Rana sylvatica

Lithobates sylvaticus or Rana sylvatica, commonly known as the wood frog, 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.

DESCRIPTION

• Wood frogs range in size from 51 to 70 mm (2.0 to 2.8 inches) in length, with females generally being larger than males.

•  Adult wood frogs typically exhibit shades of brown, tan, or rust-colored skin and often sport a dark eye mask.

• Individual frogs have the ability to alter their coloration; Conant (1958) even observed one individual that displayed both light brown and dark brown hues at different times.

• The underparts of wood frogs are pale with a yellow or greenish tint, and in northern populations, the belly may exhibit faint mottling.

• Their body color can change seasonally, with exposure to sunlight causing darkening.

REPRODUCTION

• L. sylvaticus primarily breeds in ephemeral pools rather than permanent water bodies such as ponds or lakes.

•  This is believed to provide some protection for the adult frogs and their offspring (eggs and tadpoles) from predation by fish and other predators of permanent water bodies.

•  Adult wood frogs emerge from hibernation in early spring and migrate to nearby pools. There, males chorus, emitting duck-like quacking sounds.

• Wood frogs are considered explosive breeders; many populations will conduct all mating in the span of a week.

• Males actively search for mates by swimming around the pool and calling. Females, on the other hand, will stay under the water and rarely surface, most likely to avoid sexual harassment.

•  A male approaches a female and clasps her from behind her forearms before hooking his thumbs together in a hold called "amplexus", which is continued until the female deposits the eggs.

•  Females deposit eggs attached to submerged substrate, typically vegetation or downed branches. Most commonly, females deposit eggs adjacent to other egg masses, creating large aggregations of masses.

• Some advantage is conferred to pairs first to breed, as clutches closer to the center of the raft absorb heat and develop faster than those on the periphery, and have more protection from predators.

•  If pools dry before tadpoles metamorphose into froglets, they die.This constitutes the risk counterbalancing the antipredator protection of ephemeral pools.

•  By breeding in early spring, however, wood frogs increase their offspring's chances of metamorphosing before pools dry.

• The larvae undergo two stages of development: fertilization to free-living tadpoles, and free-living tadpoles to juvenile frogs.

• During the first stage, the larvae are adapted for rapid development, and their growth depends on the temperature of the water.

• Variable larval survival is a major contributor to fluctuations in wood frog population size from year to year.

• The second stage of development features rapid development and growth, and depends on environmental factors including food availability, temperature, and population density.

• Following metamorphosis, a small percentage (less than 20%) of juveniles will disperse, permanently leaving the vicinity of their natal pools.

• The majority of offspring are philopatric, returning to their natal pool to breed.[27] Most frogs breed only once in their lives, although some will breed two or three times, generally with differences according to age. The success of the larvae and tadpoles is important in populations of wood frogs because they affect the gene flow and genetic variation of the following generations.

HABITAT

Wood Frog Behavior and Habitat:

• Wood frogs are forest-dwelling organisms.

• They primarily breed in ephemeral, freshwater wetlands known as woodland vernal pools.

• Long-distance migration is a crucial part of their life history.

• Individual wood frogs have a wide range, covering hundreds of meters, as they move between breeding pools and nearby habitats such as freshwater swamps, cool-moist ravines, and upland areas.

• Genetic neighborhoods of individual pool-breeding populations extend more than a kilometer from the breeding site.

• Conservation efforts for this species must take into account a landscape perspective, considering multiple habitats at appropriate spatial scales.

• Wood frogs are adept at camouflaging themselves with their surroundings.

Seasonal Behavior:

• During the summer months, adult wood frogs are found in moist woodlands, forested swamps, ravines, or bogs.

• In the fall, they leave their summer habitats and migrate to neighboring uplands for overwintering.

• Some wood frogs may choose to overwinter in moist areas.

• Their hibernacula (hibernation locations) are typically in the upper organic layers of the soil, under leaf litter.

• Overwintering in uplands near breeding pools allows adults to have a short migration to thawed pools in early spring.

• Wood frogs are mostly diurnal, meaning they are active during the day and are rarely observed at night, except possibly during breeding choruses.

• They are among the first amphibians to emerge for breeding, usually right when the snow melts, alongside spring peepers.