LATER CALLING SPECIES
Northern Leopard Frog
Pickerel Frog
Eastern Gray Tree Frog
Green Frog
American Bullfrog
Northern Leopard Frog (Rana pipiens)
Click here to hear the call of the Northern Leopard Frog
Photo by: James Harding
Once abundant throughout the state, northern leopard frog
populations have been declining since the 1970s. The year 2001 may be the beginning of a reversal of this
trend. Results from the Michigan
Department of Natural Resources statewide volunteer survey, Ann Arbor's citywide
survey, and the Rouge Watershed Frog and Toad Survey all show that this species
was heard in more blocks in 2001 than in past years.
Since the cause of the initial decline was never isolated and is probably
due to a combination of factors, it is difficult to explain the recent increase.
Future surveys will reveal whether this is a real recovery.
Northern leopard frogs are medium to large size frogs (2 -
4.4 in. long) with round spots on the back and sides and a light belly. You may
recognize this frog from biology class as they are the frogs of choice for
dissections (lab grown). They
prefer ponds that stay wet until August and the marshy edges of lakes for
breeding. In the summer, mature
adults can be found far from any wetlands.
The call of the leopard frog is one of the most unusual. It has been likened to a snore or to the sound made when a balloon is rubbed on something. Males usually float when calling and inflate sacs on the sides of the mouth rather than a throat sac.
Pickerel Frog (Rana palustris)
Click here to hear the call of the Pickerel Frog
Photo by: James Harding
Pickerel frogs are closely related to the northern leopard
frog and are rare in the Rouge Watershed and only locally common in the state.
They prefer spring fed ponds and sunny wet meadows and are extremely
sensitive to water pollution. By
site, they are distinguished from the leopard frog by their squareish spots and
yellow groin and inner hind legs. They
tend to be slightly smaller than the Leopard Frog, ranging in size from 1.75 to
3.43 inches long.
The call of the pickerel frog is similar to the snore of the northern leopard frog but is more abrupt and flatulent.
Eastern Gray Tree Frog (Hyla versicolor)
Click here to hear the call of the Gray Tree Frog
Photo by: James Harding
There are two species of tree
frogs in southeast Michigan;
eastern gray tree frogs and Cope's gray tree frogs. Visually there is no way to tell the two apart and the calls
can sound very similar depending on weather conditions. Both species have the ability to change color and range from
gray to bright green, depending on the background.
Gray tree frogs are found in brushy habitats in immature,
deciduous woodlands. For breeding,
they do not use temporary ponds. Outside
of the breeding season, they are often heard calling from trees.
Their round sticky toe pads enable them to climb well and they will often
stick on windows or walls adjacent to porch lights and catch insects.
Gray tree frogs are small to mid size frogs, ranging from 1.25 to 2.4
inches long.
The call of the eastern gray tree frog is a musical trill, beginning around May through the first of June.
Green Frog (Rana clamitans )
Click here to hear the call of the Green Frog
Photo by: James Harding
Click on photo for larger picture
Green frogs are one of Michigan's largest species, growing
up to 6 in. long. They are
widespread around the state where there are permanent ponds and can tolerate the
widest variety of conditions of any anuran species.
They have reportedly survived a dip in a highly chlorinated swimming
pool. Often mistaken for bullfrogs,
green frogs have a dorsolateral ridge that is absent in bullfrogs.
Males can be distinguished from females by the size of the tympanum or
eardrum. In males, the eardrum is
larger than the eye; in females it is smaller than the eye.
Green frogs have the longest window of breeding, calling
from May through July and even into August.
The tadpoles take 3 months to mature and often over winter before
metamorphosis, making permanent ponds crucial for their success.
The green frog call sounds like a banjo string being plucked.
Bullfrog (Rana
catesbeiana)
Click here to hear the call of the Bullfrog
Photo by: James Harding
Click on photo for larger picture
The state's largest frog, the bullfrog, can grow up to 8
in. long and live up to 10 years. These
frogs are not very common throughout the state and may be declining.
They require permanent ponds for breeding and prefer abundant vegetation.
Like all frogs and toads, they are predators, and their large size allows
them to eat smaller frogs and tadpoles. In
turn, humans prey on bullfrogs for their legs.
Bullfrog tadpoles take 5-6 warm months to transform.
Since tadpoles do not hatch until June, tadpoles must over winter and
some even over winter twice before becoming frogs.
Bullfrogs make a rum-rum-rum sound when they start calling in June.
*Cope's Gray Tree Frog could also be found in the Rouge Watershed but its presence has not been confirmed due to the difficulty of distinguishing the call from that of the gray tree frog.