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So, earlier, I read online (http://io9.com/butterflies-remember-a-mountain-that-hasnt-existed-for-509321799) that Monarch butterflies veer east during their southward migration to avoid a mountain that no longer exists. If this is true, how do butterflies know to continue avoiding the "mountain" after countless generations, and does it have to do with evolution? Do other animals have similar abnormalities in their migration routes?

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  • $\begingroup$ here's the original paper - I couldn't find support for this hypothesis in the paper but that was only a quick skim read (and the manuscript only features one brief reference to lake superior) jeb.biologists.org/content/199/1/93.full.pdf $\endgroup$ – rg255 Jul 3 '15 at 7:54
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If you think about it, monarchs must have a pretty strong genetic component to migration since often they only make one round trip at most in a lifetime. But its not as simple as passing a map in the DNA.

If a mountain springs up on the route, the 'common sense' of the butterflies are still operational and they will tend to find their way around it.

The paper discussed here is older. More recent Monarch butterfly migration of some genetics that have been done shows some traits that are related to migration patterns by sampling over many butterflies whose patterns vary tremendously.

Glancing over the paper, I'd say that there may be some 'muscle' memory in migration, but probably the mechanisms encoding the route of migration are not yet discernable. This is far from something we understand well.

The insect is following patterns of behavior but doesn't turn into a robot just because its migrating. Migration patterns are probably linked to a series of environmental cues.

Changes in climate or shifts in magnetic fields can change migration patterns. Butterflies would be very different than say migratory birds in terms of the social and environmental markers for migration.

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    $\begingroup$ I think it depends on the route taken and which population you're talking about (western vs. eastern US), but my understanding is that both migration directions are multi-generational, so any individual is not necessarily covering the same ground as its parents did. $\endgroup$ – MattDMo Jul 3 '15 at 14:43
  • $\begingroup$ Thanks for the review @MattDMo I can't find any reference of Monarchs living longer than 8 months. I just re-reviewed several sites. post a link? the wikipedia article seems to refer to the fact that Monarchs have mulitple breeding waves (called generations) over the year where their lifespans can vary tremendously (4 wks <-> 8 mos). $\endgroup$ – shigeta Jul 4 '15 at 13:02

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