A Family of Frogs

Strawberry poison dart frog

This species of poison dart frog is well known for its attentiveness to its children. (Photo by Mehgan Murphy, Smithsonian's National Zoo)

With Thanksgiving just past and Christmas around the corner, this is a time of year many people turn toward family. While frogs are not the most social of animals and certainly do not celebrate the holidays, they do have a wide range of ways to care for their young.

The vast majority of frogs and toads reproduce by laying eggs in streams, ponds, vernal pools, or any other body of water they can find in the spring. The American bullfrog (Rana catesbeiana) and spring peeper (Pseudacris crucifer) are two common examples native to the United States. In both species, males stake out territories on the edge of a pond and call loudly to attract females. Once they mate, the eggs are laid in or near the water. After this, mom and dad are basically out of the picture.

However, these tadpoles are perfectly capable of taking care of themselves. In some species, they gather in large groups, oftentimes with siblings. Amazingly, even in this mostly hands-off approach to parenting, family still comes first!

Now, we can head to some of the more dedicated parents of the amphibian world.

First up is a species of poison dart frog well known for their attentiveness to their children, the strawberry poison frog (Oophaga pumilio). This little frog is common in the rainforests of Central America, from Nicaragua to Panama. The eggs of the strawberry poison frog are not laid in the water so the males take up the duty of carrying water in their cloaca to keep the clutch of eggs moist. These dedicated fathers can even move around to take care of multiple clutches at the same time!

After one to two weeks, the eggs hatch and the female takes over care. She spreads out the tadpoles between small pools of water in bromeliads by carrying them on her back, giving each one its own pool. Finally, she will continue to care for the tadpoles by feeding them unfertilized eggs until they are large enough to begin metamorphosis.

Luckily, the strawberry poison frog is listed as a species of least concern by the IUCN because of its large and widespread population.

It cannot be said that all male frogs abandon their babies before they are adults. Darwin’s frog (Rhinoderma darwinii) is almost unique in the extraordinary effort males put into caring for their young.

After the eggs are laid and fertilized, the male stays around to guard the eggs. A few days before they hatch, he gulps them down into his vocal sac, where they will grow and develop all the way into adults. There are special glands in the male’s vocal sac that secrete food for up to 19 tadpoles that he may be carrying. Once they are old enough, the young hop out of dad’s mouth to start life on their own.

Darwin’s frog is currently listed as vulnerable by the IUCN due to habitat destruction in its native country of Chile.

As you can see, not all frogs take the hands-off approach our native species do in the United States. Some frogs are very dedicated parents. This season at dinner, ask yourself (or your family!): Are we really so different from frogs?

– Andrew Franks, Zoo New England


Frog Love

Valentine's frogs

In celebration of Valentine’s Day this week, we pulled together some of the most interesting breeding rituals in the frog world. Their wooing methods and reproductive techniques are as diverse as the animals themselves—and candy and flowers are not required for success!

1. The Underwater Ballet: Surinam toads (Pipa pipa) bring the romance of the ballet to their breeding habits, performing what looks like an “underwater ballet.” While they are joined in amplexus (when the male hangs on the female’s back, grasping her around the neck), they flip through the water together in arcs; a perfect dance. As the male and female swing in synchrony, the female releases eggs and the male fertilizes them.

Panamanian golden frog (Atelopus zeteki)2. The Sign for “I Love You:” Panamanian golden frogs (Atelopus zeteki) aren’t shy. If the males can’t get their point across to a potential mate through their low whistling call, they wave their hands in seduction. Some researchers believe they may even use this to greet one another!

3. That’s a Mouthful: Now thought to be extinct, the gastric brooding frog (Rheobatrachus silus) incubated its young inside its tummy! The female swallowed the eggs after they had been fertilized and the tadpoles developed in her stomach while the female’s entire digestive system would shut down to ensure she didn’t digest her children! After about six weeks, she would give birth to up to 25 young by opening her mouth widely so the fully formed frogs could emerge and hop away.

Nest of a foam nest tree frog (Chiromantis xerampelina)4. Whipping up a Frenzy: When two male foam nest tree frogs (Chiromantis xerampelina) find true love, they shack up in a nest of foam. But it’s up the female to build it and she whips up a foam nest out of skin secretions with her back feet before blending between 500 and 1,200 eggs into the froth. Sometimes this process includes more than one pair of frogs—or more than one male at a time!

5. Flying High: Wallace’s flying frog (Rhacophorus nigropalmatus) spend almost all of their time in trees, coming down only to mate and lay eggs. These frogs are very particular, however, about where they lay their eggs, preferring the smelly wallowing holes of the nearly extinct Asian rhinoceros! They seem to risk getting stepped on in exchange for at least some protection from potential predators who are scared off by the rhinos.

6. Paternal Instincts: In the case of the Darwin’s frog (Rhinoderma darwinii), it’s up to the father to rear the young. After the female lays the eggs, the male then guards them before picking up all of the survivors and carrying them around. The tadpoles develop in the male’s baggy chin skin, feeding off their egg yolk. When they are tiny froglets (about half an inch), they hop out and swim away, leaving pops on his own again.

7. Egg Mania: The female blue mountain tree frog (Litoria citropa) lays about a thousand eggs on the floor of a rocky pool of water during the spring and summer. When the eggs are fertilized, she kicks them so they disperse and have a greater chance of survival in the case of a targeted attack. The female frog can reproduce only at the age of 2 or 3 years old.

Banded horned tree frog (Hemiphractus fasciatus) 8. Hitchin’ a Ride: The eggs of the banded horned tree frog (Hemiphractus fasciatus) get pushed into a sack on the female’s back as the male fertilizes them. These frogs breed by direct development, which means that when they are born, they pop out as kid frogs instead of baby tadpoles. Then they stick around for awhile, taking a ride on mom’s back.

Lexie Beach, Smithsonian’s National Zoo

–Unless otherwise indicated, photos by Brian Gratwicke, Panama Amphibian Rescue and Conservation Project