The last Saturday in April is the annual Save the Frogs Day, created by ecologist Kerry Kriger to highlight the growing dangers faced by frogs worldwide. But what about toads? Shouldn't we save them, too?

Yes, but toads are frogs — sort of. Both belong to Anura, an order of amphibians generally called "frogs." About 5,000 species are known to science so far, and we keep discovering new ones.

"There is no scientific distinction between 'frogs' and 'toads,' although most anurans are usually referred to as one or the other," biologist Heather Heying explains in a post on Animal Diversity Web.

So why do we bother? Because children's author Arnold Lobel wasn't alone in distinguishing Frog from Toad. There are real differences, but in typical amphibian fashion, they can be a little slippery.

The greatest story ever toad

Toads mostly fit into the family Bufonidae, whose nearly 500 species are considered "true toads." (It's the only all-toad family in Anura.) At the other end of the spectrum, about 600 species in the family Ranidae are specified as "true frogs." That leaves thousands of anurans somewhere in between.

An eastern American toad relaxes in Jacques-Cartier National Park, Quebec, Canada. (Photo: Cephas [CC BY-SA 3.0]/Wikimedia Commons)

A red-eyed tree frog clambers through a Costa Rican rain forest. (Photo: Matt MacGillivray [CC BY 2.0]/Flickr)

Most frogs have long legs and smooth, moist skin, adaptations that help them swim, leap and climb in watery habitats. Toads, on the other hand, tend to walk around drier environments on stumpier legs. They're also known for rougher, bumpier and less colorful skin (but it's a myth they spread warts.)

Frogs usually lay eggs in grapelike clusters, while toads typically lay theirs in long chains — although, just to keep things interesting, a few toads are the only members of Anura that bear live young.

Sometimes a frog's or toad's face gives it away. Frogs are known for relatively big, bulging eyes, and toads can often be recognized by distinctive poison glands located behind their eyes.

"Prominent skin glands ... are characteristic of many (though not all) bufonids, and contribute to the 'toad gestalt' that many people can identify," Heying writes. True toads also have other trademark features, including facial skin ossified to the skull, a total lack of teeth and something called the Bidder's organ, a rudimentary ovary found in both sexes that can turn adult males into females.

Just when scientists start to unravel their taxonomic trickery, though, frogs and toads blur the lines even more. Some non-toad frog species have rough, warty skin, for example, and some toads are brightly colored, bug-eyed or slimy. Lots of species could reasonably fit into either category.

The Panamanian golden frog is a critically endangered toad native to Central American cloud forests. (Photo: Brian Gratwicke [CC BY 2.0]/Flickr)

A leap of faith

Careful taxonomy is critical for understanding and protecting wildlife, but semantics isn't the point of Save the Frogs Day. Nearly a third of all known amphibian species are currently threatened with extinction, placing them among the most endangered classes of animals on Earth.

Frogs and toads now face an array of environmental dangers, namely habitat loss, overharvesting, invasive species, infectious diseases, climate change, pesticides and pollution. These often overlap, and while they may seem unrelated, they can compound each other. Certain pesticides may weaken frogs' immune systems, for instance, inviting infections like the globe-trotting chytrid fungus.

Chytrid is now decimating frog species worldwide, likely assisted by humans' habit of moving frogs far outside their native ranges. That habit has also turned some frogs and toads into environmental scourges themselves, including invasive species like cane toads in Australia or coqui frogs in Hawaii.

Save the Frogs Day was created by Save the Frogs, a nonprofit founded in 2008 to raise awareness and resources for amphibian conservation. Check out Save the Frogs' website for year-round guidance on how to save frogs — and toads.