Founding Frog-ers

Gray tree frog

This colorful and shimmery frog could compete with any fireworks. (Photo by Brian Gratwicke, Smithsonian Conservation Biology Institute)

Frogs found within the United States of America can be red, white, and sometimes, in rare cases, blue. As their names suggest, the California red-legged frog (Rana draytonii), Northern red-legged frog (Rana aurora) and the American white-lipped frog (Leptodactylus fragilis) embody America’s more patriotic colors. Blue frogs, however, are a rare oddity, with the color sometimes appearing in bullfrogs, green frogs and leopard frogs that are deficient in yellow skin pigments. In honor of the Fourth of July, we thought we’d take a closer look at frogs found in the States.

The United States is home to a diverse group of frog species. According to the IUCN Red List, there are 87 species of frogs living in the United States. Texas has the most with 45 species, while Alaska has only three. In general, there is more diversity in the South, with states such as Alabama, Florida, Georgia, Louisiana, Mississippi and North Carolina hosting more than 30 frog species, according to the Association of Zoos and Aquariums.

Though most American species of frogs live in freshwater environments, the Southern leopard frog (Lithobates sphenocephalus) can live in brackish or saltwater habitats. Frogs in the United States also make unique sounds. The barking tree frog (Hyla gratiosa) is named after its low-pitched calls that sound like a dog or a goose. The dusky gopher frog (Lithobates sevosus) is an endangered species with a call that AmphibiaWeb describes as a “deep snore” or “outbound motor.”

Because of the changes in seasons in many places, some frog species in the United States have incredible ways of surviving cold weather too. The wood frog (Lithobates sylvaticus) freezes in the winter, letting its breathing and heart stop. Then, during thawing season, it resumes life!

Sadly, 10 frog species found in the United States are endangered. These frogs depend on us to protect their habitats and reduce the threat of chytrid, a fatal amphibian disease. On this day of independence, we should think about the wildlife that continues to define our country in unique and diverse ways.

The list of IUCN-listed endangered, critically endangered and extinct (in the wild) frog species in the United States includes:

  1. Relict leopard frog (Lithobates onca)
  2. Dusky gopher frog (Lithobates sevosus)
  3. Ramsey canyon leopard frog (Lithobates subaquavocalis)
  4. Southern mountain yellow-legged frog (Rana muscosa)
  5. Sierra Nevada yellow-legged frog (Rana sierra)
  6. Wyoming toad (Anaxurus baxteri)
  7. Arroyo toad (Anaxyrus californicus)
  8. Yosemite toad (Anaxyrus canorus)
  9. Houston toad (Anaxyrus houstonensis)
  10. Armagosa toad (Anaxurus nelsoni)

Nadia Hlebowitsh, Smithsonian’s National Zoo

Hoppy Halloween from the Panama Amphibian Rescue and Conservation Project!

Most of us who studied “Macbeth” in high school know that the chanting witches in the story used many ingredients in their brew, from “eye of newt” to “toe of frog.” In fact, throughout history, amphibians—mainly frogs and toads—have been superstitiously considered either good luck symbols, or more commonly, signs of evil or the devil. Today, though all of the readers of this blog know how incredible frogs are, there are even phobias associated with the animals:

Batrachophobia: Fear of amphibians (frogs, newts, salamanders, etc.)
Ranidaphobia: Fear of frogs
Bufonophobia: Fear of toads

In honor of the spookiest holiday of the year, we’ve compiled a list of freaky frogs and frog facts that may just creep you out (though we suspect most of you will think, “wow, cool!”).


Luzon fanged frog (Limnonectes macrocephalus)

A number of frog species, like the Luzon fanged frog here, have bony jaw protrusions that resemble fangs. (Image courtesy of Rafe M. Brown)

Most frogs that swallow their prey whole compress their eyeballs down into their heads to push the food down their throats to swallow it! In addition, there are a number of frog species that have bony jaw protrusions that resemble fangs, and they eat anything from rats to snakes to even birds! Scientists believe the “fangs” help the frogs hold onto quickly moving prey.

Speaking of teeth, there is also the vampire flying frog (Rhacophorus vampyrus), native to Vietnam. Adult flying frogs have webbed fingers and toes, which allow them to jump and glide from tree to tree. Though not really vampires, the adults are nocturnal and do like to come out at night. In addition, this species’ tadpole stage is the only one known to have “fangs,” which disappear as they mature.

The paper highlighting the discovery of the “fangs,” explains that they are not true fangs, but rather “keratinized hooks” on the sides of their mouths. It is highly unlikely that the tadpoles actually suck blood, and researchers are currently studying these so-called fangs because their function is unknown. Head researcher, Jodi Rowley, suspects that they may help the tadpoles anchor themselves underwater or somehow aid in eating.

For Whom the Frogs Scream…

Did you know that some species of frogs, like the smoky jungle frog and American bullfrog, scream? When a frog does so, it is considered a distress call, usually a high-pitched noise emitted when a predator snatches them up, or when they are stressed or handled. Nobody knows what the exact purpose of the cry is, but researchers believe it is a defensive mechanism that aims to startle or disorient a predator enough that the frog will be released and it can escape.

Take a listen in this video from the BBC.

Cool Zombie Frogs!

Wood Frog (Rana sylvatica)

This practically frozen solid wood frog can quite literally come back to life. (Image courtesy of Janet Storey)

When it comes to the living dead, you may not believe your eyes when we show you the wood frog. These frogs can quite literally come back to life after being practically frozen solid. Native to cooler North American habitats, they can remain around 70 percent frozen for about four weeks in their burrows thanks to a natural antifreeze chemical in their blood, as well as a fluid balance mechanism within their bodies that moves water to areas less likely to be damaged by ice crystals. Their bodies then completely shut down, suspended in a cryostasis. When the weather gets warmer and the frogs begin to thaw, their organs will slowly begin functioning again—even the heart will begin to slowly beat—and within a day, the frog will be back to normal.

See a frozen wood frog thaw and hop away:

What on Earth is THAT? A Prehistoric Monster?

Indian purple frog (Nasikabatrachus sahyadrensis)

It appears this frog would be a good candidate for the monster mash. (Image courtesy of Sathyabhama Das Biju)

This isn’t a monster, but it may be just as unusual looking as one. The Indian purple frog (Nasikabatrachus sahyadrensis) is found in the Western Ghats in India. Only just discovered in 2003, it is rare and researchers believe it evolved separately from its closest relatives, the Seychelles frogs, for more than 130 million years. These frogs live mostly underground and come up only to breed during the monsoon season.


Turtle frog

The turtle frog appears to be a turtle without a shell, but is actually a frog! (Image courtesy of Evan Pickett)

Is this the Blob? Nope! It is known as the turtle frog (Myobatrachus gouldii), found in southwestern Australia. It is called the turtle frog because it looks like a turtle without its shell! It spends its entire life almost completely underground in burrows in sandy soil, eating termites from within its own colony tunnels. The frogs only emerge to mate during rainy season, but lay eggs that hatch into froglets underground.

Creepiness Continued

Surinam toad (Pipa pipa)

Tadpoles grow within pockets on the back of female Surinam toads, then eventually emerge as toadlets. (Image courtesy of Peter Janzen)

The Surinam toad is another one of the creepier amphibians you will see—it is also one of the flattest, resembling road kill or plant debris. They live in the Amazon River Basin of South America in moist lowland forests, swamps and freshwater marshes.

Perhaps the most amazingly creepy thing about this animal is the way it reproduces. The female will lay eggs that the male attaches to her back. The eggs embed themselves into her skin, which grows to form a type of pocket around each one. The tadpoles grow within these pockets, then eventually emerge as toadlets, as in the photo shown.

Check out this video:

Another creepy reproduction method was unique to the two species of now-extinct gastric-brooding frogs (Rheobatrachus family), native to eastern Australia. Female frogs incubated their eggs and babies developed within their stomachs. When ready, the babies would crawl out her mouth.

These Frogs Eat Almost Anything!

Ornate Horned Frog (Ceratophrys ornata)

These big-mouthed frogs have been known to eat all kinds of prey, ranging from rats to other frogs. (Photo by Brian Gratwicke, Smithsonian Conservation Biology Institute)

Perhaps some of the most frightening yet fascinating types of frogs are within the Ceratophrys genus. These are ‘horned’ frogs, possessing an elongated flap of skin that resembles a little horn on the upper eyelids. Also called Pac-man frogs, these large, aggressive, roundish frogs have insatiable appetites and will try to eat almost anything, even if it is bigger than they are. Examples of prey include insects, mice, rats, fish, other frogs, reptiles, etc. These frogs have even been known to eat their mates and go after smaller livestock!

In fact, one of the largest frog fossils ever discovered, a species that scientists call “Beelzebufo ampinga” or “devil frog,” was a close relative to these guys. Beelzebufo may be the biggest frog fossil ever found, dating to around 70 million years old, and grew to about 16 inches in length. It may have even gone after newly hatched baby dinosaurs.

Other well-known frogs that have quite an appetite are bullfrogs and green tree frogs. These have also been seen eating anything from rats to snakes to other frogs.

For images of frogs dining, click here… if you dare…

Talk About a Mad Science Lab!

Glass frog

Glass frogs have such transparent skin that you can see their organs. (Photo by Mehgan Murphy, Smithsonian's National Zoo)

Glass frogs are not scary, but they are a little creepy. These adorable frogs lack pigment on the skin of their abdomens, which allow their organs to be perfectly visible through the skin!

In addition to glass frogs, you may have heard of ghost frogs. These frogs are obviously not spirits, but members of the Heleophrynidae family. Native to South Africa, these frogs live in streams and their name probably stems from the fact that many are found in a place called “Skeleton Gorge.”

Lastly, and this is TRULY scary:

Epomis beetle

The Epomis beetle eats its prey, including frogs, from the inside out. (Image courtesy of Gil Wizen)

Imagine going to take a bite of a nice delicious hotdog, only to find that as you open your mouth, it springs a set of pincers, clamps onto the inside of your mouth, and begins to eat you instead!

The Epomis beetle does just this, and may be the last thing a frog will ever try to eat—since the frog will almost always become a meal itself. The Middle Eastern beetles specialize in preying on amphibians—mainly frogs—in a most unique and horrifying way.

The larvae of these beetles lure a frog by waving its antennae and then wait for the frog to try to snatch it up. When it does, the larvae will latch onto the attacker’s mouth with its double-hooked jaws, and, turning the tables, it will eat its prey alive. The larvae have become very adept at this, as frogs are all they eat, though the adults will eat a variety of amphibians by biting the victim’s back, paralyzing the prey, and eating it at its leisure.

Sara Bloom Leeds, Smithsonian’s National Zoo

The frog who cried “duck!”

Wood frog (Lithobates sylvaticus)

Wood frog (Lithobates sylvaticus)

Cute Frog of the Week: January 31, 2011

Don’t get confused if you hear a quack and there isn’t a duck in sight. You might’ve just heard the call of the wood frog, whose duck-like quack can be heard coming from moist wooded areas and ponds throughout the Northern United States, Canada and Alaska. If you see a small brown frog with a dark eye mask in the woods, it is likely to be a wood frog. There are no other species with a similar appearance in North America. This cute masked creature measures from 1-2 ¾ inches long and its color varies with temperature and gender; female wood frogs are often larger and redder. Reproduction takes place in late winter/early spring at ponds where there may often still be a layer of ice—but don’t worry about these frogs freezing! Unlike most other frogs, wood frogs can tolerate the freezing of their blood and other tissues. These frogs can survive many freeze/thaw events during winter, allowing up to 65 percent of their total body water to freeze. Cool, eh?

Photo entered by wombatarama at

Every week the Panama Amphibian Rescue and Conservation Project posts a new photo of a cute frog from anywhere in the world with an interesting, fun and unique story to tell. Be sure to check back every Monday for the latest addition.

Send us your own cute frogs by uploading your photos here:

Brrr…it’s cold outside! How do frogs and toads survive?

Wood frog (Lithobates sylvaticus)

Throughout the winter, wood frogs (tadpole shown here) stop breathing, their hearts stop beating, and ice crystals form within their hibernating bodies. (Photo by: Brian Gratwicke, Panama Amphibian Rescue and Conservation Project)

Last week, as I was taking in the beauty of the snow-covered New England landscape, I started thinking about amphibians. With more than a foot of fresh snow covering the ground, I began to wonder where all of the frogs and toads go in the winter. We received so much snow from this recent snowstorm that I had to shovel a small path so our Boston terrier could navigate the backyard. If he needed help getting through the snow, how was a small frog or toad going to navigate the cold, wintry earth?

Well, it turns out that frogs and toads, particularly in the Northeast and other colder climates, spend their winters quietly tucked away while they hibernate in the mud at the bottom of lakes, carefully concealed in logs and tucked under leaf litter. Some toads even bury themselves to hibernate. Others continue to swim all winter long. Green frog and bullfrog tadpoles hatch in the summer and then spend all winter living and swimming below the ice in the nearly freezing water.

But none of these species compare to the wood frog when it comes to cold weather adaptations. This hearty frog is one of the more cold-adapted species with a natural habitat range extending farther north than any other amphibian species. In fact, the wood frog is the only frog found north of the Arctic Circle. These frogs hibernate during the winter in terrestrial or forested wetlands in very shallow earth. What’s most amazing is that the wood frog is so adapted to cold temperatures that its tissue can actually freeze and thaw.

Throughout the winter, wood frogs stop breathing, their hearts stop beating, and ice crystals form within their hibernating bodies, according to the Minnesota Department of Natural Resources. A special antifreeze they produce keeps liquids from freezing inside their cells and killing them. When spring arrives and the temperature rises, the frogs “thaw” and they emerge from hibernation.

The strategic advantage to this adaptation for the wood frog is that they are the first frogs out in the early spring, while other frogs are still hibernating deeper below. They are the first ones heard singing (the noise sounds like a chorus of “quacks”) and they begin breeding once they emerge. By late April, thousands of tiny black wood frog tadpoles can be found in vernal pools. Tadpoles develop quickly in order to metamorphose to froglets before the vernal pool waters dry up by late summer.

So, the next time you see a snowy landscape, take a moment to think about frogs and toads and their amazing cold weather adaptations. It’s incredible to think that just beneath the smooth sheet of glistening ice covering a pond that small tadpoles could be swimming through the freezing waters, or that a small toad or frog could be snugly nestled within a hollowed log deep in a winter slumber.

– Brooke Wardrop, Zoo New England