As for other northern frogs hibernating close to the surface in soil and/or leaf litter, wood frogs tolerate the freezing of their blood and other tissues. Urea is accumulated in tissues in preparation for overwintering, and liver glycogen is converted in large quantities to glucose in response to internal ice formation. Both urea and glucose act as "cryoprotectants" to limit the amount of ice that forms and to reduce osmotic shrinkage of cells. Frogs can survive multiple freeze/thaw events during winter if not more than about 65% of the total body water freezes.
There are no similar species. If you see a small brown frog with a dark eye mask in the woods, it's a wood frog. The first evasive leap is fast and long. Close observation will often glimpse a second short dive under the leaf litter, making the frog appear to disappear.
The feeding motor pattern of the wood frog, basically similar to that of other ranids, is triggered by prey movement and consists of a bodily lunge that terminates with the mouth opening and an extension of the tongue onto the prey . Note that the ranid tongue is attached to the floor of the mouth near the tip of the jaw, and when the mouth is closed the tongue lies flat, extended posteriorly from its point of attachment. In the feeding strike, the tongue is swung forward as though on a hinge, so that some portion of the normally dorsal and posterior tongue surface makes contact with the prey. And it is at this point in the feeding strike that the wood frog differs markedly from more aquatic Rana species, such as the green frog, leopard frog, and bullfrog . The wood frog makes contact with the prey with just the very tip of its tongue, much like a toad . A more extensive amount of tongue surface is applied in the feeding strikes of the other 3 frog species, with the result that usually the prey is engulfed by the fleshy tongue and considerable tongue surface contacts the surrounding substrate.
Rana sylvatica primarily breeds in ephemeral pools rather than permanent water bodies such as ponds or lakes. This is believed to provide some protection of 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. Females deposit eggs in floating masses, often aggregated with those of other females in rafts. 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. If pools dry before tadpoles metamorphose into froglets, they die. This constitutes the risk counterbalancing the anti-predator protection of ephemeral pools. By breeding in early spring, however, wood frogs increase their offspring's chances of metamorphosing before pools dry. Following metamorphosis, a small percentage (less than 20%) of juveniles will disperse, permanently leaving the vicinity of their natal pool. The majority of offspring are philopatric, returning to their natal pool to breed.
Adult wood frogs spend summer months in moist woodlands, forested swamps, ravines, or bogs. During the fall, they leave summer habitats and migrate to neighboring uplands to overwinter. Some may remain in moist areas to overwinter. Hibernacula tend to be in the upper organic layers of the soil, under leaf litter. By overwintering in uplands adjacent to breeding pools, adult Rana sylvatica ensure a short migration to thawed pools in early spring.
The wood frog has a complex life cycle that depends on multiple habitats, damp lowlands, adjacent woodlands. Wood frog habitat conservation is, therefore, complex, requiring integrated, landscape-scale preservation.
Regulation of 5'-adenosine monophosphate deaminase in the freeze tolerant wood frog, Rana sylvatica.(Research article)
Apr 22, 2008; Authors: Christopher A Dieni ; Kenneth B Storey (corresponding author) BackgroundSeasonal temperatures below 0[degrees]C...
Winter Snowfall Determines the Occupancy of Northern Prairie Wetlands by Tadpoles of the Wood Frog (Lithobates Sylvaticus)
Nov 01, 2011; Introduction Climate warming and increased climate variability in the future could reduce the number and seasonal persistence of...