This species can be brown to reddish or copper-brown with blacks spots scattered over its back. The underbelly of the species is whitish, with a reddish colouration appearing on the lower belly and undersides of the hind legs as the frog gets older. Bones on the undersides of the hind legs can be seen through the translucent skin. This species has a dark eye mask above a narrow, cream-coloured jaw stripe on each side of the face.
Juvenile frogs may be active both nocturnally and diurnally, whereas adult frogs are primarily active nocturnally (AmphibiaWeb 2009).
AmphibiaWeb (2009) provides the following breeding information for Red-legged Frogs: this species breeds during a 1-2 week period between January and March, depending on locality; egg masses consist of between 300 and 5,000 eggs; egg masses are nearly always attached to emergent vegetation, submerged beneath the surface in the deepest water available, eggs hatch after 6 to 14 days depending on water temperature; larvae typically metamorphose in 3.5 to 7 months, but some overwinter and transform after more than 12 months in the larval stage; males may attain sexual maturity at 2 years, females at 3, and adult frogs may live 8 to 10 years.
Adult Red-legged Frogs primarily eat invertebrates, while juveniles feed on algae.
Terrestrial stages of the Red-legged Frog are most typically found at lower elevations, below 200 metres, but have been recorded at over 1000 metres (Ovaska and Sopuch, 2004). It is associated with streams, ponds or marshes, but may also be found far from water in moist forests. It can be found in a variety of stand types of various successional stages, but usually will not remain in clearcuts. Its breeding habitat includes permanent and ephemeral bodies of water with abundant emergent vegetation.
The Red-legged Frog occurs along the Pacific coast of North America from southern British Columbia to Baja California del Norte. In British Columbia, it is found throughout Vancouver Island, the Gulf Islands and the Lower Mainland, west of the Coast Mountains. Its distribution along the coast north of the Fraser River is poorly known, but historical records suggest it may have been found as far north as Kingcome Inlet (Waye, 1999; Ovaska and Sopuck, 2004).
The Red-legged Frog is in the Family Ranidae (true frogs), a large group containing 754 recognized species (AmphibiaWeb 2006), which is found worldwide except for Caribbean and Oceanic islands. In British Columbia, the Red-legged Frog is represented by the Northern subspecies, Rana aurora aurora, which also occurs in Washington, Oregon, and the northwestern corner of California. It is a medium sized frog (snout-vent length 30-100 mm). Its name refers to the translucent red coloration of the undersides of the legs and belly.
As with many species, the main threat to this frog in British Columbia is habitat loss. In the Lower Mainland of BC, increasing wetland loss has reduced connectivity between wetlands (i.e., habitat fragmentation) thus increasing the risk of local extinctions as population losses are not replaced by new immigrants. Isolated populations are then subject to the loss of genetic diversity. Habitat fragmentation resulting from urban development, densification of road networks, and automobile traffic is an ongoing and increasing threat. Road construction can alter wetland habitats, and automobile traffic is an obvious hazard during migration of adults to breeding pools and the dispersal of transformed froglets. Indirect effects may also arise from contaminated water runoff.
The Red-legged Frog is declining in areas throughout its western North American range, including Oregon and California. The introduction of non-native species such as Bullfrogs, Green Frogs, and slider turtles can result in disease transmission, and predation and competition effects at various life stages indicating that complex interactions between habitat alteration, behaviour, and the presence of introduced species may be contributing to population declines.
AmphibiaWeb: Information on amphibian biology and conservation. [web application]. 2009. Berkeley, California: AmphibiaWeb. Available: http://amphibiaweb.org/. (Accessed: Jul 24, 2009).
Ovaska, K. and L. Sopuck. 2004. Update COSEWIC Status report on the Red-legged Frog, Rana aurora, in Canada. Report prepared for the Committee on the Status of Endangered Wildlife in Canada. Ottawa, Ontario. 46 pp.
Waye, H. 1999. Status report on the Northern red-legged frog, Rana aurora, in Canada. Report prepared for the Committee in the Status of Endangered Wildlife in Canada. Ottawa. 27 pp.
Matsuda, Brent, David M. Green, and Patrick T. Gregory. 2006. Amphibians and Reptiles of British Columbia. Handbook. Royal BC Museum, Victoria.
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2017. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
16/08/2018 6:18:07 PM]
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