During a heavy or prolonged rain every March here in Lancaster County, Pennsylvania, wood frogs emerge from dormancy under carpets of fallen dead leaves on woods floors, crawl out from under those leaves and hop, day or night, short distances to the nearest woodland pools to spawn. Males enter the cold water of snow melt and spring rain and croak hoarsely, mostly at night, to attract females of their kind into those same puddles to spawn. After a few days of spawning, those same frogs retreat under rugs of fallen leaves before cold weather returns and catches these cold-blooded critters in the open. Their tadpoles are left to fend for themselves in those pools that might dry out by mid-summer. The fast-developing tads are pitted in a race against retreating water.
Able to withstand colder temperatures than most amphibians can, wood frogs are fairly common in the northeastern United States and through much of Canada and Alaska. And they are the earliest spawning of true frogs, the genus Rana. Only three inches long, wood frogs are mostly brown, which allows them to blend into the dead leaves they hop over in search of invertebrate food. And they have a black mask over each eye that helps break up their form, camouflaging them.
Today's frogs, toads and salamanders are small, adaptable remnants of the long ago age of amphibians. Amphibians have soft, smooth skins that must be at least moist for them to survive. If their skins dry, they will die. And true to being amphibians from the distant geologic past, most species live two lives, the first in water, and the other on land, to an extent, depending on the kind.
All amphibians today, including Rana frogs, are predatory, consuming a variety of invertebrates and other small critters. Frogs' and toads' tongues are anchored to the front of their mouths so that sticky organ can be flipped out to snare an invertebrate with the stickiness then flip that victim into the broad mouth. Many years went into the trial and error of developing that type of tongue for catching food. It is unique.
Pickerel, green and bull frogs are other common and widespread species of Rana in the Middle Atlantic States, as elsewhere. But southern leopard and carpenter frogs are Rana species that are limited in range and numbers in this same geographic area.
Pickerel frogs spawn in the shallows of permanent ponds and wetlands in April in this area. Males emit deep, rolling snores while under water to entice females into the ponds to spawn. Three and a half inches long and slim in build, pickerels are basically beige in color, with darker rectangles scattered randomly across their upper parts, all of which camouflages them. Pickerels' skins emit a bad-tasting secretion that helps protect them from predators.
Green frogs and bull frogs must be closely related because they appear pretty much alike and have similar lifestyles. Males of both species liven most ponds, wetlands, slower creeks and backyard goldfish ponds in the Middle Atlantic States, as elsewhere in the United States, with their vocalizations to attract females of their respective kinds for spawning in those bodies of water. From the middle of May to mid-July one can hear the gulping and twanging of male green frogs and the low moaning of male bull frogs. Tadpoles of both species take two years to develop into small frogs. Herons, mink, larger fish, turtles and other kinds of predators eat many of those tads before they leave the water as froglets.
Green frogs and bull frogs are mostly a dark, brownish-green, which allows them to blend into vegetation surrounding the water they dive into when threatened. Fully grown greens are about four inches long while mature bull frogs are up to eight inches long, the biggest frog species we have here in the Mid-Atlantic States. Both species are abundant in this area, and the best known by most people, due to these amphibians' loud vocalizing, often from the same bodies of water at the same time.
Green frogs and bull frogs vocalize mostly at night, but one can hear them at times during the day. One male will start calling and others chime in until there is a chorus of one species or the other, or both at once for a few minutes until they get quiet again. I can stimulate green frogs and bull frogs to gulp or moan by imitating their calls near where they are sitting on the edges of permanent water. I start when the frogs are quiet, a few join in, and more, until their is a full-blown chorus for a couple of minutes.
Southern leopard frogs are dull-greenish-brown with darker circles on their upper parts, which camouflages them. They range from New Jersey south along the coastal plain to the Deep South. Males utter short croaks to initiate spawning. Like all their genus, southern leopards spawn in shallow water.
Carpenter frogs are so-called because their choruses sound like the rhythmic hammering of several carpenters working at once. This species ranges from the New Jersey pine barrens along the coastal plain to southern Georgia. They are three inches long and brown, with two beige stripes along each flank.
Rana frogs have some characteristics in common, but, of course, differences that set them apart as distinct species. The adaptable green frogs and bull frogs are the most common and widespread of their clan, even colonizing some backyard goldfish ponds where they vocalize and spawn, adding another dimension of wildness to those human-made habitats. Listen and watch for Rana frogs. They are an adaptable relic of the far-distant past that has taken a seat in the present and, probably, into the future.
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