Ministry of Environment
|Common Name:||Green Frog|
|Scientific Name:||Lithobates clamitans|
|*Exotic species are species that have been introduced into areas where they do not naturally occur.|
The Green Frog is not a native species in British Columbia. Natural populations of Green Frogs are found throughout eastern North America. In some areas they are the most common frogs to be found. Years ago, small populations of Green Frogs were introduced to B.C. in the Lower Mainland and Southern Vancouver Island, possibly through the pet or fish bait trade.
Green frogs are the classic “pond frogs”; they are medium-sized, green or bronze in colour, and have a habit of sitting fairly upright among or on aquatic plants – including, of course, water lily pads.
Adult Green Frogs resemble Bullfrogs, another introduced species, but are smaller and have distinct dorsolateral folds. These are raised folds of skin which extend fron the head most of the way down the sides of the frog’s back. Green Frogs can be up to 10 centimetres long from snout to rump, making them larger than most native frog species in B.C.; they can also be recognised by the large tympanum (“ear”) behind each eye. Male frogs have tympana approximately twice the diameter of their eyes, while females have tympana about the same size as their eyes. Male Green Frogs have a yellow throat, which can be very bright during the breeding season.
Tadpoles have long, oval bodies with pointed snouts. They are olive green with vague dark blotches and a cream belly.
Green Frogs have a loud, distinctive call that sounds almost exactly like a stretched rubber band being plucked.
Green Frogs are strongly aquatic, both as adults and in the tadpole stage. In their natural range they prefer permanent ponds or slow streams with plenty of vegetation, and it is likely that they seek out such habitats in B.C. as well. Adult frogs tend to stay quite close to the water’s edge when they leave the water to bask or feed, though as juveniles they can and do disperse overland to new ponds.
Green Frogs breed in permanent ponds in early summer – later than most native frog species in B.C. Males are territorial and will stake out territories countaining good egg-laying habitat, in order to attract females. They advertise and defend these territories by calling loudly. Smaller males do not defend territories, but wait instead around the edges of a larger male’s territory in order to “sneak” matings with females attracted by the calling male.
Females lay eggs in a single layered mass on the water’s surface, about 15 to 30 cm across. Each egg mass may contain up to 5000 eggs. Tadpoles hatch out within a few days, depending on water temperature, and develop over the course of the summer; juvenile frogs emerge in late summer if the eggs are laid early in the season, or the tadpoles from later egg masses may overwinter in larval form. Green Frog tadpoles in B.C. probably overwinter as tadpoles, but this has not been studied. Green Frogs reach sexual maturity two to three years after metamorphosis. Their lifespan in the wild is unknown, but Green Frogs in captivity have lived up to ten years.
Adult Green Frogs remain active in cool weather, but will hibernate in winter conditions by burrowing into the mud at the bottoms of ponds.
Adult Green Frogs feed in the water, taking a variety of aquatic invertebrates and flying insects that land on the surface of the water. They have also been recorded eating small fish or frogs. Tadpoles graze on algae and detritus.
At present, we don’t know how far Green Frog populations have spread in B.C., or whether they are expanding. They are present throughout much of the Lower Mainland, but their presence in a wetland may sometimes be masked by the more obvious presence of Bullfrogs.
The current consensus among biologists is that Green Frogs do not seem to have as much of an impact on native frog species as Bullfrogs do. Green Frogs are smaller and less aggressive than Bullfrogs. However, Green Frogs do compete with native frogs for food and habitat, and there is a risk that this extra pressure may be the final straw for some native populations. For this reason, we would like to keep a watchful eye on habitats invaded by Green Frogs.
Since we don't have much information on the current distribution of Green Frogs in B.C., you can help by reporting sightings to B.C. Frogwatch.
You can help prevent the further spread of Green Frog populations by learning about these animals and sharing that knowledge with others. Never move frogs or frog spawn between ponds, no matter how tempting it may be to have frogs in your garden pond. You risk introducing an exotic species such as Green Frogs or Bullfrogs to a new location; you also risk transferring fungal or viral diseases between populations.
Under B.C.’s Wildlife Act, Green Frogs are considered wildlife, and it is illegal to capture, transport or sell them. If you notice new Green Frog colonies, or anything else that causes you concern, be sure to contact B.C. Frogwatch and we’ll see if we can help.
- The species name, “clamitans,” means “clamouring” in Latin – in other words, this is the loud-mouthed frog!
- Green Frogs are called Banjo Frogs in some parts of their range, because of their loud plunking call.
Photo © Russ Haycock. No reproduction or distribution without permission.