Bronze Frog (Lithobates clamitans)
Description and Morphological Characteristics
Bronze frogs, a subspecies of Green Frogs, are medium sized ranging from 2-3 ½ inches in length. The have relatively smooth skin and their color can vary from greenish or pale brown, to deep bronze. Some may have brown or blackish spots scattered across the back but the majority are a solid color. Their belly is white with dark mottling or markings and males typically have a yellowish throat. A light green upper lip is common for both males and females and they have large eyes with a prominent tympanum, the center of which is elevated. They feature strong dorsolateral ridges that run from just behind the eye, over the eardrum and onto the trunk, extending only 2/3 the length of their body. They have crossbars on their long hindlegs and all toes are webbed except for the fourth and fifth toe, which extends well beyond the webbing.
Range
Their native range extends from southeast Canada, south to central Florida, and from the east coast, west to east Texas. Though they are found in north and south Illinois, they are absent from the central Illinois prairie. This species has been introduced west of it’s range in Utah and Washington, as well as north in British Columbia and Newfoundland.
Habitat and Feeding
This species can be found near permanent and semi-permanent shallow waters including swamps, along the margins of lakes or ponds, and slow-moving streams. These frogs are primarily nocturnal and during the day they take shelter among vegetative debris and tree trunks near the water’s edge. Though they require moist environments, Green frogs will often venture further into terrestrial habitats in search of better foraging opportunities, before returning to the pond. Their diet consists of insects, worms, other small invertebrates, and even smaller frogs. They are a solitary species and spend most of their lives hiding under some type of cover.
Breeding and Reproduction
Breeding is triggered by warmer temperatures and adequate rainfall, occurring from March to August in the majority of its range. The season may start later and end earlier the further north they are located. Bronze Frogs commonly migrate to overwintering sites upon the end of the breeding season. The advertisement call of this species is a sharp twang, resembling the sound of a plucked banjo string, and is repeated multiple times in succession at random intervals. Males call out to court females and eggs are laid among emergent vegetation in small masses, containing anywhere from 1,000 to 7,000 eggs. Tadpoles hatch within a few days of deposition and metamorphosis can take as long as a year.
Conservation
Bronze frogs are common throughout their range and not under any federal protection. They are classified as game species in some states and are protected in terms of bag limit and hunting season. They are listed as threatened in the state of Kansas and are therefore protected by state law. Local population declines have been attributed to loss/fragmentation of habitat, urbanization, and vehicular traffic. Bronze frogs are grouped together with Green frogs on the Texas Parks and Wildlife Black List.
Pertinent References
Forstner, J. M., Forstner, M. R. J., and Dixon, J. R. 1998. Ontogenetic Effects on Prey Selection and Food Habits of Two Sympatric East Texas Ranids: the Southern Leopard Frog, Rana sphenocephala, and the Bronze Frog, Rana clamitans clamitans. Herpetological Review 29:208-211.
Lamoureux, V.S., Maerz, J.C., and Madison, D.M. 2002. Premigratory Autumn Foraging Forays in the Green Frog, Rana clamitans. Journal of Herpetology 36:245-254.
Maerz, J.C., Blossey, B., and Nuzzo, V. 2005. Green Frogs Show Reduced Foraging Success in Habitats Invaded by Japanese knotweed. Biodiversity and Conservation 14:2901-2911.
Saenz, D., Fitzgerald, L.A., Baum, K.A., and Conner, R.N. 2006. Abiotic Correlates of Anuran Calling Phenology: The Importance of Rain, Temperature, and Season. Herpetological Monographs 20:64-82.
Account Author: Hailey Hester
Photos: James Childress
Edited by Christopher Schalk
Bronze frogs, a subspecies of Green Frogs, are medium sized ranging from 2-3 ½ inches in length. The have relatively smooth skin and their color can vary from greenish or pale brown, to deep bronze. Some may have brown or blackish spots scattered across the back but the majority are a solid color. Their belly is white with dark mottling or markings and males typically have a yellowish throat. A light green upper lip is common for both males and females and they have large eyes with a prominent tympanum, the center of which is elevated. They feature strong dorsolateral ridges that run from just behind the eye, over the eardrum and onto the trunk, extending only 2/3 the length of their body. They have crossbars on their long hindlegs and all toes are webbed except for the fourth and fifth toe, which extends well beyond the webbing.
Range
Their native range extends from southeast Canada, south to central Florida, and from the east coast, west to east Texas. Though they are found in north and south Illinois, they are absent from the central Illinois prairie. This species has been introduced west of it’s range in Utah and Washington, as well as north in British Columbia and Newfoundland.
Habitat and Feeding
This species can be found near permanent and semi-permanent shallow waters including swamps, along the margins of lakes or ponds, and slow-moving streams. These frogs are primarily nocturnal and during the day they take shelter among vegetative debris and tree trunks near the water’s edge. Though they require moist environments, Green frogs will often venture further into terrestrial habitats in search of better foraging opportunities, before returning to the pond. Their diet consists of insects, worms, other small invertebrates, and even smaller frogs. They are a solitary species and spend most of their lives hiding under some type of cover.
Breeding and Reproduction
Breeding is triggered by warmer temperatures and adequate rainfall, occurring from March to August in the majority of its range. The season may start later and end earlier the further north they are located. Bronze Frogs commonly migrate to overwintering sites upon the end of the breeding season. The advertisement call of this species is a sharp twang, resembling the sound of a plucked banjo string, and is repeated multiple times in succession at random intervals. Males call out to court females and eggs are laid among emergent vegetation in small masses, containing anywhere from 1,000 to 7,000 eggs. Tadpoles hatch within a few days of deposition and metamorphosis can take as long as a year.
Conservation
Bronze frogs are common throughout their range and not under any federal protection. They are classified as game species in some states and are protected in terms of bag limit and hunting season. They are listed as threatened in the state of Kansas and are therefore protected by state law. Local population declines have been attributed to loss/fragmentation of habitat, urbanization, and vehicular traffic. Bronze frogs are grouped together with Green frogs on the Texas Parks and Wildlife Black List.
Pertinent References
Forstner, J. M., Forstner, M. R. J., and Dixon, J. R. 1998. Ontogenetic Effects on Prey Selection and Food Habits of Two Sympatric East Texas Ranids: the Southern Leopard Frog, Rana sphenocephala, and the Bronze Frog, Rana clamitans clamitans. Herpetological Review 29:208-211.
Lamoureux, V.S., Maerz, J.C., and Madison, D.M. 2002. Premigratory Autumn Foraging Forays in the Green Frog, Rana clamitans. Journal of Herpetology 36:245-254.
Maerz, J.C., Blossey, B., and Nuzzo, V. 2005. Green Frogs Show Reduced Foraging Success in Habitats Invaded by Japanese knotweed. Biodiversity and Conservation 14:2901-2911.
Saenz, D., Fitzgerald, L.A., Baum, K.A., and Conner, R.N. 2006. Abiotic Correlates of Anuran Calling Phenology: The Importance of Rain, Temperature, and Season. Herpetological Monographs 20:64-82.
Account Author: Hailey Hester
Photos: James Childress
Edited by Christopher Schalk
