(Intro)

J: It's Valentine's Day!  I was just about to check the mailbox to see if we got any Valentines from our friends.  Wow, Squeaks, we got a whole bunch.  Let's read them.  The first one is sort of wet.  Oh, no wonder, it came from our friend Mickey the (?~0:23) shark.  Let's read it!  "Roses are red, the ocean is blue, I lost all these teeth, but I'm glad I found you."  That's so sweet!  Sharks are awesome and this video has some amazing facts about them.

When you think of a shark, what do you picture in your mind?  Do you think of a big fin sticking out of the water or maybe a huge set of sharp teeth?  Sharks are some of the most famous animals in the ocean, but do you know what makes a shark, a shark?  Well, for one thing, all sharks are fish.  That might not surprise you since they live and swim in the water, but sharks are a special kind of fish.  One of the things that makes them different from other fish like goldfish is that sharks have a special skeleton.  Our skeletons are made of bone and so are the skeltons of most kinds of fish, but a shark skeleton isn't made of bone.  It's made of cartilage and you can have cartilage on your body, too.  You can feel it right now.  Touch the tip of your nose.  Wiggle it around.  How's it feel?  What about your ear?  Can you bend it?  You sure can, because the tip of your nose and your ear aren't filled with bone, they're filled with cartilage.  Cartilage is a lot lighter than bone and it bends easily, so having a skeleton made of this stuff helps sharks swim farther and faster than if their skeletons were made of bone.

Now let's look at another body part that sharks are famous for: their teeth.  Have you ever lost a baby tooth and then an adult tooth grew in?  Well, sharks lose their teeth all the time, throughout their entire lives, and they just keep growing new ones.  How can they do that?  You and I just have one row of teeth in our mouths, but sharks have lots of rows of teeth on the top and the bottom.  

So when a shark loses a tooth, another tooth that's right behind it can just swoop on up to take its place.  Because they always have new teeth to replace the old ones, some sharks can lose thousands of teeth during their lives.  

Alright, the next cool thing about shark: their skin.  If you could rub the skin of a shark, you'd find that it would feel smooth if you ran your hand in one direction, but if you rubbed your hand the other way, it would feel rough, like a cat's tongue.  That's because a shark's skin is covered in tough bony scales that actually look a little like tiny teeth.  These little scales are stacked on top of each other like tiles on a roof.  This helps sharks swim through the water quickly and quietly.  

So those are some of the things that all sharks have, but there are over 450 types of sharks in the world and that means a lot of differences, too.  Take a look at this one.  It's called a whale shark, and it's the biggest shark there is.  In fact, it's the largest fish in the whole world.  Whale sharks can grow to be as long as a school bus, but even though they're so big, they eat tiny plants and super small animals called plankton that float in the water, but not all sharks are as big as the whale shark.  

Some can also be tiny.  Meet the dwarf lantern shark.  It's so small that it could fit in my hand.  This shark lives in the deep ocean where there's very little light, so it has big eyes to help see in the dark, plus it has a really neat feature: it has special organs on its belly, fins, and tail that actually glow.  Scientists think this might help the lantern shark lure in prey for it to eat.  Plus, when it's in shallower water where there's more light, these glowing lights can help it blend in to avoid predators.

Finally, I'd like you to meet a very special shark.  Say hello to the greenland shark.  This big shark spends most of its time swimming in very cold water, hanging out near the sea floor looking for an easy snack, but scientists have recently discovered something amazing about these animals.  Greenland sharks can live to be up to 400 years old.  Of all the animals in the world with backbones known as vertebrates, greenland sharks live the longest, at least that we know of, but scientists are still discovering new kinds of sharks all the time, so who knows what kinds of super sharks are still out there waiting to be found.

Ohh, this next one from Mei, the giant panda, all the way from (?~4:20), China.  Oh, look, Squeaks, she sent us candy, too.  Oh man.  Oh, it's bamboo.  Let's read the card.  "There once was a panda so rare, we could barely find it a pair, but if you'll be its mate, boy, that would be great, what better friend than a bear?"  Mei is a great friend, and I'm glad people are helping the pandas.  In this next video, we talk about why pandas have a problem and how people can help.

I'm thinking of an animal.  It's black and white, furry, and kind of looks like  a teddy bear.  You're right, Squeaks, it's a panda.  Kids all over the world have heard of pandas, but have you ever seen one?  If you're lucky, you may have seen one in a zoo, but I'm pretty sure you've never come across one just walking around.  That's because pandas are very rare and we can learn a lot from them about what all kinds of animals need to survive in the wild.

The animals you and I know as pandas are actually called giant pandas, and they're bears, in the same family as brown and black bears, and pandas, like all animals, need certain things to live, like food, water, and a place to sleep and be safe.  We call the place where an animal has all of these things that it  needs to live its habitat.  The place where you live is your habitat, but let's find out what a panda's habitat looks like.  All pandas that live in the wild, that is, they aren't in zoos, can be found in the mountains of China.  The weather there is cool and wet, and the forests in these mountains make up the panda's habitat.  Pandas make their homes, called dens, in places like the stumps of old trees or inside big hollow logs, so these mountain forests give pandas a place to sleep and be safe, but a habitat also needs to provide food for the animals that live there and the panda's favorite food, by far, is a plant called bamboo.  

Pandas eat a lot of bamboo and quickly.  They have to eat a lot to get as big as they do, but the problem with the panda's diet is they don't eat much else.  The fact is, they're very picky eaters, so a panda's habitat has to have a lot of bamboo growing in it.  Luckily, the cool wet forests are China are a great place for growing bamboo.  All in all, these forests are the perfect habitat for pandas, but there is a problem.  The pandas' habitat is getting smaller.  A long time ago, there used to be a lot of mountain forest for the bears to live in, but people started cutting down a lot of the forest to make room for buildings and to use the wood for fuel.  As they did this, the pandas' habitat got smaller and separated into pieces.  Pandas started to have problems finding enough food to eat and safe places to have their babies, and as their habitat got smaller, so did the number of pandas, so today there are far fewer pandas than there were a long time ago.  Scientists think that there are fewer than 2,000 pandas living in the wild today, but there is good news.  Once people learned that pandas were in trouble, they started to do things to help them.   People aren't allowed to cut down the trees in the pandas' habitat anymore and scientists and volunteers have planted bamboo and trees to try and make the pandas' habitat bigger again.  It's hard work, but lots of people are trying to solve the problem.  So pandas are already famous for being cute and cuddly but they're also a great example of how all animals need a healthy habitat in order to survive and how sometimes, we can help protect it for them.

Huh, this next one has got to be from Dino.  "From the tip of my nose, to the tip of my tail, I've got dino-size love that could tip all the scales."  Aw, can you tell how much Dino likes dinosaurs?  Remember when he came by and he taught us all about them?  Alright, guys, we invited a friend over to hang out today.  He's a lot of fun.  His name is Dino and he loves dinosaurs.  

He has all kinds of dinosaur costumes.  

D: It's true.  Dinosaurs are so cool.

J: And who are you wearing today, Dino?

D: T-Rex.  My favorite dinosaur right now is actually the ankylosaurus, but they had four legs so that costume is kinda awkward.  Plus, I got grape juice on it so my dad has to wash it.

J: Well, I think you look great.  You might already have guessed this, but Dino knows all sorts of things about dinosaurs.

D: I love reading about them.  I've read all the books about them in the library.

J: Well, why don't you tell us a little bit about what you've learned so far.  Maybe you can start with this: what makes a dinosaur, a dinosaur?

D: Hey, good question, Jessi.  There were all kinds of dinosaurs that lived millions of years ago.  Some had two legs, like t-rex here, and some had four legs like ankylosaurus.  Some ate plants and some ate other animals, but they all had a few things in common.  

J: Like what?

D: Well, one way to tell whether an animal was really a dinosaur or not is to look at its legs.

J: Its legs?  Really?

D: Yeah.  Let me show you.  First have a look at this guy.  It's a komodo dragon.  It's the biggest lizard in the world today that lives on some islands in Asia, but komodo here isn't really a dragon.  It's a reptile.  It has scaly skin and a long tail and I can totally see how some people might think it looks kind of like a dinosaur, but look at its legs.  Its legs stick out from the sides of its body, so its feet are out on the sides, too, almost like it's doing push-ups.  

J: Oh, okay, I see what you're talking about there, but how did a dinosaur's legs look?

D: Well, have a look at this skeleton of a stegasaurus.  This fellow lived in North America millions of years ago and its feet are directly underneath it.  Dinosaurs' legs were kind of like posts for pillars that held up their heavy bodies.  If their legs stuck out to the sides, they wouldn't be able to stand up, so dinosaurs had their feet directly underneath them, while other reptiles like lizards and alligators and komodo dragons have legs and feet that stick out to the sides.  Not that there's anything wrong with that, I mean, some of my best friends are lizards and alligators.  They're just not dinosaurs.

J: Cool!  I've learned something already.  Well, how else could you tell if an animal that lived a long time ago was a dinosaur?

D: A lot of things that dinosaurs had in common weren't so much about how they looked but about how they lived.  For example, dinosaurs only lived on land.  

They didn't live in water and they couldn't fly.

J: Couldn't fly?  Really?

D: Really.  You've probably seen pictures of an animal like this before, right?  They were amazing flying reptiles and they lived back in the time of the dinosaurs, but they weren't dinosaurs.  They were pterosaurs, a whole different type of ancient reptile.  Unlike the dinosaurs, they had hollow bones and big flaps of skin like wings which they used to fly.  They also had really long narrow skulls with big brains inside, but dinosaurs didn't have any of those things.  I mean, I've never seen a t-rex with wings, have you?

J: No.  No, I can't say that I have.  But you also said that dinosaurs didn't live in the water?

D: Nope.  They only lived on land.  There were all kinds of huge reptiles that lived in the oceans back in dinosaur-times, but none of them were dinosaurs.  They were different in a lot of ways.  Like some were called plesiosaurs and didn't lay eggs like dinosaurs did.  They just gave birth to live babies.  Could you believe that?  And another kind of swimming reptile were the mososaurs.  They were actually related more to snakes than to dinosaurs.  Just like snakes, that could open their mouths so wide that they could actually eat things that were bigger than their own heads.  Kinda wish I could do that, especially with apples.  I love me some apples.

J: So I can see from the fins and flippers on these swimming reptiles that they were adapted to life in the water.  So if I see a fossil or a picture of a reptile that lived a long time ago that had fins and flippers, I know it's not a dinosaur, right?

D: That's right, Jessi.  Dinosaurs lived only on land and stood with their feet right under them instead of to the sides.

J: Got it.  Thanks for sharing what you've learned with us, Dino.

D: Oh believe me, Jessi, I could go on all day.  

J: Oh, I bet you could.  

Alright, what's next?

S: Hi, Jessi.

J: Oh, hi, Sam.  What are you doing here?

S: Well, I'm glad you asked.  See, in addition to being an excellent astronomer, I'm also an excellent poet and I wrote a poem that I wanted to share with everybody.  May I read it?

J: Oh, of course you can.  I can't wait to hear it.

S: One second.  

J: Okay.

S: I have eaten the bugs that were in the forest and which you were probably saving for morning.  Forgive me.  They were delightful, so sweet and so crunchy.  

Thank you.  

J: That was great, Sam, and as my valentine to you, here's a whole bunch of cool stuff about bats.

I'm thinking of an animal.  It's small and furry.  It can be pretty cute and it flies around at night.  Can you guess what animal it is?  That's right, I'm thinking about bats.  Some people think bats are scary, maybe because they only come out at night or maybe because sometimes they live in dark places or maybe it's because some species of bats, called vampire bats, survive by drinking blood, but you probably won't ever run into a vampire bat.  Only three species of bat are blood drinkers.  The rest of them, over 1200 species, eat fruit, nectar, bugs and other small animals.  If you ask us, bats are totally awesome.  Here are just three of our favorite things about them.

To start, some bats can hear their way in the dark.  That's because they don't rely on their eyes like we do.  Instead, bats use sound to find their way around.  Have you ever yelled into a big empty room or a canyon and heard your own voice shout back at you?  That's called an echo, the sound of your voice moves across the room, to the walls, and then bounces back to your ears.  As a bat flies through the night, it does something really similar.  It makes a sound and then carefully listens for the echo, and the way the echo comes back can tell the bat a lot about what's around it.  This special skill is called echolocation.  If the echo comes back quickly, that means there must be something pretty close to it, becuase the sound only travels a short way before bouncing back, but if the echo takes a long time to bounce back, then the bat knows that the object is further away.  Bats can tell not only how far away something is, but also how big it is and how fast it's moving all from using echolocation, and since bats are constantly using echolocation to figure out the world around them, you'll often see them flying around with their mouths open to keep making sounds to bounce back.

Another thing we like about bats, they really like to hang out.  Bats hang upside down in quiet dark hidden places like the roof of a cave or the underside of a bridge, but how?  When I hang upside from the monkey bars, after a while, I start to feel like my head is going to explode.

Bats can hang for a long time because their bodies are built for life upside down. The little pathways through their bodies that blood moves through called arteries have special valves in them that only let blood through one way. As the bats heart beats, the blood has to keep moving through the bats body in one direction. That keeps the blood from getting stuck in the bats head while hanging upside down.
That's a pretty neat trick! But you know another thing that's easy to like about bats? They make really great moms!Bats usually have one baby, called a pup, in a year. At the beginning of that pups life it clings to its mothers bell all the time while the mom wraps her wings around it. Maybe we should stop calling good snuggles bear hugs and start calling them bat hugs!
And thousands of moms and their pups can live together in a huge group called a nursery. Even when it's cold outside the nursery stays warm because of all those bats hanging close together. Plus, when mom needs to go out and find food, she can just drop her baby off at the nursery with all the other moms and pups. When she comes back you might think it would be hard to find your baby again, I mean, there are thousands of pups that look just like hers. But bats and her pups can recognize each other through their smells and their voices. So when the pup calls out, the mom can fly right to it. It would be like trying to find your family in the midde of a crowded amuesment park, except all of the other kids in the park are calling out for their mother too! So what do you think? Aren't bats scary cool?
Ok, there's one left, and it's from you Squeaks! Oh, what a great surprise!
"Whenever I get hungry, I look around for snacks. Grains, and fruit, and vegetables, and even cracker jacks! Left and right are lots of things on which little rats can dine, but it doesn't matter what we eat dear, as long as you are mine."
Ahhh, that's super cute! Thanks Squeaks! I really like you too, and I really like rats. Do you remember when we learned all about them? Today is a day that Squeaks has been looking forward to for a long time. That's because today we're going to learn all about rats!

When you think of rats, you might think of animals that live in creepy places like empty buildings, or dark alleys, or even sewers. But rats make their homes in lots of places from deep underground to high up in trees. In fact, a lot of what people think they know about rats isn't true at all.

So Squeaks and I thought it would be fun to play a little game.  I'll say something about rats, and then you guess whether that sentence is true or false then Squeaks can tell us the right answer.  You ready?  Let's play.  True or False, rats are dirty animals?  What do you think?  False.  Rats are actually very clean.  Rats lick their fur to keep it clean.  They also lick their paws and then use them to clean their faces and whiskers.  When animals clean themselves like this it's called grooming, and rats groom a lot.  They sometimes clean themselves even more than cats do.  People often think rats are dirty because some rats can carry diseases that make us sick.  So while a rat isn't dirty, if you see a rat running around where you live or think there might be one, you should leave it alone and tell a grown up.  

Okay, let's try another one.  True or false: rats like to swim.  That's a tough one.  This one is definitely true.  Rats are really good swimmers.  Scientists have learned that rats can tread water or swim in one place for up to three whole days without a break.  That's awesome.  They're good at swimming long distances, too.  Rats can swim almost a kilometer without stopping and they can hold their breath for about three minutes.  That's way more than you could.  Okay, let's try another one.  

True or false: rats have excellent eyesight?  This one is false.  Rats can't see very well at all, but they make up for it using their other senses to stay away from predators, to find food, and to find their way around.  Take, for example, a rat's sense of smell.  A rat's nose is so sensitive that it can learn about another rat just by smelling it, like whether it's sick or not.  Rats have even been known to smell each other breath to see what they've been eating. 

If a rat smells that smell again, it knows that whatever is making that smell is good to eat. A rats' hearing is also excellent.  Try it. Hold your hand in front of your face and gently rub your pointer and thumb together.  Can you hear anything?  A rat can.  Noisies that we can't hear, or can't hear very well, can sound perfectly clear to a rat.  

Ok, here's another good one.  True or false,  rats can chew through cement.  Whoa, now that sounds extraordinary. Do you think it's true or false?  Believe it or not, this one is true.  A rats mouth has everything it needs to chew through some really hard stuff.

Rats belong to a group of animals called rodents.  Rodents  use their incisors or their front teeth to bite, and like all rodents, a rats' incisors never stop growing.  Rats need to chew on things to keep them from getting too long, so rats chew, and chew, and chew a lot. The fronts of a rats' incisors are harder than your teeth.  They're even harder than some metals like copper and iron. But, these extra hard teeth are only one thing that makes a rat a champion chewer.  

Put your fingers on your face, just in front of your ears and below your cheekbones.  Now, open and close your mouth.  Can you feel those muscles move?  These muscles move your jaw, the bottom part of your mouth.  Rats have special jaw muscles that help them bite.  And, they can bite hard.  Rats can bite harder than a Great White Shark.  So, between their strong jaw muscles and hard teeth, rats can chew through wood, metal, plastic, and yes even cement.  

Alright, let's try one more. True or false, rats are not very smart.  Of course Squeeks, this one is definatly false.  Rats are very clever. They can learn very quickly. Some times, even faster than people can.  They are also great at remembering things and they can solve problems like how to get where they want to go.

Rats aren't only smart, they're also kind to each other.  Rats have been known to share food with other rats, and have even been known to figure out how to open another rats' cage to set them free. 

So I'm glad my best friend is a rat.  I want to thank all of our amazing friends for these great Valentines, and I want to thank you for joining us today.  

Do you have any questions about the incredible animals we learned about today, let us know.  Grab a grownup to help you leave a comment down below or send us an e-mail to kids@scishow.com.  Thanks for joining us, and if your celebrating it, Happy Valentines' Day.  

music