|Common Name:||Green Frog
|Scientific Name:||Lithobates clamitans
*Exotic species are species that have been introduced into areas where they do not naturally occur.
At a Glance
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.
Home Sweet Home
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.
This is the Life
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.
What’s on the Menu?
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.
How Are They Doing?
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.
How You Can Help
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.