Dr Richard Holland, discussed the orientation and navigation in bats also mentioning why they are an ideal model animal for homing and mammal migration.
Birds may have been thought to be an equivalent study species for bats, however they orient themselves by very different methods.
Birds use the inclination of the earth’s magnetic field as a compass and map by which to navigate, however Richard Holland’s research showed that homing bats instead use a ‘sunset calibrated magnetic compass.’
The homing bats used, showed that they calibrated their compass using the band of polarised light at sunset, which was tested by rotating the band by 90o (causing the bats to travel 90o in the wrong direction); migrating bats used the suns disk to calibrate their compass, which was tested by presenting the bats with a mirrored image of the sunset, causing them to travel 180o in the wrong direction.
However bats do not have innate migrating direction, as juveniles travel in many directions as opposed to a more focused direction of travel for multiple individuals.
The way they detect electromagnetic energy is undetermined
Bats use their compass by detecting the earth’s magnetic field, however the way in which they use it is still undetermined.
They appear to use a magnetic particle as their compass, which can be tested by exposing them to a magnetic pulse, disorienting their magnetic compass. They also become disoriented when their cornea is anaesthetised (a test done on mole rats, to similar affect).
This showed that the magnetic particle in use may exist somewhere in the eye, however it has not been definitely proved to exist there.
He concluded by drawing up that bats navigate using a sunset calibrated compass (using either the suns disk, or bands of polarised light), which is detected via a magnetic particle potentially existing within the eye.
It was fascinating
The methods used and effort put into the studies was fascinating, and it was encouraging to see the amount of hands-on studying being done.
This seminar has made me strongly contemplate looking into hands-on work with animals, such as radio-tagging; however more than everything I find in particular the Function and mechanism questions of great interest, and I believe it would be extremely fulfilling to help answer them, and will also be looking into ways in which I may go about asking and researching them. I also loved the opportunity to see how an individual’s physiology and mechanisms can change to better suite its behaviour, and am wanting to see more of this in the future, in my own research or others.
The research can be found online [1], [2].
Lukas Edwards, 14th February 2020
Biology Express: Zoology 