Goal-dependent current compensation and drift in surf scoter flocks.

Ryan Lukeman,Alexis Christie,Ronald C Ydenberg

doi:10.1186/s40462-016-0068-7

Ryan Lukeman, Alexis Christie + Show 1 more

Open Access

https://doi.org/10.1186/s40462-016-0068-7

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Abstract

BackgroundAnimals moving through air or water toward a goal frequently must contend with fluid currents, which can drift the actual path of the animal away from the direction of heading. Whether, and to what degree, animals compensate for currents depends on the species and environmental context, but plays an important role in the movement ecology of the species. In this paper, flocks of surf scoters (Melanitta perspicillata), an aquatic diving duck, were individually tracked during collective foraging in the presence of sideward water currents to assess the individual compensatory response while moving from open water toward the foraging location versus return to open water.ResultsDuring short-range movement toward the foraging location, surf scoters moved more slowly, and compensated for currents by orienting diagonally into the current to maintain a perpendicular track to the goal. In contrast, during return to open water, surf scoters moved faster, and maintained a perpendicular orientation away from the foraging location, and allowed the sideward current to drift their track diagonally.ConclusionsSurf scoters show a behavioural flexibility in response to currents, alternately using compensation and drift as the movement goal and consequent cost of accuracy change.

Highlights

Animals moving through air or water toward a goal frequently must contend with fluid currents, which can drift the actual path of the animal away from the direction of heading
We describe the movements of a group of surf scoters (Melanitta perspicillata) to and from a foraging site
A typical dive cycle for the flock included time spent in open water, followed by collective surface-swimming toward the dock area, where the flock dove under the water surface with a high degree of synchrony to forage on mussels (Mytilus trossulus) attached to the pilings

Summary

Introduction

Animals moving through air or water toward a goal frequently must contend with fluid currents, which can drift the actual path of the animal away from the direction of heading. Any organism travelling through moving air or water toward a goal must account for the fact that its actual track will be shifted from its heading (i.e. the direction it is pointing). This is called ‘drift’, and has been studied extensively among diverse taxa of long-distant migrants [1, 2], who must compensate for winds or currents to reach their goal. The Costa Rican fish Brycon guatemalensis lives in fast-flowing streams and consumes fruits that fall from overhanging trees They accelerate toward the point of impact before a falling fruit has even hit the stream surface, adjusting their heading to take the current into account [4]. Stream fish such as Arctic grayling (Thymallus arcticus) must take account of the

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