Animal Navigation Question Page 09

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Animal Navigation: Magnetic Sense 2009 Questions Page

Kendall Sorensen, Horowhenua College 20 October 2009

Because the brain uses so much energy does the body use the extra body fat as energy in the first few years?



Wiki

Do you think the anomalies could be a reason why whales beach themselves?


Michael Walker, Scientist, University of Auckland. From the Seminar

Yes, magnetic anomalies are associated with strandings of whales, and in particular, it seems, areas where there are steep sided valleys are a problem. Particular species of whales are prone to strandings. Pilot whales, in particular, are prone to strandings in the spring and autumn months. They are deep water animals, and come into shallow water chasing squid. They don’t understand where they are, and end up going on to beaches and getting trapped onto land. Strandings also occur with magnetic storms from sun spot activity. The earth has solar winds that send blasts of charged particles that can cause auroras and also affect the magnetic feel of the earth, which can, in turn, also cause strandings of whales. Both variations in the magnetic field noise in both space and time can cause strandings.


Onehunga High School

Why is magnetic sense more beneficial than other forms navigation such as sight or smell? What selection pressures could have resulted in this being present in only a few species?


Michael Walker, Scientist, University of Auckland. From the Seminar

Animals have to move to harvest energy. The further and more efficiently an animal can move over distances to harvest energy, the more energy the animal can capture. The efficiency comes from the ability to navigate. This ability would have been selected for long before animals moved out into the land, when they lived in the sea. In the sea, you can’t see very far (at the most 50, 60 metres), and its very deep, and as soon as you go any distance offshore, you would lose sight of any land marks under the sea, and you would also be passively carried by currents, so you really need a specific system that would enable you to figure out your position without being able to see or smell anything.


Saint Cuthbert’s College

How does the bacteria and magnetite get inside of the birds?


Michael Walker, Scientist, University of Auckland. From the Seminar

The bacteria have been making the magnetite for three thousand million years, so it was developed very early in the history of life on earth. The birds make the magnetite themselves, as do fish. The ability to make magnetite may have been developed as a result of a indosymbiotic event where magnetic bacteria ended up inside something that later became a eukaryote (a cell with a nucleus.) Once the genetic programme is established, it’s pretty much there in everybody.


Horowhenau College.

How was the scanning electron micrograph of the magnetic crystals taken? Wouldn’t the magnetism deflect the electrons?


Michael Walker, Scientist, University of Auckland. From the Seminar

You can use the effect of the magnetite on the electrons to identify the magnetite (using electron defraction.). The electrons heat up, so you put magnetic bacteria in an electron microscope and you turn the beam up and then you cook the cell and blow it up inside of the electron microscope.


Green Bay High School.

Does the brain size have any effect on the amount of sensory cells?


Michael Walker, Scientist, University of Auckland. From the Seminar

Depending on the species, you can have quite significant differential growth of different parts of the brain. For instance, humans are very visual, whereas bats have brains where the auditory section is very developed, similarly with snakes that can detect infra-red or sharks that can detect electrical fields. Different parts of the brain can grow larger when those parts of the brain handle sensory information from particular sensory systems that are really important to that animal.


Onehunga High School.

Does high sensitivity to magnetic fields come at the expense of other sensory navigational senses?


Michael Walker, Scientist, University of Auckland. Jacquie Bay, Liggins Institute. From the Seminar

Not likely. The magnetic sense is very good for navigation over long distances (anything from 10km to 10,000 km) however its resolution seems to be limited to 1-2 km so it will get you close to home, but won’t take you into the front door. Tests have been done with homing pigeons where they put frosted contact lenses over their eyes where the birds could see it was light but they didn’t have much form vision. The birds were equipped with radio transmitters so they could be tracked. The birds flew to about 1-.5 km around their home loft, but did not enter it, supposedly because they could not see it. There are multiple sensory systems that are working together that enable the navigation so that it can happen.


Tangaroa College.

If so many different types of animals have a magnetic sense for navigation, why is it not present in humans?


Michael Walker, Scientist, University of Auckland. From the Seminar

Humans are very visual organisms and humans live on land where land propagates over very long distances so they can see a long way and use land marks pretty effectively and also would generally not need to move fast.


Horowhenau College.

Would pieces of magnetite still be present in the fossilized bones of birds?


Michael Walker, Scientist, University of Auckland. From the Seminar

The magnetite involved in the use of navigation is stored in soft tissue, so it may not be preserved in bones. However the magnetic bacteria carrying magnetite would be able to be detected, because it goes back three thousand million years ago, very early in the history of life on earth, so all fossils carried bacteria, and the magnetite is one of the earliest one known.


Wiki Question

Has the anomaly experiment been done with young birds to see whether it affects birds with no homing experience?


Michael Walker, Scientist, University of Auckland. From the Seminar

Such experiments have been done, and the evidence from homing pigeons suggests that if you take the pigeons away from their lofts when they are untrained, they will ‘home’, but they will not be able to ‘home’ very well or very fast.