Functional responses in animal movement explain spatial heterogeneity in animal–habitat relationships

• Published in: Journal of Animal Ecology
• Main Authors: Mason, Tom H. E., Fortin, Daniel
• Other Authors: Loison, Anne, Natural Sciences and Engineering Research Council of Canada, Fonds de Recherche du Québec - Nature et Technologies
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2017
• Subjects: caribou; Rangifer tarandus
• Online Access: http://dx.doi.org/10.1111/1365-2656.12682; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2F1365-2656.12682; https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/1365-2656.12682

Summary Understanding why heterogeneity exists in animal–habitat spatial relationships is critical for identifying the drivers of animal distributions. Functional responses in habitat selection – whereby animals adjust their habitat selection depending on habitat availability – are useful for describing animal–habitat spatial heterogeneity. However, they could be yielded by different movement tactics, involving contrasting interspecific interactions. Identifying functional responses in animal movement, rather than in emergent spatial patterns like habitat selection, could disentangle the effects of different movement behaviours on spatial heterogeneity in animal–habitat relationships. This would clarify how functional responses in habitat selection emerge and provide a general tool for understanding the mechanistic drivers of animal distributions. We tested this approach using data from GPS ‐collared woodland caribou ( Rangifer tarandus ), a prey species under top‐down control. We tested how caribou selected and moved with respect to a key resource (lichen‐conifer stands) as a function of the availability of surrounding refuge land‐cover (closed‐conifer stands), using step selection functions. Caribou selected resource patches more strongly in areas richer in refuge land‐cover – a functional response in habitat selection. However, adjustments in multiple movement behaviours could have generated this pattern: stronger directed movement towards resource patches and/or longer residency within resource patches, in areas richer in refuges. Different contributions of these behaviours would produce contrasting forager spatial dynamics. We identified functional responses in both movement behaviours: caribou were more likely to move towards resource patches in areas richer in refuge land‐cover, and to remain in these patches during movement steps. This tactic enables caribou to forage for longer in safer areas where they can rapidly seek refuge in dense cover when predators are detected. Our study shows that functional ...