But Why, a podcast for curious kids, is known for serious answers to silly questions sent in by kids just like you.

But did you know that But Why is now a book series?

Our first book, Our Lama's Ticklish, answers questions from real kids about farm animals.

This colorfully illustrated book is perfect for kids ages 8 to 10.

And our second book, Do Fish Breathe Underwater, explores the underwater world of the ocean.

Learn more at butyKids.org slash books.

Music This is But Why? A podcast for Curious Kids from Vermont Public.

I'm Jane Lindholm.

On this show, we take questions from curious kids all over the world, and we go out and find answers.

This fall, on an exceptionally rainy afternoon, the But Why team drove over to New York City to visit a place called Governor's Island.

We had to take a ferry to get there.

We went all the way to Governor's Island, in the rain, because we wanted to learn about a very specific project and a very specific animal. See if you can guess what it is.

These animals live in salt water. They're pretty small. Most species could fit in the palm of your hand when they're an adult.

They filter as much as 50 gallons of water per day per animal, straining out pollutants and cleaning the

environment around them. They have no brains and no eyes, but they do have a heart, and they're

famous for making pearls. That last fact might have given it away. We're learning about

oysters today. When you think about New York

City, oysters probably aren't the first thing that springs to mind. But over a hundred years ago,

New York was known as the oyster capital of the world. You could buy oysters from carts all

across the city and oyster shells were used in building

construction. The oysters themselves helped keep New York Harbor clean. Over time, though,

the oyster population declined, a result of over-harvesting and water pollution. And when New York

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