In the Basin, we call it Mud Season. Winter's freeze loosens its grip on the water on the waters around us. The dirt road that I live on becomes gooey, ice fishing is done for the year, roadside snow banks slowly disappear, and water flows into the low spots all over the landscape. If you are like me, you wait for even warmer weather before really being active in the outdoors. But for our local amphibians, there's no time like the present to getting moving & shaking; and for male frogs and toads, calling for a mate!
So why the hurry? Why not wait until warmer weather, when cold-blooded animals like frogs should be more active? For some frogs, it's all about the water. Specifically, how long will water be there to support their tadpoles? For wood frogs, as soon as their vernal pool breeding habitats (like in the photo to the left) start holding water, the clock starts ticking for eggs (see photo below) to hatch & tadpoles to grow up to adulthood.
If the males aren't out making their distinctive "quack" that signals the start of breeding, there is a good chance that no wood frog tadpoles will emerge from their ephemeral woodland pools before they dry up for the season.
For other frogs like Spring Peepers (pictured below), whose cricket-like call surrounds us in Springtime sound, there is a longer time window to get out and make some noise. They are less picky about their breeding habitats and will use shallow wetlands and pond edges that may never dry out, or at least be around for many weeks. And because they are in less of a rush, you might hear their calls throughout spring.
But don't expect to hear each frog species singing alone; often they will be heard along with other early-breeding species like American toads and Gray Treefrogs. Who you might hear depends both on the time of year as well as the habitats for both the tadpoles and the adults that are available in the immediate area.
So why should we care? Well, besides helping us out by consuming a large number of insects, amphibians are thought of as proverbial "canaries in the coal mine"- indicating when environmental conditions are changing... and sometimes for the worse. Their skin is thin and permeable so chemicals move easily into their bodies, they are directly tied to ecologically important wetland habitats that are disappearing world-wide, and their life-cycles are relatively short (3-7 years) so large negative changes will affect their populations relatively quickly. Finally, it is the noise that they make that makes it relatively easy and cheap to monitor their populations over time- even if you just do it for fun in your own backyard.
For more information about monitoring amphibian populations, see the Vermont Reptile and Amphibian Atlas.