The northern red-legged frog is found along the east coast of North America in Canada and the United States. They live in watercourses and neighboring areas of damp forest.
They feed on a range of animal prey such as insects, amphibians and small animals.
Male northern red legged frogs gather at the breeding sites a couple of weeks before mating and may call for up to 14 hours each day to attract mates.
A range of threats are impacting the survival of the northern red legged frog. These include destruction of habitat, introduced predators, grazing in their habitat by livestock and drought.
Read on to learn more about these amazing amphibians.
The hind legs of the red-legged frog are red giving them their name. Across the rest of the body they are brown or reddish brown with black flecks patterning this. Some individuals exhibit large, dark spots across the body.
A cream colored line runs from the eye to the back of the mouth. In the groin area they have yellow and green motled coloration with black spots. On the underside they have red on the arms, hind legs and lower bellies.
Their skin is smooth except for a prominent fold down each side of the body. The feet are webbed which helps them to swim.
Males in the south of the range possess a pair of vocal sacs which are lacking in the northern population.
A female northern red-legged frog is larger than the male. They reach a length of 10cm (4in) long with males measuring 6.8cm (2.6in) long.
Northern red-legged frogs are carnivores which feed on insects, small mammals and amphibians.
North America is the native home of the northern red legged frog. They are found along the east coast of Canada and the United States.
In Canada they live in British Colombia and in the United States they live in the states of California, Oregon and Washington.
These animals have been introduced to Chicagof Island in Alaska and Nevada.
They can be found in ponds and streams in coastal mountains. They are rarely found far from water. Breeding takes place in a temporary or permanent wetland pond, lake or slow-moving stream. They often seek a fish-free water body for their breeding site.
Close to these watercourses they require emergent riparian vegetation which they can use to escape predators and for shade. They may also leave the water and travel some distance in to damp woods and forests.
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At the start of the breeding season the males will sit underwater and call to the females. They have been recorded to call for as long as 14 hours each day. This occurs in early spring. During this time the water is cool.
The male will grasp the female and fertilize the eggs externally as she lays them. Between 500 and 1,300 eggs are deposited in a gelatinous mass. This is attached to aquatic vegetation under the water. Eggs are colored black on top with white underneath and are surrounded by a jelly envelope.
Eggs hatch after a 4-7 week gestation period and at hatching are a tadpole. Tadpoles are colored brown.
These spend 11-14 weeks developing in the water. Some may overwinter though and not metamorphose for as long as 12 months.
Sexual maturity is reached between 2 and 4 years old. Females tend to mature later than males.
Outside of the breeding program these amphibians are mostly solitary.
Across most of the range they are active by day but in California the species is considered nocturnal.
Red-legged frogs will produce a call which is a series of low-pitched pulses.
Each year they may undertake a hibernation underwater during winter. They have also been known to undertake this in mammal burrows or moist leaf litter.
Predators and Threats
The presence of different predators across their range is suggested as one reason that California frogs are nocturnal while those in the rest of the range are nocturnal.
Prey is avoided by quickly leaping to water using the strong back legs.
Other threats include habitat degradation and destruction, introduced predators and disease. Livestock grazing in streams, off road vehicle activity and drought also produce a threat to their survival.
No full assessment of the adult population exists. It is thought to include over 10,000 mature individuals but is declining.
Rana aurora was previously considered a subspecies and group with Rana draytonii. Further study has determined the two to be separate studies with only a small overlap in population. The pair differ in size, breeding season and vocal sacs.
These frogs used to be harvested in large numbers for their legs which were seen as a delicacy.
Oregon Department of Fish & Wildlife, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons
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Jackson, T. and Chinery, M., 2012. The illustrated encyclopedia of animals of the world. London: Southwater.
Canadianherpetology.ca. 2021. Northern Red-legged Frog. [online] Available at: <http://www.canadianherpetology.ca/species/species_page.html?cname=Northern%20Red-legged%20Frog> [Accessed 26 July 2021].
Californiaherps.com. 2021. Northern Red-legged Frog – Rana aurora. [online] Available at: <http://www.californiaherps.com/frogs/pages/r.aurora.html> [Accessed 26 July 2021].
AmphibiaWeb. 2021. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 26 Jul 2021.
Brown, S. 2000. "Rana aurora" (On-line), Animal Diversity Web. Accessed July 26, 2021 at https://animaldiversity.org/accounts/Rana_aurora/
Daniel, W. M., 2021, Rana aurora Baird and Girard, 1852: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=68, Revision Date: 8/20/2019, Peer Review Date: 8/20/2019, Accessed: 26 Jul 2021
Burke Museum. 2021. Northern Red-legged Frog. [online] Available at: <https://www.burkemuseum.org/collections-and-research/biology/herpetology/amphibians-reptiles-washington/northern-red-legged> [Accessed 26 July 2021].
IUCN SSC Amphibian Specialist Group. 2015. Rana aurora. The IUCN Red List of Threatened Species 2015: e.T58553A78906924. https://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T58553A78906924.en. Downloaded on 26 July 2021.