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.
Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK.
Nicolas E
NE
Humphries
Nuno
N
Queiroz
Jennifer R M
JR
Dyer
Nicolas G
NG
Pade
Michael K
MK
Musyl
Kurt M
KM
Schaefer
Daniel W
DW
Fuller
Juerg M
JM
Brunnschweiler
Thomas K
TK
Doyle
Jonathan D R
JD
Houghton
Graeme C
GC
Hays
Catherine S
CS
Jones
Leslie R
LR
Noble
Victoria J
VJ
Wearmouth
Emily J
EJ
Southall
David W
DW
Sims
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