The Mont Saint-Hilaire Biosphere Reserve is home to tens of thousands of green frogs. Their colour ranges from brown to green, except for their upper lip, which is always green.
They can be distinguished from bullfrogs by the ridges that run from their eyes two-thirds of the way down their backs. Their call sounds remarkably like a stretched rubber band being plucked. Unfortunately, ponds polluted by agricultural waste have produced many deformities in the green frog population, but those living on the mountain are in good health.