Plains Leopard Frog (video)

Plains Leopard Frog at the Homer Lake Wetland, 4/8/2021

We've already met the northern leopard frog, a new species record for Champaign County. If you were to go back to that post and compare the photos, you might include that the two species could be distinguished by their colors, as the photo above shows a rather dark plains leopard frog vs. the very green northern leopard frog pictured there, but you'll see that the plains leopard frog in the video below is just as green as the northern leopard frogs in the earlier post. As it turns out, both species come in brown and green variations*, so color is of no use in distinguishing between them. One of the most useful visual distinctions for the plains leopard frog is the dorsolateral fold -- the flaps of raised skin that begin behind each eye and run to the back end of the frog. In the photo above if you follow that line back toward the frog's back leg you'll see that there is a break in it and where it continues after the break it is offset toward the middle of the back. This is characteristic of the plains leopard frog. For comparison, here's a photo of a northern leopard frog with a clear view of its dorsolateral fold -- you can see that it is unbroken from front to back.

Northern Leopard Frog showing Unbroken Dorsolateral Fold, 3/31/2021

Another clue is the fact that the spots on the back of the northern leopard frog tend to be larger than its eyes. What I find most helpful, however, is the difference in their calls. You can compare calls by watching the video below and comparing to the included in the post about northern leopard frogs. Particularly unique to the northern leopard frog is the rumbly snoring sound they produce as part of their calls.

Plains Leopard Frog Calling at Homer Lake, 4/9/2021

* With regard to color variations in leopard frogs between green and brown, green is the dominant trait and brown is recessive, so in the normal course of events you would expect to find more green in any population of leopard frogs. However, a study done at Colorado State University found that in northern leopard frogs, the brown individuals develop from tadpole to adult significantly faster than the dominant green variety. This turns out to be a great advantage in waters where there are predators that prey on tadpoles -- less time as a tadpole increases the chances of surviving to adulthood. Thus, in the study, they found that in such ponds there are more brown northern leopard frogs than green, whereas in waters without predators, the green frogs dominate as expected. See an article about the study at https://www.colorado.edu/asmagazine/2020/02/18/why-do-leopard-frogs-come-two-colors for more on this.