Wood Frog

Lithobates sylvaticus

Physical Description

A small to medium sized frog averaging 3.5-7.0 cm (1.4-2.8 in.) SVL. Wood Frogs are variable in color, ranging from very dark brown to light tan or red[1]. A key diagnostic feature for identifying Wood Frogs is the presence of a dark brown “robbers mask” on the sides of their heads, in addition to prominent dorsolateral ridges running the length of the frog. Adult Wood Frogs are sexually dimorphic: Females are the larger sex and generally much redder in appearance, while males are duller colored, smaller, and nuptial pads on their thumbs.

Vocalization

The call of male Wood Frogs are said to resemble quacking ducks, comprised of irregular and abrupt chuckles repeated 1-5 times[1]. Calls are amplified by a pair of vocal sacs on the frogs' sides.

Habitat

Breeding habitat

Permanent and temporary water sources, including ponds, lakes with shallow margins, wetlands and slow-moving stream sections. Wood Frogs can also be found breeding in flooded fields, ditches, and ornamental ponds.

Non-breeding habitat

Wood Frogs are thought to be fairly sensitive to upland habitat loss. Wood Frogs utilize moist terrestrial habitats, including forested wetlands, stream margins, and rocky ravines[2][3].

Geographic Distribution

Wood Frogs have the northernmost range of any amphibians species in North America, reaching eastern Canada west to Alaska; south along the Appalachians to northern Georgia[4].

Reproduction and Juvenile Growth

Wood Frogs are one of the first amphibians to breed annually in many parts of North America, oftentimes arriving at breeding ponds before the ice has completely thawed. Annual migrations generally occur on warm, rainy nights in February-April depending on the regions climate. Wood Frogs are explosive breeders, with individuals remaining at wetlands for only a few nights. Males arrive at breeding sites first and begin calling, with females arriving shortly thereafter. The call of male Wood Frog has been likened to that of a quacking duck in the woods[3]. Eggs are deposited in communal clusters generally in the shallow margins of breeding sites. Females lay between 500 and 1,500 eggs encapsulated in a protective gelatinous coating and fecundity is strongly correlated to female body size. Ovum diameter is 1.9-2.6 mm.

Eggs hatch into free-swimming tadpoles within 7-21 days with hatching time being largely dependent on water temperature. Tadpoles take an additional 30-60 days to develop and metamorphose. Larval developmental period is also dependent on a number of factors, including water quality, food availability, the presence of predators, and the density of competitors. Juveniles reach sexual maturity 1-4 yrs after metamorphosis.

Diet

Wood Frogs feed primarily on arthropods, including insects, small arachnids, and worms.

Predators

Herons, raptors, snakes (including hognose and garter snakes), snapping turtles, and mammals prey on adult Wood Frogs. Egg and tadpole stages are preyed on by numerous species of larval ranids, including green frogs, and bullfrogs, as well as larval ambystomid salamanders and adult Notophthalmus newts.

Etymology

“Lithobates”: (Greek) – “Litho” means “a stone”, “bates” means “one that walks or haunts”

“sylvaticus”: (Latin) – “amidst the trees”

References

  1. White, JF, and AW White. 2007. Amphibians and Reptiles of Delmarva. Tidewater Publishers, Centerville, MD.
  2. Baldwin, R. F., A. J. K. Calhoun, and P. G. deMaynadier. 2006. Conservation planning for amphibian species with complex habitat requirements: A case study using movements and habitat selection of the wood frog Rana sylvatica. Journal of Herpetology 40: 442-453
  3. Rittenhouse, T. A. G. and R. D. Semlitsch. 2007. Postbreeding habitat use of wood frogs in a Missouri oak-hickory forest. Journal of Herpetology 41: 645-653
  4. Conant, R. and J. T. Collins. Reptiles and Amphibians: Eastern/Central North America. Houghton Mifflin Co., Boston

Classification

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