That great old song tells us that “Jeremiah was a bull frog.” Maybe so, but I’m here to tell you that Ezekiel, shown here, is NOT a bull frog. He’s a friend of mine who lives in our pond and happens to be a green frog.
The two species of frogs – greens and bulls – often are difficult to tell apart, unless you can get close to them and apply the little-known “dorsolateral folds” test. I’m about to reveal that test, which is less scientific than it sounds and won’t threaten the livelihoods of herpetologists who specialize in amphibians.
Those dorsolateral folds are ridges of skin that appear on both bull frogs and green frogs. The ridges extend behind the eyes and curve around the ear drums (the “tympanums”) of both species. However, they stop at the eardrums on the bulls, while their top lines/folds continue on the greens all the way to the green frogs’ butts. That is, the bulls only have something like inverted Nike Swooshes® around their eardrums; the greens have those Swooshes plus racing stripes along their bodies.
Of course, a bull frog also can be twice as large (up to 8 inches) as a green frog (up to 4 inches). But, it’s unlikely that the two will appear side-by-side for long before the bull eats the green. (Both these frogs will eat any live thing that they can get their mouth around.)
If you’re viewing a single frog and aren’t any better than I am at mental measurements, that size knowledge probably won’t help much. Besides, there are small bulls and large greens that can complicate computations. (Images taken in Brooklin, Maine, on June 1, 2024.)