Thursday, August 28, 2014

Green Frog

A Green Frog sits on a rock in front of my home's small pond.

     The most common pond frog in our region is the Green Frog (Lithobates clamitans melanota, formerly classified as Rana clamitans melanota). Although it is the typical and most widespread of our frogs, despite its name, it is not always green. They can vary in skin color, though usually they're green to brown and often have blotches. These mid-sized amphibians have white bellies and are are best told apart from the the very similar looking Bull Frogs by the fold of skin that forms a ridge along their sides. This dorsolateral fold curves around the ear drum in Bull Frogs. 
     Males have an ear drum (tympanum) that is larger than the eye, while female tympanums are about the same size or slightly smaller than their eyes. This by the way is true in Bull Frogs as well. Males also tend to have bright yellow throats when in breeding condition. Even if you don't see them though, you can often tell that Green frogs are about because they commonly give a high pitched "squeenk" call when they are startled and jump into the water. 

A male Green Frog showing the large tympanum (ear drum) and bright colored throat, as well as the dorsolateral skin fold typical of all Green Frogs. 

     Otherwise, males also can be identified by the rubber-band like twang call they give when trying to attract mates and establish territories. Females lay a raft-like mass of about 1,000-7,000 black-and-white eggs that hatch about a week after being laid. The tadpoles are plump with pointy tails, often taking about 90 days to metamorphose into froglets by the Fall. Sometimes however, a few tadpoles overwinter as tadpoles, the only local frogs to do so other than Bull Frogs. Adult Green Frogs overwinter on the bottom of ponds or slow steams, under the leaves and mud.

A Green Frog Tadpole feeding on algae at the bottom of a pond. 

     These frogs are one of the first to colonize new water systems. They have been known to disperse up to 3 miles from their natal pools, often following streams or travelling over land during wet weather. 
     Many things eat Green Frogs, from dragonflies while they are tadpoles, to herons, egrets, larger bull frogs, raccoons, and so many other predators. Even humans eat their frog legs. If they survive all these dangers, they can live for 5 or so years. These frogs often struggle vigorously when captured, unlike so many other frogs that just seem to give up once caught. 
     Some studies have demonstrated that aquatic invasive alien Japanese Knotweed plants reduce foraging success in these animals (since less things eat the exotic plant to begin with). Otherwise, they can survive in even small, clean bodies of water. I have 3 that live in my tiny 100 gallon home pond. I love the way they jump when I get nearby (though at times I can get right next to them without their moving), usually accompanied with a "squeenk" and "kerplunk." I also enjoy the one male that calls every summer and when they stake out my porch lights during wet weather for fallen bugs. They may be common, but I find Green frogs quite interesting, like I find most "wildlife" that lives in my backyard. So next time you go by a pond, listen for their telltale calls and see if you can get close enough to really observe them. 

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