Northern leopard frog

Appearance

The northern leopard frog is a fairly large species of frog, reaching about 11 cm in length. It varies from green to brown in dorsal colour, with large, dark, circular spots on its back, sides, and legs.

Each spot is normally bordered by a lighter ring. A pair of dorsolateral folds starting from the back of the eye run parallel to each other down the back. These dorsolateral folds are often lighter or occasionally pinkish in colour.

There is also a pale stripe running from the nostril, under the eye and tympanum, terminating at the shoulder. The ventral surface is white or pale green. The iris is golden and toes are webbed.

Tadpoles are dark brown or grey, with light blotches on the underside. The tail is pale tan.

Status

This species was once quite common through parts of western Canada and the United States until declines started occurring during the 1970s. Although the definitive cause of this decline is unknown, habitat loss and fragmentation, environmental contaminants, introduced fish, drought, and disease have been proposed as mechanisms of decline and are likely preventing species recovery in many areas. Many populations of northern leopard frogs have not yet recovered from these declines.

Behavior

Males make a short snore-like call from water during spring and summer.

Habitat

Northern leopard frogs have a wide range of habitats. They are found in permanent ponds, swamps, marshes, and slow-moving streams throughout forest, open, and urban areas. They normally inhabit water bodies with abundant aquatic vegetation. They are well adapted to cold and can be found above 3,000 m asl.

Reproduction

The northern leopard frog breeds in the spring. Up to 6500 eggs are laid in water, and tadpoles complete development within the breeding pond. Tadpoles are light brown with black spots, and development takes 70–110 days, depending on conditions. Metamorph frogs are 2–3 cm long and resemble the adult.

Food

They eat a wide variety of animals, including crickets, flies, worms, and smaller frogs. Using their large mouths, they can even swallow birds and garter snakes.

Predators

Northern leopard frogs are preyed upon by many different animals, such as snakes, raccoons, other frogs, and even humans. They do not produce distasteful skin secretions and rely on speed to evade predation.

Uses

The northern leopard frog produces specific ribonucleases in its oocytes. Those enzymes are potential drugs for cancer. One such molecule, called ranpirnase, is in clinical trials as a treatment for pleural mesothelioma and lung tumours. Another, amphinase, was recently described as a potential treatment for brain tumors.