What is a toad?
What is the difference between a frog and a toad? I get asked that once in a while. As is usually the case with me I have to give a long-winded answer. Simply, and from a North American standpoint, the distinction is relatively easy. Toads are terrestrial. The have short limbs and a stout body. They have warty skin and make little hops. Frogs are smooth, sleek, and live in ponds. And they can leap like, well, frogs. But once you start moving beyond our borders you find the differences are not so easy. In the tropics many frogs are terrestrial or arboreal and their body shapes come in all sorts of varieties. Breeding behaviors also come in innumerable varieties.
Bufo granulosus – a ‘true’ toad from South America
Biologically the answer to the question is: nothing really. Toads are just a type of frog much like our standard pond frogs are types of frogs. Toads are represented by the family Bufonidae but contain a number of genera. From a biologist’s standpoint toads are distinguished by an organ called the Bidder’s organ. What this organ does is not known but it may play a role in sex development or determination or it may be an ancient organ that no longer plays a direct role in toad function. So in the family tree of frog biology, toads make up a branch of that tree. And there is so much frog diversity that to single toads out as a distinct group really isn’t useful. In fact biologists know that the group known as toads are so diverse that they likely don’t make a simple branch and may be made up of unrelated branches. So a toad is just a type of frog.
Hemiphractus scutatus – this sit and wait leaf litter predator is not a toad. It is in the group of casque-headed frogs.
This tiny frog is in the family Bufonidae so that makes it a ‘toad’ – it is the South American Dendrophryniscus minutus.
Pristmantis cerasinus is a small terrestrial frog in the group known as rain frogs.
Atelopus varius is in a large and severely endangered genus known as harlequin toads – it is considered a toad.
One of the few ‘true’ frogs in Central America this is Rana vaillanti.
Ending this lesson with a toad – this is the Central American smooth toad, Bufo Haematiticus. This is likely to be in a different genus once biologists reassess it.