context are the fastest moving individuals in a different context. The authors highlight how behavioral consistency and plasticity are important aspects of the movement ecology framework. By linking variation in resource distribution across landscapes to individual consistency and plasticity in movement behavior, the authors bridge concepts from the fields of animal personality and movement ecology.

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Abstract

Movement provides a link between individual behavioral ecology and the spatial and temporal variation in an individual’s landscape. Individual variation in movement traits is an important axis of animal personality, particularly in the context of foraging ecology. We tested whether individual caribou (Rangifer tarandus) displayed plasticity in movement and space-use behavior across a gradient of resource aggregation. We quantified first-passage time and range-use ratio as proxies for movement-related foraging behavior and examined how these traits varied at the individual level across a foraging resource gradient. Our results suggest that individuals adjusted first-passage time, but not range-use ratio, to maximize access to high-quality foraging resources. First-passage time was repeatable and intercepts for first-passage time and range-use ratio were negatively correlated. Individuals matched first-passage time, but not range-use ratio, to the expectations of our patch-use model that maximized access to foraging resources, a result that suggests that individuals acclimated their movement patterns to accommodate both intra- and inter-annual variation in foraging resources on the landscape. Collectively, we highlight repeatable movement and space-use tactics, and provide insight into how individual plasticity in movement interacts with landscape processes to affect the distribution of behavioral phenotypes, and potentially fitness and population dynamics.