Wood Frog (Rana sylvatica)
Description: Wood Frogs are brown or reddish-brown with beige dorsolateral folds. Most have a black "mask" that covers their eyes (see above pictures). Their belly is usually tan and their toes are partially webbed. Wood Frogs are members of the family Ranidae, which includes other "true frogs" like Leopard Frogs, Green Frogs, and Bullfrogs, with whom they share the same genus (Rana).
Habitat/Ecology: Wood Frogs prefer woodlots near marshes or ponds. They spend most of their time away from water, under wet leaves and organic debris, except during the breeding season when they come out into the open to mate in wetlands. In other parts of the Upper Midwest, I have seen juvenile Wood Frogs that have remained near, or within, a pond or wetland well past metamorphosis. On the other hand, adult Wood Frogs that I have encountered were some distance from water (usually in a moist wooded area). In my opinion, they are more terrestrial than other representatives of the family Ranidae found within Wisconsin. These frogs eat insects, worms, and slugs. Although they seem to be less tolerant of human disturbance than other Ranids, I have found one in a suburban area near Madison, WI.
Remarks: Wood Frogs are the earliest frog species to begin calling in Wisconsin. Males have been witnessed by some to start calling when ice is still present on the water (usually in March). However, unlike other frogs, their breeding season is very abrupt and may last only two or three weeks. Their call is a series of short "croaks" that resembles ducks quacking. They are medium sized frogs (2 to 2 3/4" snout to rump length) that are usually only seen during the breeding season. Like Spring Peepers and Gray Treefrogs, they can survive partial freezing during winter hibernation due to an "anti-freeze" produced by their cells.
I have not heard Wood Frogs calling within the La Crosse area. However, their mating period is so early and abrupt that I may have missed them. I have heard them calling at sites in nearby Houston County (Minnesota) for two consecutive years (2000 and 2001). I am interested in knowing if they exist within the La Crosse River Marsh (Myrick Park) and hope that anyone who has positively heard them there (or anywhere else within La Crosse) will contact me. I have also been told that they are heard calling in the Seven Bridges area. It is possible that the flood of 2001 may have adversely affected their reproduction. In habitats where I have witnessed Wood Frogs calling in Minnesota (2001), females appeared to have deposited many egg masses in areas that eventually dried after flood waters subsided. Consequently, no Wood Frog tadpoles or metamorphs were found at those sites later in the season.
Wood frogs in amplexus (La Crosse County, WI)
Wood Frog will often lay their eggs in large groups within a pond. The picture on the left is of approximately 15 egg masses found at a site near the Chippewa River in Wisconsin. The picture on the right is of a single wood frog egg mass from Houston County, MN.