Why Do Frogs Make so Much Racket?

It is springtime and love is in the air for many critters. As the winter air warms, it fills with the sounds of birds, insects, and, of course, frogs and toads. Why does this happen? Many animals make noises as warning signals, or to mark territories. However, most of the noise that you hear a frog make is all in the name of love. The noises that frogs create are 'calls' and they do just that; they call out to potential mates.

It might be interesting to note that only male frogs call. This is because the female has to be especially choosy. A female can lay eggs only once, maybe twice, a year whereas a male can mate several times. So, the male contribution to produce offspring is much less costly than the female contribution. Therefore, if a male chooses a suboptimal mate his loss is not as great as if a female were to choose carelessly. This pattern also holds true in bird species, where drab females select males based on the brilliance of their feathers.

Calls are created when air fills pouches on the throat, called the vocal sac. The air vibrates within the vocal sac and sound is created. The quality of the sound produced can vary with environmental variables such as temperature. The sounds created can be quite loud and can carry for miles, attracting females from neighboring ponds. In fact, the call of the spring peeper has been said to have the same decibel level as an airport runway! Oftentimes frogs of the same species will congregate within a single pond and form what is known as a chorus. The noise of a chorus can travel farther than the sound from a single individual. So, more females may be attracted to larger choruses.

Each species has its own call, so females of one species are attracted to males of their own species. While the frogs' calls may all seem the same to us, there are definite differences. Calls that males make can vary according to size and health of the animal. In this manner, females can judge male quality based on the quality of the calls produced. In fact, research has shown that male grey treefrogs that produce long calls are preferred by females over shorter-calling males. Furthermore, offspring (tadpoles) produced by females choosing long-calling frogs tend to grow bigger faster, which ultimately helps their survival.

So, when you hear the shrill whistles of a spring peeper, the high-pitched trill of an American toad, or the rhythmic galum-galum a of bullfrog, know that you are hearing mother nature's way of keeping the fittest frogs in your pond.