This is the fourth year my friend Pete and I have been participating in our local frog and toad count, and even though we've done various routes to hear as many different species as we could, some of the frogs, such as wood and leopard, had eluded us. Until Sunday night, that is, when we finally heard the wood frog (Rana sylvatica)!!!!! Good gravy, it's cute — I wish we could see them, not just hear them, but not only is the survey done at night, but they like to stay hidden. (Plus, these frogs are small. Woodies are about 2 inches long, and spring peepers and chorus frogs are only about an inch long.)
Our favorite pond (southwest corner of Stone School and Morgan Roads) was alive and kicking with very loud frogs calls, not only from the wood frog, but also from spring peepers and chorus frogs. This recording really gives a feel for the exuberance and volume! The wood frog's unique call sounds kind of like a chuckling duck or two metal stress-relief balls being rubbed together. The spring peepers sound like high-pitched birds singing, and it's hard to hear the chorus frogs.
In this recording, it's easy to pick out the wood frogs from the spring peepers. We noticed that when a car drove by, the wood frogs stopped calling, but the spring peepers kept right on going. So we waited for a car to pass and then started recording, so that you first hear only spring peepers and then, gradually, a wood frog starts and then they all chime in.
There were also a few chorus frogs (whose call sounds kind of like running your finger down a plastic comb) in the pond, but it was hard to hear them above the peepers and wood frogs. (The peepers were everywhere in the pond, but the woods were concentrated in one fairly small area.) There were, however, two chorus frogs calling in a pond on the other side of the road, which you can distinctly hear here.
As reported last time, wood frogs have "explosive breeding" which means they only call for about two weeks (in late March/early April in southeastern Michigan), whereas most other frogs call/mate for a month or more. Wood frogs hibernate on land and have a glucose-based "antifreeze" in their blood that gets them through the long and harsh Michigan winters.
Wood frogs prefer moist, wooded habitat and breed in vernal pools, flood areas, forested swamps, and still backwaters. Wood frogs lay eggs communally, meaning each female deposits her eggs into one larger grouping. The globular egg mass increases the number of eggs that turn into tadpoles (which takes two months) by helping the eggs stay moist and warm, and reducing predation (the eggs get eaten from the outside in). In general, very few frog eggs ever turn into tadpoles let alone frogs because so many of them are eaten by other animals. Fortunately, frogs lay a LOT of eggs to ensure some survive (spring peepers lay about 750-1,200 eggs each!) This communal egg laying also explains why the woodies we heard were all grouped in one little area.