How do lizards grow their tails back?

Summary

Episode Overview

Podcast: But Why: A Podcast for Curious Kids
Episode: How do lizards grow their tails back?
Host: Jane Lindholm (Vermont Public)
Date: April 17, 2026
Guest: Adam Claus, Collections Manager of Herpetology, San Diego Natural History Museum
Main Theme:
This episode dives deeply into the fascinating world of lizards, answering kids’ questions about these reptiles. Topics include why lizards have scales, how they regulate their body temperature, the remarkable ability of many lizards to shed and regrow their tails, their tongues, how some can walk up walls, and more. Recording takes place in the San Diego Natural History Museum’s reptile and amphibian specimens vault.

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Key Discussion Points & Insights

1. The Museum Vault and Adam Claus’s Job

• [04:20] Adam explains the vault is three floors underground, housing preserved invertebrate, reptile, and amphibian specimens—"sort of like a library, where instead of books...we have preserved specimens."
• [06:23] On his job:
  “I get to basically be a kid as an adult.” (Adam Claus)
  He collects and studies lizards, snakes, and amphibians, contributing to scientific knowledge.

2. Preserving Specimens

• [07:01] – [10:10]
  • Specimens are preserved in jars or steel tanks, mostly with ethanol to prevent decay.
  • Notable detail: Specimens can reveal what lizards ate, parasites inside, or species distribution changes.
  • Oldest specimens are over 150 years old, enabling long-term study.

3. What is a Lizard?

• [11:16] – [12:24]
  • Lizards are reptiles with scaly skin, enabling them to retain water and live in dry habitats.
  • Unlike salamanders (amphibians), lizards’ scales are the big differentiator.
• Quote:
  “A lizard is always going to have scales on its skin.” (Adam Claus, [12:04])

4. Why Do Lizards Have Scales?

• [13:19] – [14:21]
  • Scales act as an impermeable barrier, like human fingernails, to keep moisture in.
  • Scales allow lizards to live in deserts and prevent water loss.

5. Are Lizards Cold-Blooded?

• [14:21] – [16:32]
  • Common misconception: Lizards are not “cold-blooded” in the sense often taught. Their body temperature changes with the environment and can sometimes be warmer than humans.
• Quote:
  “It’s hard to argue that that’s cold blood in that particular context. It’s just that their blood temperature, it varies.” (Adam Claus, [16:03])

6. Sleep and Hibernation

• [16:41] – [18:05]
  • Lizards in cold climates may hibernate; in warm climates, they can be active year-round.
  • All lizards sleep, but some are nocturnal and sleep during the day.

7. Lizard Tongues and Licking Eyes

• [18:55] – [22:27]
  • Only some lizards, e.g., some geckos, can lick their own eyes—because they have a transparent scale (not an eyelid) covering the eye.
  • Many lizards use their tongues to collect sensory information (taste the air for smells) and manipulate food. Chameleons use sticky, extendable tongues for catching prey.
• Quote:
  “They’ve co-opted their tongue to do the work for them. So it’s basically they’re cleaning their eyes.” (Adam Claus, [19:26])

8. How Many Kinds of Lizards?

• [22:50]
  • Over 7,000 described species, with more being discovered.

9. How Do Lizards Stick to Things?

• [24:26] – [25:40]
  • Some lizards (not all) have toe pads covered in tiny hairs, increasing surface area, allowing van der Waals forces to "stick" them to surfaces.
  • Not suction cups (unlike some frogs).

10. The Famous Lizard Tail Trick

• [28:01] – [30:47]
  • Many (but not all) lizards can intentionally shed their tails to escape predators. The tail breaks at a specific crack in the bone, with minimal bleeding thanks to contracting muscles.
  • The regrown tail has cartilage inside (no bone), and its scales and coloration are imperfect compared to the original.
• Quote:
  “The regrown tail never, ever looks exactly like the original. So you can always tell when a lizard has broken off its tail if you look really closely.” (Adam Claus, [30:24])

11. Why Do Lizards Have Different Teeth than Humans?

• [31:10] – [32:17]
  • Tooth shape reflects diet—herbivorous lizards have shearing teeth, carnivorous ones have sharper teeth for gripping prey.

12. Do Lizards Poop and Pee? What’s Special About It?

• [32:24] – [33:56]
  • All lizards poop and pee. Their pee is usually not liquid but a chalky solid (uric acid), conserving water, especially useful in deserts.

13. Meet Local Lizards

• [34:02] – [37:23]
  • Western fence lizards (“blue bellies”): Known for push-up displays and blue bellies in males.
  • Chuckwalla: Large, herbivorous, inflates body to wedge in rocks.
  • Banded gecko: Small, nocturnal, can vocalize (“squeak”).

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Notable Quotes and Memorable Moments

• On the museum collection:
  "You can open up every specimen in every jar in this room and you can read it like a book." (Adam Claus, [04:56])

• On job satisfaction:
  "It's sort of like drowning in chocolate for me to be in this room." (Adam Claus, [05:23])

• On describing new species:
  “It feels really cool. It’s a real thrill…when I turned 30, I was finally able to do that.” (Adam Claus, [23:22])

• On tail regrowth:
  “They don’t regrow the bone…but what they can grow is like a little cartilaginous rod that grows out…it never, ever looks exactly like the original.” (Adam Claus, [29:47])

• On lizard excretion:
  “All lizards poop and pee. I can say that unequivocally, no exceptions. The weird thing about their pee is that most lizards do not pee a fluid the way we do.” (Adam Claus, [32:59])

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Timestamps for Important Segments

• [04:20] Introduction to the museum vault
• [06:23] Adam shares how he became a lizard scientist
• [11:16] What counts as a lizard
• [13:22] Why lizards have scales
• [14:21] Lizards: cold-blooded or not?
• [16:41] Sleep and hibernation in lizards
• [18:55] Lizard tongues and eye licking
• [22:50] How many kinds of lizards are there?
• [24:26] How do lizards stick to walls?
• [28:01] How and why lizards lose and regrow their tails
• [31:10] Why do lizards have different teeth than humans
• [32:24] Do lizards poop?
• [34:25] Notable native lizards in the Southwestern US

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Memorable Kids’ Questions (Sampling)

• "Why do lizards have scales?" —Quinton (Anchorage), Rowan (Houston), Finn (Raleigh), Otis (Torquay)
• "Why are lizards cold blooded, and why are people not?" —Evelyn (Quebec)
• "Do chameleons sleep or hibernate?" —Grayson (Pittsburgh)
• "Why do lizards and snakes stick their tongues out so often?" —Agatha (California)
• "How do lizards stick to things?" —Grace (Tempe), Nicholas (Halifax)
• "How do lizards grow their tails back?" —Rehan (Jakarta), Luis (Fort Collins), Lenka (Czech Republic), Thomas (Pennsylvania)
• "Do lizards poop or pee, or both?" —Maeve (Massachusetts), Alice (Rutho)

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Tone and Language

• The tone is enthusiastic, curious, and highly accessible, suiting young listeners. Adam Claus’s answers are detailed yet explained in kid-friendly language, often with analogies (e.g., scales = fingernails, cartilage in ears/nose).
• The co-hosts and guest maintain a playful and respectful vibe, sometimes joking (“not pickles, definitely not pickles”), and reinforcing curiosity.

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Conclusion

This episode serves as a comprehensive primer on lizards, effectively answering kids’ burning questions about reptile biology, behavior, and ecology, while introducing scientific reasoning and the excitement of discovery. Adam Claus’s expertise and engaging explanations, paired with Jane Lindholm and Sarah Bake’s facilitation, make for an episode packed with memorable facts and playful, informative exchanges. The episode concludes with a teaser for a coming episode on even more lizard wonders, and a reminder to kids to keep sending in their questions.

Transcript

[Jane Lindholm]

Hi, it's Jane. Every summer my family makes a list

[Sarah Bake]

of the things we want to do

[Jane Lindholm]

while the weather is warm. It includes things like how many different lakes we want to jump into, what animals we hope to see, and new crafts we want to try out this summer. But why has made a Summer Bucket List and an invitation to you to join the but why Fan Club so you can get it. New members of the fan club will get a special but why Summer Adventure Kit with a notebook, a magnifying glass, a drawstring bag and a list of fun summer activities and adventures to have together. With a $10 a month donation, you're supporting all we do at Boatwide to explore and encourage curiosity and learning. And you're getting the Summer Adventure Kit. Check it out and make your [e-mail] donate before we get started, here's a note for the adults who are listening. One thing experts and parents tend to agree on is that learning to swim isn't just about strokes, it's about confidence, safety and consistency. Goldfish Swim School takes a thoughtful approach to swim lessons, combining research based teaching with a warm, kid friendly environment, making swim lessons feel encouraging, not intimidating. They offer year round swim lessons for children as young as 4 months up through 12 years old. Safety is never optional at Goldfish. Every lesson includes dedicated professionally trained lifeguards on deck, all certified through Ellis and Associates, a global leader in lifeguard training. If you're ready to take the next step, Goldfish Swim School has a special offer just for listenerswaved membership and your first lesson free at participating locations. Head to goldfishswimschool.com free free. Find your local school and use promo code. Free to enroll. It's an easy way to get started with lessons that focus on safety, confidence and real progress in the water. Support for but why comes from Progressive Insurance Fiscally responsible financial geniuses. Monetary magicians. These are things people say about drivers who switch their car insurance to Progressive and save hundreds. Visit progressive.com to see if you could save Progressive Casualty Insurance Company and affiliates. Potential savings will vary. Not available in all states or situations. This is but why A podcast hello for curious kids from Vermont Public, I'm Jane Lindholm. On this show we gather all kinds of questions from all kinds of kids, from all kinds of places. And then we gather a few of the questions and present them to someone who might at least have some of the answers. Today we've gathered questions about one specific type of animal and we're going all the way from Vermont to San Diego to get those answers for you. The animals we're going to learn more about today are lizards. Here in Vermont, where I live, we only have one type of lizard. In fact, there's only one type of lizard that lives in all of New England, the region Vermont is part of. It's called the five Lined skink, and it's endangered here in Vermont. It's only found in two towns here and I've never seen one. I love lizards. That probably comes as no surprise to those of you who have listened to a lot of episodes. I think I say I love the animals we're about to talk about in every animal episode we make. But since we don't have many lizards in my neck of the woods, I took advantage of a recent work trip to California and made a beeline for a place that has lots of lizards, like thousands of them. But here's the the lizards in the place I visited are not alive. I went to a museum with a research facility where they study reptiles and amphibians and they preserve specimens of each species so they can study them and even after those individual animals are dead. Let's go there right now.

[Adam Claus]

This is the vault. So this is the deepest part of the whole museum. We're about three floors underground right now. And the room is sort of divided into two halves. So the half off to the left here, this is all of the wet preserved invertebrate collections. And then everything on the right hand side of the room facing me, these are all the reptile and amphibian specimens that I manage as the collection manager of herpetology here at the Natural History Museum.

[Sarah Bake]

So to give kids a little bit more of a sense, when you say the specimens you manage, we are talking not about live animals.

[Adam Claus]

We are not. So we're talking about all animals that were once alive, but which are now dead and preserved. So these are not replicas, these are all real animals that were once alive. And you can sort of think of a collection like this as a library, where instead of books in my library, we have preserved specimens. And so just like a book, you can open up every specimen in every jar in this room and you can read it like a book. You can look at what that specimen was eating before it died. You can look at what kinds of parasites it might have inside its body or on its body, like ticks or parasitic worms. And we can track change across space and change across time. So there's so many different things that we can learn from dead animals that help us to better protect and understand how to conserve them in the wild. And so it's a really powerful resource. I tell people it's sort of like drowning in chocolate for me to be in this room.

[Sarah Bake]

It's a little bit weird to say drowning in chocolate when you're also talking about dissecting animals and seeing what they ate and what ticks they have on their body.

[Jane Lindholm]

Okay, Yeah. I still think it's weird to associate chocolate with preserved reptile specimens in jars of alcohol. But who am I to yuck someone else's yum. And the someone else we're talking to here is Adam Claus. His official title is collections manager of herpetology at the San Diego Natural History Museum. But sometimes it's hard to understand what someone does just from their title. So I asked Adam to explain what his job actually is.

[Adam Claus]

So I get to basically be a kid as an adult. So when I was about the age of many of you who are listening right now, I was catching lizards in my backyard in Southern California, and I was marking them with different dots of colored paint so I could tell which one was which and how many are in my yard. And so I kind of get to do that all the way to today as an adult. I get to go out outdoors, outside in wild places, and sometimes in suburban areas, and I get to catch lizards, I get to catch snakes, I get to learn about them, and then I get to share that information with everybody through scientific publications. So writing down what I see, interpreting what I see, and then sharing those results, what I'm learning with the world.

[Jane Lindholm]

In addition to going out and looking for wild animals, Adam also keeps track of all those specimens we were looking at. When I visited the museum, you heard him mention that we were deep in the bottom of the museum. It's a big, climate controlled room that has almost 80,000 specimens or preserved animals. The specimens are stored in jars that are filled with liquid, usually a kind of alcohol that preserves the animals so they don't decay or deteriorate. They're mostly in jars with white lids that kept reminding me of pickle jars. Some small pickle jars and some other really, really big pickle jars. Except instead of pickles, the jars were full of rattlesnakes and turtles and other things that were definitely not pickles. Most of the animals in the collection come from the local area, Southern California, and the Baja peninsula of Mexico. They have over 1700 different species of reptiles and amphibians in the collection.

[Adam Claus]

And by reptiles and amphibians, just to be clear, we mean things like crocodilians. Snakes, lizards, turtles. We have one tuatara. And then for amphibians, those are the three main groups are salamanders and newts, frogs and toads. And then the really weird group that almost nobody's ever heard of, they look like giant earthworms, but they. They're not earthworms. They're amphibians. And these are called the Caecilians, and they are strictly tropical. So we don't have any in our region or any in the US but we have a few specimens in the collection.

[Jane Lindholm]

Before we got to the questions, I was there to ask Adam about all of your lizard questions. I asked him if he could show us something in the collection.

[Adam Claus]

How about we open up a tank? Yeah. Okay. And so in the room, as we mentioned, most of the specimens are kept in jars, but glass jars usually don't get manufactured much larger than one gallon in size. So if we have specimens like really big iguanas or really big snakes that just don't fit inside a gallon jar, we have to have another way of storing them. And our solution is these steel tanks that we fill with fluid and we store the animals in there. So I'm going to open up one of these tanks right now.

[Sarah Bake]

This is tank 10. And it says on top of it, iguanads.

[Adam Claus]

Yes. So these are like iguanas. And then we have a Gila monster. And then, weirdly enough, we have a few Galapagos tortoise feet. Just the feet, not the shell, just the feet.

[Sarah Bake]

Wow. The smell is really distinct when you open it up.

[Adam Claus]

Yep.

[Sarah Bake]

So it smells if you're an adult, kind of like Sherry.

[Adam Claus]

Sure. So it's actually the exact same chemical that, you know, adults drink in their alcoholic beverages. It's ethanol or ethyl alcohol. So it's not toxic per se, but the way it preserves the animals is it just makes a solution, a mixture of ethanol and water that bacteria and fungi cannot live in. So if a bacterial cell were to get dropped into this fluid, all the water would get sucked out of it and it would die.

[Sarah Bake]

So if I coughed into it, it wouldn't damage anything?

[Adam Claus]

If you cough, it wouldn't damage anything at all? Yeah.

[Sarah Bake]

So what do you do with these iguanas that are preserved in here? It's very cool looking. They're sort of. Some of them are preserved where they're sort of curved around their own tails.

[Adam Claus]

So we can do all manner of things. People can study the genetics, we can look at their DNA. We can look at how their coloration varies between males and females. We can look at how coloration might vary in certain parts of their distribution versus others. We can cut them open if we wanted and see what they were eating. We can cut them open and see what kinds of parasitic worms might be living in their bodies. And sometimes those can be brand new species that nobody's ever described or given a name to. We can do so many things. It's almost an unlimited number of questions. And what's really fascinating about collections like these is that they're super long term. So a lot of these specimens are decades old. Some of the specimens in our collection are more than 150 years old. And so what that means is these specimens could be potentially used for things in the future that we don't even have any idea that we could even ask these questions.

[Sarah Bake]

Now, I'm glad you showed me the iguanas because what we're here to talk to you specifically about today are lizards. And iguanas are a kind of lizard. So can we share some of the questions from kids that we got about lizards?

[Adam Claus]

Yeah, let's do that.

[Sarah Bake]

Maybe you can explain, since we were talking about reptiles and amphibians, what lizards are.

[Adam Claus]

Sure. So lizards are vertebrates. So they have backbones just like we do vertebral columns. And they're also characterized by usually having very scaly skin. And so that helps them to avoid drying out. So the scales help keep the moisture inside their bodies. And so a lot of reptiles, like lizards, they can live in really, really hot, dry places like deserts because of how the scale keeps all their water in their bodies.

[Sarah Bake]

So lizards are reptiles, not amphibians?

[Adam Claus]

That's correct.

[Sarah Bake]

Some lizards look a lot like salamanders, but salamanders are amphibians. And salamanders have scales, Right? Or do the skin not have scales?

[Adam Claus]

That gets back to what defines a lizard. So those scales are the big differentiator. So salamanders are going to have smooth sort of wet scale skin, or at least moist skin, somewhat similar to ours, versus a lizard is always going to have scales on its skin. That's the big separating or the big, that's the big differentiator between those two groups.

[Child Questioners]

Hi, my name is Quinton and I am six and a half years old and I live in Alaska, Anchorage. And my question is why do lizards have scales? Hi, my name is Rowan, I am six years old. I live in Houston, Texas. And my question is why do lizards have scales? My name's Finn and I'm five years old and I live in Raleigh, North Carolina. I want to know why do lizards have Scales. My name is Otis, I live in Torquay, Australia and my. And I'm six, about to send seven. And my question is, why do lizards have scales?

[Sarah Bake]

Can you go a little deeper into

[Jane Lindholm]

the scales of lizards?

[Adam Claus]

Yeah, so it really helps them to live in a lot of different habitats that would otherwise be very difficult for them to live in. The deserts, as I mentioned, are one of the prime examples. Deserts are very hard places for animals to live in because they're so dry and because they're so hot. And so when you have a protective layer of armoring over your skin like scales, which is what lizards do have, that opens up a whole realm of possibilities for places on the earth that they can live in and maybe avoid competition from other species that don't necessarily have those protections on their skin. And so that gives them the ability to live in places with less competition.

[Sarah Bake]

You also mentioned the scales help them keep moisture in. How do scales do that?

[Adam Claus]

So you can think of scales as sort of, they're very similar to your fingernails. So they're hard, they're impermeable to water. And so water doesn't travel through the scale the way it does through your skin. And so that's basically how it works. It's like a barrier. That's a good way to think of.

[Child Questioners]

I'm from Quebec, Canada and my name's Evelyn, I'm six years old. And why are lizards cold blooded? And why are people not cold blooded too?

[Adam Claus]

This is a really, really great question and I'm glad that you asked this one. So it's actually not true technically that lizards are cold blooded. The way it works is the big differentiator between lizards and say humans is that we maintain our body temperature and hence our blood temperature at a really consistent temperature. And we do that, which part of the reason we do that is to make sure that all of our organs are at the sort of the same optimal conditions for operating.

[Sarah Bake]

So if I go sledding in Vermont and it's 1 degree Fahrenheit, my body temperature is still staying around 98. And then if I come here to San Diego and I hike up the hills at 80 degree weather, my body temperature is still right around 98 degrees.

[Adam Claus]

That's right. But if you were a lizard and you went from the Arctic to the deserts, your blood temperature and your body temperature would mimic whatever the surrounding temperatures are. So sometimes that means that lizards blood temperatures are quite cold and other times it can mean that their blood temperature is quite a bit warmer than ours. So on average, yes, their blood Tends to be a little bit colder than ours, but it can also be quite a bit warmer than ours. So it's just their blood is not. It's not at a fixed temperature the way humans and mammals are. Their blood temperature varies according to the environment.

[Sarah Bake]

I thought that's what cold blooded was. So why do you say they're not technically cold blooded? This is like science that goes against what I was taught as a kid.

[Adam Claus]

So it depends on what you mean by cold. Right. If cold means colder than human blood, then it's not true because there are many lizards in many contexts that can have blood temperatures well over 100 degrees. And so that's. It's hard to argue that that's cold blood in that particular context. It's just that their blood temperature, it varies. It's not consistent.

[Sarah Bake]

I see. So it's almost like it's just a bad name for the way we regulate our temperature or the way they regulate their temperature.

[Adam Claus]

That's right. It's kind of an oversimplification of what they do.

[Sarah Bake]

Got it.

[Jane Lindholm]

Phew.

[Sarah Bake]

I was gonna have to review my whole worldview here if that was not the case. We have another question from Grayson.

[Child Questioners]

I'm Grayson. I'm five years old. I live in Pittsburgh, Pennsylvania. My question is, do chameleons sweep or hibernate? Because in the wildcats. So I saw them awake at night.

[Sarah Bake]

So Grayson wonders, do chameleons sleep or hibernate? How do lizards think about those two things? Which are quite different.

[Adam Claus]

They are quite different. So hibernation is typically something that a lizard is going to do if it lives in a really seasonal environment, where if it gets really cold during the winter and much warmer during the summers. During the winter, the lizard might cease or stop most of its activity. Its blood temperature will get quite cold, and it won't really be running its metabolism anymore. So it won't need to feed, it won't need to eat, and they'll just sort of like go into a long sleep, roughly analogous to what like a bear does during the winter. Right. But if you're a lizard that lives in a more warm or a more stable environment, you can be active all year round and you never really have to hibernate. Sleeping is a different matter. So sleeping is something that pretty much every vertebrate needs to do at some point on a daily cycle. And lizards are no different. So all lizards have to sleep similar to the way humans have to sleep.

[Sarah Bake]

So specific then to chameleons. Yes, they sleep. And are chameleons hibernators Most chameleons live

[Adam Claus]

in pretty warm climate. I think most chameleons, it's safe to say, do not hibernate, but there might be some that do, I'm not sure. The other thing to keep in mind is that some lizard species are fully nocturnal. So they're sleeping during the day and being out and about, foraging and looking for food and looking for mates at night. So that's the other important thing to remember when we're talking about lizards sleeping is they don't all sleep at night. Some of them sleep during the day.

[Jane Lindholm]

I looked this up, Grayson, and it appears that chameleons are generally not known to be nocturnal. But I've seen the Wild Kratts episode you're talking about, and there is that chameleon in the dark. That episode, though, also features another animal, a type of lemur known as an aye aye. And that animal is. Is nocturnal. So maybe the Wild kratts took some artistic liberties to make the episode work.

[Child Questioners]

I'm Julian. I'm five. I'm from Houston, Texas. And my question is why do lizards can stick their tongue out to their eye and we can't? My name is Agatha, I'm a six and I live in California. My question is, why do lizards and snakes and other reptiles stick their tongues out very often?

[Sarah Bake]

Tell us about lizard tongues.

[Adam Claus]

Yes, there's a couple things going on there. So first of all, only a few lizard species can actually lick their eyes. Most lizards, in fact, cannot, any more than most humans cannot lick their eyes. Right. But a lot of geckos can. And part of the reason why they do this, I'm generalizing a little bit here, but part of the reason is that a lot of geckos have a thin transparent scale that covers their eyes. And so they don't have eyelids. And so to clean their eyes, to clean the scale that covers their eyes, they don't have eyelids to do it. So they've co opted their tongue to do the work for them. So it's basically they're cleaning their eyes. Is the reason why they lick them

[Sarah Bake]

is that is eye scale different from a nictitating membrane that some animals have that can come down and protect their eye, but is different from an eyelid.

[Adam Claus]

It's very different in the sense that the scale is not related to an eyelid structure at all. It's a scale just like any other scale on the animal's body, except it's transparent.

[Sarah Bake]

So they can see through it.

[Adam Claus]

They can see through it, yeah. And that's also the case for snakes. Every snake has the same type of eye. They have a transparent scale covering the eye. And this is why some people don't like snakes when they see them, because they think they have this rigid, unblinking stare, right? Well, it's because they literally can't blink. They don't have eyelids.

[Sarah Bake]

So when a snake is about to shed its skin, sometimes its eye looks cloudy. And is that because it's sort of separating all of its scales from its body?

[Adam Claus]

Exactly. So because the scale over the eye is just like any other scale, it gets shed when the snake sheds its skin. And during that process, a very thin layer of moisture gets produced between the new skin and the old skin. And when you're looking at the eye, you're basically looking at that cloudy moisture separating the two scales. And it's only once the old scale gets sloughed off that the transparency comes back.

[Sarah Bake]

But lizards don't shed. Or do they?

[Adam Claus]

They absolutely shed. All lizards shed their skin, just like snakes do.

[Sarah Bake]

So you might see a lizard with a. A foggy eye, too.

[Adam Claus]

If it's one of the lizards that doesn't have eyelids, that's a possibility.

[Sarah Bake]

Okay, so back to their eyes. And their tongues is where we were really supposed to be going. So some of them can lick their eyes, but most can't. So what do they use their tongues for?

[Adam Claus]

So they use it for similar things that we use it for, for sort of manipulating food and moving food around within their mouths. Other species or groups like command chameleons, for instance, have highly adapted tongues where they're shooting the tongue way outside the mouth, and the tongues are very sticky, and they glom onto a prey item, like a cricket that they want to eat, and then the tongue pulls that cricket back into the mouth. That's sort of an extreme case. And then another purpose for the tongue is that a lot of lizards use it to sense smells in their environment. So they're using their nose similar to the way we use our nose. But the tongue is sort of the secondary sensory mechanism where they're detecting smells by sticking their tongue out and tasting the air or tasting the ground, as the case may be. So multipurpose tongues for a lot of animals.

[Sarah Bake]

Do lizards have forked tongues?

[Adam Claus]

Some do and some do not. So it depends on the group of lizard. So you can imagine a Komodo dragon, for instance, they have very deeply forked tongues. But your bearded dragon, which is you might have as a pet at home, they have just a tiny, tiny little fork at the tip of the tongue, but it basically looks like your tongue unless you're looking really closely.

[Sarah Bake]

Do you know how many kinds of lizards there are?

[Adam Claus]

There are over 7,000 described species of lizards and there are more being described every day. And so that's something that I do as part of my work as a scientist. So I've participated in the description of three new lizard species in my life and we're working on a couple more right now.

[Sarah Bake]

That's so exciting. What does it feel like to find a new lizard that hasn't been, as you, as you say, described before, that, you know, human. That doesn't mean that humans didn't know about it before, but it hasn't been put into the scientific record. What is it like to do that?

[Adam Claus]

It feels really cool. It's a real thrill. So one of my childhood dreams was to do this when I was the age of many of you listening right now. I wanted to describe new species when I was, was a boy. And so when I turned 30, I was finally able to do that.

[Sarah Bake]

What did you name them? Did you get the naming rights?

[Adam Claus]

Absolutely. So we were part of a team, so it wasn't just me. And so the team agreed for this particular lizard, we wanted to call it the Sierra Morena Arboreal alligator lizard. So it's kind of a mouthful, but they're very cool lizards that live up in the forest canopy. And that's part of the reason why this one went undiscovered for so long is because. Because they're really out of sight of where most humans are when they're walking in the forest.

[Sarah Bake]

What about its scientific name?

[Adam Claus]

Scientific name is Abronia.

[Child Questioners]

My name is Grace and I'm five years old and I live in Tempe, Arizona. And my question is, how do lizards stick to things? Hi, my name is Nicholas, I live in Halifax. I'm six years old and my question is is how do lizards attach to walls?

[Adam Claus]

So it's a little bit complicated and I will just say that it's not the same type of sticking. That is like when you think about stickiness, like if it's a post it note or tape, it's not that way on the lizard's feet. They don't have technically sticky toes. What they do have is toes that have these really big patches on the underside of the toes that have all these teeny, teeny, tiny, tiny hairs. And those hairs increase the surface area of those toe pads, they're often called. And so when they touch a surface, they have all this surface area from the toe that's contacting whatever it is that they're touching. And there's these very strange forces that only apply in really small distances. They're called van der Waals forces. It's a very complicated name. And basically these van der Waals for forces are what allow geckos to stick, quote, unquote, stick their feet to the walls.

[Sarah Bake]

So they don't have suction cups.

[Adam Claus]

They do not have suction cups. Some frogs do. Frogs use a suction cup action. But with lizards, it's a very different style of stickiness.

[Sarah Bake]

And not all lizards can stick to walls.

[Adam Claus]

Goodness no. There's actually only a small subset of lizards that can stick to walls. Most lizards cannot climb walls like that.

[Jane Lindholm]

Coming up. You may have heard that lizards can lose their tails and then grow new ones. Is that true? Stay with us. But first, a message for the adults who are listening. Support for our program comes from Oak Meadow, providing secular student centered homeschooling curriculum and a teacher supported distance learning school for K through 12. Oak Meadow has encouraged kids to follow their curiosity and uncover the answers to but why? For 45 years. To learn more, visit oakmeadow.com this show

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[Jane Lindholm]

this is but why? I'm Jane Lindholm and today we're learning all about lizards with Adam Claus, who manages the Reptile and Amphibian collection at the San Diego Natural History Museum. We did the interview down in the basement of the museum, where 80,000 specimens are preserved in jars full of liquid for scientists to be able to study and learn from them. Adam has been answering all kinds of lizard questions you've sent us. So let's get to some more.

[Sarah Bake]

Lizards are famous for being one of the kinds of animals that sometimes loses their tail and can grow it back. And we have a lot of kids who are wondering how they do that.

[Child Questioners]

Hi, I'm Rehan. I live in Jakarta, Indonesia. I'm six years old. And my question is, how do lizards grow their tails back? Hi, my name is luis. I am 11 and I live in Fort Collins, Colorado. And my question is, how do lizards tails grow back? Hello, my name is Lenka, I'm seven years old. I live in the Czech Republic. And my question is, when lizard's tail falls off, why does a new one grow? My name is Thomas, I'm four years old. I live in Pennsylvania Harmony. And my question is, why do lizards lose their tails?

[Adam Claus]

So not all lizards can break their tails, or at least not intentionally, but many lizards can. And they do it as a defense mechanism, as a way to escape a predator. So you can imagine if a dog or a cat were to attack a lizard and just grab it by its tail, the lizard would want to sort of separate itself from the tail, which is somewhat disposable, right? It can live without its tail, and then it can use that mechanism to sort of escape while the dog or the cat or whatever it is that attacked it is focused on the tail. And so most lizards that can lose their tails in that way, on each bone of the tail, each vertebra, there's actually a crack. And that cracks serves as the point where that tail will break if you squeeze it or grab it really tightly. So they're adapted to lose their tails. It doesn't really hurt them. They bleed very little when this happens. And in fact, the muscles at the tip of the tail where the break happens, they all clench down and prevent a lot of blood loss. So it's not great for the lizard, but they've adapted to where it's not this potentially lethal event in their lives. And then they regrow their tails. Because a lot of lizards use their tails for things like balance when they run or balance when they're climbing, they'll often use it as sort of a device or a way for males to signal their health to females. And so having a full tail is really important to some lizards for reproduction. And so the way they regrow it is they don't Regrow the bone. They can never regrow the bone, but what they can grow is like a little cartilaginous rod that grows out. It has a little bit of muscle and soft tissue around the edges and scales on the outside for the skin. But the regrown tail never, ever looks exactly like the original. So you can always tell when a lizard has broken off its tail if you look really closely, because the scales aren't the right size, the scales aren't the right color, and there's no bone inside. So if you X ray a lizard, you can know for sure if a tail is regenerated because the bones will. Will just stop and then it's just cartilage from then on.

[Sarah Bake]

Cartilaginous is one of my favorite words. It's such a good word. And if you want to think about what is cartilage versus what is bone, you can feel in your nose, the part that wiggles but is a little bit hard. That's cartilage. Or you have cartilage in the top of your ears and you can kind of bend it, but it still gives your body part that structure.

[Adam Claus]

Yeah, that's right. That's exactly right.

[Child Questioners]

Hi, my name's Talia. I'm six years old. I live in Marina, California. My question is, why do lizards have different teeth than humans?

[Adam Claus]

So it's mostly related to their diet. So if you have an herbivorous lizard, it's going to have teeth that are going to be slightly different for shearing off and then chewing up leaves or vegetation, versus a lizard that might be feeding on insects, and it needs to sort of capture its prey and hold onto it with much larger, sharper teeth. So it really all depends on what you're eating. Humans sort of have a mixture of teeth, right? We have a couple sharp teeth in our mouth, and then towards the back we have our molars, which are better for grinding food. And so we're well adapted to sort of eat both meat and plants. But most lizards don't do that sort of that breadth of what they can eat. They sort of specialize on one type of prey or another. And so their teeth just reflect that, that diet.

[Sarah Bake]

Are some lizards carnivores?

[Adam Claus]

Most lizards are. There's very few lizards that don't eat any meat, per se. Yeah.

[Sarah Bake]

All right, so here's one that we always have to answer for every animal, because it's just. I don't know, I think it fascinates us.

[Child Questioners]

Hi, my name is Maeve. How old are you? I'm six years old.

[Adam Claus]

Where do you live.

[Child Questioners]

And I live in Lanes, Massachusetts. And my question is, do lizards, do lizards poop or pee or do they have a combined? My name is Alice, I'm four old and I'm even Rutho. And my question is, why do lizards poop?

[Adam Claus]

All lizards poop and pee. I can say that unequivocally, no exceptions. The weird thing about their pee is that most lizards do not pee a fluid the way we do. Their pee is actually a solid, sort of chalky white or whitish yellow substance that's called uric acid. And so they do that to help reduce the amount of water that they lose from their bodies. And so this is particularly common in lizards that live in hot, dry places because pee creates a lot of water and water is really valuable if you're in the desert. So you don't want to lose a lot of your body's water by peeing. And so what lizards do instead is they concentrate their urine down to this chalky white substance. And that's how they get rid of their nitrogen waste. Instead of using water to dilute the nitrogen waste and expel it from the body. Poop is just kind of poop. It's the waste materials or the materials that an animal can't digest in its stomach or in its intestine, and so it's just pooped out as waste.

[Sarah Bake]

What color is that?

[Adam Claus]

Typically brown. But it can depend. It can depend.

[Sarah Bake]

When I got here to San Diego from Vermont and I knew I was going to come and talk to you, I was on a mission to see a lizard as quickly as possible. And I landed at night, so I didn't have a chance at night because we talked about how they're not going to necessarily be out as much in the night when it's cooler. And then in the morning I went for a walk and I saw a western fence lizard. Tell me about those.

[Adam Claus]

So they're really great lizards. I think you may have heard me talk about earlier, the lizards that I was catching in my backyard as a kid growing up, that was the lizard. So they're often sometimes called blue bellies because on the underside of their bellies, the males in particular, the boys, they will have these bright blue patches and they. And they use those to signal both to other male lizards. Hey, this is my territory, stay away. As well as to signal to female lizards, hey, I might make a good mate. I'm really healthy and vigorous. And so what they do is this really distinctive display that we call the push up display. So they will sort of push their Belly out so that it's sort of flattened. And then they will literally do push ups from their front legs to show off their bellies to any other lizards that happen to be standing, standing by.

[Sarah Bake]

Well, that lizard was either not a male or not impressed by me. It did not do any push ups.

[Adam Claus]

Sometimes they'll even do push ups at people if they sort of feel threatened and they're like, get away from me. This is my territory. They'll push up at you. They're very spunky.

[Sarah Bake]

What are some other cool lizards that are native to this area in the Southwest? Southern California and Mexico?

[Adam Claus]

The Baja Peninsula, there's so many. Southern California and the Baja Peninsula are some of the best places to be a lizard biologist because there's so many different types. One of the most famous one is a lizard that some of you may have heard of. It's called the chuckwalla. So this is the second largest lizard species in California. They're about the size of a bearded dragon and similar to a bearded dragon. They're sort of plump, right? They have a big belly. They're strict herbivores, so they're only eating plant material. And they like to live in rocks, specifically, like rock crevices. And so when chuckwallas feel threatened, they will enter a rock crevice and they'll wedge themselves as deeply as they can and then they'll gulp air into their lungs and they'll blow up their body like a balloon with air in their lungs. And by wedging themselves in with that air pressure, it's impossible to pull them out unless you do what the first peoples or the Native Americans would have done. Because these are such large lizards, they have really meaty legs. So there's a lot of dietary value in a lizard like that. So they would take chuckwalla sticks, basically a sharpened stick, and they would pop the chuckwallas like balloons and then pull them out from the rocks. So that's one.

[Jane Lindholm]

It's a good technique.

[Adam Claus]

It is a good technique. It worked. It worked. And you can find them in the deserts of Southern California as well as in parts of Arizona, southern Utah. So they're pretty widespread. Another really popular lizards or type of lizard is the banded gecko. So these are much smaller lizards. Unlike the chuckwalla, which are active during the day, the banded geckos are mostly active at night. And if you go and drive slowly on desert roads in the spring and summertime, you can find these geckos crossing the roads, walking along. And they're also pretty special because if they feel threatened. They can squeak. They can actually vocalize. Very few lizards can do this, but banded geckos are one of them.

[Sarah Bake]

Geckos are kind of famous for. For their vocalizations, right?

[Adam Claus]

Yeah, a lot of geckos can squeak.

[Jane Lindholm]

Geckos are very cool, but so are a lot of other kinds of lizards. We're going to end today's episode here because it's already getting really long. But we're going to come back with a bonus episode next week where we can get really specific about some extra cool kinds of lizards and your questions about them. Like how do chameleons change color? What's a Komodo dragon? And how did it get that name? What's the smallest lizard in the world? And have you ever heard of a tuatara? Looks just like a lizard, but is it Adam Claus, who manages the reptile and amphibian collection at the San Diego Natural History Museum, will be back to answer even more of your questions in that bonus episode. As you know, you can ask us a question on just about anything. Have your adult help you record you asking the question. They can use one of the free voice apps that comes on a smartphone and if you aren't able to talk or you don't want to share your voice, you can have your adult type out your question, then send it to questionsutwhykids.org we really wish we could answer all of your brilliant and thought provoking queries, but we do listen to them and sometimes, like in this episode, we come back to them months or even years after you've sent them.

[Sarah Bake]

It's hard not to get them answered right away.

[Jane Lindholm]

I know, but did you know we have more than 20,000 questions. We are trying as hard as we can to get to as many as we can. But why is made at Vermont Public and distributed by prx. Our producers are Sarah Bake, Melody Beaudet and me, Jane Lindholm. Joey Palumbo is our video producer and Luke Reynolds wrote and performed our theme music. If you like our show, please give us a review or a like on whatever platform you use to listen to us. We'll be back in one week with an all new episode. Until then, stay curious.

[Adam Claus]

From prx.