April — Cold-blooded chorus in one mixed-up spring

Phenology is all mixed up in spring 2010!

With the first snow-free March on record and record-high temperatures, flora and fauna of Minnesota seem to be well ahead of their normal schedules. Among the unusually earlier emergents have been the early spring frogs — boreal chorus frog (Pseudacris maculata), spring peeper (Pseudacris crucifer) and wood frog (Rana sylvatica). Chorus frogs have the opening act and typically start singing almost immediately after their pond thaws. In northern Washington County I usually hear them around the last week of March or later. This year I first heard them on March 16, roughly 10 days early.

Chorus frogs have a long "show time" so to speak, so you may still catch a performance by the time this publication comes out. Their song is easy to identify as it sounds like someone running their thumb over the teeth of a comb. Spring peepers with their very high-pitched "peep", and wood frogs, which sound an awful lot like muttering ducks, join the choir shortly after the chorus frog.

These three species can often be heard together in one pond, as in this recording taken on March 31st at William O'Brien State Park. Crank your computer volume as high as it will go, but it won't come close to the deafening sound that came out of this tiny pond — my ears are still ringing. Chorus frogs are the overwhelming sound, though it's hard to distinguish the individual voices. More distinctive are the individual "peeps" and "quacks" of the peepers and wood frogs. As much fun as hearing the frogs, is to actually watch these tiny animals at the surface of the water, inflating their throats, and to marvel at the volume of sound they emit.

Chorus frogs and peepers are the smallest of Minnesota's frogs, measuring only about one inch long. They are two of the five species of tree frogs in the state, all of which have distinctive large toe pads that help them attach to leaves and other surfaces (and which make them particularly endearing to humans, for some reason). Wood frogs are at least double that size and are among the six "true frogs" in Minnesota. There are 14 frog and toad species in Minnesota all together, and not enough space here to write about them all. Fortunately, there are some excellent online resources to learn more, hear frog and toad calls, and find out about local volunteer survey projects:

— Karen Schik, Ecologist & Project Manager