El Niño, Frogs & Ponds
Air Date: Week of March 27, 1998
How does nature benefit from El Niño? This year's storms left the ground along the coasts so saturated that today even brief showers leave pools of water standing on roads and in fields. And as Aileen LeBlanc, of member station WHQR in Wilmington, North Carolina reports, certain amphibians are finding this year's weather not only perfect, but essential.
CURWOOD: The arrival of Spring signals, at least officially, the winding-down of the most extreme El Niño season on record. California and the Southeastern US were especially hard hit by tornadoes and record rains that left death and destruction in their wake. The storms also left the ground along the coast so saturated that today even brief showers leave pools of water standing on roads and in fields. People are not pleased by this turn of events, but as Aileen LeBlanc of member station WHQR in Wilmington, North Carolina, reports, certain amphibians find the weather not only perfect but essential.
LE BLANC: The woods on the backside of the island of Carolina Beach are dense and thick with underbrush. A few downed trees from our last hurricane lie across the path. It's quiet and undeveloped here, a real contrast to the boardwalk and the beaches on the ocean side. Herpetologist Andy Wood leads the way toward a remote wetland: the breeding ground for a whole community of amphibians.
WOOD: We probably should see a couple of snakes, too.
LE BLANC: Really?
WOOD: Because it's nice and sunny, first good sunny spring day.
LE BLANC: Along the way the naturalist teases this city dweller.
They're coming out to sun themselves?
WOOD: Well, that and look for stuff to bite just because they're in the spring are really foul-tempered. You've got to get rid of that extra venom that's been packed up in there. Go ahead and see, there goes one.
LE BLANC: He's joking about the snakes, thank goodness. Besides, we're not here to find snakes. We're looking for frogs and salamanders, which thrive in springtime ponds called ephemeral, or vernal, pools. Andy Wood runs education programs at the nearby North Carolina Aquarium. He spends his spare time dipping nets into these tiny temporary ponds wherever he can find them. For 14 years he's been recording the ebb and flow of vernal pool populations here. He says thanks to the El Niño rains, this is a bumper year for his amphibious friends.
WOOD: For the past 10 years that I've been coming out here, this is only the second year that there's been water in here. And that last year it wasn't nearly as deep as this. In here are animals that have waited since 1989 to reproduce. And I was in here last week looking and seeing what was going on, and sure enough I found some marbled salamander larvae.
LE BLANC: The pond is about an acre and a half across and way deep, says Andy. Three-and-a-half feet deep in the middle. Though it's still early, the day is warm and there are buds and flowers on the bushes and overhanging trees. My boots stop below my knees, but Andy wears thigh-high waders, so he takes a long-handled net out into the pond and dips for marbled salamander larvae.
WOOD: Now, there's not a lot in here. It isn't like there's a gazillion larvae. You'd really have to look, you have to work the pond. Well, there's one. (Laughs) Maybe there is a bunch.
LE BLANC: The salamander larva looks kind of like a large tadpole with teeny feet. Around what I would call its neck floats a willowy thing like a feather boa.
WOOD: And that big collar of feathery structures, those are the gills. In the larval stage these guys get oxygen from water. As an adult they get oxygen from air.
LE BLANC: Vernal pools provide safe haven for many amphibians: the barking tree frog, the Maysbees salamander, fairy shrimp, spring peepers, and the marbled salamander. These animals, Andy Wood says, can't reproduce in year- round pools because the fish in those waters would prey on the small tadpoles and larvae. Few predators live in vernal pools. But the critters which breed here take a chance each year on the rain.
WOOD: As summer winds down and the air temperature starts to cool, the ground temperature starts to cool. Then we start getting some fall rains. That stimulates the females to start migrating to these low depressions. It's their natal pool; it's where they were spawned. And when conditions start to feel right for her, she'll lay her eggs and curl around the eggs and stay with them. And then around November into December, when we start getting the good winter rains, then the water starts to pool up in the bottom of the pond. The soil saturates, starts to pool. The eggs hatch. But not until there's really a lot of water in this pond. If there's not enough water in the pond, it will dry out before the larvae can transform into adults.
LE BLANC: Thanks to El Niño, a warming Pacific ocean current, much of the Southeast has been drenched this winter, many places receiving 30 to 300% more than normal rainfall. Wilmington is at the high end of that scale. Andy Wood believes that some of the amphibians in the pools he watches are in synch with El Niño.
(Flowing water, bird calls)
WOOD: It may be that El Niño plays a distinct role in the reproductive cycle for certain populations of marbled salamanders and other ephemeral pool inhabitants.
LE BLANC: These marbled salamanders, Andy Wood says, may have learned to wait for El Niño's rains. The adults, he believes, live up to 15 years, so they can afford many a dry year in between the wetter ones. But what if the females return to their natal pool and find that it has been replaced by a house or a parking lot? In most states ephemeral pools receive no wetlands protection because frankly, they're often not wet, or they're too small or nobody knows about them. The animals which have adapted to the fickleness of nature have no defense against the bulldozers. Andy Wood believes that habitat loss has reduced many populations of vernal pool breeders in this area, and some species are threatened with extinction.
LE BLANC: Bolstered by our success with the marbled salamander, we decide to poke around in another vernal pond near Sunny Point Military Terminal. A male chorus of spring peeper frogs fills the night air with their mating song. This area is a buffer zone for the military base and therefore completely undeveloped.
LE BLANC: The pond is wide and dark. We train our flashlights into the gin-clear water as we wade in, and lots of tiny tadpoles swim through the beams. We whisper out here because we're intruders: two huge booted humans with bright lights in the middle of a nursery.
WOOD: (whispers) Oh, look! Oh, look!
LE BLANC: (whispers) What?
WOOD: (whispers) Oh, look! Do you see that frog?
LE BLANC: (whispers) I sure do.
WOOD: (whispers) Oh, man! That's about as significant a find as we could hope for. That is a Carolina crawfish frog. Which is an endangered species. And this is its home. This is its only home. How neat. Not many people get to see one of these.
LE BLANC: What's he doing sitting there just underwater?
WOOD: Hoping that we will pass by. (Laughs) Hi, there. See how wide the head is? Kind of a mottled body color. It's -- it's not a dashing animal, but they are so neat. They're just a -- they burrow into the ground, they inhabit these pools as their breeding site. They're very secretive. And, you know, I guess for somebody who is interested in birding this is like seeing a rare bird. And being able to put it on your life list.
LE BLANC: Andy Wood says he's only seen a handful of the Carolina crawfish frogs in his 38 years of looking. The crawfish frog is endangered, he says, largely because so few ponds like this one are left. One of the pools he used to visit is now a mega-store parking lot on what used to be the edge of town. He visited that site at mating time and watched the frogs hopping about on the pavement, confused. But at least for this year, El Niño has filled these vernal pools to overflowing.
(Footfalls and spring peepers)
WOOD: Bye, peepers. Don't do anything I wouldn't do.
LE BLANC: It's been a blessing for spring peepers, marbled salamanders, Carolina crawfish frogs, and all the others who have been waiting for the rains to come. For Living on Earth, I'm Aileen LeBlanc in Wilmington, North Carolina.
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