How do magnetically-sensitive animals react to a reversal in Earth's field?

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Offline FredL

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See turtles (logger head) return to the same beach they were born on to lay their eggs.  Apparently they refuse to lay eggs on any other beach.  They use the earth's magnetic field for navigation. 

How do such species survive a reversal of the earth's magnetic field?
« Last Edit: 12/05/2009 00:11:33 by chris »


Offline Karen W.

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Welcome to the forum FredL!

I don't really know the answer to your question, but it is a sad thought that they may not suvive in those circumstances!

I wonder if they can be slowly coaxed to change their directions and breed on another island?

"Life is not measured by the number of Breaths we take, but by the moments that take our breath away."


Offline Don_1

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It is true that sea turtles do return to the beach where they were hatched to lay their eggs, just as salmon return to the river in which they were spawned, to mate. But the Loggerhead is unique in that tagged individuals have been known to lay eggs on different beaches.

It has been suggested that we are heading toward a polar flip in 2012: Doomed, we're all doomed it tell you! Run for the hills
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Offline Bored chemist

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Is the answer to the thread title "the same as they did last time"?
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Offline chris

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Very good BC!

The answer is that animals must be able to combat the effect of magnetic polar reversal since this occurs, on average, every 200,000 years or thereabouts. Since many species are millions of years old, this suggests that there have been several pole-flips over this time, arguing that they are capable of adapting.

The most likely answer is that since the flip is actually a more gradual reversal - over several thousand years rather than an abrupt phenomenon - there is sufficient time for magnetically-sensitive animals to respond and adapt their behaviour. It's also the case that the internal compasses in species like this are not fixed but can be recalibrated, usually with reference to the Sun's setting position, which is always west. This means that regardless of the position of magnetic north the animal always knows a fixed bearing.

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