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Wood Frog (Rana sylvatica): Overview Wood frogs rouse from their hibernation sites and begin their annual migration to breeding ponds when spring rains and melting snow saturate the ground (some males move closer to breeding pools to hibernate in the fall). They are able to hibernate at much shallower depths (under rotted logs/stumps, leaf litter, under stones and mats of moss) than the mole salamanders because within five minutes of freezing, wood frogs can accumulate high levels of glucose in the liver and leg muscles. Glucose is then released into the bloodstream and tissues to act as a natural antifreeze. Although spring peepers are more commonly thought of as the harbingers of spring, wood frogs often appear first. They are remarkably adapted to the cold; it is not unusual to find the earliest migrants swimming in a pool still partially covered with ice. Wood frog calling (a duck-like quacking), mating, and egg-laying occur mainly in the early night hours and gradually diminish toward dawn. Calling and breeding activities can also occur during daylight hours in undisturbed areas. Wood frogs are known as explosive breeders because the entire sequence of appearance, mating, egg laying, and return to the terrestrial habitat is accomplished in a brief time. This may be as short as a week in some pools but may extend up to 30 days. The emerging tadpoles transform into adults some six to 15 weeks later. Young tadpoles feed on algae and microorganisms they scrape from aquatic plants. As they grow older, some other vegetation and animal matter is consumed. Adults spend the summer in cool, moist woods and consume a wide variety of invertebrates including slugs, spiders, and worms. Little is known about the ecological role of wood frogs in upland forests. They are present in large numbers in northeastern woodlands. One estimate put the total biomass of wood frogs in 50 acres of forest adjacent to a breeding pool to be over 150 pounds! Given their abundance and diet of forest invertebrates, it is likely that wood frogs influence decomposition rates and nutrient cycling in upland forests. To see more information about wood frogs, click Next. To return to the overview of four species common to vernal pools, click Overview. To go to the previous page, click Back. |
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