There's a type of white-tailed deer that's unique to the Florida Keys.

It's been on the endangered species list for nearly 60 years, and only about 800 of them remain.

And its habitat is under growing threat from rising sea levels.

William Brangham has the latest in our series, Saving Species.

These tiny deer roam freely across front yards

and graze on the side of the road on some of the many islands of the Lower Florida Keys.

They are very gentle, very, very gentle.

And the longer you live here, the more you want to protect them.

The key deer is the smallest subspecies of the North American white tail deer.

They're about the size of a golden retriever.

They only come to about 24 to 30 inches at shoulder height, so they are substantially smaller,

and they're only found here in the Lord of Keys.

The first written record of the key deer came from a 16th century Spanish shipwreck

survivor.

They currently live on only about two dozen of the Keys' 1,700 islands, swimming or wading

between them and living in the mangroves, pine rocklands, and freshwater wetlands.

Climate change is the thing that's going to get them.

But it's those very habitats that are under threat from rising sea levels.

Chris Berg is with the Nature Conservancy.

This is a success story until now.

These animals have been doing very well.

They've been coming back.

...