Why don't carnivores need to eat their vegetables?

[REWINDING SOUNDS] AUDIO TRACK: Brains On!

MOLLY BLOOM: You're listening to Brains On from MPR News and Southern California Public Radio. We're serious about being curious. I'm Molly Bloom, and it's great to be back. I've been away having and taking care of my baby daughter Lulu. And to those listeners who have written in wondering-- and yes, there really are listeners who have written in wanting to know-- she is very cute.

But as much as I like talking about her, we are not only here to talk about the baby. We are here to answer a question. And it's a good one? Kayam from Duchess, Alberta, wrote in with this question. He wrote, we have to eat vegetables to be healthy. Why do carnivores not require the same nutrients and minerals found in vegetables? That is an excellent question, Kayam.

Well, this is definitely not a scene that you will ever hear at a cheetah's dining room table.

DAD CHEETAH: Eat your vegetables, please.

CHILD CHEETAH: Do I have to?

DAD CHEETAH: Yes.

CHILD CHEETAH: Why?

DAD CHEETAH: Because vegetables provide you with essential vitamins, minerals, and fiber.

MOLLY BLOOM: OK, so there are a few reasons this conversation would never happen. First off, cheetahs don't speak English, they speak cheetah. Also, cheetahs don't care for formal dining areas, much less tables. But most importantly, it's because they're carnivores. Carnivores are animals that eat other animals. Some examples are snakes.

[HISSES]

Lions

LION: Rawr.

MOLLY BLOOM: And owls.

[HOOTS]

Humans.

HUMAN: Um, hello.

MOLLY BLOOM: As well as animals like chipmunks.

CHIPMUNK: Chipmunk, chipmunk.

MOLLY BLOOM: Bears.

BEAR: Growl.

MOLLY BLOOM: And bluejays--

BLUEJAY: Tweet, tweet.

MOLLY BLOOM: --are omnivores. That means we eat both animals and plants. And then there's herbivores. Like elephants.

[TRUMPETS]

Cows.

COW: Moo.

MOLLY BLOOM: And rabbits.

RABBIT: Hop, hop.

MOLLY BLOOM: They eat only plants. So imagine some animal pals going out for lunch at the hot new salad bar in town.

[CLINKING]

RABBIT: This salad bar is amazing. The carrots are cut into five different shapes. Did you see them, gazelle?

GAZELLE: Of course, Rabbit. You couldn't stop pointing at them.

RABBIT: No, yeah.

GAZELLE: Their fresh grass selection is very impressive. Organic, gluten free, artisan cut. You can really taste the difference.

MOUSE: Not to mention, oh, this fruit. So fresh. Mouse loves fruit.

[CHOMPS]

RABBIT: Hey, Lion, what's up with the empty plate? Do you mean to tell me you couldn't find a single thing to eat from this eye-popping selection?

LION: Well, Rabbit, I'd say this place is more targeted at the herbivores among us.

RABBIT: Oh, right. Well, it was Gazelle's turn to pick the place.

GAZELLE: Don't blame me. He's just a picky eater. Besides, it has five starfish on Yowl, so you know the food is good.

LION: Actually, Gazelle, I couldn't eat that grass even if I wanted to, which I most certainly don't.

GAZELLE: What? But it was grown using no harmful pesticides by local farmers. It actually came from the front yard.

LION: My digestive tract is not built like yours. Mine is basically an elegant tube. In and out goes the food. You have a four chambered stomach that allows you to break down the tough fibers of plants, like grass. With help from all those wonderful little microorganisms living in your gut. And you and Rabbit and Mouse all have places where those tough morsels can sit and be digested over time.

Me? Not so much. My food passes through at a much quicker pace. I even have a different set of microorganisms tailored to my more refined tastes in food.

MOUSE: Bummer for you, then. More for Mouse.

[CHOMPS]

GAZELLE: Mouse, don't be rude. We need to find something for him to eat.

RABBIT: Yeah, Mouse. Maybe this server knows if this salad bar has any secret non-vegetarian options. I mean, they got to have something right, Mouse? Mouse? Mouse? Where'd you go? Wasn't she just here a second ago?

GAZELLE: I could have sworn maybe she went to go find the waitress?

RABBIT: Yeah?

LION: How odd. Well, I'm sure she'll turn up eventually. One way or another.

GAZELLE: Well, riddle me this, Lion. If you can't eat plants, how do you get all the vitamins and minerals and stuff that you need? I get that from my grass. It's chock full of good stuff.

LION: Well, you know there are vitamins and minerals in the things I eat, too.

GAZELLE: Like what?

LION: Well, organs are very nutrient rich. And then there's bones, a great source of calcium. Viscera isn't just a beautiful word. It tastes divine.

GAZELLE: Bones?

[SNICKERS]

Get a lot of that, Rabbit. He eats bones. Rabbit? Now Rabbit, too? They're probably both in the bathroom. Yeah, they probably went to the bathroom.

LION: Sometimes I enjoy some fur, too.

[GULPS]

My favorite, however, is the liver. Delicious.

GAZELLE: Yeah. So that sounds great. You know, I just remembered I have an appointment.

LION: Oh, really? Where?

GAZELLE: Somewhere else. Not here. Got to go!

[CLINKS]

[GALLOPS]

LION: You know what? I'm full, too. Till next time, Gazelle. Waitress, waitress? Can I get the check? I think my friends won't be paying for their meals. Unfortunately.

[VOCALIZING]

AUDIO TRACK: Brains On.

MOLLY BLOOM: So the reason carnivores don't need to eat their vegetables-- they can't process plants the way herbivores do. And they've evolved to get all the nutrients they need from the animals they eat. We're going to hear more about feeding animals in a little bit. But first, we're going to feed your ears. It's time for the mystery sound.

[MYSTERY SOUND CUE]

AUDIO TRACK: Mystery sound.

MOLLY BLOOM: Here it is.

[CHIRPING]

Any guesses? We'll be back with your answer right after this.

Do you have a question you want to hear answered on Brains On, a mystery sound to share, or a drawing? Maybe you want to show us what that fabulous new salad bar looks like. You can email us any time. We're at brainson@m-- as in Minnesota-- pr.org. You can also find our physical mailing address as well as all of our past episodes at brainson.org.

Now it's time for the ceremonial reading of the newest additions to the Brains Honor Roll. These are the kids who keep this show going with their questions, creativity, and high fives.

[MUSIC PLAYING]

[LISTING HONOR ROLL]

AUDIO TRACK: Brains Honor Roll. High fives.

MOLLY BLOOM: Now back to that mystery sound. Let's hear it one more time.

[CHIRPING]

What's your guess? Here's the answer.

MORTON: Hello. I'm Morton, and I'm four years old.

FEENY: I'm Feeny. I'm four years old.

NICO: Hi, I'm Nico. I'm seven years old, and I'm almost eight. We're from Sterling, Virginia.

FEENY: That was the sound of our four week old chicks.

MORTON: Their names were Chirpy, Chappy, Flowers, Fluffball, and Flap. And they were very cute. They are also very, very messy.

MOLLY BLOOM: Did you guess right? Did you guess that that was the sound of chicks? Chicks are baby chickens, and they're omnivores. They eat insects as well as seeds, fruit, and other plant matter. And as we just learned, omnivores, herbivores, and carnivores all have very different ways of digesting and getting the nutrients they need.

In a place like the National Zoo in Washington DC, it's someone's job to make sure all the animals, from ants to zebras, get the right nutrition.

MIKE MASLANKA: My name is Mike Maslanka. I am the head of the Department of Nutrition Science for Smithsonian's National Zoological Park and the Conservation Biology Institute.

MOLLY BLOOM: The carnivores there rely on Mike for their diet.

MIKE MASLANKA: In a zoological setting, when it comes to feeding carnivores, we can't feed out gazelles to our cheetahs. So what we do is we feed out commercial meat mixes that have nutrient profiles that look like those gazelles. What we do is we have a ground beef that mixes in other nutrients that those carnivores need. As with most solutions, they're not always perfect.

And so in this case, we also feed bone, and we also feed whole prey. So things like rabbits and rats and mice. Because all of those things are important for us to provide a balanced diet and provide variety. When these animals first came in to zoo settings, they were fed carcass. And then because that was difficult, they migrated towards feeding them slab meat, which is basically steak. And they weren't getting that calcium.

So we had lions and tigers and cheetahs that had metabolic bone disease. So then we created these commercial diets. But they're soft diets, and they don't require a lot of chewing. They meet all the nutrient needs. But from a behavioral standpoint and from a physical standpoint, they might not be meeting some other needs. So now we're coming all the way back to the beginning and saying, hey, maybe we ought to go back to feeding more carcass? Because it's better for these animals in terms of providing them with a wider variety of nutrients, more fiber, and then giving them something in a physical form that challenges them to eat.

It's interesting. With every new case that we have and every time that we really dig down deep into a new species, there are so many things to be excited about and learn about. One day, we're working on how to feed a colony of leaf cutter ants. And the next day, we're working on feeding zebras. And the next day, it's Komodo dragons. And the next day, it's migratory passerine birds.

MOLLY BLOOM: So there are still mysteries for scientists like Mike to solve.

MIKE MASLANKA: One of the research projects I'm involved with is looking at the diet of whale sharks. We don't know where whale sharks go for probably six months out of the year. We don't know where they're bred. We don't know where they give birth. The biggest fish in the ocean-- this shouldn't be difficult to figure out. And yet we still don't know that.

[MUSIC PLAYING]

MOLLY BLOOM: That's it for this episode of Brains On. Brains On is produced by Marc Sanchez, Sanden Totten, and me, Molly Bloom. Many thanks to Julie Churchill, Eric Ringham, Anna Weggel, and Lizzie and Matt Sepock. If you're a fan of the show, consider leaving a review in iTunes. It really helps spread the word about Brains On.

You can also keep up with us on Instagram and Twitter. We're at @brains_on. And of course, there's Facebook, too. We'll be back soon with more answers to your questions. Thanks for listening.