Bronzing Backyard Frogs



Adult male Bronze Frog (not the babies I have in my pond)

 Well, that was blatantly misleading. Of course we are not taking frogs out of nature and plating them with metal. But I've got to get you into this blog, and headlines are good bait.

This post is actually about a new and interesting species we didn't know we had out at Haman Farmopolis: the Bronze Frog. In a recent post, "Toad Whisperer," I mentioned that we had a bunch of tads in the pond out back that had recently morphed into some kind of unidentifiable frog/toad. A few days ago I identified the newcomer as a Bronze Frog. I was not aware of this type of frog, but it turns out that the species is common across the southeast U.S.

Last summer, I thought I had a Northern Green Frog in the pond because it was big and made the classic "loose banjo string" call. The problem was that I was out there looking at it by flashlight at night, the only time the frog would announce his presence. Actually, it must have been a male Bronze Frog. It also must have banjoed up a starry-eyed, music-loving female to produce the adorable froggies that I have today. It's easy to misidentify these guys because they are subspecies of the same animal, and have the same banjo call. Green frogs are distributed both as Bronze Frog to the south, and Northern Green Frog, to the north of a certain line. On the south side, they have this unusual bronze color. To the north, they are remarkably green. In either case, they are often mistaken for bullfrogs because of their large size. Take a look at the species distribution map, courtesy of Wikipedia.

Species distribution of Rana clamitans (Wikipedia)

The thing I find most fascinating is that according to this particular map, I live at the exact intersection of bronze and green: In Little Rock, Ark., smack in the middle of the state. If you look at Arkansas on the map, you will see that the dark blue portion -- the range of the Bronze Frog, roughly follows the bottom edge of the Ozark Plateau and the Ouachita Mountains through the state. As you rise into the hills -- and into the Ozark Plateau --  it's Northern Green Frog territory. Below that, bronze. So, I have a shot in Little Rock at seeing both subspecies.

(A quick sidebar: Arkansas is broken into six main natural divisions: Ozarks, Arkansas River Valley, Ouachitas, Coastal Plain, Mississippi Alluvial Plain and Crowley's Ridge. Little Rock sits right at the three-way intersection of the Ouachitas, the Missippii Alluvial Plain add the Coastal Plain. If you go just a few minutes north or west, you are solidly in the Ouachitas. A little bit southwest, and you are greeted by the Coastal Plain. A tad to the east, hello alluvial plain. For a brilliant read on the subject of Arkansas' fascinating natural divisions, see "The Natural Divisons of Arkansas," by the Arkansas Natural Heritage Commission. It is a classroom guide written by Thomas L. Foti.)

The literature says that the Bronze Frog is shy by nature. That must happen later in life, because I have experienced the joy of watching these little guys sunning themselves on my lily pads and jumping into the water if I get within five feet. I stand back about 10 feet and watch them through binoculars. As they grow, typically the adults spread out to areas away from their birth pools. As they age, they also start using the famous call which has given the species the nickname "Banjo Frog." The latin name for the Bronze Frog is Rana clamitans clamitans. Rana is the Latin word for "frog." Clamitan means "noisy" a nod to the impressive, attention-getting call of the male.


According to the Texas Parks and Wildlife website (East Texas has a pretty good range of Banjo Frogs) the bronze frog grows up to 2 to 4 inches. The frog is distinguished by a by a bronze or brownish body, white belly with dark, irregular blotches, and a bright green upper lip and nose. The babies in my pond have a sort of stripy yellow and dark lip.

Males can have yellowish throats. Banjo Frogs are smooth-skinned, as are all true frogs. They have long hind legs with webbed toes. Most interestingly, a  fold of skin, called a lateral line, begins behind the eye and runs two-thirds the length of body. This lateral line is quite distinguishing, and can help you identify the frog. The tympanum, or ear disc, is quite exaggerated in males, making them look kind of freakish.

"Their diet includes small frogs, worms, insects, and other small invertebrates," says Texas Parks and Wildlife. "Birds, fish, and small carnivores (meat eaters) prey on the bronze frog. It reaches sexual maturity in the first full summer after metamorphosis. Breeding season begins in early spring and lasts through the summer. Females lay 2,000 to 4,000 eggs in small masses attached to underwater vegetation. Eggs are 1.5 mm when laid, but grow to 6 mm as cells divide."

Personally, I found the eggs of the Banjo Frog this spring when I was clearning up in the pond. I had experimented with a solar-powered floating fountain  that was disguised as a fake water plant. When I turned the fountain over to see if it needed to be unclogged, I found a mass of clear jelly eggs. Inside each egg I could see a little dark spot -- the tadpole in waiting. Frankly, I was just waiting it out to see what came from the eggs. Now we know. 

The eggs incubate over one to two weeks and the tadpoles are green with small, dark spots. They can grow to 1.5 inches, which is why I thought I might have Bull Frogs in my pond. The species lives seven to 10 years, and spend most of their lives as nocturnal, solitary hunter, remaining under logs and in crevices most of the time.

I am most proud of this: The moist, permeable skin of the Banjo Frog -- and all other frog specieiss -- makes it highly sensitive to polution. So if you see it, the water quality is pretty good. Go pond!