Environmental context explains Lévy and Brownian movement patterns of marine predators.
An optimal search theory, the so-called Lévy-flight foraging hypothesis, predicts that predators should adopt search strategies known as Lévy flights where prey is sparse and distributed unpredictably, but that Brownian movement is sufficiently efficient for locating abundant prey. Empirical studies have generated controversy because the accuracy of statistical methods that have been used to identify Lévy behaviour has recently been questioned. Consequently, whether foragers exhibit Lévy flights in the wild remains unclear. Crucially, moreover, it has not been tested whether observed movement patterns across natural landscapes having different expected resource distributions conform to the theory's central predictions. Here we use maximum-likelihood methods to test for Lévy patterns in relation to environmental gradients in the largest animal movement data set assembled for this purpose. Strong support was found for Lévy search patterns across 14 species of open-ocean predatory fish (sharks, tuna, billfish and ocean sunfish), with some individuals switching between Lévy and Brownian movement as they traversed different habitat types. We tested the spatial occurrence of these two principal patterns and found Lévy behaviour to be associated with less productive waters (sparser prey) and Brownian movements to be associated with productive shelf or convergence-front habitats (abundant prey). These results are consistent with the Lévy-flight foraging hypothesis, supporting the contention that organism search strategies naturally evolved in such a way that they exploit optimal Lévy patterns.
Humphries
Nicolas E
NE
Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK.
Queiroz
Nuno
N
Dyer
Jennifer R M
JR
Pade
Nicolas G
NG
Musyl
Michael K
MK
Schaefer
Kurt M
KM
Fuller
Daniel W
DW
Brunnschweiler
Juerg M
JM
Doyle
Thomas K
TK
Houghton
Jonathan D R
JD
Hays
Graeme C
GC
Jones
Catherine S
CS
Noble
Leslie R
LR
Wearmouth
Victoria J
VJ
Southall
Emily J
EJ
Sims
David W
DW
D000823:Animal Identification Systems; D000818:Animals; D005075:Biological Evolution; D017753:Ecosystem; D005106:Exploratory Behavior / Q000502:physiology; D005399:Fishes / Q000502:physiology*; D005502:Food; D016013:Likelihood Functions; D008124:Locomotion / Q000502:physiology*; D008386:Marine Biology; D008954:Models, Biological; D010473:Perciformes / Q000502:physiology; D011235:Predatory Behavior / Q000502:physiology*; D012623:Seawater; D012754:Sharks / Q000502:physiology; D013550:Swimming / Q000502:physiology