Understanding scales of movement: Animals ride waves and ripples of environmental change

• Published in: Journal of Animal Ecology
• Main Authors: van Moorter, Bram, Bunnefeld, Nils, Panzacchi, Manuela, Rolandsen, Christer M, Solberg, Erling Johan, Saether, Bernt-Erik
• Other Authors: Norwegian University of Science And Technology (NTNU), Biological and Environmental Sciences, Norwegian Institute for Nature Research, orcid:0000-0002-1349-4463
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley-Blackwell for British Ecological Society 2013
• Subjects: Alces alces; foraging; Fourier transform; GPS; migration; NDVI; phenology; resource; spatiotemporal scales; snow; Animal locomotion; Ecology; Evolution (Biology)
• Online Access: http://hdl.handle.net/1893/15694; https://doi.org/10.1111/1365-2656.12045; http://dspace.stir.ac.uk/bitstream/1893/15694/1/Understanding%20scales%20of%20movement.pdf

1. Animal movements are the primary behavioural adaptation to spatiotemporal heterogeneity in resource availability. Depending on their spatiotemporal scale, movements have been categorized into distinct functional groups (e.g. foraging movements, dispersal, migration), and have been studied using different methodologies. We suggest striving towards the development of a coherent framework based on the ultimate function of all movement types, which is to increase individual fitness through an optimal exploitation of resources varying in space and time. 2. We developed a novel approach to simultaneously study movements at different spatiotemporal scales based on the following proposed theory: the length and frequency of animal movements are determined by the interaction between temporal autocorrelation in resource availability and spatial autocorrelation in changes in resource availability. We hypothesized that for each time interval the spatiotemporal scales of moose Alces alces movements correspond to the spatiotemporal scales of variation in the gains derived from resource exploitation when taking into account the costs of movements (represented by their proxies, forage availability NDVI and snow depth respectively). The scales of change in NDVI and snow were quantified using wave theory, and were related to the scale of moose movement using linear mixed models. 3. In support of the proposed theory we found that frequent, smaller scale movements were triggered by fast, small-scale ripples of changes, whereas infrequent, larger scale movements matched slow, large-scale waves of change in resource availability. Similarly, moose inhabiting ranges characterized by larger scale waves of change in the onset of spring migrated longer distances. 4. We showed that the scales of movements are driven by the scales of changes in the net profitability of trophic resources. Our approach can be extended to include drivers of movements other than trophic resources (e.g. population density, density of related individuals, ...