Order Anura, Family Ranidae. These are typical frogs with adults
being truly amphibious, living at the edge of water bodies and entering the
water to catch prey, flee danger, and spawn. This profile covers medium-sized
ranids. Also, all frogs are somewhat poisonous to some degree, but most of them
aren't harmful to humans.
Description
The green frog (Rana clamitans) is usually found near shallow
freshwater throughout much of eastern North America. Two subspecies are
recognized: R. c. clamitans (the bronze frog; ranges from the Carolinas to
northern Florida, west to eastern Texas, and north along the Mississippi Valley
to the mouth of the Ohio River). However, the R. c. melanota (the green frog;
ranges from southeastern Canada to North Carolina, west to Minnesota and
Oklahoma but rare in much of Illinois and Indiana, introduced into British
Columbia, Washington, and Utah.
Body Size
The green frog is a medium-sized ranid usually between 5.7 and
8.9 cm snout-to-vent length. Its growing period is mainly confined to the
period between mid-May and mid-September. But the females are generally larger
than males. But the adults typically weigh between 30 and 70 g. The average
lifespan of Green Frog is approximately 16 years, fairly long compared with
other frogs.
Habitat
Adult green frogs live at the margins of permanent or
semi-permanent shallow water, springs, swamps, streams, ponds, and lakes. Green
frogs primarily to inhabitant the banks of streams. They also can be found
among rotting debris of fallen trees. Juveniles prefer shallower aquatic
habitats with denser vegetation than those preferred by adults. Moreover, Green
frogs inhabited aquatic habitats about two-thirds of the time and terrestrial
habitats the remaining time. The green frog relies on terrestrial habitats for
feeding and aquatic habitats for refuge from desiccation, temperature extremes,
and enemies. Ponds used by green frogs are usually more permanent than those
used by other anuran species.
Food Habits
Adult R. clamitansare terrestrial feeders among shoreline
vegetation. They consume insects, worms, small fish, crayfish, other
crustaceans, newts, spiders, small frogs, and molluscs. The terrestrial beetles
often are their most important food item but noted that any locally abundant
insect along the shoreline may be consumed in large numbers. There is a
pronounced reduction in food consumption during the breeding period for both
males and females. During the breeding season, males spend most of their energy
defending breeding territories, and
Green Frog females expend their energy producing eggs. Fat
reserves acquired during the rebreeding period compensate for reduced food
intake during the breeding period. Also, green frogs consume most of their food
in the spring and eat little during the winter. Food eaten in the spring,
summer, and fall consists mostly of terrestrial prey. whereas winter
food is composed mostly of aquatic prey.
Juveniles (sexually immature frogs) eat about half the volume of
food as do adults over the course of a year. Green frogs eat their cast skins
following molting; the casting of skin is frequent during midsummer.
Temperature regulation and daily activities. Green frog's
activity period varies by frog size, with larger frogs being primarily
nocturnal, small frogs being diurnal, and middle-sized frogs (5 to 7 cm SVL)
being equally active during day and night.
Hibernation
Adult green frogs overwinter by hibernating underground or
underwater from fall to spring. The frogs hibernating in mud and debris at the
bottom of streams approximately 1 m deep. The adults usually hibernate in
restricted chambers within rock piles or beneath plant debris, while juveniles
are more often found in locations with access to passing prey. The frogs begin
emerging when the mean daily temperature is about 4.4C and the maximum
temperature is about 15.6C for 3 to 4 days. Juvenile frogs enter and exit
hibernation after adult frogs.
Breeding activities and social organization
Green frogs breed from spring through the summer, spawning at
night. Female green frogs stay in a nonbreeding habitat until it is time to
spawn. In preparation for breeding, males establish territories near the shore
that serve as areas for sexual display and as defended oviposition sites. Males
establish calling sites within their territories where they attempt to attract
females. Females visit male territories to mate and lay their egg masses. The
masses are contained in films of jelly and are deposited in emergent, floating,
or submerged vegetation; they hatch in about 3 to 6 days. Adults are solitary
during non-breeding periods.
In the southern part of their range, green frog tadpoles
metamorphose into frogs in the same season in which they hatched, while in the
northern part, 1 or 2 years pass before metamorphosis. Tadpoles that hatch from
egg masses laid in the spring usually metamorphose that fall, while those
hatching from summer-laid eggs typically overwinter as larvae and metamorphose
the following spring.
The most tadpoles are 2.6 to 3.8 cm SVL at the time of
transformation. Those that transform in late June or early July grow rapidly,
adding 1.4 to 2.0 cm SVL in the first 2 months and 0.4 to 0.7 cm SVL more
before hibernation. Tadpoles that transform at approximately 3.1 cm SVL may
reach between 5.0 and 5.8 cm SVL before hibernation. Therefore, newly
transformed frogs often move from lakes and ponds where they were tadpoles to
shallow stream banks, usually during periods of rain.
Home range and resources
The species' home range includes its foraging and refuge areas
in and around aquatic environments. During the breeding period, the male's home
range also includes its breeding territory. It is roughly 80 percent of adult
frogs captured in the spring and again in the fall occupied the same home
ranges.
Population density
During the breeding season, green frog densities at breeding
ponds can exceed several hundred individuals per hectare. Adult male frogs
space their breeding territories about 2 to 3 m apart. The sexual maturity is
attained in 1 or 2 years after metamorphosis; individuals may reach maturity at
the end of the first year but not attempt to breed until the next year. Most
females lay one clutch per year, although some may lay two clutches, about 3 to
4 weeks apart. In natural populations, green frogs can live to approximately 5
years of age.
Similar Species
1. The
river frog (Rana heckscheri) is slightly larger than the green frog (8.0 to
12.0 cm SVL) and is found in swamps from southeast North Carolina to central
Florida and southern Mississippi.
2. The
leopard and pickerel frogs (Rana pipiens and its relatives, and Rana palustris)
are medium-sized and strongly spotted. There are four leopard frogs whose
ranges are mostly exclusive from each other but overlap with the green frog.
The pickerel frog has a similar range with gaps in the upper Midwest and the
southeast.
3. The
mink frog (Rana septentrionalis) is only slightly smaller (4.0 to 7.0 cm) and
is found on the borders of ponds and lakes, especially near waterlilies. It
ranges from Minnesota to New York, north to Labrador.
4. The
carpenter frog (Rana virgatipes) is about the same size as the green frog (4.1
to 6.7 cm) and is closely associated with sphagnum bogs and grasslands. It has
a coastal plain range from New Jersey to Georgia and Florida. The bullfrog and
pig frog are much larger ranid species.
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