Marine animal behaviour: neglecting ocean currents can lead us up the wrong track

Abstract

Tracks of marine animals in the wild, now increasingly acquired by electronic tagging of individuals, are of prime interest not only to identify habitats and high-risk areas, but also to gain detailed information about the behaviour of these animals. Using recent satellite-derived current estimates and leatherback turtle (Dermochelys coriacea) tracking data, we demonstrate that oceanic currents, usually neglected when analysing tracking data, can substantially distort the observed trajectories. Consequently, this will affect several important results deduced from the analysis of tracking data, such as the evaluation of the orientation skills and the energy budget of animals or the identification of foraging areas. We conclude that currents should be systematically taken into account to ensure the unbiased interpretation of tracking data, which now play a major role in marine conservation biology.

Active dispersal in loggerhead sea turtles ( Caretta caretta ) during the ‘lost years’

“…Because the ocean is a complex and dynamic environment, inferences about the directed movement of an individual animal within the open ocean require attention to the underlying physical processes that shape migratory pathways [8,12,13]. This is especially true for ocean currents, which have been shown to play key roles in sea turtle ecology [7,8].…”

“…It is now known that oceanic dispersal is a product of passive and active movements [7][8][9][10]. Emerging studies have begun to recognize that even early-stage turtles rely on some level of active swimming to achieve success with long-distance ocean transport [3,5].…”

Straight as an arrow: humpback whales swim constant course tracks during long-distance migration

“…Animal tracking research demonstrates that diverse taxa can maintain constant courses, suggesting that precise directional orientation is a common feature of marine animal migration [10][11][12]. Here, we present satellite tag-derived location data for 16 humpback whales migrating away from low-latitude coastal habitats in the South Atlantic and South Pacific Oceans between 2003 and 2010.…”

Navigating the flow: individual and continuum models for homing in flowing environments

“…A complicating factor is the flow in the surrounding medium, from ocean and river currents for aquatic organisms to wind for airborne populations [4][5][6]. Flow can be benevolent or malevolent: on the one hand, movement is energetically demanding and currents provide a useful conveyor belt; on the other, a powerful current or storm could transport population members into inhospitable or unfamiliar environments.…”