Green Frog (Rana clamitans)
Pictured above: Male green frogs have typanums (or ear drums) that are larger than their eyes (left), whereas females do not (right).
Is this picture on the bottom of a male or female? (picture courtesy of the USGS, Onalaska, WI).
Description: Dorsally, Green Frogs are olive or green, with this color sometimes fading on the hind quarters. Males may have bright yellow chins and larger tympanums than females. dorsolateral folds of these frogs may be reduced or appear absent, which can cause them to be confused with Bullfrogs. They are medium to large frogs (2 ˝” to 4 ˝ “ snout to rump length). Green Frogs are members of the family Ranidae, which includes other "true frogs" such as Leopard and Bullfrogs.
Habitat/Ecology: Green frogs like deep permanent ponds or wetlands that do not dry-out or completely freeze. I have also witnessed them along well vegetated shores of lakes in northern Wisconsin and Minnesota. They are reported to rarely venture far from water and I have never found one too far from a pond or wetland. They spend most of their time in vegetation along muddy banks hunting for insects or vertebrates small enough for them to swallow. They are heavily preyed upon by many wetland predators, such as herons, egrets, mink, and raccoons, to name a few.
Remarks: Males usually begin calling mid June and continue through early August. Their call is a singular “plunk” that is said to resemble a rock being thrown into water or a rubber band being plucked. Green frogs tend to remain near the water to avoid predators. Unlike most other frogs, their tadpoles will over-winter in the sediments and metamorphose into frogs the following summer. Green frogs are sometimes mistaken for Bullfrogs, however bullfrogs have no dorsolateral folds and grow much larger.
I have heard Green Frogs calling within the Myrick Park marsh for two consecutive years (2000 and 2001). I have found adults and newly metamorphosed frogs for at least three to four years in a row. They seem to have a moderate rate of survival within the marsh. During late summer and early fall, I have seen large numbers of them making their way to the La Crosse River (that runs through the marsh) where I assume they hibernate, due to it not freezing and probably remaining high in oxygen all winter. I have also found many Leopard Frogs and several Toads here at this time of year.
I have found adult Green Frogs on Goose Island and they assuredly exist in other areas of La Crosse as well. They seem to be relatively abundant where the proper habitat exists (permanent water that doesn't completely freeze).