Of the 7,537 species of amphibians, 6,631 are frogs and toads.
Anura, the order of frogs, comprises 55 families including Ranidae, often referred to as “true frogs.”
With a name like “true frogs,” you might think ranids are a unified bunch. Think again: There are no definitive traits among family members, though most lack ribs, have teeth on their upper jaws and have horizontal pupils.
Ranids are found on every continent but Antarctica and in a wide range of habitats, from trees to deserts.
Wherever they roam, or hop, home is where the nest is — especially for tidy types such as the túngara frog, common in much of Central and South America. Like many other frogs, the túngara create foam nests for their eggs.
The túngara build their nests in a distinct, three-phase process. The layered construction does a great job of protecting eggs from predation and overexposure to oxygen.
It takes two to make the foamy goo the frogs use, by the way. During mating, the female releases a precursor made of protein, which the male collects using his feet. He then incorporates air by vigorously kicking his legs. Voila, frog foam.A Diane's bare-hearted glass frog. Brian Kubicki/Costa Rican Amphibian Research Center
Don’t wrinkle your nose — that goo may one day save your life. In March, researchers announced long-lasting, non-toxic túngara frog foam could be the perfect delivery method for antibiotics and other drugs used to treat severe burns.
While some frogophile elitists may claim there is a difference between frogs and toads, science doesn’t formally recognize one.
That said, just like ranids are often called “true frogs” colloquially, members of the Bufonidae family within Anura are called “true toads.”
One thing that’s not true about toads is that they have anything to do with toadstone. First mentioned by Pliny the Elder in the first century as “frog stones,” people believed these small, dull-colored objects were talismans that had all kinds of medicinal and magical value.
Science check: They’re actually just fossilized teeth of the fish Lepidotes.
What makes a toad “true,” then? Thick, warty skin and a lack of teeth, plus a Bidder’s organ. The latter is a mysterious, ovary-like structure that is present in both sexes of bufonids during development, but in adulthood remains only in males.
First described in 1758, the exact function of the Bidder’s organ remains unknown.
Something else that remains unknown about true toads, true frogs and all the other anurans: how they will fare against increasing habitat destruction and climate change. A 2015 study suggested that extinction rates for frog species have increased fourfold since the 1970s.
The researchers estimated, conservatively, that more than 3 percent of frog species have gone extinct in the past four decades, and about 7 percent more could be lost in the next century.Kermit the Frog is in a class all by himself. Jim Henson Productions/Everett Collection
Although many species of frogs are endangered, it’s not all bad news. Researchers still find previously unknown species every year. In 2015, for example, seven new species were discovered just in southern Brazil’s Atlantic Rainforest.
But don’t think you have to venture deep into the rainforest to discover new frogs. In 2012, the previously unknown Zakerana dhaka popped up in the middle of the capital of Bangladesh, one of the world’s most densely populated cities.
In 2015, another frog new to science made a pop culture splash: Hailing from Costa Rica, Diane’s bare-hearted glass frog (Hyalinobatrachium dianae), named after the senior author’s mom, bore a noticeable resemblance to a celebrity frog known to reside on Sesame Street.
Speaking of Kermit, an early version of the famous frog, who debuted on TV in 1955, was made from a pingpong ball and an old coat discarded by puppeteer Jim Henson’s mother. From those humble beginnings, Kermit made it all the way into the Smithsonian’s National Museum of American History, suggesting that while it might not be easy being green, it sure is golden.