Bio 281 2011 Lecture 7 - Orientation and navigation

Orientation and navigation Orientation “Compass sense” X Orienting via the sun • Requires clock sense (time-compensation) • Clock can be shifted X Orienting via the sun pigeon (rock dove) • Pigeons clock-shifted by six hours • Moved west from home loft, released 0600 • Where did they go? mallard Orienting via the sun Orienting via the sun Why did they head north? Remember where sun is in the sky! Monarchs migrate more than 4500 km 1 Orienting via the sun Monarch butterfly migration Clock-shifting changes orientation direction No UV, no flight; orientation direction returns with UV Several northbound generations How do they know where to go? Monarch butterfly migration Constraints on using a sun compass Cyclic orientation hypothesis What about migration phenomenon makes this explanation appealing? Lincoln Brower Orientation via the moon Orientation via celestial cues • Not widely used by birds • Short distance movements by insects 2 Orientation via celestial cues Orientation via celestial cues Young indigo buntings in these conditions Stars rotate around Polaris Polaris and nearby stars moved to new position Oriented normally (south) Oriented 180° from Polaris Stephen Emlen planetarium experiments Birds orient correctly on clear night sky Regardless of whether they are clock shifted Orientation via celestial cues Young indigo buntings in these conditions Polaris blacked out Oriented normally (south) 1/3 stars around Polaris blacked out Stars rotate around Betelgeuse Oriented randomly Orientation via celestial cues Raised under spring photoperiod + shown spring constellations Raised under fall photoperiod + shown spring constellations Oriented north Oriented south Oriented 180° from Betelgeuse Orientation via celestial cues Orientation via celestial cues Conclusions: 1. Learn celestial orientation in first summer 2. Celestial map is not time-compensated 3. Physiological state is critical What if stars don’t move? pied flycatcher blackcap warbler 3 Geomagnetic cues Inclination map gives directionality (poleward vs. equatorward) Geomagnetic cues What problem does this create for trans-equatorial migrants? Geomagnetic cues Geomagnetic cues Magnetic field drifts, reverses Reversals don’t disrupt behavior, disturbances do Field is subject to disturbances Geomagnetic cues Field is subject to disturbances Geomagnetic cues N. perceived location Helmholtz coils Importance of redundancy Directionality determined by geomagnetic cues S. perceived location 4 Geomagnetic receptors What mechanism is responsible for magnetic sense? Magnetite model and radical-pair model Geomagnetic receptors garden warbler “Cluster N” in forebrain processes magnetic information from eyes magnetite (Fe3O4) granules Retina produces putative sensor molecules called cryptochromes Both retina and Cluster N produce ZENK protein during magnetic orientation Blue light causes pair of radicals with unpaired electrons Cluster N active in nocturnal migrants, not in sedentary birds Sensory deprivation decreases activity in migrants Piloting via landmarks Used when animal gets close to home Piloting via landmarks Navigation Ability to determine position in space X Pigeons’ use of human landmarks X Can be based on egocentric or geocentric cues “Map sense” 5 Navigation: egocentric cues Navigation: path integration Path integration helps ants estimate return vector Path integration = dead reckoning Cataglyphis fortis in Sahara Navigation: path integration Path integration: how do they do it? Ants trained to turn made return vector errors Calculate angles via polarized light Do these errors represent a real problem for Cataglyphis ants? Navigation: geo- and egocentric Landmark information retinotopically stored, used for image matching on return trip Calculate distance via internal pedometer Can pigeons navigate? 1. Path integration 2. Home-based gradient 3. Map sense (geocentric) Pigeons deprived of path information find their way home Does not require compass sense 6 Geomagnetic maps Geomagnetic receptors control Magnetic anomalies impair orientation high-intensity magnetic pulse silvereye juveniles Olfactory navigation? adults Olfactory navigation Evidence of olfaction in orientation deflector lofts Anosmic pigeons have difficulty orienting Olfactory navigation Do pigeons have an olfactory “map”? Mosaic map = odor sources represent discrete features in landscape Gradient map = spatial variation in airborne chemicals Problem = do gradients exist? Problem = limited area 7