Northern Leopard Frog (Rana pipiens)

Description
Northern Leopard Frog

Size

  • The northern leopard frog is the largest frog found in Alberta.
  • On average, adult frogs can range from 50 to 130 millimetres (two to five inches) in length, measuring from the tip of the nose to the base of the tail.
  • Adult female leopard frogs can be much larger than the males.

Appearance

  • Either green or brown, with a pale white belly. A few leopard frogs, found in southern regions
  • Can be easily identified by its large dark spots bordered with pale rings. These spots can be found dotting the back, sides and legs of the frog. Occasionally, leopard frogs will be unspotted.
  • Has prominent, light-coloured dorsolateral folds; these are glandular ridges that separate the back from the sides of the frog, and that run along the frog’s back from the eyes to the tail.
  • Can sometimes present with a light stripe on the upper jaw.
  • Has long hind legs and large feet with well-developed webbing between the toes.

Voice/call

  • During mating season, males call to attract females. The call is low-pitched and can sound like someone rubbing a balloon, or like a short guttural snore followed by several clucking or grunting noises.
Distribution
Northern leopard frog distribution in Alberta
  • At 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 of small populations from the northeast corner of the province, northern leopard frogs appear to be absent from most of central Alberta. Reduced populations are found in the mixed grassland in the south.
Natural History

Habitat

  • The northern leopard frog is found in a variety of habitats and is relatively cold-adapted.
  • This frog is associated with a wide range of permanent water bodies, and can often be found along the edges of ponds, marshes, streams, rivers and lakes.
  • Leopard frogs prefer clear, clean water in open or lightly wooded areas. They rarely occur in dense forested areas.
  • The larger size of the leopard frog allows it to conserve water, so the frog can travel away from its typically moist habitats to drier ones in search of food. After rain or a heavy dew, leopard frogs can be found long distances from water.
  • Unlike most other frogs, the northern leopard frog hibernates under water at the bottom of ponds.
  • Northern leopard frogs can be widely dispersed outside of the breeding season. In the spring, adults will congregate at breeding ponds and begin calling.

Food

  • Tadpoles for this species feed upon plants and algae, though they may feed occasionally on dead tadpoles or dead invertebrates.
  • Northern leopard frog adults will eat almost anything they are able to catch.
  • Prey for adult leopard frogs includes:
    • insects
    • mice and other small vertebrates
    • small fish
    • worms
    • other frogs or tadpoles
  • Cannibalism has been reported with this species, young leopard frogs may be eaten.
  • Most feeding activity occurs on land and at night, but leopard frogs will also feed during the day if something draws near to their resting site.

When active

  • In Alberta, the active season for this frog runs from April to October.
  • Are most active in warm, wet weather, or at dawn or dusk if the climate is not too cool.
  • Will rest during the day in wet areas or shallow pockets in the soil, areas where they can absorb moisture and avoid predators. The frogs bask in the sun to raise their body temperature and speed food digestion.
  • After sunset, will hunt for food either in the water or on land.
  • In the winter months, leopard frogs will hibernate on pond or lake bottoms or under stones in springs, streams, or rivers. Such sites are a stable environment to spend the winter, as long as the water has enough oxygen.
Reproduction and Growth
Life Stage Apr May Jun Jul Aug Sep
Breeding Breeding Bar: April 10 to June 10
Eggs Hatch Eggs Hatch Bar: April 15 to June 22
Transformation Transformation Bar: June 22 to September 22

Breeding behavior

  • Northern leopard frogs in Alberta begin their mating behaviour starting in late April or early May. Males call from the water to attract females. Calling may take place during the day, but grow more persistent, loud and intense after dark as males search for breeding females.
  • Since leopard frogs hibernate in ponds, they may not need to migrate to a breeding site.
  • 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. Most breeding takes place in May and is completed by early June.
  • The eggs, about 1.7 millimetres (0.07 inches) in diameter are laid in large flattened spherical masses of up to 7,000 eggs per mass, although the average number may be closer to 4,000
  • Egg masses are either attached to aquatic vegetation or on the pond bottom, as eggs must remain in water to survive.
  • The eggs will hatch in one to three weeks, depending upon the water temperature.

Appearance of young

  • When first hatched, tadpoles range from 8 to 10 millimetres (0.31 to 0.40 inches) long.
  • The tadpoles are dark grey or brown, with gold speckles and a whitish underside.

Growth process

  • As they grow, the tadpoles of northern leopard frogs become larger and more massive than any other tadpole in the province, averaging about 75 millimetres (three inches) long, although some tadpoles have been observed to be over 100 millimetres (four inches) in length.
  • It can take 9 to 12 weeks for the tadpoles to transform into juvenile frogs, at which time the froglets will be about 25 millimetres (about one inch) long. These froglets will not become sexually mature until two or three years later.
Conservation and Management

Status

Classified as At Risk in the current Status of Alberta Wildlife report. See the Status of the Northern Leopard Frog in Alberta report at:

Designated as a Threatened species under the Wildlife Act regulations. See the northern leopard frog profile at:

Issues

  • Populations are nonviable or are at serious risk of declining to nonviable levels.
  • Leopard frogs in Alberta are limited by their small population size and fragmented habitat areas, as small populations can be vulnerable to even minor disturbances in their ecosystem.

Current management

  • Amphibian Monitoring in Alberta

    The northern leopard frog is being monitored under the Alberta Volunteer Amphibian Monitoring Program (AVAMP) and the Researching Amphibian Numbers in Alberta (RANA) program.
  • Multiple Species at Risk (MULTISAR) program

    The northern leopard frog is a focal species of the MULTISAR (multiple species at risk) program. Key elements of the program include:

    • surveying local populations
    • assessing the ecological status of the habitat
    • developing management recommendations and habitat enhancement projects
    • monitoring the species' response over time


    MULTISAR strives to conserve multiple species at risk by working cooperatively with landowners and lease holders to implement voluntary beneficial management practices on native prairie habitat.
Similar Species
  • Columbia spotted frog
    About the same size; however, its spots are much smaller and lack the light rings around them.
  • Wood frog
    Can also have some spots on it, but its prominent eye mask readily identifies it. Wood frogs are also smaller and more brown, and may have a light stripe down the middle of the back.

 

Page Information

Updated: Jul 25, 2013