MICHEL MARTIN, HOST:
Wildlife enthusiasts have been flocking to a park in northern Virginia looking for some unusual frogs.
RAYNA BELL: They're blue green tree frogs - blue individuals of the green tree frog species.
MARTIN: Rayna Bell is the curator of amphibians and reptiles at the California Academy of Sciences. She's studied blue frogs. And that's not easy to do because it turns out they're pretty rare.
BELL: I still have never found my own blue frog in the wild (laughter). For instance, if I had a graduate student who was really interested in studying blue frogs as their dissertation project, I would say, that's a terrible idea because you have very little chance of ever finding one in your entire career.
LEILA FADEL, HOST:
Bell first heard rumors of blue tree frogs in Virginia around seven years ago. Based on recent photographs from Huntley Meadows Park in Alexandria, Bell says it doesn't look like just one frog.
BELL: At least for that particular species, there are a couple of pockets in sort of the mid-Atlantic area that maybe have higher proportion of these blue individuals.
MARTIN: So why exactly do some green tree frogs turn out blue?
BELL: It could be a mutation in one of the genes that's responsible for either producing or metabolizing yellow pigments.
MARTIN: And if you take the yellow out of a green frog, you're left with a blue frog. Bell says the genes that make yellow pigment are not well understood in frogs.
BELL: The other option is that there's something different about their diet, because for a lot of frog species, they get yellow pigment from their food. And then the third option is that there's something about the environmental conditions.
FADEL: It's not clear whether the blue color helps with survival. Bell's guess is that it hurts.
BELL: Green frog species usually are green because it helps them blend in with their habitats and not be detected by predators. And so blue tends to be a much more conspicuous or showy color.
FADEL: Bell says there are many unanswered questions. Do the frogs start green and then change into blue? Are they born blue? Do they pass on their color to their offspring? The wildlife hobbyists staking out at the Virginia park may help find answers.
BELL: Having nature enthusiasts spread out around the world taking pictures of things that they see when they're out is orders of magnitude more powerful than what over a century of scientists have been able to document.
MARTIN: So if you run into a blue tree frog, help a scientist out - take some pictures.
(SOUNDBITE OF SONG, "BLUE")
BILLIE EILISH: (Singing) And I'm still so blue. And it's not true. Transcript provided by NPR, Copyright NPR.
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