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An emerging movement ecology paradigmRan Nathan1
The Movement Ecology Laboratory, Department of Evolution, Systematics, and Ecology, Alexander Silberman Institute of Life Sciences,
The Hebrew University of Jerusalem, Jerusalem 91904, Israel
M
ovement of individual or-ganisms, one of the most
fundamental features of lifeon Earth, is a crucial com-
ponent of almost any ecological andevolutionary process, including majorproblems associated with habitat frag-mentation, climate change, biologicalinvasions, and the spread of pests anddiseases. The rich variety of movementmodes seen among microorganisms,plants, and animals has fascinated man-kind since time immemorial. Theprophet Jeremiah (7th century B.C.), forinstance, described the temporal consis-tency in migratory patterns of birds, and
Aristotle (4th centur y B.C.) searched forcommon features unifying animal move-ments (see ref. 1).
Modern movement research, however,is characterized by a broad range of spe-cialized scientific approaches, each de-
veloped to explore a different type of movement carried out by a specificgroup of organisms (2). Beyond thisseparation across movement types andtaxonomic (or functional) groups, move-ment research divides into four different‘‘paradigms,’’ the random, biomechani-cal, cognitive, and optimality approaches(1), which are loosely linked to eachother. Although movement research isextensive and is growing rapidly (2),specialization has its cost: measurementand analysis tools are repeatedly rein-
vented, and lessons learned from oneline of research often do not affect oth-ers. Most importantly, we lacked a cohe-sive framework that would serve as aunifying theme for developing a generaltheory of organism movement.
This Special Feature lays the founda-tion for ‘‘movement ecology’’ as a unify-ing paradigm for studying all types of movement involving all organisms. Theterm movement ecology has been used
occasionally in the literature [as of Au-gust 2008, a search of movement ecol-ogy in the title, abstract, or keywords inthe ISI Web of Knowledge database(http://apps.isiknowledge.com) yielded18 publications, the first of which waspublished in 1976], chiefly referring toecological interactions associated withanimal movement. However, the move-ment ecology concept underlying thisSpecial Feature is markedly different. Itrefers to a proposed scientific paradigmthat places movement itself as the focaltheme, and, by providing a unifyingframework and common tools, it aims at
promoting the development of an inte-grative theory of organism movement
for better understanding the causes,mechanisms, patterns, and consequencesof all movement phenomena.
This Special Feature is based on aninternational project held at the Insti-tute for Advanced Studies (IAS) inJerusalem from 2006 to 2007 (3). Threeof the 12 contributions, presenting ageneral conceptual framework (1), aliterature review (2), and a frameworkfor generating and analyzing movementpaths (4), are direct products of thisIAS project. Three other contributionsare coauthored by IAS group members;they illustrate applications of the pro-posed conceptual framework for seeddispersal (5), foraging and other move-ments of elephants (6), and dispersal of lynx (7). The remaining six contributions
were solicited from other researchgroups to broaden the scope of thiscollection. These include a theoreticalpaper on the link between foraging be-havior and the statistical properties of movement paths (8) and five empiricalstudies on dispersal of plants (9) andbutterflies (10), navigation of salmonand sea turtles (11), migration of vul-tures (12), and dispersal, foraging, andother movements of elks (13). Holyoak et al. (2) estimate that over the lastdecade (1997–2006) 26,000 papers re-ferred to movement. Because of thisextremely broad scope of movementecology, the fairly diverse coverage of movement types and taxonomic groupsin this Special Feature is inevitably in-complete. To foster integration, the au-thors were requested to place their
works in the context of the proposedunifying theme (1) and discuss the prosand cons of this approach.
The general framework introduced byNathan et al. (1) asserts that four basic
components are needed to describe themechanisms underlying movement of allkinds: the organism’s internal state,
which defines its intrinsic motivation tomove; the motion and navigation capaci-ties representing, respectively, the organ-ism’s basic ability to move and affect
where and when to move; and the broadrange of external factors affecting move-ment. At first glance, this frameworkappears to be primarily applicable toself-propelled sentient animals, for
which the internal motivation to moveand the ability to actively move whilemaking decisions in response to infor-
mation about the environment are com-prehensible. However, two studies in
this Special Feature (5, 9) apply thisframework to investigate the movementof passively transported organisms thatlack a central nervous system, such asplants.
Damschen et al. (9) provide the mostfundamental application of movementecology for studying plant communitydynamics, classifying plant species ac-cording to a single categorical parame-ter depicting the dispersal mode. Suchsimplifications are often compulsorybecause urgent conservation concernspreclude detailed investigations of dis-
persal mechanisms for many species.Interestingly, the predicted effects of fragmentation on community dynamics
were supported for bird-dispersed spe-cies that were studied in detail in thissystem, but not for wind-dispersed and‘‘unassisted’’ species, for which dispersalhas not yet been investigated. Wright et
al. (5) parameterize a mechanistic winddispersal model for two tropical treespecies, interpreting the movement ecol-ogy from an evolutionary context. Im-portantly, they found that surrogates of seed fate (the potential fitness conse-quences of dispersal) vary in a complex
manner with respect to atmosphericconditions (external factors), seed termi-nal velocity (motion capacity), and thetiming of seed release (navigationcapacity).
Linking Processes to Patterns and theImportance of Scale
The general challenge of identifying themechanisms underlying ecological pat-terns (14) is particularly relevant formovement research: we need to identifyphases of specific activity modes in ob-served movement paths (1, 4) and revealthe underlying mechanisms from theirstatistical properties. This Special Fea-ture illustrates two complementary waysto address this challenge. The first, ap-plied here to animals (4) and plants (5),explicitly depicts the underlying mecha-nisms and associate potential determi-nants of movement processes with theresulting patterns. The second takes the
Author contributions: R.N. wrote the paper.
The author declares no conflict of interest.
1E-mail: [email protected].
© 2008 by The National Academy of Sciences of the USA
19050–19051 PNAS December 9, 2008 vol. 105 no. 49 www.pnas.orgcgidoi10.1073pnas.0808918105
7/25/2019 An Emeging Movement Ecology Paradigm
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opposite approach: from patterns toprocesses. Bartumeus and Levin (8)quantify intermittency in movement pat-terns of animals that search, suggestingthat the switch between scanning andreorientation could infer, for example,the effects of limited perception and/ora patchy environmental structure. Witte-myer et al. (6) use time-series tech-
niques to infer about basic movementphases and formulate hypotheses aboutthe major links, such as those betweenrisk (human hunting) aversion, socialdominance, and seasonal dynamics of the resources, that underlie elephantmovements.
A major challenge in movement re-search is to explicitly link the statisticalproperties of movement patterns to spe-cific internal traits and/or behaviors.Movement ecology facilitates this inte-gration (1). The theoretical guidelinesprovided by Getz and Saltz (4) and Bar-tumeus and Levin (8) must be comple-
mented by empirical studies that delvemore deeply into the mechanistic deter-minants of movement. Lohmann et al.
(11) suggest a novel hypothesis of howsalmon and sea turtles navigate longdistances back to their spawninggrounds in essentially featureless oce-anic landscapes. Ovaskainen et al. (10)apply the harmonic radar technique toquantify small-scale movements of but-terflies originating from populations incontinuous landscapes in China and Es-tonia and from fragmented landscapesin Finland. Significant differences insmall-scale movements were found only
between butterflies from old and newlyestablished populations in Finland, sug-gesting that variation in motion capacityor internal state makes butterflies fromnewly established populations moremobile. Mandel et al. (12) analyze theeffects of atmospheric factors and to-pography on migratory flights of vul-tures, emphasizing their dependence onhigh turbulent kinetic energy (TKE)conditions in the atmospheric boundary
layer. High TKE was also critical forlong-distance wind dispersal of treeseeds (5).
A related key challenge in ecologicalresearch, identifying the key processesshaping patterns at different spatial andtemporal scales (14), was emphasized inmany contributions to this Special Fea-ture. Lohmann et al. (11) suggest scale-
dependent navigation in salmon and seaturtles, in which geomagnetic and olfac-tory imprints of the natal areas guide aphase of large-scale navigation by theEarth’s magnetic field, followed bysmall-scale navigation governed bychemical gradients to specific destina-tions. Fryxell et al.’s (13) analysis of elkmovements across five orders of magni-tude in time (minutes to years) andspace (meters to hundreds of kilome-ters) provides one of the most compre-hensive investigations of movement atmultiple spatiotemporal scales. Theyshow that elk switch among two or more
movement modes at each spatiotempo-ral scale examined. They stress thechallenge of elucidating the basic com-ponents of the movement ecologyframework and their interactions to fullyunderstand the observed movementpatterns.
The Role of Movement in DeterminingEcological and Evolutionary Processes
As emphasized in Damschen et al. (9),movement plays an important, but notexclusive, role in determining ecologicaland evolutionary patterns. However, weshould remain mindful of Daniel Jan-
zen’s assertion (as quoted in ref. 3) that‘‘an awful lot of biologists convenientlytrim [movement] out of their way of thinking to make their problems sim-pler’’. Progress in movement ecologyrequires that studies of populations,communities, and ecosystems will con-sider movement explicitly. However,movement research needs to considerconstraints and tradeoffs associated withother life history traits and should eluci-
date how premovement and postmove-ment processes such as fecundity andestablishment interact with movement toshape ecological processes and patterns.Revilla and Wiegand (7) illustrate anapplication of the movement ecologyframework to elucidate the role of dis-persal in the dynamics of lynx popula-tions in spatially structured landscapes.They propose that between-patch move-ment and within-patch demography can-not be considered as separate entities,because birth–death processes affect themovement behavior of individuals and
vice versa.
Potential Future Directions
Introducing new concepts into any disci-pline is frequently met with resistance,as part of refining and clarifying emerg-ing paradigms (15). This Special Featureaims at gearing up this process formovement ecology. There is a growingrecognition of the need to understandand predict movement processes drivingbiological invasions, the spread of pestsand diseases, and the persistence of lo-cal populations and entire species inlight of ongoing global environmentalchanges. Combined with drastic im-provements in our ability to track andanalyze movement, it is hoped thatmovement ecology will pave the way fordeveloping a unified theory of organis-mal movement. Although this SpecialFeature provides only a taste of a muchbroader scientific enterprise (2), wehope it will help accelerate scientificprogress in solving our most urgent eco-logical problems, in further elucidatingthe research questions addressed hereand other important issues such as col-lective movements of groups, large-scaleconnectivity, and movements of micro-organisms and humans.
ACKNOWLEDGMENTS. I thank the Institute forAdvanced Studies in Jerusalem for hosting andsponsoring our group, and all group members,visitors, students, Special Feature authors, re-viewers, and editors Jim Brown and David Stopakfor their help, insight, and inspiration.
1. Nathan R, et al. (2008) A movement ecology paradigm
for unifying organismal movement research. Proc Natl
Acad Sci USA 105:19052–19059.
2. Holyoak M, Casagrandi R, Nathan R, Revilla E, Spiegel O
(2008)Trendsand missingparts inthe studyof movement
ecology. Proc Natl Acad Sci USA 105:19060–19065.
3. Holden C (2006) Inching toward movement ecology.
Science 313:779–782.
4. Getz WM, Saltz D (2008) A framework for generating
and analyzing movement paths on ecological land-
scapes. Proc Natl Acad Sci USA 105:19066–19071.
5. Wright SJ, et al. (2008) Understanding strategies for
seed dispersal by wind under contrasting atmospheric
conditions. Proc Natl Acad Sci USA 105:19084–19089.
6. Wittemyer G,Polansky L,Douglas-HamiltonI, GetzWM
(2008) Disentangling the effects of forage, social rank,
and risk on movement autocorrelation of elephantsusing Fourier and wavelet analyses. Proc Natl Acad Sci
USA 105:19108–19113.
7. Revilla E, Wiegand T (2008) Individual movement be-havior, matrix heterogeneity,and thedynamicsof spa-tially structured populations. Proc Natl Acad Sci USA
105:19120–19125.8. Bartumeus F, Levin SA (2008) Fractal reorientation
clocks:Linking animalbehaviortostatisticalpatternsofsearch. Proc Natl Acad Sci USA 105:19072–19077.
9. Damschen EI, et al. (2008) The movement ecology anddynamics of plant communities in fragmented land-scapes. Proc Natl Acad Sci USA 105:19078–19083.
10. Ovaskainen O, et al. (2008) Tracking butterfly move-ments with harmonic radar reveals an effect of popu-lation age on movement distance. Proc Natl Acad Sci
USA 105:19090–19095.
11. Lohmann KJ, Putnam NF, Lohmann CMF (2008) Geo-
magnetic imprinting: A unifying hypothesis of long-
distance natal homing in salmon and sea turtles. Proc
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12. Mandel JT, Bildstein KL, Bohrer G, Winkler DW (2008)
Themovementecologyof migrationin turkeyvultures.
Proc Natl Acad Sci USA 105:19102–19107.
13. Fryxell JM, et al. (2008) Multiple movement modes by
large herbivores at multiple spatio-temporal scales.
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14. Levin SA (1992) The problem of pattern and scale in
ecology. Ecology 73:1943–1967.
15. Graham MH, Dayton PK (2002) On the evolution of
ecological ideas: Paradigms and scientific progress.
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Nathan PNAS December 9, 2008 vol. 105 no. 49 19051
