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1、TheJournalofExperimentalBiology203,3745–3754(2000)3745PrintedinGreatBritain©TheCompanyofBiologistsLimited2000JEB2902THEDEEPFOVEA,SIDEWAYSVISIONANDSPIRALFLIGHTPATHSINRAPTORSVANCEA.TUCKER*DepartmentofBiology,DukeUniversity,Box90338,Durham,NC27708-0338,USA*e-mail:vtucker@duke.eduAc
2、cepted25September;publishedonWWW14November2000SummaryRaptors–falcons,hawksandeaglesinthisstudy–havesideways.Atdistancesof40mormore,raptorslookedtworegionsoftheretinaineacheyethatarespecializedforsidewaysattheobject80%ormoreofthetime.Thisacutevision:thedeepfoveaandtheshallowfovea
3、.Thedependenceofheadpositionondistancesuggeststhatlineofsightofthedeepfoveapointsforwardsandraptorsusetheirmoreacutesidewaysvisiontolookatapproximately45°totherightorleftoftheheadaxis,whiledistantobjectsandsacrificeacuityforstereoscopicthatoftheshallowfoveaalsopointsforwardsbutbi
4、nocularvisiontolookatcloseobjects.approximately15°totherightorleftoftheheadaxis.TheHavingtheirmostacutevisiontowardsthesidecausesaanatomyofthefoveaesuggeststhatthedeepfoveahastheconflictinraptorssuchasfalcons,whichdiveatpreyfromhigheracuity.greatdistancesathighspeeds:ataspeedof70
5、ms-1,Severalspeciesofraptorsinthisstudyrepeatedlymovedturningtheirheadsidewaystoviewthepreystraightaheadtheirheadsamongthreepositionswhilelookingatanwithhighvisualacuitymayincreaseaerodynamicdragbyobject:straight,withtheheadaxispointingtowardstheafactorof2ormoreandslowtheraptord
6、own.Raptorsobject;orsidewaystotherightorleft,withtheheadaxiscouldresolvethisconflictbydivingalongalogarithmicpointingapproximately40°tothesideoftheobject.Sincespiralpathwiththeirheadstraightandoneeyelookingraptorsdonotrotatetheireyesnoticeablyinthesockets,sidewaysattheprey,rather
7、thanfollowingthestraightthesemovementspresumablycausetheimageoftheobjectpathtothepreywiththeirheadturnedsideways.Althoughtofallontheshallowanddeepfoveae.Themovementsthespiralpathislongerthanthestraightpath,aoccurredapproximatelyevery2sonaverageinhawksandmathematicalmodelforan‘id
8、ealfalcon’showsthatthefalcons,andapproximatelye
