AT THE SMITHSONIAN

A Mother’s Journey: How Strawberry Dart Frogs Are Born at the Smithsonian National Zoo

February 26, 2010

It took 10 minutes to spot just one strawberry dart frog in the terrarium at the National Zoo, hidden carefully in the folds of a lush green leaf and staring with beady black eyes into the early morning sunlight.

Though about 20 of the frogs live there, the tank’s dense vegetation makes it easy for the animal to disappear from sight.

“Usually they’re a little more active, but they’re just getting used to the light,” says the frogs’ keeper, Justin Graves, who is at the tank before the Zoo opens to check on the animals.

The vegetation in the terrarium mimics the frogs’ native environment in the rainforests of Central America, Graves says. The rainforest is one of the only places the frogs can successfully raise young tadpoles, but the terrarium has proven to be a successful alternative: The zoo recently welcomed it’s first brood of baby strawberry frogs.

Unlike most frogs, which lay thousands of eggs at a time only to abandon them, female strawberry dart frogs lay about six eggs at a time, Graves says. And it’s the father who protects the pea-sized eggs, urinating on them for the next 10 days until they hatch into tadpoles.

The mother carries each tadpole on her back and climbs two to three feet into the trees (though in the wild, it could be up to 40 feet) to find each of her babies their own home in a small pool of water. Often, she finds it in the base of a bromeliad plant leaf, which naturally forms a small cup with the plant’s stalk. The mother spends each day of the next few months checking on her young and bringing them food, traveling back and forth between the ground and their homes in the leaves.

Bromeliad leaves abound in the zoo’s tank, which has given the mother strawberry frogs plenty of room to carry tadpoles. It’s also given the tadpoles enough distance from the other species of frogs (lemur frogs, glass frogs and green and black arrow frogs) that live in the tank, who could otherwise compete with the strawberry frogs for food, Graves says.

In the wild, strawberry dart frogs are best known because they’re poisonous to touch—a result of the bugs and plants they eat, which causes toxins to be released from their skin. But at the zoo, workers like Graves can control the frogs’ diet, so they can be handled (as long as you don’t have any cuts or abrasions).

At a time when so many amphibians are in danger of extinction, being able to give the frogs the space they need to reproduce is crucial for further study of the animal, including it’s elusive behavior, Graves says. The zoo has a team of volunteers who come in each day to track the animals’ movements, down to the minute: what they’re doing, how they’re moving and where exactly they’re hiding. Some of them even have names (like one little fellow named Emerson).

It’s important to understand amphibians like the strawberry frog, Graves said, so stronger conservation efforts can be made before they're completely gone from the wild. “This is kind of their last refuge," he said.