Caribou movement as a correlated random walk |
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Authors: | C M Bergman J A Schaefer S N Luttich |
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Institution: | (1) Department of Forest Resources and Agrifoods, Wildlife Division, P.O. Box 3014, Station B, Goose Bay, NF A0P 1E0, Canada, CA |
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Abstract: | Movement is a primary mechanism coupling animals to their environment, yet there exists little empirical analysis to test
our theoretical knowledge of this basic process. We used correlated random walk (CRW) models and satellite telemetry to investigate
long-distance movements of caribou, the most vagile, non-volant terrestrial vertebrate in the world. Individual paths of migratory
and sedentary female caribou were quantified using measures of mean move length and angle, and net squared displacements at
each successive move were compared to predictions from the models. Movements were modelled at two temporal scales. For paths
recorded through one annual cycle, the CRW model overpredicted net displacement of caribou through time. For paths recorded
over shorter intervals delineated by seasonal behavioural changes of caribou, there was excellent correspondence between model
predictions and observations for most periods for both migratory and sedentary caribou. On the smallest temporal scale, a
CRW model significantly overpredicted displacements of migratory caribou during 3 months following calving; this was also
the case for sedentary caribou in late summer, and in late winter. In all cases of overprediction there was significant positive
autocorrelation in turn direction, indicating that movements were more tortuous than expected. In one case of underprediction,
significant negative autocorrelation of sequential turn direction was evident, indicating that migratory caribou moved in
straightened paths during spring migration to calving grounds. Results are discussed in light of known migration patterns
and possible limiting factors for caribou, and indicate the applicability of CRW models to animal movement at vast spatial
and temporal scales, thus assisting in future development of more sophisticated models of population spread and redistribution
for vertebrates.
Received: 14 July 1999 / Accepted: 15 November 1999 |
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Keywords: | Caribou Correlated random walk Movement Rangifer tarandus Ungulate |
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