BIEB 166 Lecture 11 (WI13)

3 Pages

Biol/Ecology, Behavior, & Evol
Course Code
BIEB 166
James Nieh

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Lecture 11 Migration Lobster migration - For escape from stormy weather, safer in deeper water - Safety in being in large group - Might not have a leadership position Magnetotaxis revisited Hammerhead sharks (A.P. Klimley) - Sharks make nightly migrations to feed, with the same path everyday ○ The path is not straight - Shark tracking using ultrasonic telemetry transmitters - Data: depth, temp., light, direction of travel - Bottom topography, magnetic field topography - Sharks follow geomagnetic abnormalities - Sensing and respond to the Earth's magnetic field 1. Geomagnetic anomalies - Highly correlated with the deviation of the magnetic field - Orienting to the strong magnetic field Homing pigeons (Keeton and Walcott) - Magnetimpaired homing on cloudy days - On the cloudy day, when the magnetic distractor is on, they cannot orient their path - Even the magnet is turned on in a sunny day, it doesn't distract the bird - Bird's path randomly scatter Migratory bird orientation - Calibrating to the earth's magnetic field for long distance migration 1. Trip restlessness of migratory birds in Spring and Fall (measure with Emlen funnel cage) - In the fall, they tend to go South, and in spring, they tend to go north 2. Travel at night, can see stars (which gives true north) - The number of degree for the true north changes through time - Magnetic north ≠ true north - Finding true north: axis of rotation of celestial cues--polarized light during the day, stars at night 3. Planetarium Studies - Artificial stars, change location as the experimenter wanted - The birds follow the direction of the stars (even the location of the stars change) 4. Savannah Sparrow Experiment - Place birds in a cage where they can see the stars - They can see and learn where the true north is by learning the movement of the stars - While they see the sky, expose them to a strong artificial magnetic field - Wire coils producing strong artificial magnetic field ○ Create the magnetic field of the north direction (90 degrees off relative to the stars) - Put them in a dark room (no sky view) and test their orientation to the Earth's magnetic field ○ They have to use their magnetic senses to orient their direction - If they could see the stars, they'd follow the way of the star, otherwise, they'd follow the magnetic field they could sense Sun compass orientation (special case of menotaxis) Trail-following ants (Santschi) 1. Mirror experiment 1. Mirror experiment - Ant is walking back home from food source - Menotaxis ○ Orienting an fixed angle of sun, in order to get home ○ The sun has to be on my right in order to make sure I'm to the right direction - Ant sees sun from opposite direction (from the mirror) ○ From 180 degrees of the right direction - Orientation of a fixed angle to the sun
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