Green Frog

Description

This species is a mid-sized true frog. Adult green frogs range from 5–10 cm (2.0–3.9 in) in body length (snout to vent, excluding the hind legs). The typical body weight of this species is from 28 to 85 g (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.

Behavior

Green frogs are commonly found sitting on the shore line pointed towards the water. If approached, the frog will quickly jump into the water and either swim to the bottom or float at the surface with only their eyes out. This species is usually diurnal, although they are active at night when temperatures are warm.

Green frogs start to awaken once daytime temperatures rise above 10 °C (50 °F), though they will not breed until temperatures are consistently warm.

Tadpoles are detritivores that sift through the substrate looking for morsels. Tadpoles consume decaying plant matter and will also feed on dead animals such as frogs that drowned. Tadpoles can be found sunning themselves in shallow water, retreating into deeper water when disturbed. They are active during the winter and can be seen moving around under the ice.

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.

Feeding

Green frogs will attempt to eat any mouth-sized animal they can capture, including insects, spiders, fish, crayfish, shrimp, other frogs, tadpoles, small snakes, and snails. Tadpoles will eat nearly anything organic.

Conservation 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

The two recognized subspecies of L. clamitans are:

• Lithobates clamitans clamitans (Latreille, 1801) – bronze frog
• Lithobates clamitans melanota (Rafinesque, 1820) – northern green frog