Checklist of Amphibian Species and Identification Guide
Wood Frog, Rana sylvatica
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| The Wood Frog is characterized by its prominent black "mask" extending from the tip of its snout through the eye and tympanum. The typanum, or tympanic membrane, can be called the frog's eardrum. It is located in most species directly behind the eye. A light middorsal stripe is often present, as in these two individuals above, but there is much variation and some have a weak or even no stripe. The Wood Frog is a medium sized frog reaches lengths up to 2.75 inches. The color is generally brown, but may vary from various shades from olive green to almost black. There may even be variations of color within the same individual. Note the contrasting color differences of two individuals from the same area shown in the photo below left. |
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| Wood Frogs are found from Alaska through much of Canada where winters are very severe. They survive by being able to withstand being frozen down to −5°C (23°F) or lower. They do this by increasing the amount of glucose stored in their cell fluids. The high concentration acts as antifreeze, lowering the freeze point. By preventing the cells from freezing on the inside the cell membrane is not ruptured, and the frog survives. Nevertheless, 1/3 of the frogs body fluids, mainly interstitial fluids (fluids between the cells) can become frozen during the winter without harming the frog. |
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