Pickerel frogs are green with a paired series of squarish blotches extending down the back between the dorsolateral folds. Some individuals have paired rounded spots but adult pickerel frogs have bright yellow on the inner surface of the thighs instead of the white typical of leopard frogs. There is a light line on the upper jaw and the dorsolateral folds are continuous past the thighs. These frogs are a little smaller than those in the Rana pipiens complex ranging up to three inches (76 mm). No other Iowa frog has paired squarish dorsal blotches. No subspecies of Rana palustris are recognized.

    The call of pickerel frogs is a "snore" similar to that of northern leopard frogs though not as loud. Pickerel frogs often call from under water. The cold springs and trout streams of northeastern Iowa provide typical habitat for these frogs. There, they can be recognized by their distinctive behavior. When disturbed, they jump into the fast water and hide on the bottom beneath submerged water plants where they may remain until the predator tires of looking for them. Pickerel frogs occur in scattered populations along the Mississippi River. They are found inland in a band that is about two counties wide in northern Iowa but only one county wide in the southern part of the state. These frogs have a skin secretion that is more toxic to predators and other animals than are the skin secretions of most other ranids. The secretion on their skin may kill other frogs put in the same bag with them. Pickerel frogs are not protected in Iowa but are rarely used for fish bait because of their reputation for being toxic to other animals.