[HN Gopher] A study on how turtles navigate using the Earth's ma...
___________________________________________________________________
A study on how turtles navigate using the Earth's magnetic field
Author : gmays
Score : 161 points
Date : 2025-02-14 18:29 UTC (1 days 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.
| stevenwoo wrote:
| There are tracking studies on some of the turtles that navigate
| from Gulf of Mexico to Atlantic and back that appear to know
| where the favorable currents are so there is alot of genetic
| memory like the Monarch butterfly migrations taking multiple
| generations to get from North America to Mexico.
| 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
| carrozo wrote:
| oh. more turtles.
| joshuaturner wrote:
| I just find their karate abilities quite remarkable
| 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.
| blueflow wrote:
| Most people haven't been in an MRI, either. I only know
| about their existence from TV.
| Retric wrote:
| That doesn't really matter here. ~300k people in the US
| get an MRI per year (significantly more are near the
| things) and they have been around since the 1970's.
|
| If simply waving weak magnetic fields in people's faces
| were enough for anything close to 1% of people to notice
| then it would be common knowledge at this point.
|
| When the signal is strong enough you don't need careful
| experiments to pick out the difference. IE the rest of
| the universe outside of earth isn't made of antimatter
| because our telescope's aren't on fire. https://what-
| if.xkcd.com/114/
| daveguy wrote:
| Let me break it down for you.
|
| In electromagnetic fields both an electric field and a
| magnetic field are produced. They are orthogonal to one
| another (in 2D with 2 vectors this is perpendicular,
| orthogonal is when the vector is in a different dimension
| with respect to multiple reference dimensions). So,
| detection of a magnetic field could be based on the
| detection of this orthogonal electric field in the
| presence of a magnetic field. Highly sensitive electrical
| detection cells triggered by a magnetic field would be
| orientation specific, because the more "out of
| orientation" the less strong the signal.
|
| Also, we could easily have chalked this effect up to a
| "weird side effect" of metallic taste during MRI[0] which
| would be more pronounced when the head is moved during
| the MRI[1].
|
| Hopefully it is clear now why "I think lots of people
| would have noticed it" is not a great argument against
| the possibility of humans evolving the detection of
| magnetic fields. Please let me know if I can clarify
| anything.
|
| [0] https://mriquestions.com/metallic-taste.html
|
| [1] https://pubmed.ncbi.nlm.nih.gov/17969179/
| Retric wrote:
| Sure, you can clarify why you think someone walking up to
| and then getting inside an MRI would only experience a
| specific orientation?
|
| It's obviously false, but I'm curious why you assume it
| would be the case.
|
| As to your example, that's _well known_ even with only 1
| in 20 people experiencing it, thus demonstrating my
| point.
| daveguy wrote:
| Apparently you have not had an MRI or studied MRI.
|
| 1) The people operating the MRI are outside the magnetic
| field.
|
| 2) The patient in the MRI is oriented such that the
| magnetic field is directed from head to toe (where the
| effect on sensing apparatus in place which might detect
| earth's magnetic field while standing or sitting would be
| approximately zero, _no matter the magnetic strength_ ).
|
| 3) Instructions for the patient in the MRI are to remain
| as still as possible to reduce imaging noise. So, most
| patients do not move their head much at all.
|
| I'm sorry you seem to be unwilling to even consider the
| physics, and apparently didn't bother to look at the
| second reference. I am also sorry that I am having
| trouble explaining concepts that most biomedical
| engineers readily understand as the reasons why "but
| MRI!" is not a valid argument. Regardless, I hope you
| have a wonderful weekend.
| Retric wrote:
| > The people operating the MRI are outside the magnetic
| field.
|
| That's not how magnetic fields work. It's not some sci-fi
| force field that cuts off instantly, the field drops off
| quickly but it doesn't disappear. Which is why as
| mentioned in your second link _workers noticed the
| effect_.
|
| > unwilling to even consider the physics
|
| Again, you're seemingly unaware of the actual physics
| involved.
|
| MRI's operate via two different electromagnets which
| create magnetic fields. A really strong one which is on
| 24/7, and a separate field which is turned off and on in
| operation and thus doesn't correlate with earths magnetic
| field.
|
| So when you walk up to the machine you're "in" the same
| giant field just as when you're inside the machine (or
| even sitting in some other room in the hospital if we
| want to be pedantic). This is why it's relatively common
| for chairs etc to be yanked across the room and smack
| into the machines.
|
| And thus, if people could directly sense the orientation
| of earths magnetic field, being anywhere near an MRI
| would be a really obvious and novel experience.
| daveguy wrote:
| Oh good, they noticed the effect too. It's almost as if
| many people experience the effect, but somehow to you
| it's impossible for any humans to be able to take
| advantage of the effect at lower field strengths.
|
| When you walk up to the machine it's not turned on. Then
| non-participants go to the small enclosed control room
| and then the magnet is activated. Every time you respond
| you reveal how little you know about MRI and weaken your
| case. You should stop while you are behind.
|
| Also, you should lookup faraday cage. They're like magic
| to someone who has never heard of them, and they're used
| in MRI control rooms.
|
| I feel sorry for your apparent inability to accept you
| might be ignorant about anything. I hope you grow out of
| it one day. Enjoy your weekend, I won't be responding
| again.
| Retric wrote:
| > When you walk up to the machine it's not turned on.
|
| False. MRI: https://mriquestions.com/is-field-ever-
| turned-off.html
|
| _Permanent magnet scanners are permanently "on" by
| definition.
|
| Resistive electromagnet scanners, in theory, can be
| turned on and off. However, it may take 30-60 minutes for
| their magnetic fields to stabilize after being off and
| hence they are generally left continuously on during
| daily operations. To save electricity, they are usually
| turned off or have their power levels reduced after
| hours.
|
| Superconducting scanners remain on at all times as long
| as superconducting temperatures are maintained. The main
| field may be ramped down for servicing in a controlled
| manner with minimal loss of cryogens in about 30 minutes
| and restored in a few hours, but this is performed only
| occasionally. In the event of an emergency, all
| superconducting scanners have a "quench" button that
| releases liquid helium into the atmosphere and turns
| their fields off within a few seconds._ Dumping that
| helium is inherently expensive and only done in a serious
| emergency.
|
| "Faraday cages cannot block stable or slowly varying
| magnetic fields, such as the Earth's magnetic field (a
| compass will still work inside one)."
| https://en.wikipedia.org/wiki/Faraday_cage
|
| > then the magnet is activated
|
| _A_ magnet not _THE_ primary one. Here's a reasonable
| though simplified explanation of why there's multiple
| magnets involved:
| https://www.youtube.com/watch?v=NlYXqRG7lus
|
| Anyway, it's clear you have many fundamental
| misunderstandings so I can see how you'd come to such
| wildly inaccurate conclusions.
|
| > it's impossible for any humans to be able to take
| advantage of the effect at lower field strengths.
|
| The actual literature investigating the effect describes
| why it doesn't work on earths magnetic field.
| daveguy wrote:
| Someone who does not know that MRI has variable field
| strength is someone who truly does not know the basics of
| MRI.
|
| Maybe this source will clue you in as to why your
| understanding of MRI is fundamentally flawed:
|
| https://pmc.ncbi.nlm.nih.gov/articles/PMC4632105/
|
| Good luck buddy.
| Retric wrote:
| I'm aware, which is why I've said repeatedly there's
| multiple magnets involved one vastly weaker than the
| other which is kept on...
|
| But wallow in your ignorance, it brings a little dark joy
| knowing _I am simply better than you in a real tangible
| way._
|
| You're unable to erase signs of your failure, and as long
| as HN lasts anyone can know my dominance.
| daveguy wrote:
| Hahaha. Thank you for the laugh. It must be great walking
| around with such an unwavering sense of superiority.
| Enjoy the dark joy of your perceived vast superiority and
| try not to have a breakdown when you come crashing back
| to reality. May you never crash and forever be certain in
| your vast delusions of superiority all the rest of your
| days. Very rarely have I seen a more foolish certainty.
| Congratulations.
| Retric wrote:
| You could join on the dark side.
|
| All it takes is learning how the fundamental forces of
| the universe work.
|
| Ok, in this context having a friend who works in medical
| imaging was useful, but that's just a trivial matter.
| 725686 wrote:
| You should probably approach some of the people investigating
| this.
| GrumpyNl wrote:
| Sounds more like you can taste static electricity.
| 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.
| kQq9oHeAz6wLLS wrote:
| I found "Natural Navigator" by Tristan Gooley to be a
| fascinating read with a lot of good ways to train your
| navigation skills without instruments.
| 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.
| burnished wrote:
| I think its different - you're keeping track of something,
| whereas some creatures can evidently just feel the earths
| magnetic field.
| 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?
| Biologist123 wrote:
| I can just imagine the experimental set-up..."son, what the
| f** are you doing". "Chill out dad, I'm just going to blind
| fold you and run some electricity through this coil, and you
| have to tell me where New Bedford is, got it". "I told you
| you ain't getting no inheritance". Etc
| 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.
| climb_stealth wrote:
| Not sure, but I wouldn't think so. They'd basically spring
| out of the elevator with no hesitation.
| AngryData wrote:
| Atleast when I was younger I always felt like I could point
| towards north within 20-30 degrees at any time. I tried testing
| it out many times, and was right the vast majority of the time,
| even when trying to eliminate possible subconscious factors
| like sound reflections and what surface I was standing on. We
| do technically have the right associated nerves and structure
| for it, but obviously underdeveloped compared to animals who
| use it to live and survive, so I would totally believe it is
| possible to some extent, atleast among some people.
|
| I would attribute part of it to practice, because when I was
| younger I spent a lot of times in the woods where you can
| easily get turned around following animal trails and skirting
| around obstacles, and finding your way back out accurately was
| extremely helpful.
| kaushikt wrote:
| Same with my old man. He is a farmer in southern India. All the
| farms nearby are super identical with tall beetlenut trees. Im
| often confused where we are and which direction is the house,
| he is not. He has set over a 100 water gates across the farms
| and the instructions he gives is always east face or turn the
| gate north facing as an example.
| hn_throwaway_99 wrote:
| The aboriginal language Guugu Yimithirr,
| https://en.m.wikipedia.org/wiki/Guugu_Yimithirr_language, uses
| cardinal directions instead of relative, e.g. "That man is to
| the west of her" instead of "That man is to the left of her",
| which of course means that speakers need to be aware of the
| direction they are facing at all times, and thus these people
| have a remarkable sense of direction.
|
| Can't remember where I first heard about this, I think it may
| have been a Malcolm Gladwell book, but in any case if you
| search you can find lots of articles on the topic.
| burnished wrote:
| Foxes can, and a brief search suggests cats may also?
| 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.
| gwerbret wrote:
| > 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.
|
| The paper (which is here [0] by the way, they failed to provide
| a link in the article) indicates that these turtles have been
| known to orient themselves using magnetic fields. The new
| finding is that they're also able to use magnetic fields as a
| map -- they can identify a location based on its specific
| magnetic fields. And apparently, the "mapping" involves a
| different neurobiological mechanism from the "orientation".
|
| 0: https://www.nature.com/articles/s41586-024-08554-y
| wkyleg wrote:
| Interesting that they don't know exactly how they are perceiving
| magnetism. I suppose it could be an internal brain mechanism, but
| if that were to be able to operate without direct outside sensory
| input, there might be all kinds of other potential latent
| abilities in animals.
|
| More likely, this might be the same as the mechanism which exists
| in birds, who can effectively see the Earth's magnetic field in
| their eyes, although an internal magnetic detection system
| present in animals would be much more interesting. See
| https://royalsocietypublishing.org/doi/10.1098/rsif.2019.029....
| Birds essentially perceive the Earth's magnetic field through a
| chemical process in the receptors for red and green light in
| their eyes, and are believed to have special cells in their beak,
| brain stem, and possibly their vestibular system as well. It can
| be disrupted fairly easy by magnetism or different wavelengths of
| light.
|
| There are obvious other strange implications of this as well,
| although I'm not sure how much real evidence there is to support
| them. For instance, there are many concerns about the effects of
| EMF exposure, as well as that EMF can affect plant life. There is
| research on magnetic and electric brain stimulation as well. At
| the most out-there level, there is the research into remote
| viewing and things like telepathy. So, to whatever extent this
| actually exists, there are interesting implications for the
| phenomenological experience of other forms of animal life.
|
| Regardless, it is interesting to see research that is actually
| showing new and intriguing things regarding different forms of
| perception (I guess this is arguably ESP, or at least a new
| sense) that are not complete crank nonsense. I've always felt
| like my sense of direction was a sort of 6th sense; I guess it
| really could be.
| samldev wrote:
| Go Heels!
| dahart wrote:
| > "The big question is always the mechanism," Goforth said.
| "What's the mechanism and what is the sensor? We know that for
| the visual sense, you have eyes; for the sense of smell, you have
| a nose; and for hearing, you have ears. But no receptor like that
| has been identified for the magnetic sense, and the mechanism
| remains unknown."
|
| Interesting, I just barely listened to a Radiolab episode about
| magnetoreception in birds today [1]. The mechanism is thought to
| be cryptochrome, a type of protein that exhibits quantum effects
| when exposed to blue light [2]. The RadioLab story mentioned this
| mechanism was first proposed in the 70s (I think?) and it was
| heresy at the time a didn't get published. Now there's a SciAm
| article about it [3], and lots of blog posts. I wonder why this
| isn't mentioned? Isn't there a pretty good chance the mechanism
| is the same?
|
| * edit: BTW while listening to the podcast I was reminded of
| Haidinger's Brush [4] - the fact that many humans can see
| polarization, once they know what to look for. I wonder if it's
| potentially related to navigation since the polarization effect
| is strongest at 90 degrees from the sun... i.e., generally north
| and south, in the morning and evening, for much of the earth.
|
| [1] https://radiolab.org/podcast/quantum-birds
|
| [2] https://en.wikipedia.org/wiki/Cryptochrome#Magnetoreception
|
| [3] https://www.scientificamerican.com/article/how-migrating-
| bir...
|
| [4] https://en.wikipedia.org/wiki/Haidinger's_brush
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