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| Norther Green Frog (Rana clamitans melatona) Photo by Brad Sylvester, copyright 2011, all rights reserved |
Today’s new species for What Lives in my Yard is the Northern Green Frog (Rana clamitans melanota), not to be confused with the green tree frog. The Northern Green Frog is the first of the taxonomy Class Amphibia or Amphibians to be recorded in this blog (although I am fairly certain, not the last).
My Frog Trap
In a sense, you can say that I discovered these frogs in my yard by setting a trap. Not the usual kind of trap, but an effective one nevertheless. I put a small man-made pond in my backyard two years ago. It has a stone waterfall, some plants to provide shade, and a 100 gallon or so reservoir/ pond. When the streams dry up each year, usually in July, it is the only permanent pool of water on my property, discounting a mud hole or two at the far end of the forest.
In July, therefore, this little pond becomes a very attractive bit of real estate for animal species that need water, like frogs, for example. The water is the bait and the lack of water elsewhere is the barrier that keeps the frogs there once they take the bait, especially when dryer summer weather arrives, limiting their opportunity to move again. There are also a number of insects that take up residence or breed in the pond as well. At present, it contains hoards of what appear to be daphnia, but until I get a USB capable microscope running, they’ll have to wait.
The Wanderlust of Young Green Frogs
It is ordinary for juvenile green frogs (less than two years old) to travel when it rains or is wet enough for them to be comfortable away from their home pond. If they find another body of water, they may take up residence there. If they stayed in one spot, the survival rate would probably be higher (since they are less vulnerable to foxes and other land predators which are numerous in New England), but the home pond would become a bit crowded as the males tried to defend their breeding territories against the maturing juveniles. Since they get bigger each year for four or five years, the juveniles would get pushed out anyway, so their natural wanderlust serves them well.
Meanwhile, there are three Northern Green Frogs living in the pond all of a smaller size consistent with them being juveniles. I toyed with the idea of netting one and getting some better photos, but you can see all the identifying features in the photos I already took, so there was no need to disturb them further.
| Click the image for a slide show of my Northern Green Frog images |
Identifying Features of Northern Green Frogs
The first and most obvious identifying feature for a Northern Green Frog is the pair of defined ridges on its back. You can see them in the photo at the top left of this post. They run from the ear circles down to its rump. The underside of the green frog is white with dark irregular spots, especially at the intersection of the white and green or brown - as is also visible in the photo. It has a prominent lighter green area above its mouth and may have a bit of the white coloring from its underside also showing just above the mouth. Overall coloration can range from quite green to a muddy brown. There’s a southern variant called the bronze frog because of its color which is classified as Rana clamitans clamitans.
Tadpoles of the green frog tend to have yellowish undersides.
Frog Limb Deformities
Green frogs are one of the species that have been reported in recent years with limb deformities which, as memory serves, have been attributed to chemical contamination and also parasitic infection, perhaps facilitate by a chemically-compromised immune system, although it has been years since I read that in a newspaper, so I can’t say for certain that I’m recalling it accurately, so I should check to be sure. Wait here a minute, I’ll be right back… Yes, there it is at the National Institute of Environmental Health Sciences from a 2002 Penn State study: Limb deformities caused by physical intrusion of Trematode parasites facilitated by depressed immune systems caused by agricultural run-off.
The three frogs I have in my pond have none of that. Although the valley below the mountain could have significant agricultural run-off, any frogs that can travel far enough to reach my pond most like don’t have extra legs slowing them down, so it’s certainly a non-random, self-selecting healthy sample.
Frog Legs and Essence of Frog
Well, I have to say that I have never caught frogs for food, but green frogs, especially the full-sized ones of 4-5 years old or more, are a suitable species from which frog legs may be harvested to be cooked and eaten, although bull frogs are more commonly used for this purpose in the United States. At any rate, for those so inclined, froglegs.org has a list of recipes that is lengthier than I would have imagined. I do have to confess, however, that I have tried fried frog legs at Les Chefs de France, a restaurant in the French Pavilion at Disney’s Epcot Center, and I had a dessert dish that was described to me as “Essence of Frog” with a very light maple syrup while in southern China, which I was told, “would improve my virility.” Both were quite good.
Quick facts about the Northern Green Frog (Rana clamitans melanota)
Lifespan: In captivity, according to the University of Michigan, green frogs can live for about 10 years. That’s much longer than I would have guessed, although I knew some species of frogs, including the green frog, may remain tadpoles for more than a full year.
Lifecycle: Green frogs reach sexual maturity at two years old. They lay as many as 7000 eggs in an annual clutch, with an occasional second clutch of up to 1500 more eggs. With egg masses of that size and a 10 year lifespan, it’s obvious that a very small percentage of those eggs will survive to adulthood or we’d really have a plague of frogs.
Eggs hatch into tadpoles in 3-7 days. From there, development may take one of two paths. Either the tadpoles will undergo metamorphosis in about three months becoming frogs before the winter, or they will overwinter as tadpoles, hibernating in the mud until the following spring. These individuals may take as long as 22 months to metamorphosize into juvenile frogs. Once they do, however, they reach sexual maturity at the same overall age as the early metamorphs, at two years old.
Habitat: fresh-water wetlands, ponds, and lakes
Diet: Adults: Mostly insects and some other small animals opportunistically. Tadpoles: diatoms, algae, zooplankton.
When the northern green frog is here: All year round.
Range: From Texas to Florida in the south and up through Central Canada along that same east to west stretch.
IUCN Redlist status: Least Concern
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