Spring is here, which means it’s time for our amphibious friends to come out of hibernation!
There are 14 species of frogs and toads in Minnesota—all of which survive the winter in one of three ways: buried underground, frozen beneath the leaf litter, or at the bottom of a lake. When the air starts to warm and the ice thaws, northern amphibian species such as ours must take advantage of the limited spring and summer months for breeding.
Most species of frogs and toads select mates through vocalizations. Male frogs produce a call by pushing air from their lungs, through their larynx, and into their oral cavity where air currents vibrate the frog’s vocal cords. The sound produced by the vocal cords resonates and is amplified using a throat pouch that inflates while calling.
Female frogs can detect subtle differences in each vocalization, even in a chorus of individuals. They listen to calls as indicators of fitness (which in biology means an organism’s ability to survive and reproduce).
As temperatures begin to rise, keep your ears open when you’re outside. Listen closely—especially at night. We’ve included a four common frog and toad species below to help you identify what you hear.
Common Croakers of Minnesota:
Common name: American toad
Scientific name: Anaxyrus americanus
Quick ID: Adults 2–4 inches, males are generally smaller than females, and have a gray throat that inflates during vocalization. Back is gray to brown, with white to tan underside. Some individuals may be more of an olive color, or even light red depending on environmental conditions. Dark speckling around body and thick, bumpy skin on back. Pronounced cranial crest between and behind eyes, and one large parotoid gland behind each eye. Toes are long and thin for burrowing in the mud.
Breeding: Vocalizations begin in early to mid May, peaking in late spring, but calls can be heard throughout the summer. Females lay between 2,000 and 20,000 eggs in strings on underwater vegetation.
Fun fact: The parotoid glands behind each eye secretes bufotoxin, a neurotoxin that deters predators by making the toad unpalatable. Bufotoxin is a mild toxin that is not dangerous to humans, but may cause irritation if it gets into your eyes.