Frogs announce Spring is Here!

On Thursday and Friday here in central Virginia, we had a February warm spell, with the high above 70º F!  A pond is near my house, and, on my way home yesterday, I heard the definitive sound of spring: peepers.  In this part of the country, spring peepers are the harbingers of spring, but, in other places in North America, the duty is served by different species.  Check out the map, showing who announces Spring’s arrival in your area.

The first frog to sing in your area. (Disclaimer: This map is based on general climate. Depending on differences in elevation and temperature within a particular area, there may be exceptions.)

There are five main bringers of spring in North America: The spring peeper, the wood frog, the Western chorus frog, the spotted chorus frog, and the Pacific chorus frog.  Check out some proper introductions to these virtuosos below.

Why do frogs sing?  Frogs sing for a variety of reasons, but in spring, the male usually is singing to attract a female mate.  Only females of the same species will be attracted to these calls, which is why there are so many different sounds that different frogs make.  Frogs can also call to define their territory and to alert others to an intruder or alarm an intruder.

How do frogs sing?  Unlike us, frogs sing with their mouths closed.  They squeeze their lungs so that air flows across their vocal chords and into their vocal sac, the part on the throat of the frog that blows up like a balloon.  The vocal chords vibrate, and the vocal sac amplifies that sound, like a natural microphone.  Other frogs can hear the call, because they have sensitive circular membranes on either side of their heads, called the tympanic membrane, which catches these sound vibrations and sends their message to the brain.

When does frog calling start?  The first frog call always happens as winter weather warms, but the exact timing varies from place to place and year to year.  Because of global climate change, frog calling is thought to be starting earlier and earlier.  The citizen science website Journey North is tracking these first calls, so you can report when you first hear frog calls in your area here.


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