Wood frog

## Description

The wood frog (Lithobates sylvaticus or Rana sylvatica ) is a frog species that has a broad distribution over North America, extending from the boreal forest of the north to the southern Appalachians, with several notable disjunct populations including lowland eastern North Carolina. The wood frog has garnered attention from biologists because of its freeze tolerance, relatively great degree of terrestrialism (for a ranid), interesting habitat associations (peat bogs, vernal pools, uplands), and relatively long-range movements.

The ecology and conservation of the wood frog has attracted research attention in recent years because they are often considered "obligate" breeders in ephemeral wetlands (sometimes called "vernal pools"), which are themselves more imperiled than the species that breed in them. The wood frog has been proposed to be the official state amphibian of New York.

## Appearance

Wood frogs range from 51 to 70 mm (2.0 to 2.8 in) in length. Females are larger than males. Adult wood frogs are usually brown, tan, or rust-colored, and usually have a dark eye mask. Individual frogs are capable of varying their color; Conant (1958) depicts one individual when light brown and dark brown at different times. The underparts of wood frogs are pale with a yellow or green cast; in northern populations, belly may be faintly mottled. Body colour may change seasonally; exposure to sunlight causes darkening.

## Distribution

Wood frogs, Lithobates sylvaticus, are only native to the Nearctic region. They are found from northern Georgia and in isolated colonies in the central highlands in the eastern to central parts of Alabama, up through the northeastern United States, and all the way across Canada into Alaska. They are found farther north than any other North American reptile or amphibian.

Wood frogs inhabit a wide variety of habitats including tundra, thickets, wet meadows, bogs, coniferous and deciduous forests. Wood frogs are aquatic breeders and require fish-free seasonal or semi-permanent bodies of water to reproduce, but will migrate from their primary habitat to breed. These frogs seek out terrestrial locations with ample cover to hibernate which may or may not be near a breeding pond.

## Behavior

Wood frogs are a diurnal species. These frogs perform seasonal migrations to breeding ponds in late winter or early spring. Individual wood frogs show significant breeding site fidelity and will often migrate within the same area throughout their lives. Though they amass at breeding ponds, these frogs are mostly solitary.

Wood frog tadpoles have been shown to have the strongest powers of kin recognition yet discovered in amphibian larvae. These tadpoles can recognize kin using maternal and paternal factors. They have been documented (by marking them with dye and releasing them into natural habitats) to aggregate back together. This may be a survival mechanism allowing them the potential benefit of food, thermoregulation, and defense against predators.

## Diet

Adult wood frogs eat a variety of terrestrial insects and other small invertebrates, especially spiders (Order Araneae), beetles (Order Coleoptera), moth larvae (Order lepidoptera), slugs (Order Stylommatophora) and snails (Order Stylommatophora). Wood frog larvae consume algae, decaying plant and animal matter, and eggs or larvae of other amphibians.

## Reproduction

Wood frogs exhibit "explosive" breeding in late winter or early spring when the first warm rains occur. Frogs wake from hibernation and migrate to breeding ponds. Individuals show some site fidelity year to year. Not much information is known regarding how males attract a mate. In an explosive breeding situation the success of the male in finding an available and willing female is strictly density-dependent.

## Population

### Population number

Although the wood frog is not endangered or threatened, in many parts of its range urbanization is fragmenting populations. Several studies have shown, under certain thresholds of forest cover loss or over certain thresholds of road density, wood frogs and other common amphibians begin to "drop out" of formerly occupied habitats. Another conservation concern is that wood frogs are primarily dependent on smaller, "geographically isolated" wetlands for breeding. At least in the United States, these wetlands are largely unprotected by federal law, leaving it up to states to tackle the problem of conserving pool-breeding amphibians.
The wood frog has a complex lifecycle that depends on multiple habitats, damp lowlands, and adjacent woodlands. Their habitat conservation is, therefore, complex, requiring integrated, landscape-scale preservation.
Wood frog development in the tadpole stage is known to be negatively affected by road salt contaminating freshwater ecosystems.