How Animals Navigate Without GPS (Magnetic Fields, Instinct & More)

Ever wonder how birds, eels, whales, or even bugs find their way without a GPS? In this episode of Wildly Curious, Katy Reiss and Laura Fawks Lapole uncover the jaw-dropping science behind animal navigation.

From locusts using sky maps and magnetic fields, to eels migrating thousands of miles to a secret oceanic birthplace no one’s ever seen (seriously), and birds that may be using quantum mechanics to see the Earth’s magnetic field—it’s a global tour of natural way-finding.

🌎 How do animals "see" magnetic fields?
 🧭 What is magnetoreception and how does it work?
 🌌 Can birds actually use quantum mechanics to navigate?
🐟 Why do we still not know how eels reproduce?

This episode explores what researchers are learning—and why the military, ocean shippers, and conservationists are all paying attention.

🎧 Perfect for curious minds, nature nerds, and anyone who's ever questioned how animals seem to have better internal GPS than humans with smartphones.

Transcript

katy: Do you, you have nature news? Do you wanna do yours? I have nature news too.

laura: Oh, it'd be crazy if it was the same thing.

katy: It would be crazy. Go ahead. Let's see. I,

laura: mines paleontology.

katy: no, mine's different. Okay. Whew.

laura: someone send me this one. And it was pretty cool. So a previously unknown reptile species, was discovered back in the thirties, but they actually hadn't analyzed it yet. Not until 2019,, they just live in some museum for forever.

Finally, someone's we should look at these bones.

katy: Oh, I, I did see this. I did see

laura: Okay, cool. So yeah, it was, it's named Amira. It lived 247 million years ago in what's now France during the Trias. But what's really cool and unique about this fossil is that had this interesting skin crest, that was neither feathers or scales.

 When they analyzed it with a CT scan, they were like, this is, it's a new type of skin structure they've never seen before.

katy: Huh,

laura: So they're not sure, so during this time [00:01:00] period, they said that there wasn't as much competition with through, this was just after an extinction event.

So like nature is open, baby, like you can evolve however you want. So they did. And I guess

katy: That needs to be on a t-shirt, by the

laura: you can evolve however you want. Like just, and 

katy: is over right now. Now evolution is open. Evolve into whatever you want,

laura: so I guess without selection pressures, lots of different adaptations can happen. And so there was this new type of skin structure.

They're assuming like any type of crest that it was obviously for signaling or breeding or some kind of

katy: Or was it,

laura: literally no idea. But it's, just the fact that there's more than just scales and skin out there. And there might not, there isn't any more, but that doesn't mean that there wasn't.

So we just have to keep an open mind, like when we're looking at this kind of stuff, it's practically like looking at aliens. We know they're carbon based, but sky's the limit otherwise.

katy: I've been seeing a lot, from that I saw a lot of memes because I had a lot of people online send me [00:02:00] that story. And then from that I had a lot more than people send me. There's been all these meme circulating about because hair can't be fossilized, we can't roll out that dinosaurs look like, and then it's just dinosaurs with a bunch of different hairdos and stuff like that.

They had so many people send them to

laura: I keep seeing ones online where it's like, what if they were fatter than they were?

The best one I saw they were like, what if a T-Rex was actually had the body type of sparrow? Because Sparrow, they've got the same bones, but like sparrows have that head and then that chunky little bird body. What if the T-Rex was more like that? Not lean? Yeah. Like

katy: yeah,

laura: what's your nature news? 

katy: Mine is that killer whales have been found to use kelp brushes to slough off rough skin.

laura: I did see this. Yes. Yes.

katy: Yeah. So,

laura: form of Allop. Preening or something.

katy: Yeah, essentially. So , they found, at first, I say they used drones with quote unquote, really good zoom is what they kept emphasizing because they [00:03:00] wanna make sure that they understand that the drones aren't messing with the whale behavior.

It literally is super high, far away. They're zooming in really far. And once they realized what to look for, once they saw this and then they were like, oh, that's what they're doing. Then they picked up on it like that. They were frequently doing this. So they go down, they grab certain types of kelp, like not, not all of it.

So they're, they're looking for certain

laura: We all have our favorite brushes.

katy: no, right.

laura: I'm not using one of those circular ones.

katy: No. Right. And so they, they pull it out and then they like rub their bodies, you know what rub it between their bodies and stuff like that. And it's I don't know, like a a, a exfoliator, yeah, yeah. A whale loofah. So.

laura: use each other. 'cause they don't have hands.

katy: No, right. Is that I mean? Yeah,

laura: it up and down.

katy: yeah. Right.

Well, on today's episode, that was all the Nature news, but on today's episode we are talking about nature's GPS and How Animals Find Their Way [00:04:00] without

laura: Without tools. Without

katy: Yeah. Without tools. Yeah, without tools other than in their nos. So we've done a previous episode on migration and we've talked a about a lot of these things, but we've never really gone in depth into the well, how, like we talked about like the Wild Beast,

laura: Or like I talk, I definitely remember talking about what does the migration look like?

katy: Yeah. Why does migration look? But we didn't go into like the biology. Yeah. The how of it. So that's what we're gonna go into this episode is a little bit more of the how. So Laura and I each picked different animals. And this one we knew what each other, 'cause we just took groups of

laura: Yeah. So we don't know what species, but we do know, like we, we tried to see if we could have some variety. Like I have an insect. And a fish And you have a

katy: Birds and

laura: Okay. Yeah. Because a lot of planet Earth, a lot of these animals are migrating, using very similar thing like brain tools. But I was lucky enough that my two species do not use the same type, which [00:05:00] I was pretty stoked

katy: Oh, good.

laura: And if you don't mind, I'll go first because it actually ties off of last week.

katy: Oh, perfect.

laura: last week you should go back and listen to it. We did swarms of locusts and I just happened to choose the desert locust as my migratory species. I was like, perfect. So I am not gonna go into the biology of everything because you should just go back and listen to our

katy: And it was a,

laura: It was

a good 

katy: episode, guys. Yeah. So it wasn't super long, so yeah, go listen to that one.

laura: get your biology.

katy: Yeah, they're overstimulated.

laura: Yeah. Hashtag relatable. So migratory locusts, , which we did talk about in our swarms episode, and as Katy said real quick, they go through two phases, the solitary and the gregarious. And both of them do migrate. It's just that the swarms do it in way bigger numbers.

But how do they know where they're going? So as you can imagine, you might wanna know where a giant swarm of locus is headed next. Right? They, so you can predict where they're going. And that's, we did not cover that last time, which I'm really glad about.[00:06:00] 

katy: and I actually mentioned that I just didn't have, I was like, this is a mini episode. I couldn't go into it too

laura: Yeah. Well now we do.

So it isn't just about the food. Like when we think of locus, we think of like bottomless pits of eating, which we talked about, and that's how devastating they are. But is it that they're following their bellies in just any willy nilly direction? No. So scientists think that this swarming behavior.

Is not just to help them survive in an area with harsh and changing conditions. Because these are, in particular, as Katy talked about, these migratory locusts. Most of them they're desert locusts really. Or migratory is kinda like a catchall term, but mostly it's the desert locust.

They're dealing with because they live in a desert drought and rain and these conditions vary and they're really harsh. So of course they're gonna swarm to get away from these conditions. But they actually think that it's also to colonize new areas after rainfall. So these locusts want to find the rain

katy: Yeah,

laura: their eggs can only be laid in moist soil.

They cannot lay them [00:07:00] where it's dry.

katy: The desert, locusts, and

laura: desert, but so yeah, apparently they have to have, there has to be enough water in the soil to be absorbed by the egg for them to survive. So they're like, gotta find a rainstorm. 

katy: good lord. 

laura: thing to do. So they need to follow the rain and they're moving between seasonal breeding areas.

Three of them spring, summer, and winter. I don't know if they just don't really have a fall or that they're just not really moving in the fall. But between those three seasons, they're moving all over Northern Africa and the Middle East, just all over. Some of it's back and forth. Some of it's more circular, but they definitely are doing something and they're following these patterns.

So the swarms themselves, they do that. They migrate in two different ways during when they're solitary versus swarm. So the swarms move in the daytime, which is different than when they're solitary and they're nocturnal and they move forward as a giant front, like cloud front. They're just going forward in a.

katy: Which is the terrifying

laura: And in a [00:08:00] rolling movement, so like the guys at the front, they land, they eat for a while, they let the ones pass over them, and then once things start to clear out, then they get up and move again. So it's just a constantly rotating feeding machine. They travel.

katy: think I feel like makes it worse,

that It's

just like a revolving

laura: is. Or it's just a seemingly like the machine aspect of it, like the unfeeling machine of destruction.

They move between five and 130 kilometers per day. That's significant. And, but they do stay cohesive. So because they are a swarm, they aren't just, going anywhere. They're definitely staying together. Probably due because of pheromones. And scientists have found that typically these swarms are flying down wind, which makes sense.

You're a bug. You can't really go that much against the wind.

katy: They're just like, let's go.

laura: yeah,

katy: I

laura: put on their little goggles and

katy: yeah.

laura: the wind. But I mean, they will to a certain extent, [00:09:00] but usually it's downwind

katy: Well, 'cause that's using up energy. I mean,

laura: it's actually more, which is cool 'cause like you're like, well dove, of course they're gonna take the path of Lee resistance.

Yes. But it's also for another reason. So they have found that yes, they're flying downwind, but they're flying to this point called the Intertropical convergence zone. 

katy: Oh yeah. 

laura: is when trade winds are coming south, monsoon winds are coming north and they hit each other. And this is where rain occurs.

And that rain belt is moving up and down Africa, depending on the season,

katy: like, we gotta find that moist dirt.

laura: Sweets, they gotta find the belt. So they go there and going down wind. So if you think about weather and how storms work, air pressure when it's high, the wind, is going up. Low pressure is storm weather, so those, that wind is going, whew.

That's why you feel the wind. Whenever there's about to be a storm, the air is dropping. So the little locusts are following that downhill current, like a sled [00:10:00] right into the rain, which is what they're hoping for. However, they don't always fly down wind sometime, and sometimes they're blown off course, but they do seem to be, they do redirect themselves, which shows some level of orientation.

Like it's not just follow the wind where it takes us guys,

There's something else. , So when they, what they think, this is very hard to study in a lab setting because it's a swarm of locusts, right? Like you either have to do field observations or a lab. 

katy: Yeah. 

laura: lab ha in the field, they've only been able to choose their, variables. They can only do so much in the field and they're doing five locusts at a time. They're little mini swarms. But basically what they found is that their eyes and their brain, because we actually know a lot about locust brains from studying them for a really long time, is that they're really good at detecting patterns of polarization, which is how light filters through the atmosphere 

katy: Yeah. 

laura: and they can tell the position of the sun [00:11:00] as the brightest spot in the sky, which is helping them use basically a sky map.

katy: I just also like that they don't know it's a sun. They're just like the bright

laura: spot. Yeah. Follow the bright spot or avoid? It depends. So they have these really amazing photo receptors in their eyes to really pinpoint things. And, when that's combined with the position of the sun, at some level their brain has, if you're gonna use the sun to orient yourself or anything in the sky, you also have to be able to tell time to some degree because it changes where it is depending on the time of day.

katy: Yeah. And you have to 

laura: yeah, their brains are capable of doing such a thing. They believe, because of these experiments that they've done. So like they're turning their heads to follow certain things. It's a lengthy scientific article. Dive into it if you want to. But they can detect polarization.

That's probably what's happening. Mixed together with [00:12:00] directional cues from the. then just following each other's pheromones.

katy: hmm.

laura: Now, when it comes to them in their solitary phase, things are a little different because they're not coming out during the daytime. So they are not orienting using a sky map because they actually can do this on moonless nights.

These little solitary locusts, this is before they get into these giant swarms, they're still moving around 'cause they wanna look for food. Usually it's less than a ki less than a kilometer per night. But once it, that first rainfall hits, they will fly up to 250 kilometers in one night to find that sweet spot.

And that's why they're all coming together and then start to get crazy and gregarious. On those moonless nights, they're like, okay, they can't be following the Moonlight or the Starlight. They are, when the wind is high, they're going downwind because they're not fighting it. But when the wind is low, they would be following Compass bearings.

So they are orienting themselves somehow. They think, dung beetles can use the Milky Way. So is it the stars? [00:13:00] Is it something else we don't know. And then does that switch, do they not need that part anymore? There's still a lot of unknowns here. But there is a method to the madness of both the solitary and the swarm, which is pretty cool because they fly into very different ways at very different times.

katy: yeah. Hmm. And it's not just very different ways, very different times. It's the same species that

laura: They just have literally changed, like Dr. Jack and Mr. Hyde like level of change.

katy: Yeah. Which is just, yeah. That is the cra That's the crazy part, is it's the same, the same individuals

laura: yeah, yeah. And if you look up the term sky map, that is a scientific term for how some animals navigate and typically it's through sunlight or moonlight. So sky maps.

katy: Sky maps, I talk about that a little bit here. , So for mine, I talked about birds, then birds and mammals. So the first one, I'm gonna talk about is the magnet reception.

Or the magnetic [00:14:00] compass. And I think that this is, whenever people talk about birds or if you remember bird migrations, this is typically the one that people think of. So one of the ways that birds find their way is by literally sensing the earth's magnetic field. And this is why it is kind of a big deal as everybody's saying oh, the earth's magnetic field is shifting some, it's gonna affect a lot more things than just birds.

And this is definitely affects the migration here. So it's sort of like an internal compass. And that ability, like I said, is called the magnet reception. And it's not just some vague sixth sense, it's an entire sensory system that's built into their

laura: Yeah. Yeah.

katy: Which is crazy. I remember Laura, were you in my Yes.

Alright. I don't think we've ever told this story before. So our advisor, who is just a unique guy.

laura: It was the best way to teach about this. I

katy: It, it really was. But I will start by saying, this was one of the few years he, no, no. Cops were called on him because he would take his, he would take his class, [00:15:00] he would blindfold all of us, pile us all into a white van Dry.

Yeah. Which was a school's van, but I don't think it had, I don't know if it had,

laura: had a 15 passenger van. I, you're right. I don't think it's in Malone. On the

katy: I don't, yeah, I don't think it said anything on it. So it just, , a grown man with a bunch of clear kids all blindfolded, just driving aimlessly around the city. And he was intentionally trying to get us off, like our senses

laura: driving all over

katy: and, and, and, and zigzagging. And then we would just show up at a random place and we would take off our blindfolds and then we would have to say, here's where the direction of school is.

Here's this, this is where I think I am. And he would ask us a series of questions to just attest it.

laura: No, and he took us out one by one. It also

katy: Yeah. One by one.

laura: one by one by the shoulder out there and then take off the blindfold so we couldn't hear each other and be influenced.

katy: yeah, so we 

laura: it looked real sketch, but it was really fun. I remember being 90 degrees off.

katy: yeah, it, I was a, I was a little off, but I [00:16:00] also remember, we ended up in some random park, by the campus, like not too far from campus, but still it was like in a park, a bunch of kids with blindfolds on in a 15 passenger white van after he had driven us around through alleyways, like trying to completely throw us off.

But again, like Laura said, it really does when you're that disoriented,

like, I'm, I'm somebody who does have,

laura: of, of like true orientation. Yeah.

katy: , And I normally do, I'm normally one who, if I go wonder, if I go someplace one time, I'm normally pretty good with, I can repeat that based off of what I'm seeing around me.

But when you don't.

laura: cues for sure. But I'm really good at remembering the root after one or two times.

katy: Yeah, me too. But whenever you're blindfolded, you have no sense of anything. And it wasn't like, oh, let's just see where the sun is sort of thing. Because even that, I don't remember if it was like

laura: because it, because you didn't know where you are. You didn't know where you are relative to school. That was what it was. It wasn't even like fine north. Okay. Easy with the sun. But it was like [00:17:00] find where we started

katy: Yeah, yeah. Find the direction where we started. 

laura: impossible. 

katy: Yeah. But it was interesting 'cause you really did get to feel hey, this is confusing and humans have evolved. We really have lost any sense of anything. All right. So how does this for birds then, this magnet reception, how does this actually work?

Well, scientists think there are two main mechanisms and both are wild in their own right. And then you put 'em together. It's just crazy altogether. So the first, it's in their eyes, specifically in proteins called crypto chromes that are found in the retinas of many birds. These crypto chromes are light sensitive and under the right conditions, especially in blue or UV light, they undergo a chemical reaction that's affected by the earth's magnetic field, which is 

laura: cool. So they actually visually can see the

difference. That's amazing. 

katy: The current leading theory is that this lets birds see, like you just said, the magnetic fields as patterns of light and dark. [00:18:00] Not like a compass rose floating in the sky sort of thing. But think of a lot of the video games that you can use your senses, and it's kind of that trail, and you can see where animals have walked or see where a person

laura: I'm also envisioning like the aurora, you know what I mean? Like 

for a bird it's ah. 'cause the, since the aurora is magnetic too, it's like when 

we can 

katy: Just follow that. Yeah, just follow that kind of thing. The, and then there's the second theory, which is the magnetite. It's a magnetic mineral that's found in bird beaks and even parts of their brain. So think of magnetite at a natural, I don't know, compass 

laura: that stick together, right? If you can buy

katy: Yeah, it can be. Yeah. Yeah, yeah.

And this is sensitive to magnetic forces, and it may help birds detect the strength and inclination of the earth's magnetic field. The feeling, their latitude or altitude, and being able to depict where we are here. But here's where we take a sharp turn into the bizarre quantum biology.

And this is a whole, I'm not gonna

get deep into this. 

laura: [00:19:00] biology. I'm

katy: I'm not gonna go

laura: where our listeners are like, I guess.

katy: 'cause this gets, this gets crazy, but European robins, for example, seem to rely on quantum

laura: oh my gosh. Freaking robins just,

katy: No right to make magnetic reception work according to a 2001 review in nature physics.

The chemical reactions inside the, crypto chromes involve pairs of electrons whose spin states are entangled. All right? And the earth's magnetic field affects how long that entanglement state lasts, which in turn influences the bird's visual perception of direction that makes it possibly the only known biological system that depends on the quantum effects to function.

That's a leading theory. The amount of research that has, gone into it, there's a lot, but it's not I don't know, I guess it's not solidified. Yes, because again, it's anything quantum anything is just what the heck?

What is happening thing. So [00:20:00] in other words, birds may be the only animals, possibly the only organisms that navigate by literally using quantum mechanics.

laura: wild

katy: Another way that they use is again, like we know sun compass and celestial cues, which Laura talked a little bit about this, so I'm not gonna go, tend into it.

But birds are able to use a position of the sun in the sky like a compass. But here's the genius part. They don't go oh, there's the sun must be west. They actually adjust for the time of day, and this is where the circadian rhythm kicks in the internal clock that lets them estimate what direction they're heading based on where the sun should be at the time.

So like Laura talked about, yeah, it should be, they should know. Same thing with nocturnal migrants. Again, I'm not gonna go over this, 'cause Laura kind of talked about it too. Back in the 1960s though, researchers built little planetariums for birds, which I think is just like adorable. Anyway, and they put migratory birds in these dome shaped setups, projected the night sky, and then rotated the stars.

And when they did [00:21:00] that, birds would actually change directions of where they needed to go. So that was like a

laura: kind of like they did not quite the same thing. They didn't do with the,

with the planetarium, but with the locusts. They stuck them in a box and they tethered their little tiny locust bodies while they flew and they, and like when they would change light like sunlight rather than, 

it was similar. 

katy: yeah. So something like this is a lot easier for us to understand and to study over quantum anything.

laura: because our bodies can do this, right. We can navigate by the stars in the sun. 

And we do this, some of us more so than others, but

katy: yes. But we've configured this one out, so this is a lot more, I don't know, widely accepted, widely understood, and widely studied. And everybody's yep, nope. This is a thing. This is a hundred percent thing. Whereas the quantum side of it, I think it's still so far outside of our understanding.

laura: our eyes just can't do that. We

katy: Yeah.

'cause [00:22:00] yeah, we, 

laura: even, it's hard to conceptualize something that you can't

katy: we can't even

laura: Yeah. Like

katy: So another way that birds actually, use is visual landmarks and topography. All right? They have the magnet, magnet reception. And they read the sun and the stars, but sometimes they just go full Google Street view and they rely on visual landmarks to find their way.

And it's not just, oh, hey, here's this. No. It's they build a map in their heads and they know the coastline. Rivers, valleys, yes. Nowadays it's highways, buildings, intersections, like they remember and they use, think of like the MVPs of this system. A hundred percent was a homing pigeon. They didn't just memorize one route.

They can create what's called like a cognitive map, like Laura was talking about earlier. It's a mental image of the landscape from above. And in one study, published in nature, pigeons were released from unfamiliar locations. And rather than flying in a straight line. They followed winding roads, [00:23:00] railroads clearly recognizing and using these landmarks to orient themselves to be like, ah, I feel like, I need to go over here to, so that way we can find their way back.

It's almost like you can take them a little bit farther outside of their comfort zone in a way, and they'll use these visual cues to help get themselves back. And again, homing pigeons, they were the a plus students here. And even long distance migrations like storks and geese are believed to use major topographical features.

laura: a mountain range that we always pass over.

katy: yeah. What's the geese? I know you talked about the geese that go over Everest.

laura: Yeah, yeah, yeah. I think, was it, bar? Bar or something? Bar headed, goose Bar,

katy: I think so. Bard. Yeah, I think it is that one. But yeah, they go over over the Himalayan mountains, which is, which is nuts. And they're very consistent, like across continents year after year, if you guys ever use eye naturalist or, that's how I found the painted buntings this year.

I looked at where the hotspots were in my area 

laura: the same route. Yeah, 

katy: in the previous years. Yeah, they're gonna [00:24:00] follow the same pathway and so that's why I was able to figure it out, intercept em and use that. Briefly too, , some use olfactory cues, smell as a map, vultures, the ones that have a stronger sense of smell, pigeons again, , 'cause they are the, kinda like the low key rock rockstar.

Yeah. And so they think that. What are they smelling? Birds attack volatile atmospheric compounds. Basically tiny airborne chemicals that vary depending on the environment.

So it's inherited maps and learned routes and so they pick it up from the flock from the year before and then they're like, oh, I know where to go this time. I know what to do. I know how to, if we get blown off course, 'cause it happens if a storm comes through and shifts this course, we can figure out how to get back.

Yeah. So some of the big questions that science is still chasing, obviously anything with the cryptochrome, are they really using quantum entanglement or is it something else? 'cause again, this is something that some people are starting to do research on, but it's still highly debated, [00:25:00] high, still highly controversy,

that's one of the big questions. How do birds integrate multiple navigational systems? I was reading some really cool papers on , yes, we have a lot, we have a good bit of research on the different systems, but it seems like birds are layering multiple different things. How does one, let's say if, the smell okay, if they're relying on smell, how do, if that gets all messed up, is do they have a default or is it Yeah.

Or any, yeah. And so it's just all of those different layers. So anyway, so yeah, so birds, they definitely rely on a bunch of different types and a different bunch of different varieties. One, I like birds, but I'm definitely gonna be following up on this whole quantum

laura: And how cool would it be if they could finally , make me some, make some goggles, let's let us experience

it. 

katy: And people knock her like, well, okay, well who cares if the bird migrations are thrown off? No, we should care. Okay. Because pollinators are so many species, and we've talked about that in several other episodes. So many species of plants and things that we rely on rely on these pollinators and things.

And if we don't have 'em, if they get thrown off [00:26:00] course and they start to die, then it's, it's all game over. , Yeah, it's definitely interesting. This Bird one in particular it was tough to keep it at a high level because there's so much research out there and so many theories because it's not just one thing, it's so many different

laura: Yeah. And insects. Well, and this, this will lead us into our next one, , insects and fish are much lower down the evolutionary chain, then birds and mammals. So it only makes sense that as an animal progresses through evolution, they're coming up with more and more systems because their brains are getting more sophisticated and things like that.

My insects, they're using sky maps and probably visual cues. I know we've talked about monarchs before. They're following wind patterns down to Mexico. They're not, they don't have special eyeballs that let them see magnetic fields. They might be able to, maybe we, might be some that do feel magnetic stuff, but it doesn't surprise me that it's more basic, which then leads me to my next thing, which is fish.

Not much more sophisticated than [00:27:00] insects, but a little. And I specifically wanted to focus on the American eel because I cannot talk about this fish enough. I just think that eels are so cool

katy: dude, it's cool, but also so insane.

laura: yes. The whole thing. Yeah. So

katy: Are you gonna talk about he, how We don't really know where eels come from. Okay. 

laura: yeah.

yeah, yeah. 'cause that's like the best part of this whole thing.

Like,

katy: I know we've mentioned that before in previous episodes, but I, I really don't think it can be stated

laura: Yeah, yeah, yeah. There aren't very many mysteries left on our world, I feel like,

katy: But this is one of 

laura: the eel to keep going. So real quick. Bit of background because not everybody knows what an American eel is. You everybody thinks of, electric eels and things like that.

It's the only freshwater eel in North America. They're slimy like you would imagine an eel is. They can be found in the great lakes and in rivers and streams up river of the Atlantic Ocean and the Gulf Coast. They're not over by California, like this side of the States and North America. But some do stay in brackish water [00:28:00] near the coast at maturity.

Males can be about a foot and a half and females can get up to four feet, which is significant and up to nine pounds. They hunt at night and they can live anywhere from five to 40 years. It just depends on conditions in particular. If they live in brackish water, a lot of times they live longer because they mature more slowly.

And

katy: they mature slower in brackish 

laura: water.

I guess just conditions are probably harsher.

katy: Yeah,

laura: And then, they are an endangered species according to the IUCN. There used to be so many freaking eels, like it was an industry. Now they're in trouble. For many reasons, not just overfishing, but also damning up rivers and habitat loss and all kinds of stuff.

But only really in the past 20 years has research really taken off on these elusive fish. I don't know if people just didn't care before then, or nobody was like, somebody should study that. What is happening to these eels? But thankfully we did. And so the story 

of 

katy: think, I think a lot of them, it is one of those things that, because it wasn't an issue before, everybody's just [00:29:00] oh, whatever. EEO it kinda like fish. Yeah. Whatever, fish like, eh, whatever.

Don don't 

laura: they're around and there are so many of them. And then all of a sudden there wasn't so many of them, so they were like, I guess we better figure out where they're all going. So there are two kinds of migratory fish and. They're actually navigating the same way, which is nice that I'm, it's covering both at the same time.

When I talk about eels, you've got raus, which is salmon. They're spending most of their life in the ocean, and then they go to fresh water to breed. Eels are the opposite. They're CDRs, which means they spend most of their life in fresh water and go to the ocean for breeding. In particular though, the one reason I chose eels is because this whole thing is not that well understood.

All we know is that they head

katy: Literally all we

laura: all we know is that they head to the sargasso sea, which is warm in about 2 million square miles. So we're like, there's somewhere in this 2 million square miles. It's surrounded on all sides. It's the only sea that doesn't have any land [00:30:00] borders, and it's only called a sea because it's surrounded on four sides by current.

So it's basically its own little sea. And it's full of vegetation, like crazy amounts of seaweed and stuff like that. So it's like a jungle in the middle of the ocean 

katy: yeah, 

laura: on all sides by currents, which just sounds cool. And to this day, it is 2025. No one has ever seen an EEA eggs before, anywhere in the Sargaso Sea.

How I'm telling, if I was a millionaire and I had just money to burn, I would go camp myself in the middle of the Sargasso Sea and I would be diving every day to see this happen.

katy: Yeah.

laura: My claim to fame would be, I saw it, I saw them spawn, I saw the mate. 'cause we all of sudden never seen that. I would see them mate, and then I would eat them lay eggs and I would be a total voyeur and be 100% on or with it

katy: Yeah, it is, it is a complete mystery as to all, like Laura said, all we know is that they go there. And beyond that, we have no

laura: because, and like again, how have we not. [00:31:00] I just can't believe that Noah has been like, I'm going to go and I'll go. But I guess it's probably the funding, like who can afford to stay there long enough And then because of how densely vegetated it is, we can't rely on drones 'cause you can't see

anything. They could be going way down there to do stuff. 

katy: yeah. 

laura: like machines

katy: Pri they need 

laura: real eyes. Yeah, it makes

katy: They need such good privacy. This is like the, the Bigfoot of the sea, like the, we're

laura: know they're having sex, we just don't know how they do it.

katy: Yeah.

laura: and, and it matters. But what we do know then is once 

they're 

katy: need to know.

laura: yeah. That once they're there and they lay their eggs, their larva hatch and these larvae are leaf shaped, just tiny clear leaves that float through the ocean and they transform into what's known as glass eels.

And they're called that because they're see-through this is all the same species. Mind you, it's just different steps, have different names like. Larva, tadpole, frog lit, that kind of thing. So the glass eels are like two [00:32:00] inches long, little threads. Okay. In the middle of the ocean. 'cause the Sargasso Sea, forgot to say is, in the North Atlantic, northeast of Cuba, basically if you went straight east out from Georgia and Florida, you'd run into the Sargasso Sea.

So they eventually somehow end up on the coast of North America once and then they're gonna start their journey inland. They head upstream and grow into four inch long little eels called Elvers, which is so cute.

katy: Yeah, that is a cute name,

laura: And then, and then even larger, what's called yellow eels. And this is what they stay basically most of their time as.

They're like a yellowish color and they're just existing and they just exist in streams and rivers for at least a decade before they reach maturity. Sometimes 30 years, they're just hanging out. I cannot tell you guys. I guess this, how many summers ago was this? Maybe three summers ago. Lost my crap.

katy: I can't blame

laura: a summer camp, and [00:33:00] found an eel. I was like, all the campers were like, okay, this is cool. But I was like, you guys, this is crazy. We just found an eel, like I was freaking out. couldn't catch it. But I saw it. I had it in my hands for a second and it was not, it had to have been an eel and it must have been one of these yellow eels.

'cause it was probably only like this long, but still like pretty long.

katy: That's pretty good.

laura: Yeah. And I knew it wasn't a snake because of the way it felt. I was like, it's a freaking evil.

katy: yeah.

I mean, you are a biologist, so you do know what you're

laura: yeah. 

katy: I trust you to say, yeah, to to know the difference between an eel and a snake. 

laura: yes, yes. So after this. Decade or 30 years even. They go through what's called silvering.

They actually turn a silver color, but more importantly they get reproductive organs 'cause they didn't need 'em until then. So they go through puberty, they get the reproductive organs, they get chubbier and they get bigger eyes, all of that.

katy: I like how they're like, you know what, also you [00:34:00] need, you're gonna get some sex organs and bigger eyes like.

Yeah, 

laura: um, so then they start that migration back to the ocean. 'cause they need to get chubby. I they can take their grand old time, I guess as babies heading

katy: I guess.

laura: you still think would be the harder thing to do. Fighting currents going upstream, but they get chubby to go back down I think.

'cause they need to go it faster. They usually do this in the fall and winter time, but how do they know where to go? Honestly, I'm sorry to tell you, we still don't actually know about American eels, but we do know about their cousins, the European eel, which is basically the European version.

They actually, crazily enough, I had no idea of this. European eels also migrate to the Sargasso Sea to reproduce all eels. They just heard the Sargasso Sea was the place to be, and like ones from Europe, once from the Americas, they're like, this is it.

katy: This is it. Yeah. So it goes back to then what? Okay. There has to be something [00:35:00] else other than Habitat that makes us so perfect.

laura: just, yeah, it's eel, topia. I don't know.

katy: Yeah.

laura: I so 

katy: There's gotta be some like secret eel club

laura: Yeah. Yeah. Well, and so they obviously from literally other sides of the Atlantic Ocean are finding the same place. And not only do they have to go to there, then they have to go from there to where they're going and Sure. Could they just be floating around?

Yeah. But , they also might end up anywhere in the Atlantic Ocean if 

katy: exactly. Yeah. 

laura: so what the current theory is, based on some really cool lab studies on European eels is that they also think it's magneto reception. Kind of like Katy said.

katy: But, but again, it's like, why here? Like, what, what there, what is 

laura: know. We have no idea about that.

We just know that we're, we think that this is how they do it. So in a lab, they eliminated all other orientation cues? No, no light, no any, just. Little black [00:36:00] boxes. But they could always orient using magnetic north. Not that they would point north, but using magnetism, they could always orient themselves and they would change direction.

So this guy built these multi chambered systems and he would take a few, he had little baby glass eels. He would pull 'em out and he put 'em in a different chamber at different, on different days, and he could control the magnetism of each of these chambers. And then in this chamber there was like 12 doorways that they could just choose where to go next.

And they would choose based on the magnetism of the surrounding chambers and this one. And what they found was that when there, so on different points of planet earth, there are different intensities of magnetism, which Katy brought up for a second with your Magnetite stuff. So it's not just like even.

Even magnetism. It's just not like that's north. Okay, yes, yes, yes. But it's more intensely north [00:37:00] the further you go

and it's weaker when you get towards the equators, you might be feeling a tug at the equator where you're feeling pulled

when you get 

closer. So 

katy: has to be insane to be like, I knew you took Oh yeah. Like you just, and you don't know why. You just have to go.

laura: just being bold. Well, and so if, so he, because there are these different points, obviously in the Atlantic Ocean from the Sargasso sea to Europe, there are levels of, of intensity. So he was mimicking specific locations along their route, and based on those locations, they would always choose a chamber that would be in a direction that would take them into the Gulf Stream.

If you put their little chambers on a map, they would always go, depending on the magnetism. Of each section, they would always choose. This way gets me to the Gulf Stream, that current. So when they're born, they know I must get in the Gulf Stream, like [00:38:00] I need the Gulf Stream, whatever that means to their little head.

They just know it's innately born. This is not a learned thing. This is just in their brains. They know. And it also depends on water temperature. I don't know if it was a different study or the same study, but basically when the water temperature was a certain level, that was a cue for migration.

So I think this was a different study on adults. If it was migrating temperature, they would always orient a certain direction. But if it wasn't migrating temperature, they would just willy-nilly sw swim around. So it was not just orientation, it was also water temperature. So that the two things combined are helping them navigate.

So scientists think that they follow increasing magnetic activity when they're babies and they reverse that in their heads when they're adults. They're like, I wanna feel less tug. Like they go decreased magnetic activity, which is pretty mind blowing considering this is a fish.

katy: Yeah. And Neil, yeah.

laura: And [00:39:00] that none of this is learned.

It's just born knowing all of this complicated magnetism stuff. And that we still have so few answers, but salmon also use magnetic reception. It's just like basically opposites. We just know a lot more about salmon and 'cause they're not going in these, they're coming instream to spawn.

We see it happen where they're not going to some mysterious ocean location. 

katy: yeah. 

laura: of this stuff so

katy: what's interesting too is I just looked on a map. Did you know that the Sargasso Sea and the Bermuda Triangle significantly overlap?

laura: And we also talked about the Brita triangle when I talked about sharks two weeks ago, because that is a crazy magnetic field thing there. There's gotta be something it must be easy to locate. I also thought was really interesting about this is that they brought up, so eels have been around for a very long time. In the evolutionary scheme of things or in the timeline of earth. 

katy: Yes. 

laura: when our oceans, during the ice age, our oceans were much lower, like [00:40:00] significantly lower because of all of the glaciers. So like migrations for these eels weren't actually that long back in the day, but they have increased significantly with changes of both ocean currents and sea levels rising.

So

katy: All right. I just found my next rabbit hole. I'm gonna deep dive into this whole Bermuda Triangle, Sargasso Sea, and the evolutionary history of like where we think, you know what I mean?

Like we had Pangea we, yeah, yeah. Has it where and why, because, yeah. It's, it is just bizarre that there's so 

laura: Earth's magnetic field does change, ocean currents do change. It might always not be where it was, but these port eels are now trapped in this thousand mile migration because they're like, I need this sargasso sea. They just now have to ride currents for a lot longer and rely more on navigation than they ever have before.

katy: yeah. Which is crazy. But then, but also 'cause a longstanding theory at the Bermuda Triangle is magnetic something is bizarre here. And so,

laura: stuff [00:41:00] up and, and I'm sure we'll talk about this at the very end too, but the reason why any of this is even being researched. I mean, yeah. Is it cool? A hundred percent. Most of US conservation people or biology people would just research this for the sake of researching. But the reason why money is being put towards it is because there are human implications for navigation.

The Navy is interested in this

katy: Oh,

laura: they want, they're thinking actually navigating through magnetism is probably better than through satellite imagery. So we need to invent a magnetization system to help ships navigate through the ocean

katy: Yeah.

laura: least different than 

we do now. Yeah, 

exactly. Better than a compass. Yes.

katy: All righty. Talking about magnetic fields and everything, let's then jump into mammals, because again, as we were talking about how we're increasing complexity here, so we have the birds and then we have the mammals, which is a higher, for the most part, a higher, intelligence level on all kinds of thing.

So instead of soaring through the sky, many mammals are [00:42:00] place-based travelers. They build deep mental maps on their surroundings. They remember the landmarks. They track scent trails, and they pass that knowledge on generation after generation, whether it's a bear return to the same berry patch year after year, caribou following ancient migratory paths through the Arctic, or humpback whales crossing oceans with crazy precision.

laura: considering there's very few landmarks in an ocean like.

katy: Yeah. Yeah, there's nothing. So again, the magnets. They definitely have a sense of earth's magnetic field, which again, I would be interested then to see when did we ever have 

laura: away? Yeah, 

katy: Yeah,

When did it go

laura: I dunno if we'd ever be able to figure that out, but it would be amazing because they've definitely like you'd have to start by looking at current indigenous peoples

katy: Well, 'cause we always followed the animals. We followed animals, you know what I mean? 'Cause we were the hunting gatherers and, you know, and so we followed

laura: yeah. We're not really migrating. We're following

katy: we're following them. Yeah. I don't think that we've ever [00:43:00] migrated to rely on on

laura: yeah. You're totally right.

katy: Yeah.

laura: stuff.

katy: Yeah. But, turns out that some mammals also seem to sense that the earth's magnetic field, oddly enough.

One that I didn't really know about, but I'm gonna talk briefly about here. Moles

laura: Oh, that makes sense. You're underground. How else are you gonna know where to go?

katy: Right. Specifically European mos. First of all, I'm in Texas now. I grew up outside of Pittsburgh. Finding moles. A garden, I remember that was a horror. Like you could not shove a shovel into the ground without being like, am I gonna hit a mole today?

Am I gonna hit a mole today? You don't have that worry down here. So, I mean, that's kind of a relief. But that's one of the unearthed childhood fears that this brought up again is are am I gonna shovel a mole in half today? Kind of, kind of thing because it happened. 'cause they're everywhere up north.

But mos European MO species, wind tested in controlled lab settings show a clear preference for building nests along the north [00:44:00] south axes, which is fascinating. Yeah, they're underground. No sun, no stars, no nothing. And still they're aligning like North south, which 

is 

laura: That's bizarro.

katy: Right Bats too. Experiments with species like the big brown bat, suggest they rely on mag magnetic cues when navigating an unfamiliar terrain.

So it's like they'll use visual cues and everything like that until they're in UN something unfamiliar. Then they're like, let's figure this out. And research. Yeah. And researchers altered magnetic fields in the lab and the bats definitely change directions suggesting that they are calibrating some sort of internal compass and, but here's where it gets kind of even weirder.

Cows deer. A 

laura: I feel like I've heard about that they orient themselves certain directions.

katy: Yeah. So a 2008 study used Google Earth. Yes. Like Google Earth, that we all know to analyze body orientation of [00:45:00] thousands of cows and wild deer all over the world. And what did they find an overwhelming tendency for these animals to stand in a north south direction, which is so bizarre.

laura: heard though that I think that, I think I've heard, I don't think I'm making

katy: While gazing, while grazing or resting. Let me just clarify

laura: I feel like I have heard in the context of natural navigation stuff that this is because of wind, grazing. Animals don't wanna be just biffed over or have to expend too much energy.

katy: be biffed

laura: You know what I mean?

So like they're orienting themselves and they also don't wanna face into the sun or away, you know what I mean? So like it makes sense that they do have a preference of 

katy: Yes, 

laura: stand this direction because you're doing most of your day standing and you're pretty broad. So

katy: yes. Yeah. And, and, and it goes back to those ROMs, like there is the same light sensitive proteins found in the bird's eyes, while mostly associated with circadian rhythms and mammals. It's possible that in some species they could contribute [00:46:00] to magnetic sensing of Hey, this is the better way,

but study after study keeps pointing. Literally in the same direction that there's something there as far as mammals who, even migrate or, or clearly don't. And mostly if cows are just, doing it while chewing grass. Like 

laura: Yeah. It's not for migration, it's for something else.

katy: Yeah. It's for some other reason, like you said, it, does it have to do with the light?

Does it have to do with the wind? Some other ways that mammals migrate, like we said with the birds is olfactory mapping. Alright. It's, the smell is a map. They use their noses, species like wolves, bears, rodents, rely on scent, memory to map their surroundings. These animals aren't just re reacting to what's immediately in front of them.

They're building olfactory landscapes, essentially remembering where certain smells are the strongest. Where trails intersect, or where food was once found. It's not just what they smell, it's where they smell it. That [00:47:00] they make these maps. Some mammals even lay down scent trails to help orient themselves.

Think about foxes, wild cats, some, domestic dogs and stuff. They mark their territory. Yes. But they also create scent references to help them track their movement and return to key locations. , 

Research suggesting that elephants can detect distant water sources or even rainfall from miles away. And they believe that's based off a scent alone. , It's like, imagine you can kind of smell when rain is coming, but imagine smelling rain coming like miles and miles away. , Spatial memory and cognitive mapping again.

Most mammals are what we call place-based navigators. They're not migrating across oceans using stars. They're building detailed internal maps about their surroundings. That's what we do. The spatial memory side of it. Say

laura: their home. Like their territory. Yeah.

katy: Yeah, yeah. And so that's for most mammals, including us, that's more what we do is , this spatial, the spatial memory.[00:48:00] 

Rats, squirrels, for example. They're pros at remembering where things are, where they cash their food, where the entrance to their burrow is. And that is all a cognitive map. The other, obviously, because we're, it's also mammals, social learning, cultural roots, let's start with whales for instance. Species like humpback whales migrate across thousands, thousands of miles every single year. And they follow the same exact paths, which.

Obviously becomes a problem if like with shipping routes and then they crisscross paths or shipping routes. And these roots are what they call cultural because they're passed down from one generation to the next. Calves follow their mothers and over time then they remember that exact path to the distance feeding ground and breeding sites and they're learning that the migration route, the same way we learned to drive the, family road trip.

You know what I mean? Whichever 

laura: Yeah, yeah,

katy: yeah. And so whichever way, your family always kind of went. That's sort of what you pick up on and where you get to go. That's why they're [00:49:00] starting to say now that people who rely on GPS so much have a much, much weaker hippocampus and part of the brain than others because we're not relying on the cognitive maps that we're building.

We're relying on a mindless thing. And so that part of our brain is getting significantly weaker. Let's talk real quick then I, we'll wrap this up here about ocean navigation. 'cause I, we've mentioned whales and everything. But now you're in the open ocean. How No roads, no landmarks. How the heck does this happen?

The short answer is we don't know everything. Again, we think that it's has to do with the magnetic fields of earth, but we're not a hundred percent, like not a hundred percent. One, it's hard to study. Two, you can't ask 'em, you can't put 'em in a lab like, so we're, our options are pretty limited.

So there's definitely, the sun plays a factor. Light polarization patterns in the atmosphere, especially at sunrise and sunset, may help some species determine direction. Even [00:50:00] over open waters. It's subtle, but if you're turned to the right, like light shifting, it can become a reliable cue.

laura: or sunset would be an easy thing for whales. Yeah,

katy: Yes. But then whenever you get into more oceanography temperature and salinium gradients that they think that they're picking up on, 'cause you're gonna, some parts of the ocean are gonna have, be saltier essentially than other parts.

Temperature. That's why you have currents and so are they remembering the currents and how, and knowing, oh hey, that's cold water. I need to go, you know, cold, cold, cold,

laura: hours in cold and

katy: Yeah. Then it'll get warm kind of 

laura: Yeah. 

katy: Another, and I think one of the cooler one is the infrasound, which whales are thought to detect low frequency earth sounds.

Natural vibrations from things like ocean waves crashing, on against a continental shelf, like on the bottom. Underwater earthquakes, that kind of stuff. They're starting now to think that. Whales are picking up on these like super, super, super low frequency.

Just [00:51:00] the earth sounds, the natural vibrations that earth is giving off.

laura: Yeah, because I'm sure it's like when you get closer to the poles, like if you're migrating towards a pole, the sound of that ice underwater 

that , or just the groaning of it shifting, 

katy: Yep, 

laura: that would obviously be like, I'm headed the right way if I'm headed south, you know?

katy: yep. So the big takeaway about mammals, it's, again, it may not just be using star maps, but they're running like highly involved multisensor navigation maps of some sort.

Again, it's the layering, just like it was with the birds of, Hey, I have this, and this. Let's just stack all this stuff 

laura: Well that, and the combination of mammals are known, like our whole, not goal, but our whole strategy for survival is teaching and learned behaviors so that our young have a better chance. So you can see a lot of these navigation things are learned, navigation things rather than just born instincts.

Like some of our lower evolutionary tree things.

katy: Yeah, but it's, but it still goes [00:52:00] back to food and mating. And that's, you know what I mean? That's the primary, yeah. That's the primary driver of these is I need to pass on to my genetics. I need to find food and , this is how I do it. Whereas again, humans, we haven't really had to do that, um, yeah.

In a long time. If, if ever, 'cause again, we were just talking about hunting gatherers, that was, we followed the things that were migrating, and so we didn't have to have to really do that. So, yeah. Like Laura was talking earlier, you know, there is a lot of really important things that we can learn.

One, if anything, it's how are we destroying all these, all these

laura: messing up some serious systems

katy: Yes. Especially whenever we are doing a lot more things that are throwing off, magnetic fields and 

laura: temperatures and salinity. Yeah.

katy: Yes. Whenever we mess all that stuff up, we're messing everything else up. And whenever people are like, oh, who cares about whales?

Who cares about the birds? Who cares about the bats? Again, especially the pollinator species. They are important and I don't know about you guys, but chocolate, coffee, all those kind of things [00:53:00] are I important? To me anyway, and so 

laura: That and can you imagine we're gonna start literally running into each other more? If your navigation gets thrown off, you're gonna collide. Like we're gonna run into things more like ocean or birds or whatever it is, but actual collisions.

katy: yes. So yeah, so I mean there is a lot of importance for us to be studying this sort of stuff and it is really cool. I mean it is really neat. So yeah, that's something that keep looking into there. I will say again though, because Laura was saying earlier, because there is so much financial investment in this kind of stuff, there is typically always some sort of science coming out about something.

laura: Yeah. 

katy: On how do animals migrate?

laura: for lots of reasons. Like one of the, one of the funders of eels is the dam companies. Because of laws saying that there has to be a certain survival rate, dam companies are held liable for that. And so they want to know how the eels are migrating so they can make their dams like the whole thing.

It's all tied together whether they [00:54:00] care about the animals or not. Finances and companies are involved in this stuff, so if we can harness that for the good of research, we can find out a lot of stuff.

katy: Same thing with windmill farms, they have to understand med migration patterns and things like that because they have to keep a low casually rate. So yeah, so it is definitely interesting. But because of all of this, there's constantly research being done.

There's constantly new stuff coming out. So it's definitely changing and evolving, which is really, really cool.

laura: Yeah.

katy: All right guys, make sure you go check us out on Patreon and support us if you can, , like us on all of our social media channels. Next week we will be having another mini episode, and then we will have a long, another long episode after that.

I.

laura: All right. See you guys soon.