In the Spring ...

In the spring a young wood frog’s thoughts turn to … (do frogs have thoughts or only instincts?). In the spring wood frogs emerge from their winter quarters in the leaf litter on the forest floor where they often freeze solid, their cells kept from damage by glucose that fills each cell in the fall and acts as an anti-freeze. For a more complete explanation see this site. 

But now it’s spring and the wood frogs have emerged to head for their breeding pools. Wood frogs breed early in the spring, often before the pools are completely ice-free. Those pools can be roadside ditches, pools formed from snowmelt or after heavy rains or the classic vernal pool. Irrespective of how the pools are formed, wood frogs seldom successfully breed in water that contains fish, for fish readily devour the products of the frogs’ mating.

Male wood frogs normally arrive at the breeding pools before the females and begin calling. The frogs’ calls sound remarkably similar to the quacking of a duck –

When the females arrive and enter the pool they are grasped by the males (a position called amplexus). Other males are often grasped since an amorous male will latch on to any nearby frog. Fertilization is external as the females release hundreds of eggs and the males release sperm.

A single female is sometimes seized by several males, which occasionally results in the female’s death –

The fertilized eggs form a gelatinous mass, which often adheres to adjacent egg masses –

Depending on temperature, the embryos develop rapidly and in a few days their heads, bodies and tails are easily distinguished –

Shortly afterwards the eggs hatch and the tadpoles swim forth to feed on algae and other vegetation –

The tadpoles will die if the pool dries before they mature and transform into frogs. Depending on temperature and the availability of food the tadpoles develop rapidly and in about 60 days metamorphose into small frogs –

The tiny froglets disperse into the surrounding woodland to feed on invertebrates until the fall when they take shelter below ground for the winter.

Wood frogs’ breeding season is short, lasting only a few days in early spring. The day after the video in this post was taken there was not a frog to be seen in the pool, the frogs had returned to the forest to spend the warm weather there. But there were many eggs in various stages of development in the pool. A few days later there were thousands of small tadpoles in the pool. Only a few of those tadpoles will live long enough to transform into frogs and fewer still will survive to return to breed next year.