Comments on: Turtles use the Earth’s magnetic field as a global GPS

By: Ed Yong

Ed Yong — Sat, 26 Feb 2011 22:02:24 +0000

@Ben – No one quite knows the details of how magnetic senses work in animals other than birds. If you check out the links at the bottom of this piece, you can read more about the weird quantum physics behind a bird’s magnetic sense. I’d think the turtles use something different because the radical-pair system provides birds with an internal *compass* rather than a map.

By: Ben

Ben — Sat, 26 Feb 2011 20:17:57 +0000

Does this have anything to do with quantum mechanics? http://www.wired.com/wiredscience/2011/01/quantum-birds/

By: Emmy

Emmy — Fri, 25 Feb 2011 17:08:59 +0000

@Ed Yong Thank you! I had not heard about cryptochrome. That may explain the article I read about the role of vision in red eft’s “magnetic compass”, which as of 2007 was not fully explained given that they may also use biogenic magnetite. You would know more about this than I, but the last I heard, red eft navigation research was still rather fuzzy.

My favorite animal navigation story is how seals navigate using just one star in the night sky.

By: Ed Yong

Ed Yong — Fri, 25 Feb 2011 11:59:35 +0000

@Rob – My wife and I believe that “Sir Turtlington” is the best possible name for a pet turtle. Well played, sir.

@Stonemason89 & @Kevin – There’s some evidence that power lines can disrupt the magnetic sense of cows. But it’s important to remember that it’s very unlikely any animal uses a magentic sense in isolation. It would complement vision, smell and more. Consider, for example, a migrating bird. If you shut down its magnetic sense, it might find it harder to navigate, especially in overcast conditions, but it could always use the stars, sun, landmarks etc.

Incidentally, this issue is also one of the many reasons why the magnetic sense is so fiendishly hard to study.

By: Andrew

Andrew — Fri, 25 Feb 2011 06:37:31 +0000

I get that they figure out where they are using magnetic fields, but how do these hatchlings know where they’re supposed to go? Turtle Maps?

And if turtles and other creatures are using “animal magnetism” to navigate, do they always attempt the most direct route (allowing for currents) as one would expect?

By: stonemason89

stonemason89 — Fri, 25 Feb 2011 04:07:01 +0000

So would artifically generated electromagnetic fields produced by human activity throw off the turtles’ instincts?

By: Rob Mitchum

Rob Mitchum — Thu, 24 Feb 2011 21:48:19 +0000

Great post, Ed.

My pet turtle, Sir Turtlington, has the strange habit of swimming determinedly against one wall of his tanks for 15 minutes at a time. He would always point the same direction as he was doing this odd exercise – the back wall – until we recently moved the tank 90 degrees while remodeling our living room. Now he swims against the left wall of the tank – the same direction as the back wall used to face. Magnetic fields, bored domesticated turtle habits, or is he just trying to get away from me and my wife?

By: Ed Yong

Ed Yong — Thu, 24 Feb 2011 19:14:51 +0000

Emmy there’s tons of literature. Check out the interview links at the bottom for a link to my last New Scientist feature, exactly about this. It’s a difficult sense to study for reasons described in Thorsten Ritz’s interview

By: Tom

Tom — Thu, 24 Feb 2011 19:12:00 +0000

@Kevin, the polarity of the field is unimportant. These turtles use the intensity and inclination of the field, neither of which change when the poles switch. There will be a short period when the poles are actually switching that inclination could be effected, but this would not be long.

By: Emmy

Emmy — Thu, 24 Feb 2011 18:55:16 +0000

Even cows do this. What’s amusing is how long it took humans to notice. I wish there were more literature on this sense – it seems as though we have not worked out if it is behavioral or physiological.

http://news.bbc.co.uk/2/hi/7575459.stm