Amphibians
Boreal Chorus Frog
Pseudacris maculata · also called western chorus frog
Patches of ice still cling to the edges of a prairie pool when a rising, comb-like trill breaks the silence, the unmistakable sound of a boreal chorus frog calling weeks before most other frogs have even stirred, its body still carrying the natural antifreeze that got it through the last hard freeze.
Overview
The boreal chorus frog, Pseudacris maculata, is a small, cold-tolerant amphibian native to grassland and wetland edge habitat across a broad range spanning much of Canada and the north-central United States. Its remarkable ability to survive partial freezing, unusually early spring calling, and vast northern range make it one of the hardiest small frogs on the continent.
A frog built for the edge of winter
While most frogs wait for reliably warm conditions, the boreal chorus frog is willing to call and breed the moment meltwater appears, backed by a physiological trick that lets its body survive a cold snap most other amphibians could never endure.
Status
Least Concern — widespread and generally abundant across suitable grassland and wetland habitat throughout its very broad range in Canada and the north-central United States.
Boreal Chorus Frog: common questions
How can a boreal chorus frog survive being partly frozen?
This species produces natural antifreeze compounds, including elevated glucose levels, that concentrate in its blood and tissues during a sudden cold snap, preventing the ice that forms in the spaces between its cells from causing fatal damage, allowing the frog to thaw out again and resume normal activity once temperatures rise.
Why does the boreal chorus frog call so early in spring?
This species is adapted to breed as soon as conditions allow across a cold, often subarctic range, and calling early lets it take advantage of temporary spring meltwater pools before they dry up or are claimed by competing species, sometimes resulting in this frog trilling from partially thawed water while ice remains nearby.
What does the boreal chorus frog's call sound like?
The male produces a rising, raspy trilling call often compared to the sound of running a fingernail along the teeth of a comb, a distinctive and relatively easy call to learn that is frequently one of the very first frog calls heard each spring across its range.
How is the boreal chorus frog different from other chorus frogs?
While closely related to other Pseudacris chorus frog species, this species is distinguished largely by its very broad, cold-tolerant range across much of Canada and the north-central United States, along with subtle differences in call structure and range that separate it from more southern and eastern chorus frog relatives.