Wood frogs emerge from hibernation when snow and ice melt off in the spring. In Alaska and northern Canada, this is usually in late April or early may.
At this time, males begin to congregate in breeding places such as temporary pools formed by melt water, lake edges, quiet streams, flooded meadows, and roadside ditches—wherever there is standing water for at least part of the summer. The males make low-pitched chuckling calls to attract females. Their ebbing and surging choruses can be heard throughout the long days and dusky midnight hours of early summer. Listen
A male wood frog can’t identify females by sight, so he paddles back and forth looking for other frogs. When he finds one, he clambers onto its back and clamps on with his front legs, because only by embracing and feeling another frog can he tell if it is male or female and if it’s ready to mate. If the one he embraces is nice and plump, it’s a female with eggs and he will hold on; if she’s skinny, she has already laid her eggs and he will release her; and if it’s skinny and makes a loud croak, it’s another male, so he will let it go.
Sometimes wood frogs may attempt romantic theft. When this happens, a male follows the calls of other frogs, and if he finds a neighbor who is already with a female, the intruder fights with him, trying to steal the female away.
Whatever his technique, when the male finds a ripe, fat female, he clasps her until she lays her eggs. Then he fertilizes her eggs with a cloud of sperm.
Wood frog eggs are suspended in a soft, grayish, gelatinous mass the size of an apple or plum which floats free on the water’s surface or attaches to sticks or plants. Often the eggs from several females are in one big clump containing several thousand eggs. The earliest eggs are in the center of this mass, where they absorb more heat and develop faster than the others.
It takes a week to a month for the eggs to hatch, depending on the water temperature. Tiny tadpoles emerge from the eggs, their bodies like ebony droplets with minute eyes and long, narrow wiggling tails.
Tadpoles gather in the shallows where the water is warmest. Sometimes many thousands of them swarm in a little pool, where they eat algae growing on underwater plants and debris. Tadpoles develop tiny front and hind legs and gradually absorb their tails.
Breeding in temporary pools gives the advantage of avoiding predatory fish like trout or pike, but there is also a risk of the pool drying out—hundreds of tadpoles could flop around in the muck and die, becoming food for hungry gulls, jays, mink and other predators.
But, if all goes well, in mid to late summer, tadpoles transform into miniature froglets, crawling out of the water and hopping off into the woods.
Males will mature one year later and the females will mature in their second year. Most will return to breed in the same pools where they were born.
A Solitary Life
Wood frogs live up to their name—they are usually found in or near forests. Except for the mating season, they spend most of their time on land, although seldom far from water. They can often be found in mossy woods and wetlands, along rivers, in marshes and muskegs, wet meadows, moist thickets and open grassy areas near wet places.
The wood frog leads a solitary life. It is not unusual to find one hopping along on the shady forest floor where it searches for a variety of foods. Like most frogs, these denizens of the north woods eat spiders, moths, slugs, snails, worms, millipedes and all sorts of bugs and beetles.
A wood frog’s lifespan is about 3 to 4 years.