Wood frog (Rana sylvatica)

Description
Wood Frog

Size

  • The smallest true frog in Alberta, the wood frog ranges from only 30 to 60 millimetres (about one to two inches) in length.

Appearance

  • Easily recognized by its "bandit's mask" across the eyes.
  • Generally brownish in colour and may have a white stripe down its back.
  • Hind legs are usually striped as well.
  • Belly is white, although it may have some mottling.
  • In general, the skin is quite smooth, but there may be some small warts along the sides.
  • Dorsolateral ridges are also quite prominent, but they are not light-coloured.

Voice/call

  • The call sounds like the quacking of a duck.
Distribution
Wood frog distribution in Alberta
  • The wood frog is found throughout the aspen parkland and the boreal forest. It can live at elevations up to 2500 metres (8,200 feet) above sea level, although it is absent from many areas in the Rockies.
  • It is widely found from northern B.C. to Quebec.
  • Because of its cold tolerance, the wood frog is the only amphibian in North America found above the Arctic Circle.
Natural History

Habitat

  • As its name suggests, the wood frog is forest-dwelling and is often found in damp, shady woods.
  • It is very cold-tolerant and it is found farther north than any other amphibian in the Western Hemisphere.
  • It is often found far from water and it is quite active in hunting for food.
  • In winter, it hibernates on land beneath leaf litter.
  • Because wood frogs live in moist shaded areas, they can be difficult to locate outside of the breeding season.
  • In the spring, adults congregate at breeding ponds and begin calling.

Food

  • Wood frogs subsist mainly on worms and insects.
Reproduction and Growth
Life Stage Apr May Jun Jul Aug Sep
Breeding Breeding Bar: April 10 to June 15
Eggs Hatch Eggs Hatch Bar: April 27 to June 30
Transformation Transformation Bar: June 10 to September 2

Breeding behavior

  • Depending upon snowmelt, breeding can take place from late April to June.
  • Males are quite vocal night or day during the short one- to two-week breeding period.
  • Breeding ponds tend to be shallow, clear, permanent or temporary ponds.
  • Females will each lay 2000 to 3000 eggs in large round masses of jelly.
  • Each egg is roughly 1.5 millimetres (1/2 inch) in diameter and will hatch in three weeks or a little more, depending upon water temperature.

Appearance of young

  • Tadpoles will grow from 7 to 10 millmetres (1/4 to almost ½ inch) to 50 millimetres (2 inches) during their development.
  • They are brown or dark green with a whitish underside, sometimes with a pink tinge.

Growth process

  • In 6 to 12 weeks, wood frog tadpoles will transform into froglets, depending upon the temperature of the water.
Conservation and Management

Status

The wood frog is classified as Secure in the current Status of Alberta Wildlife report, and is considered not to be at risk.

  • Status of Alberta Wildlife

Issues

  • Populations are healthy and widespread.

Current management

  • Amphibian Monitoring in Alberta
    The wood frog is being monitored under the Alberta Volunteer Amphibian Monitoring Program (AVAMP) and the Researching Amphibian Numbers in Alberta (RANA) program.

Similar Species

  • Columbia spotted frog
    although the spotted frog can have a faint mask, its belly is reddish, whereas the wood frog's belly is white.
  • Northern leopard frog
    Sometimes the wood frog is confused with immature spotted or northern leopard frogs. The northern leopard frog can be easily identified by its light-coloured dorsolateral folds and its large dark spots with a light-coloured ring around them.

Related links

  • Amphibians
    Learn about Alberta’s amphibians, their biology and how to identify various species. Also learn about the global decline of amphibian species, and efforts made to monitor and conserve them.
  • Frogs
    Find out about the common traits of frogs, and about the different frog species found in Alberta.

 

Page Information

Posted: Mar 9, 2009