Wood Frog, Lithobates sylvaticus- KS

The Wood Frog, Lithobates sylvaticus

The official state amphibian of New York, the wood frog, resides predominantly in North America, where it thrives in woodlands and swamps in the summer. In the winter, wood frogs migrate to neighbouring uplands but once the snow has thawed, they are one of the first amphibians to emerge for breeding. As with other northern-American frogs, wood frogs can tolerate the freezing of their blood and tissues. Urea accumulates in tissues in preparation for the winter, and large quantities of glycogen are converted to glucose as a response to internal ice formation. Both urea and glucose act as cryoprotectants (chemicals that protect biological tissue from freezing damage) to limit the amount of ice that forms and to prevent crenation of cells. Wood frogs range from 51 to 70 mm in length with females often being larger than males. These frogs are a brownish colour, and have an identifying patch of darker brown around their eyes. This colour ensures that the frogs can absorb sufficient heat energy to be active during the day. However, observations of these amphibians show that they are capable of varying their skin color for camouflage and heat absorption purposes. A wood frog’s diet consists of small, forest-floor invertebrates but in contrast, their tadpoles feed on plant detritus, algae and even the eggs and larvae of amphibians, including those of other wood frogs.