Description: This species is a mid-sized true frog. Adult green frogs range from 2.0–3.9 inchres in body length (snout to vent, excluding the hind legs). The typical body weight of this species is from 0.99 to 3.00 oz. The sexes are sexually dimorphic in a few ways: mature females are typically larger than males, the male tympanum is twice the diameter of the eye, whereas in females, the tympanum diameter is about the same as that of the eye, and males have bright yellow throats. The dorsolateral ridges, prominent, seam-like skin folds that run down the sides of the back, distinguish the green frog from the bullfrog, which entirely lacks them.
Green frogs usually have green heads while the body is brown, gray, or dark green. The green head can be more or less prominent on certain individuals, with some frogs only having green on the side of their heads while other frogs are green all the way down their back. The belly is white with black mottling. Male green frogs in breeding condition have yellow throats. Green frogs are darker colored on colder days to help absorb heat. Green frogs can sometimes be blue due to a genetic mutation known as axanthism that prevents the frog from producing yellow pigments (yellow and blue pigments together make the color green).
Habitat: Green frogs live wherever shallow freshwater ponds, road-side ditches, lakes, swamps, streams, and brooks are found. Green frogs can be found in vernal pools and other temporary bodies of water, but will usually not breed in them. This species is very opportunistic and is quick to colonize new water bodies such as swimming pools and artificial ponds. Most often seen resting along the shore, they leap into the water when approached. By inhabiting an ecotone, in this case the terrestrial and aquatic habitat boundary, green frogs (and other aquatic ranid frogs), by employing a simple leap, leave behind their many and faster terrestrial enemies that cannot similarly cross that boundary.
Range: Green frogs (Lithobates 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.
Diet: Green frogs will attempt to eat any mouth-sized animal they can capture, including insects, spiders, fish, crayfish, shrimp, other frogs, tadpoles, small snakes, slugs, and snails. Green frogs practice "sit and wait" hunting and therefore eat whatever comes within reach. Tadpoles will eat nearly anything organic, including diatoms, algae, and tiny amounts of small animals such as zooplankton (copepods and cladocerans).
Reproduction: Green frogs breed in permanent bodies of water. Males call from and defend territories. The distinctive call sounds like a plucked banjo string, usually given as a single note, but sometimes repeated. The breeding season is from April to August. Actual mating involves amplexus, whereby the male grasps the female with his forelimbs posterior to her forelimbs. The female releases her eggs and the male simultaneously releases sperm which swim to the egg mass. Fertilization takes place in the water. A single egg clutch may consist of 1000 to 7000 eggs, which may be attached to submerged vegetation.
Green frog tadpoles are olive green and iridescent creamy-white below. Metamorphosis can occur within the same breeding season or tadpoles may overwinter to metamorphose the next summer. Males become sexually mature at one year, females may mature in either two or three years. Research show that wild green frogs, both living in contaminated suburban backyard ponds and also in relatively pristine forested ponds, can switch sexes. This sex reversal appears to be a natural condition but it is currently unknown whether these wild sex-reversed green frogs are able to breed.
Status: The green frog is one of the most abundant frogs wherever it occurs and has no known problems. Green frogs are protected by the law in some US states.
Subspecies: None
Taxonomy: This species was placed in the genus Lithobates by Frost et al. (2006). However, Yuan et al. (2016, Systematic Biology, doi: 10.1093/sysbio/syw055) showed that this action created problems of paraphyly in other genera. Yuan et al. (2016) recognized subgenera within Rana for the major traditional species groups, with Lithobates used as the subgenus for the Rana palmipes group. AmphibiaWeb recommends the optional use of these subgenera to refer to these major species groups, with names written as Rana (Aquarana) catesbeiana, for example.
Disclaimer: ITIS taxonomy is based on the latest scientific consensus available, and is provided as a general reference source for interested parties. However, it is not a legal authority for statutory or regulatory purposes. While every effort has been made to provide the most reliable and up-to-date information available, ultimate legal requirements with respect to species are contained in provisions of treaties to which the United States is a party, wildlife statutes, regulations, and any applicable notices that have been published in the Federal Register. For further information on U.S. legal requirements with respect to protected taxa, please contact the U.S. Fish and Wildlife Service.
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