Can You ID The Frog? Bullfrog vs. Green Frog

Updated: Jul 9

Now that the weather is warming up, chances are you will start to see more frogs at ponds and creeks. One of the popular questions we hear is, “What kind of frog is that, a bullfrog?”

Can you tell the difference between a bullfrog and a green frog? (Photo by Suzy Lyttle)

Bullfrogs are pretty popular, mostly because of their size. They are huge! However, there is another suspect in our ponds. Green frogs are smaller, but they look very much like a bullfrog. With a little training, you can tell these two apart and wow your hiking buddies in the process.


Size


Generally, a bullfrog is bigger than a green frog. Bullfrogs measure about 3 ½ inches to 6 inches long, which is about the size of an adult’s open hand. Green frogs measure about 2 inches to 3 ½ inches long, which is about the size of an adult’s finger.


Although on paper these sizes seems obviously different, it may be harder to tell in the wild. If you get close enough to a frog to put a hand down for comparison, chances are it will jump away. And take a look at those numbers one more time. A young or small bullfrog could measure to be the same size as a green frog. On to your next level of training.


Ridges


If you can’t tell by the size of the frog, the next step is to look for the dorsolateral folds or ridges. They are like raised lines on the back or sides of the frog. Bullfrogs have a ridge that wraps around their ears. It is almost like it is wearing glasses. Green frogs have ridges that go from the backs of their heads all the way down to their legs.


Ears


After you show off your excellent identification skills to your friends, they may challenge you to another question. Is the frog male or female? To answer that question, take a close look at their ears. Frogs have tympanums, or external eardrums, that look like round discs. They are located just behind the eyes. If the tympanum is larger than the eye, it is a male. If it about the same size as the eye, it is a female.


Song


Now here is a trick that will tell you the frog species, plus whether it is male or female, without even seeing the frog! It is all about the song. If you hear a frog singing, that is your clue that it is a male frog. They sing to females, hoping to have the loudest song out of the bunch.


Bullfrogs have a deeply pitched song, sounding like “jug-o-rum, jug-o-rum.” Take a listen.

Green frogs have more of a single note sounding like on pluck of a banjo or guitar. Take a listen.

Congratulations! You are ready to hit the ponds and teach your friends. Wow them with your knowledge of the different species, male vs. female, and even re-create the song if you don’t hear it live.

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