Optimal swimming strategies\xa0and behavioral plasticity of oceanic whitetip sharks

Yannis P Papastamatiou,Yuuki Y Watanabe,Lucy A Howey,Gil Iosilevskii,Vianey Leos-Barajas,Edd J Brooks,Demian D Chapman

doi:10.1038/s41598-017-18608-z

Abstract

Animal behavior should optimize the difference between the energy they gain from prey and the energy they spend searching for prey. This is all the more critical for predators occupying the pelagic environment, as prey is sparse and patchily distributed. We theoretically derive two canonical swimming strategies for pelagic predators, that maximize their energy surplus while foraging. They predict that while searching, a pelagic predator should maintain small dive angles, swim at speeds near those that minimize the cost of transport, and maintain constant speed throughout the dive. Using biologging sensors, we show that oceanic whitetip shark (Carcharhinus longimanus) behavior matches these predictions. We estimate that daily energy requirements of an adult shark can be met by consuming approximately 1–1.5 kg of prey (1.5% body mass) per day; shark-borne video footage shows a shark encountering potential prey numbers exceeding that amount. Oceanic whitetip sharks showed incredible plasticity in their behavioral strategies, ranging from short low-energy bursts on descents, to high-speed vertical surface breaches from considerable depth. Oceanic whitetips live a life of energy speculation with minimization, very different to those of tunas and billfish.

Highlights

Sparse and patchily distributed prey make the pelagic environment the marine equivalent of the desert, yet some of the largest predators spend their entire lives in this ecosystem
An increase in eT has the same effect as a reduction in the standard metabolic rate, and a slow moving predator should swim slower than it would to minimize the cost of transport (COT)
Our model provides predictions as to how pelagic predators should behave in terms of diving angles and swim speeds, in order to maximize their energy surplus

Summary

Introduction

Sparse and patchily distributed prey make the pelagic environment the marine equivalent of the desert, yet some of the largest predators spend their entire lives in this ecosystem. To do so they must maintain a surplus between the energy they gain from prey E+ and the energetic costs associated with searching for prey E−1. When the average swim speed of the predator vx = X/T (2). Is much greater than the average speed of its prey, eT becomes irrelevant. Is the (instantaneous) routine metabolic rate, and the angular brackets denote an average with respect to time, so that. F is the hydrodynamic thrust, v is the swimming speed, η is the chemo-mechanical propulsion efficiency

Methods

Results

Conclusion