Journal Article

Taking animal tracking to new depths: synthesizing horizontal-vertical movement relationships for four marine predators

Hindell, Mark A, Bestley, Sophie, Gales, Nicholas J, Harcourt, Robert G, Jonsen, Ian D

2015

Overview

In animal ecology, a question of key interest for aquatic species is how changes in movement behavior are related in the horizontal and vertical dimensions when individuals forage. Alternative theoretical models and inconsistent empirical findings mean that this question remains unresolved. Here we tested expectations by incorporating the vertical dimension (dive information) when predicting switching between movement states (\"resident\" or \"directed\") within a state-space model. We integrated telemetry-based tracking and diving data available for four seal species (southern elephant, Weddell, antarctic fur, and crabeater) in East Antarctica. Where possible, we included dive variables derived from the relationships between (1) dive duration and depth (as a measure of effort), and (2) dive duration and the postdive surface interval (as a physiological measure of cost). Our results varied within and across species, but there was a general tendency for the probability of switching into \"resident\" state to be positively associated with shorter dive durations (for a given depth) and longer postdive surface intervals (for a given dive duration). Our results add to a growing body of literature suggesting that simplistic interpretations of optimal foraging theory based only on horizontal movements do not directly translate into the vertical dimension in dynamic marine environments. Analyses that incorporate at least two dimensions can test more sophisticated models of foraging behavior.

• Publisher: Ecological Society of America
• Subject: Animal Distribution / animal ecology / Animals / Antarctic fur seal / Antarctic fur seal, Arctocephalus gazella / Antarctic region / Antarctic Regions / Antarctica / Aquatic ecology / Aquatic life / Arctocephalus gazella / Behavior, Animal / Caniformia - physiology / crabeater seal / crabeater seal, Lobodon carcinophaga / East Antarctic / forage / foraging / Foraging behavior / individual movement / Leptonychotes weddellii / Lobodon carcinophaga / Marine environment / marine predators / Mirounga leonina / Movement / Predation / Predators / prediction / probability / satellite tracking / seals / southern elephant seal / southern elephant seal, Mirounga leonina / state-space model / Telemetry / Weddell seal / Weddell seal, Leptonychotes weddellii