Optimal orientation in flows:Providing a benchmark for animal movement strategies

Animal movements in air and water can be strongly affected by experienced flow. While various flow-orientation strategies have been proposed and observed, their performance in variable flow conditions remains unclear. We apply control theory to establish a benchmark for time-minimizing (optimal) ori...

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Bibliographic Details
Published in:Journal of The Royal Society Interface
Main Authors: McLaren, James D., Shamoun-Baranes, Judy, Dokter, Adriaan M., Klaassen, Raymond H. G., Bouten, Willem
Format: Article in Journal/Newspaper
Language:English
Published: 2014
Subjects:
flow orientation
animal navigation
migration
lateral drift
optimization
movement ecology
LONG-DISTANCE MIGRATION
BIRD MIGRATION
OCEAN CURRENTS
WIND DRIFT
FLIGHT
NAVIGATION
TURTLES
SEA
COMPENSATION
REANALYSIS
Gallinago media
Online Access:https://hdl.handle.net/11370/2e1a6da2-b379-4ac5-bb7d-cc58493ef622
https://research.rug.nl/en/publications/2e1a6da2-b379-4ac5-bb7d-cc58493ef622
https://doi.org/10.1098/rsif.2014.0588
https://pure.rug.nl/ws/files/39471625/20140588.full.pdf
Description
Summary:Animal movements in air and water can be strongly affected by experienced flow. While various flow-orientation strategies have been proposed and observed, their performance in variable flow conditions remains unclear. We apply control theory to establish a benchmark for time-minimizing (optimal) orientation. We then define optimal orientation for movement in steady flow patterns and, using dynamic wind data, for short-distance mass movements of thrushes (Turdus sp.) and 6000 km non-stop migratory flights by great snipes, Gallinago media. Relative to the optimal benchmark, we assess the efficiency (travel speed) and reliability (success rate) of three generic orientation strategies: full compensation for lateral drift, vector orientation (single-heading movement) and goal orientation (continually heading towards the goal). Optimal orientation is characterized by detours to regions of high flow support, especially when flow speeds approach and exceed the animal's self-propelled speed. In strong predictable flow (short distance thrush flights), vector orientation adjusted to flow on departure is nearly optimal, whereas for unpredictable flow (inter-continental snipe flights), only goal orientation was near-optimally reliable and efficient. Optimal orientation provides a benchmark for assessing efficiency of responses to complex flow conditions, thereby offering insight into adaptive flow-orientation across taxa in the light of flow strength, predictability and navigation capacity.

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