text:  This is All Things Considered from NPR News. I'm Mary Louise Kelley. And I'm Juana Summers. There's something really special that happens every spring in northern Belize in a spot that was once a Mayan metropolis. Dozens of researchers from around the world converge on a little eco lodge in a tropical forest. They gather there to study the stunning diversity of bats in the region. And that's because bats, scientists say, have a lot to teach us humans about our changing planet and even about ourselves.