What do they look like?

Green frogs are green, greenish brown, brownish, yellowish green, and olive, with some rare individuals being blue. They are generally brighter in front with small, random black spots. Their legs have dark bands across them and their skin is yellowish or white below the bands. Males usually have a bright yellow throat. Their tympanum ( visible external ear on the side of their heads) is large. The tympanum is much larger than the eye in males and is the same size as the eye in females. They have a well defined back ridge that extends from the back of the eye and continues the length of their body. Their toes are well webbed and their first fingers do not extend beyond their second fingers. The adults are 7.5 to 12.5 cm in length (3 to 5 inches).

Where in the world do they live?

Green frogs (Rana clamitans) are native only to the Nearctic region. They are found in the United States and Canada from Maine and the Maritime provinces of Canada through the Great Lakes region and into western Ontario and Oklahoma, south to eastern Texas, east into northern Florida and extending up the entire east coast of the United States.

What kind of habitat do they need?

Green frogs are found in a wide variety of habitats that surround most inland waters, including swamps, wooded swamps, ponds, lakes, marshes, bogs, banks of slow moving rivers and streams, sloughs, and impoundments. Young frogs may disperse into wooded areas or meadows when it rains. Green frogs hibernate through the winter in the mud at the bottom of a body of water.

How do they grow?

Eggs hatch in 3 to 7 days. After hatching, green frog tadpoles are usually green with small black dots and often have yellow bellies. It can take them anywhere from 3 to 22 months to begin metamorphosis into full grown frogs. Some undergo this transition before the winter, but many tadpoles go into hibernation and wait until the spring to transform. Green frogs reach their maximum size when they are 4 to 5 years old.

How do they reproduce?

Female green frogs choose their mates based on the desirability of their territories for egg laying. Satellite males may also be present during the breeding period of green frogs. A satellite male is described as a smaller male, unable to acquire and defend territories, and it is often found in areas protected by a larger male. The satellite male will wait for the opportunity to mate with a female that is responding to the larger more dominant male frog's vocalizations.

Breeding takes place in late spring. Variation in temperature and region can influence actual breeding times. The length of the breeding season is 1 to 3 months and occurs in a variety of habitats, such as swamps, ponds, marshes, bogs, and slow moving streams. During breeding each female may lay 1000 to 5000 eggs in clusters that float on the water surface or hang from water plants. Multiple egg clutches are possible, but the second egg clutch is usually smaller, with about 1000 to 1500 eggs. Eggs hatch in 3 to 5 days and complete the tadpole stage of development in 3 to 22 months.

Female green frogs nurture their eggs inside their bodies before they are laid and fertilized. Once the eggs are laid, there is no further parental involvement in their development.

How long do they live?

Average lifespan in the wild is unknown, but captive animals can live to 10 years.

How do they behave?

Green frogs are active during the day and at night. They become dormant during cold weather. Green frogs are mainly solitary, except during the breeding season, when they congregate at breeding ponds.

Home Range

Males establish breeding territories and maintain them throughout the breeding period. Territories are found in shallow water and are reported to be 0.9 to 6.1 m in diameter. Males usually sing from selected areas inside their territories while occasionally patrolling the outside edges.

How do they communicate with each other?

Green frogs produce as many as six different calls. Males attracting a mate give an advertisement call and a high-intensity advertisement call. Their advertisement call has been compared to the pluck of a loose banjo string. Male frogs defending a territory from an intruding male usually give aggressive calls and growls. The release call is given by non-receptive females and by males accidentally grabbed by another male. Finally, the alert call is given by males and females when startled or attacked by a predator.

Green frogs have an excellent sense of vision and use this to detect and capture prey.

What do they eat?

Green frogs are primarily carnivores and eat a wide variety of insects and other invertebrates from both land and water, such as slugs, snails, crayfish, spiders, flies, caterpillars, butterflies, and moths. They also eat other vertebrates, such as small snakes and frogs. Green frogs practice "sit and wait" hunting and therefore eat whatever comes within reach. Tadpoles mainly eat diatoms, algae, and tiny amounts of small animals such as zooplankton (copepods and cladocerans).

What eats them and how do they avoid being eaten?

Green frogs are preyed upon by a variety of animals. Tadpoles and eggs are eaten by leeches, dragonfly larvae, other aquatic insects, fish, turtles, and herons. Adult frogs are eaten by larger frogs, turtles, snakes, herons, other wading birds, raccoons, otters, mink, and humans.

Green frogs often look much like mink frogs where the two species occur together. This may be a form of mimicry because mink frogs have a musky skin secretion that makes them foul tasting to many predators. Green frogs do not have a foul taste, so may be taking advantage of their resemblance to mink frogs to avoid being preyed upon.

What roles do they have in the ecosystem?

Green frogs are common and abundant and serve as a food source for many other animals. They also eat large quantities of insects and other animals, thus impacting their populations.

Do they cause problems?

There are no known negative effects of green frogs.

How do they interact with us?

Green frogs are sometimes hunted for food by humans. Though they are typically too small to be economically important as frog legs, they are harvested for them sometimes. They are used by the scientific community in research and for educational purposes in biology classrooms.

Are they endangered?

Green frogs are abundant throughout all of their range. Although limb deformities and other abnomalities have been reported in green frog populations, possibly as a result of water contamination, they are still numerous and widespread.

Some more information...

One population of green frogs is known as 'bronze frogs.' They are usually bronze or brownish in color and have fairly plain markings. They also tend to be smaller than other green frogs. Bronze frogs are found in the southeastern United States.

Contributors

Merritt Gillilland (author), Michigan State University: February, 2000. James Harding (editor), Michigan State University: February, 2000.

Allison Poor (editor), University of Michigan: January, 2005.

References

Harding, J., J. Holman. 1992. Michigan Frogs, Toads, and Salamanders. East Lansing, Michigan: Michigan State University Museum.

Harding, J. 1997. Amphibians and Reptiles of the Great Lakes Region. Ann Arbor, Michigan: The University of Michigan Press.

Jenssen, T. 1967. Food Habits of the Green Frog, Rana clamitans, before and during metamorphosis.. Copeia, 1967: 214-218.

Jordan, D. 1929. Manual of the Vertebrate Animals. New York: World Book Company.

Tyning, T. 1990. Stokes Nature Guides: A guide to Amphibians and Reptiles. Boston, MA: Little, Brown and Company.

Wells, K. 1976. Multiple egg clutches in the green frog (Rana clamitans). Herpetologica, 32(1): 85-87.