Today you’ll learn about a gizmo that can repel sharks and potentially bring them back from the brink of extinction, how our brains’ internal compasses work, and how scientists learn about the sleeping habits of seals.
Today you’ll learn about a gizmo that can repel sharks and potentially bring them back from the brink of extinction, how our brains’ internal compasses work, and how scientists learn about the sleeping habits of seals.
Find episode transcripts here: https://curiosity-daily-4e53644e.simplecast.com/episodes/shark-repellant-brain-internal-compass-sleeping-seals
Shark Repellant
Brain Internal Compass
Sleeping Seals
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[SFX: INTRO MUSIC/WHOOSH]
NATE: Hi! You’re about to get smarter in just a few minutes with Curiosity Daily from Discovery. Time flies when you’re learnin’ super cool stuff. I’m Nate.
CALLI: And I’m Calli. If you’re dropping in for the first time, welcome to Curiosity, where we aim to blow your mind by helping you to grow your mind. If you’re a loyal listener, welcome back!
NATE: Today, you’ll learn about a gizmo that can repel sharks and potentially bring them back from the brink of extinction, how our brains’ internal compasses work, and how scientists learned about the sleeping habits of seals.
CALLI: Without further ado, let’s satisfy some curiosity!
[SFX: WHOOSH]
CALLI: Did you know that, by some estimates, as many as 50 million sharks are caught each year…by accident?
NATE: By accident?! How?
CALLI: Yeah. It’s called bycatch.
NATE: Right. I know about bycatch. It’s when fisheries pull up fish that they weren’t actually fishing for.
CALLI: It’s a huge problem because modern fisheries are pulling up huge amounts of fish every time they toss out a net or a line.
NATE: I’ll say - 50 million sharks as bycatch is huge. And I’m a huge fan of sharks, I am addicted to Shark Week AND Shark Week the Podcast which has a new season coming out June 26th!
CALLI: Oh, love that! I’ll have to take a listen. Anyway, back on track - combine that bycatch with changing habitats, shifting food chains, and the destruction of coral reefs and it’s safe to say that one of the world’s oldest and most important apex predators is in real trouble. But a new invention might actually be cause for hope.
NATE: Let me guess. Something to do with AI? Or a crazy new gene therapy? Or a shark repellant spray from Batman’s utility belt.
CALLI: Shark repellant…
NATE: Haven’t you seen that one?
CALLI: Nice try. But no. It is new tech, but not that new. In fact, it works because of an ancient bit of tech inside a shark’s head called the ampullae of Lorenzini.
NATE: Right, right. As I’ve said, fan of Shark Week and Shark Week the podcast. So, I know all about the ampullae of Lorenzini. They are these organs that can detect electrical fields, right?
CALLI: Shark Week has taught you well. That’s right. Scientists believe these organs evolved probably hundreds of millions of years ago, and they help sharks detect the little muscle impulses in their prey. They also think it could help them detect the Earth’s magnetic field and help them navigate thousands of miles across oceans.
NATE: So how are scientists using the ampullae of Lorenzini to stop bycatch? Are they sending sharks little emails that say “Stay away from this boat!”?
CALLI: That would make for a great Shark Week special, but no. It’s much, much simpler than that. They have built these little gadgets that they attach to fishing lines - just above the hooks. It sends out a sort of short-range electric field in pulses that the shark can detect.
NATE: Oh cool. So the pulse repels the sharks?
CALLI: That’s the idea. They think it probably overwhelms their sensory system for just enough time to make them feel like getting the heck outta there.
NATE: So is this just a theoretical device, or are they already using it?
CALLI: Okay, this is the best part. They are using it, and the results are amazing. By some counts, these doodads have reduced bycatch of blue sharks by 91 percent.
NATE: Whoa! That’s incredible!
CALLI: And there’s more good news. Rays also have the ampullae of Lorenzini, and researchers have noted a sharp decline in stingray bycatch, as well.
NATE: Wow! Okay so problem solved! Now we just have to sit back and watch shark populations spring back, right?
CALLI: As we always say on this show and I’m sorry. Not so fast.
NATE: I was afraid you’d say that.
CALLI: This is still a prototype, so it’s not ready to roll out to the entire world of global fisheries just yet. Plus, researchers noted a sharp decline in tuna catch, as well. And, of course, tuna is something they actually want to catch. So they need to do some more research to make sure that it’s not working a little too well.
NATE: Okay yeah. That wouldn’t be great. Makes sense.
CALLI: Not so useful if it actually stops you from catching any fish, right? That said, researchers are really optimistic about it, and they’re already developing a new version of it that’s smaller, easier to use, and comes with rechargeable batteries. If it does work, they want it to be a no-brainer for fisheries, and that means building a set-it-and-forget-it kinda gadget. They also are quick to note that this isn’t a silver bullet in the fight to save the sharks. There’s a lot of work to be done to drop bycatch even lower and to repair shark habitats.
NATE: So…I gotta wonder if I could attach one of these gizmos to my wetsuit the next time I’m playing in the surf? A little extra shark protection.
CALLI: Maybe? But you know you’re more likely to be struck by lightning than attacked by a shark, so you don’t really need one.
NATE: Is that true?
CALLI: I thought you said you watch and listen to Shark Week?
NATE: What about getting struck by lightning while getting attacked by a shark, has that ever happened?
CALLI: Now we’re just getting into theoretical. But I’m curious, let’s google it.
[SFX: WHOOSH]
NATE: You ever think about how it is that our brains are able to retain information on where we are at all times? That’s known as our “internal compass,” and it turns out we didn’t really know much about how it worked - until now.
CALLI: I mean speak for yourself, Nate. If I didn’t have a maps app on my phone, I’d never even be able to leave my bedroom, let alone my town.
NATE: Wait, you have to use a Maps app to leave your room? Do you live in a maze? You know what, we’ll talk about that later. This whole thing started, like it always does, with a brand spanking new study. This one comes courtesy of a certain Dr. Mark Brandon out of McGill University, who wanted to see how our internal compasses mesh with our surroundings. Sometimes you open up a compass on your phone, you need to “calibrate” it by spinning around in a circle. That’s your compass figuring out where Magnetic North is, so it knows which direction we’re facing at any given time. Our brains do the same thing - even if we don’t have the right words to express it.
CALLI: You mean how some people don’t even know the difference between “north” and “up”?
NATE: Yeah, and to be fair, with smartphone apps, they probably don’t necessarily feel like they need to anymore. But our form of “calibration” is related to a group of brain cells known as “Head-Direction” cells, or HD cells for short. As far as we know, every mammal has these cells, and we know they act as a compass of sorts for us. But Dr. Brandon’s study is the first time we’ve ever understood HOW or WHY they work.
CALLI: Awesome! So how, and why, does this work?
NATE: Brandon and his team were able to use brand new neural reading equipment to study a few mice’s brain waves. They were able to identify an interesting set of interactions between how the HD cells work and how animals perceive their surroundings. The world fluctuates around an animal, or even a human, very quickly. So like right now, if you run around your house, that’s your brain’s perception of the environment fluctuating quickly. And it turns out your compass re-calibrating itself depends on how fast your brain realizes your environment has changed.
CALLI: Whoa, seriously?
NATE: Think about it like this: run around your house. You turn left because you know there’s a hallway that leads to the living room. You turn around and turn right because you know that’ll take you back to your room. Your brain KNOWS those things are there, because it’s been perfectly calibrated to the space you’re in. Now, try doing those same directions in a hall of mirrors. Because you don’t know your way around, you will probably smack your face into a mirror very quickly - because your brain hasn’t calibrated the internal compass yet!
CALLI: That’s pretty heavy stuff. How does that work?
NATE: I know this is a complex topic, but unfortunately, that’s the most complex part. So bare with me for a sec. Think of an internal compass as a sort of three-dimensional space within our brains that function like a combination of an actual compass, one that subconsciously tells us which direction we’re facing, and a mental scrapbook that holds memories of where we’ve been. When our brains have trouble remembering something out of that scrapbook, it decalibrates the compass. To put that more directly, it makes it so our HD cells don’t fire up and power our compasses. The scientists put this system to the test by exposing mice to a constantly rotating visual cue. Using your house as an example, this would be like you remembering your hallway… except it’s spinning.
CALLI: Okay, that just sounds awful.
NATE: Surprisingly, it wasn’t. The HD system actually adapted to the rotation, which meant that the mice were constantly aware of where they were, even with some “artificial” changes. This was actually a pretty big find, because it means that researchers can now create new computer models so that they can potentially recreate the internal compass.
CALLI: Got it. So why would we do that?
NATE: Well, it’s this look into “ambiguous spaces,” like a hall of mirrors, that interested the researchers the most. You see, this kind of research benefits people who suffer from Alzheimer’s. Their spatial awareness is practically nonexistent at a certain point, whether they know the area or not - because their internal compass isn’t working to calibrate itself. The ways in which our brain processes location fluctuations is known as “network gain.” And network gain isn’t happening if HD cells aren’t transmitting. So long story short - if we can recreate the internal compass, we might be able to better understand how and why Alzheimer’s affects OUR internal compasses.
CALLI: Guess this study could help a lot of people.
[SFX: WHOOSH]
CALLI: How much sleep do you usually get?
NATE: Less than eight makes a crabby Nate.
CALLI: Okay… well then, it’s a good thing you’re not an elephant seal, because it turns out they are tied with African elephants for the mammal that gets the least amount of sleep, clocking in at two hours per day while they’re out at sea.
NATE: Yeah - a lack of sleep is one of many reasons I’m glad I’m not an elephant seal. Also, I’m not a huge fan of being eaten by a great white, either. But…back up a second. If you want to know how long an elephant sleeps, you just…watch it. But how on earth do you figure out how much a seal sleeps while it’s out at sea?
CALLI: Elephant seals spend about seven months of the year out at sea, so scientists assumed they must have developed some pretty cool way to catch some sleep out there without getting…well…eaten. So researchers designed a hat that could monitor the seals’ brain activity, heart rate, and motion.
NATE: A hat?! A seal hat?
CALLI: You heard that right. It’s a flexible head cap made out of neoprene - the same stuff they use to make wetsuits.
NATE: Cool.
CALLI: Right? They put the cap on 13 wild seals and kept five of them in a lab and let the other eight loose in Monterey Bay, California, and what they found was pretty remarkable. When they put all the data together, it turns out the seals only slept about two hours a day, but not all at once.
NATE: So they’re just taking…naps?
CALLI: Basically. They slept for about 20 minutes at a time and they did it…while diving.
NATE: Wow. Talk about a power nap!
CALLI: No kidding. They dove as deep as 1200 feet below the surface for their little naps.
NATE: So…why? Why not just find a cozy little sea sponge and kick up their flippers for a few winks?
CALLI: I mean adorable image but scientists think they do this for a couple of reasons. The first has to do with those pesky great whites. The animals that prey on the elephant seals - like great whites and orcas - tend to hunt closer to the surface. So snoozing up there just isn’t really safe. And it is especially unsafe for elephant seals because of how they sleep.
NATE: With eye pillows?
CALLI: Don’t be weird.
NATE: What? The ones in the study wear hats! So I dunno.
CALLI: Touché. But no. This has nothing to do with eye pillows. In fact, seals sleep a lot like humans. It’s called bilateral sleep, and it means that both halves of their brains experience sleep at the same time. Other seals - like fur seals - and animals like sea lions experience unihemispheric sleep, where half of their brains sleep while the other half stays alert to keep watch for predators.
NATE: Sleeping with one eye open, sort of.
CALLI: Yep. But elephant seals go fully to sleep, which leaves them vulnerable to predators, and makes these short bursts of diving sleep a pretty effective way to keep from being someone’s lunch.
NATE: Here’s a serious question: is a 20 minute naps enough? I mean…how are they able to function on such little sleep?
CALLI: They’ve evolved to function this way, I guess. But the researchers found that during these short naps, they actually enter several different states of sleep - from slow-wave sleep to REM sleep - so the quality of their rest is actually pretty good. And they more than make up for it when they hit land.
NATE: Right - you said earlier that they spend seven months a year at sea. How is their sleep different for those five months on land?
CALLI: Their time on land is like a massive elephant seal slumber party. They sleep as much as fourteen hours a day.
NATE: I would, too, if I’d only gotten two hours of sleep for the past seven months.
CALLI: That would make for a very crabby Nate.
NATE: What can I say? I need my beauty rest.
CALLI: Uh huh, I’m sure you do.
[SFX: WHOOSH]
NATE: Let’s recap what we learned today to wrap up.
CALLI: A new gadget uses a shark’s biology to stop the catastrophic problem of bycatch - which happens when sharks are accidentally pulled in when fisheries are trying to catch other fish. If you’re interested in all things sharks, be sure to listen to Shark Week the Podcast - new season out now! And mark your calendars, Shark Week starts July 23rd on Discovery.
NATE: The internal compass: how does it work? Turns out it works through a three-dimensional relationship our brains have between memory and the literal calibration of a compass that recognizes where directions are. This work will help us expand our abilities to recreate the internal compass, which could help us also possibly “recalibrate” the compasses of Alzheimer’s patients!
CALLI: Researchers designed a neoprene cap for elephant seals that can record their heart rates, motion, and brain activity and found that while they’re out at sea they sleep for around two hours a day in several short naps. And the most amazing thing: they sleep while diving hundreds of feet below the surface.