Overview
The Boreal Chorus Frog (Pseudacris maculata) is a tiny, charismatic harbinger of spring across the northern plains and boreal forests of North America. Emerging from winter dormancy while ice still coats northern marshes, its loud, vibrant breeding chorus—famously resembling the sound of a thumbnail being drawn firmly across the teeth of a stiff pocket comb—can be heard echoing across chilly prairie sloughs for nearly a mile.
Biology and Physical Characteristics
Pseudacris maculata is a miniature tree frog with smooth to finely granular skin and tiny, barely expanded toe pads. Its coloration is highly variable, ranging from olive-green to grey-brown, boldly accented by three dark broken longitudinal stripes running down its back and a prominent dark mask-like stripe extending from the snout through the eye and tympanum onto the shoulder. Breeding males develop a dark, stretchy vocal sac.
Behavior and Ecology
An astonishing survivor of extreme subarctic winter freezing, the Boreal Chorus Frog is freeze-tolerant, allowing ice crystals to freeze up to 60% of the water in its extracellular body fluids while accumulating glucose in its cells as a natural antifreeze. In earliest spring, as soon as snowmelt begins, thousands gather in shallow temporary pools, calling vigorously in cold water to initiate breeding.
Conservation and Human Impact
Classified as Least Concern by the IUCN, the Boreal Chorus Frog is exceptionally abundant and widespread across Canada and the central United States. While highly resilient, local populations are vulnerable to the drainage and filling of ephemeral spring pools and contamination from road salts and agricultural herbicides.
Interesting Factoid
The Boreal Chorus Frog can survive having more than half of its body frozen completely solid like an ice cube during harsh Canadian winters; natural glucose sugars protect its vital organs until it thaws out and begins singing in spring.