Lithobates sylvaticus

Dark "mask" across each eye; dorsolateral folds present; hind toes webbed; a light middorsal stripe may or may not be present; skin relatively smooth; maximum snout-vent length about 83 mm. Mature male: base of thumb swollen; averages slightly smaller and darker than adult female; expanded vocal sacs, one on each side, extend above forelimbs; breeding call: rapid series of 1-8 (usually 3-5) rough clacking notes; a chorus sounds somewhat like a group of softly quacking domestic ducks. Larvae: dorsum with blackish and olive-gray pigment; sides shiny bronze or pinkish; eyes dorsal; tail fin high, strongly arched dorsally; tail fins with dark spots and blotches; labial tooth rows 2/3 or 3/4; oral papillae encircle mouth, with wide gap above mandibles; papillae indented at angle of jaw, dense at sides of mouth; anus on right side at front end of ventral tail fin; maximum total length around 52 mm. Eggs: black above, whitish below, about 2 mm in diameter, each surrounded by two jelly envelopes, deposited usually communally in large globular masses about the size of a baseball or tennis ball and usually including several hundred eggs. Primary source: Hammerson (1999).

Wood frogs inhabit various kinds of wooded habitats, including the edges of ponds and streams and willow thickets and grass/willow/aspen associations. In winter or when otherwise inactive, they hide in logs, humus, leaf litter, or under logs and rocks. In winter upland habitat in eastern Massachusetts, adult males greatly outnumbered adult females in areas close to (within 65 meters of) breeding pools; two wintering areas were not used during the summer active period (Regosin et al. 2003).

Eggs are laid and larvae develop usually in vernal pools and other small fish-free ponds, temporary or permanent, in wooded (usually) or open areas. In the Shenandoah Mountains, breeding adults were 100% faithful to the ponds in which they first bred; approximately 18% of the juveniles dispersed to breed in ponds other than the one of origin (Berven and Grudzien 1991). Experiments and field observations by Hopey and Petranka (1994) indicate that adults are able to assess the presence of fishes in ponds and may change breeding sites accordingly to avoid those with predatory fishes. In northern Minnesota, successful reproduction in acidic bog water either does not occur or is a rare event (Karns 1992).

Local tadpole density may exceed 15,000/cubic meter of water (Biesterfeldt et al., Copeia 1993:688-695).

In eastern Massachusetts, density in wintering areas near breeding pools ranged from 0 to 6.3 frogs per 100 sq m (Regosin et al. 2003).

Wood frogs emege from dormancy on land and migrate up to several hundred meters to breeding pools, where they breed explosively in winter or early to late spring, with the latest breeding in the far north or high elevations. Eggs are laid in winter in the Ozarks and southern Appalachians, late February in Maryland, February-March in Missouri, mainly March in southern New England, mostly late May-early June in Colorado; mean date of breeding increases 5.2 days per degree of latitude (Guttman et al. 1991). In a particular pool, most egg deposition occurs over a brief period of several days. Eggs hatch in about 1-2 weeks. Larvae metamorphose into small frogs in spring or summer, within a few months after egg deposition. The period from fertilization to emigration from the pond averages about 11 weeks in Michigan, 13 weeks in Maryland, 15-16 weeks in Virginia (Riha and Berven 1991). In Maryland, 20,262 juveniles emerged from a single pond in one year (Berven 1988). Individuals become sexually mature in 2-3 years (in Maryland, females mainly in 2 years, rarely in 1 year; Berven 1988).