[HN Gopher] A study on how turtles navigate using the Earth's ma...
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A study on how turtles navigate using the Earth's magnetic field
Author : gmays
Score : 102 points
Date : 2025-02-14 18:29 UTC (4 hours ago)
(HTM) web link (www.unc.edu)
(TXT) w3m dump (www.unc.edu)
| actinium226 wrote:
| At first I thought this was a mnemonic and then I quickly
| realized that DTUSD is probably not something people try to
| remember
| crazydoggers wrote:
| I wonder if it's actually a form of touch sensation. Some parts
| of the body might be minutely susceptible to magnetic fields and
| the feeling is distributed across areas of the turtle. The human
| finger can sense things only a micron in size.
|
| Something like miniscule tugging of the shell in certain
| directions being felt?
| adrian_b wrote:
| In some living beings it is known that they sense the magnetic
| field with microscopic magnetite crystals (i.e. iron oxide,
| Fe3O4), that are inside some cells.
|
| The magnetic field is sensed by the magnetic forces that act on
| the magnetite crystals, much in the same way as we sense
| gravity and acceleration by the forces that act on the otoliths
| in our inner ear.
|
| While in turtles it has not been identified how they sense the
| magnetic field, one of the possibilities is that they also use
| magnetite crystals located somewhere, at least for one of the
| two kinds of magnetic senses identified in them.
| hammock wrote:
| Very cool. So they have a map sense, and a compass sense, and we
| don't know how either of them work still.
| shellfishgene wrote:
| Is there really not a single link to the actual paper in the
| press release or did I just miss it?
| ysofunny wrote:
| there's only a link to the lab (that I was able to find)
| https://lohmannlab.web.unc.edu/
| throwaway1 wrote:
| Goforth, K. M., Lohmann, C. M. F., Gavin, A., Henning, R.,
| Harvey, A., Hinton, T. L., Lim, D. S., and Lohmann, K. J.
|
| Learned magnetic map cues and two mechanisms of
| magnetoreception in turtles. Nature (2025).
|
| https://doi.org/10.1038/s41586-024-08554-y
|
| https://www.nature.com/articles/s41586-024-08554-y
|
| Full text: https://rdcu.be/d9CgI (shortened link as provided on
| the page below)
|
| ( Provided by the lab's 'Publications' page:
| https://lohmannlab.web.unc.edu/research-publications/ )
| tombert wrote:
| Turtles are my favorite animals (other than humans, and sometimes
| even more than them).
|
| Mostly I think they're just cute, which is by itself a perfectly
| valid reason for an animal to be your favorite, but I've always
| been fascinated by their ruggedness. It's not weird for a turtle
| to live to 100 years old, and it feels like they can survive just
| about anything.
|
| Having a built-in GPS just makes them even cooler.
| pak9rabid wrote:
| I like turtles
| treebeard901 wrote:
| It's turtles all the way down
| Biologist123 wrote:
| My old man - an old-fashioned cat by anyone's description -- can
| pick true north anytime, anywhere. It's made me wonder if he has
| some kind of internal magnetic compass. And now, having read
| this, I wonder if this 'turtle skill' is latent in humans but
| only emerges in a rare few.
| pinoy420 wrote:
| Can he notice when it shifts? What happens when the magnetic
| field flips?
| swores wrote:
| You maybe meant "magnetic north", not "true north"?
|
| Or if you meant what you wrote, then fairly safe to rule out
| magnetism from being involved! (I suspect it's not involved
| either way, but I don't know anything)
|
| (Explanation of the difference between true and magnetic
| norths: https://www.rmg.co.uk/stories/topics/true-north-
| magnetic-nor... )
| blueflow wrote:
| I can sense magnetic fields of some strength through my nasal
| bone. Its like a metallic taste except its not where your taste
| buds are.
|
| I don't know if its rare? I think most people just never held a
| magnet against their face.
| Retric wrote:
| People get exposed to extremely strong magic fields when
| getting an MRI. So that's probably not it.
| daveguy wrote:
| On the surface this looks like a non-sequitur. I'm not sure
| what people getting exposed to strong magnetic fields while
| getting an MRI has to do with detecting a magnetic field.
| Are you saying something like "we should have been able to
| detect this"? This doesn't seem correct to me, because the
| magnetic field is through the aperture of the MRI -- ie
| head to toe in most MRI applications. If the MRI field is
| orthogonal to earth's typical magnetic pole, you wouldn't
| expect the same signal. I'm skeptical of a claim from a
| person that they can "detect" the earth's magnetic field,
| but I don't think "we have MRIs" implies anything about
| that ability.
| squeaky-clean wrote:
| They're responding to this part
|
| > I don't know if its rare? I think most people just
| never held a magnet against their face.
|
| If it were not rare, and simply because most people
| haven't held a magnet against their nose, people would
| definitely feel it during an MRI scan, since those are
| much much much stronger than any regular magnet. An MRI
| will rip a nose piercing right out of you, a regular
| magnet you'd have around the home couldn't do that.
| Retric wrote:
| "I think most people just never held a magnet against
| their face."
|
| I don't think they comprehend just how strong an MRI is.
| You don't need to be inside the machine for it to be the
| strongest magnetic field you've experienced, that's
| likely true if you're in the room nearby. Sure it falls
| as the square of the distance, but those suckers are big.
| https://www.youtube.com/watch?v=kLjxhuybFWo
|
| For comparison earths magnetic field is ~50 microtesla vs
| an MRI at 200,000 to 7,000,000, with 1.5 million
| microtesla (aka 1.5 T or 15,000 gauss) being common.
| 725686 wrote:
| You should probably approach some of the people investigating
| this.
| hnuser123456 wrote:
| I can do that, it's just having a mental image of the room and
| building I'm in, as well as the surrounding landscape, sky, and
| where the sun rises and sets. Even if I have to pass through a
| bunch of twisting corridors, there's just a mental arrow in my
| head that's always being updated in the background when I turn.
| colonCapitalDee wrote:
| Is that something that you learned how to do? Any suggestions
| for picking up this skill?
| deepsun wrote:
| Try playing First person shooter games that don't have a
| map. But as I said in a sibling comment, it's just
| orientation using memory, not a compass.
| vlovich123 wrote:
| When I was a kid at some point I just realized I could
| close my eyes and try to visualize my room that I knew
| really well. And then I'd imagine what it would look like
| if I looked at it making a 90 degree right turn. Then
| visualizing what happens if I walked out of the room, then
| up the stairs, etc. And then trying to make sure that as
| I'm doing these turns around corners in my house,
| connecting it with if I'm facing north/east/south/west
| until it became second nature to know that. And then as I
| got older I connected it implicitly with other senses of my
| surroundings (e.g. time of day + location of sun = you know
| which direction).
|
| I'd just sit for like 5-10 minutes at a time every day
| doing that until I got "bored" by the skill. Not
| necessarily sure if it's something you can practice as I
| know there's actual brain structural differences that can
| determine whether you have this skill and how advanced it
| is, and I'd imagine it's potentially harder to rewire your
| brain for this as an adult.
| deepsun wrote:
| No, that's just orientation, I can do that too. Playing
| first-person games like Descent improves the orientation.
|
| The true compass would be if you could be blinded, walked
| through some turns, and you could still pick up north, having
| no idea about how you got into the surroundings.
| boringg wrote:
| Yeah but you can always pick up based on observational
| cues.
|
| Real test would be spin around in a dark room without any
| cues can you pick out true north.
| jagged-chisel wrote:
| I think you just said the exact same thing.
| bongodongobob wrote:
| That's just spatial awareness. Put a giant magnet by his head.
| He'll still be able to do it.
| kuhewa wrote:
| Have you ever done any of these controlled experiments with
| giant helmets or blindfolds and elaborate movements to defeat
| orientation though?
| LeifCarrotson wrote:
| Lots of people have a good "sense of direction" in terms of an
| awareness of their surroundings that _keeps track_ of cardinal
| directions. It also correlates with an ability to use other
| indicators to reinforce or reacquire this awareness.
|
| Put me on some winding singletrack in the woods, or driving
| around an unfamiliar part of town, and I'll remember an
| imaginary map of where I've been and which directions I've
| turned, and be able to tell you where north is all day. If I
| forget, there are context clues everywhere - it's late
| afternoon here in Michigan so the sun is setting in the
| southern sky, pointing south-southwest. I'm currently in a
| windowless manufacturing facility, but I know where the front
| door is and I remember that's on the west side of the building,
| so I'm facing east. It helps a lot that many roads and
| buildings are indexed to be precisely aligned with the compass.
| It also helps that my Garmin GPS watch has a built-in compass,
| so if I ever need to shoot a bearing precisely, I train and
| recalibrate this sense of direction.
|
| But if you put a blindfold on me, sit me down on an office
| chair, spin it around for a couple minutes as you wheel me down
| the hall and into an unfamiliar room...after I have finished
| retching, I hypothesize that I'd have no sensation to tell me
| where north is.
|
| I appreciate the author's study design here - the source PDF
| [1] and linked website [2] describe feeding the turtles in the
| same pool, but exposing them to varied magnetic fields by
| surrounding the pool in a giant Helmholtz coil. It's not as if
| they flew the turtles alternately to New Hampshire and to the
| Gulf of Mexico, which might leave lots of context clues in
| light or smell or taste, but as if they effectively teleported
| them to an identical pool of water with slightly different
| magnetic fields.
|
| [1]
| https://www.nature.com/articles/s41586-024-08554-y.epdf?shar...
|
| [2]
| https://oceanweb.sites.oasis.unc.edu/www.unc.edu/depts/ocean...
| climb_stealth wrote:
| Hah, I thought you meant a literal cat.
|
| Our dogs do that. There's a building we used to go up with six
| elevators. Three on each side of the hallway facing each other.
| Without hesitation the dogs will pick the correct direction to
| go coming out of the elevator. Whereas I always had to check
| because it all looks the same and depending on which side the
| elevator is on you have to turn left or right.
|
| It's like they have an innate sense of where they are.
| ryanianian wrote:
| Could there be a different smell or air-flow coming from one
| side versus the others?
|
| My apartment building has identical elevator lobbies. I
| thought my dog was smart by not leaving the elevator on
| seemingly identical incorrect floors. But actually I think
| she just knows what home smells like.
| pinoy420 wrote:
| It explains the phenomena and the response but not the mechanism.
| Anyone know?
| trhway wrote:
| >But no receptor like that has been identified for the magnetic
| sense, and the mechanism remains unknown
|
| Wasn't such a molecule found in bird's eyes?
| defanor wrote:
| It is one of the proposed mechanisms, but apparently it is
| still unclear what is actually used [1,2].
|
| [1]
| https://en.wikipedia.org/wiki/Magnetoreception#Proposed_mech...
|
| [2] https://www.scientificamerican.com/article/how-migrating-
| bir...
| PicassoCTs wrote:
| So if the poles flip- there navigation fails?
| nashashmi wrote:
| I wonder if bats have the same senses to magnetic field.
| rapind wrote:
| More proof we're just flying around on the back of a turtle on
| the back of a turtle...
| acyou wrote:
| When they first figured out that turtles use magnetic fields to
| navigate, they placed them in kiddie swimming pools in someone's
| backyard and placed large electromagnets next to the swimming
| pools. Multiple turtles reliably oriented themselves according to
| the magnetic field direction corresponding with their seasonal
| migration direction.
|
| This paper is claiming something different, something to do with
| a particular magnetic field having a behavioral association.
|
| Lot of question marks and need for some more context. Why would
| turtles evolve the dancing behavior? Does it have to do with the
| kind of food they eat and how they get that food? No, turtles did
| not evolve like dogs to dance and do tricks for food.
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