Detecting changes in the annual movements of terrestrial migratory species: using the first-passage time to document the spring migration of caribou

Abstract

BackgroundMigratory species face numerous threats related to human encroachment and climate change. Several migratory populations are declining and individuals are losing their migratory behaviour. To understand how habitat loss or changes in the phenology of natural processes affect migrations, it is crucial to clearly identify the timing and the patterns of migration. We propose an objective method, based on the detection of changes in movement patterns, to identify departure and arrival dates of the migration. We tested the efficiency of our approach using simulated paths before applying it to spring migration of migratory caribou from the Rivière-George and Rivière-aux-Feuilles herds in northern Québec and Labrador. We applied the First-Passage Time analysis (FPT) to locations of 402 females collected between 1986 and 2012 to characterize their movements throughout the year. We then applied a signal segmentation process in order to segment the path of FPT values into homogeneous bouts to discriminate migration from seasonal range use. This segmentation process was used to detect the winter break and the calving ground use because spring migration is defined by the departure from the winter range and the arrival on the calving ground.ResultsSegmentation of the simulated paths was successful in 96% of the cases, and had a high precision (96.4% of the locations assigned to the appropriate segment). Among the 813 winter breaks and 669 calving ground use expected to be detected on the FPT profiles, and assuming that individuals always reduced movements for each of the two periods, we detected 100% of the expected winter breaks and 89% of the expected calving ground use, and identified 648 complete spring migrations. Failures to segment winter breaks or calving ground use were related to individuals only slowing down or performing less pronounced pauses resulting in low mean FPT.ConclusionWe show that our approach, which relies only on the analysis of movement patterns, provides a suitable and easy-to-use tool to study species exhibiting variations in their migration patterns and seasonal range use.Electronic supplementary materialThe online version of this article (doi:10.1186/s40462-014-0019-0) contains supplementary material, which is available to authorized users.

Moose movement rates are altered by wolf presence in two ecosystems

“…The spatial dynamics between predator and prey can be difficult to disentangle, especially when prey select for areas that predators avoid and vice versa (Sih, ). FPTs have been shown to be useful for evaluating how ungulate prey respond to the likelihood of predator encounter (see Cleveland et al., ; Frair et al., ; Le Corre et al., , ), and they have provided insights beyond considering resource selection alone. The reduction we observed in moose FPT of over 40% (equivalently a reduction in nearly 2 hr) between areas of low to high predicted likelihood of wolf resource use in both northern MN ecosystems was surprisingly large and may make it difficult for moose to balance activity budgets.…”

“…Larger FPTs are associated with slower and more sinuous movements, reflective of rest and foraging behaviors, while moderate and small FPTs likely reflect movements between patches and movements to escape predators (Fauchald & Tveraa, ). FPT has been used to capture changes in movement behavior, including antipredator behavior and human avoidance, in elk ( Cervus elaphus ; Frair et al., ; Cleveland, Hebblewhite, Thompson, & Henderson, ), caribou ( Rangifer tarandus ; Le Corre, Dussault, & Côté, ), and roe deer ( Capreolus capreolus ; Le Corre et al., ).…”

Search and foraging behaviors from movement data: A comparison of methods

“…However, this approach utilizes larger areas of space beyond movement paths, and so it is not capable of identifying foraging in association with temporally ephemeral events or features that may directly change an animal's movement trajectory. Within more process-driven approaches, FPT is arguably one of the most ubiquitous methods used to identify foraging areas in both terrestrial and marine systems (Battaile, Nordstrom, Liebsch, & Trites, 2015;Byrne & Chamberlain, 2012;Evans et al, 2015;Hamer et al, 2009;Le Corre, Dussault, & Côté, 2014). FPT captures search behavior across multiple spatial scales and is particularly noted for its ability to detect nested scales of area-restricted search (Hamer et al, 2009).…”

Tactical departures and strategic arrivals: Divergent effects of climate and weather on caribou spring migrations

“…Existing approaches to estimate migration timing have been developed with application to individuals in mind (Börger and Fryxell , Le Corre et al. , Cagnacci et al. , Gurarie et al.…”