Northern Leopard Frog
Last Review/Updated: May 30, 2002
Rana pipiens
Description
The northern leopard frog can range from 50-100 mm in length. It is either green or brown, with a pale white belly. It can be easily identified by its large dark spots bordered with pale rings. The frog also has prominent light-coloured dorsolateral folds. The spotted frog is about the same size; however, its spots are much smaller and they lack the light rings around them. Wood frogs can also have some spots on them, but their prominent eye mask readily identifies them.
Natural History
This frog is found in a variety of habitats and is relatively cold-adapted. It is associated with a wide range of permanent water bodies, from ponds and marshes to streams and rivers. It can be found long distances from water, especially after rain. Prey items include insects and worms as well as small fish, or even frogs or tadpoles. Cannibalism has been reported. Unlike most other frogs, the northern leopard frog hibernates under water at the bottom of ponds. The northern leopard frog is currently on the Red List in the Status of Alberta Wildlife because it is considered to be in serious trouble. Populations are nonviable or are at serious risk of declining to nonviable levels. Changes to the regulations under the Wildlife Act have designated the northern leopard frog as an endangered species.
Breeding
Sometimes leopard frogs begin mating even before all the ice has melted from ponds. This breeding can be as early as April in some years. Since leopard frogs hibernate in ponds they may not need to migrate to a breeding site. Males call from the water to attract females. The call is low-pitched and can sound like someone rubbing a balloon. The eggs (about 1.7 mm in diameter) are laid in large masses of up to 6000 either attached to aquatic vegetation or on the pond bottom. The eggs will hatch in 1-3 weeks, depending upon the water temperature.
Larvae
When first hatched, tadpoles range from 8-10 mm in length. They become larger and more massive than any other tadpole in the province, averaging about 75 mm long, although some tadpoles have been observed to be over 100 mm in length. The tadpoles are dark grey or brown, with gold speckles and a whitish underside. It can take 9-12 weeks for the tadpoles to transform into juvenile frogs, at which time the froglets will be about 25 mm long. These froglets will not become sexually mature until 2 or 3 years later.
DistributionAt one time leopard frogs were widely distributed in the eastern half of the province, but in the late 1970s they apparently declined dramatically. Although there are a few records from the northeast corner of the province, they appear to be absent from most of central Alberta. Reduced populations are found in the mixed grassland in the south. MonitoringNorthern leopard frogs can be widely dispersed outside of the breeding season. In the spring, adults will congregate at breeding ponds and begin calling. |
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