Amphibians
Great Plains Toad
Anaxyrus cognatus · also called Plains toad
Stand near a flooded prairie field on a warm night after a thunderstorm and the noise can be almost unbearable: a wall of harsh, metallic, machine-gun trilling, each call running for the better part of a minute. It comes from Great Plains toads, blotchy grey amphibians that spend most of the year underground and pour everything into a few nights of breeding.
Overview
Anaxyrus cognatus is a medium-sized true toad, usually 5 to 9 cm long, grey to olive with large, pale-edged dark blotches and a raised hump on the snout. It lives across the Great Plains and the arid interior of North America, in prairie, farmland, and semi-desert with soil loose enough to dig into.
The call
The male’s advertisement call is one of the longest and harshest of any North American amphibian, a continuous jackhammer trill lasting up to nearly a minute. While calling, he inflates his throat sac into a long sausage shape that sticks out past his snout.
A life mostly underground
Outside the breeding season the toad burrows backwards into loose soil with sharp tubercles on its hind feet and waits out dry and cold spells. Heavy rain brings it up, and breeding is explosive, over in a few nights at temporary pools before the adults scatter again.
Status
The Great Plains toad is Least Concern and generally secure. Local declines follow the ploughing of native prairie, the draining of playa lakes and wetlands, and irrigation changes that remove its temporary breeding pools.
Great Plains Toad: common questions
How loud and long is the Great Plains toad's call?
It is among the most extreme calls of any North American amphibian. The male produces a continuous, rapid, harsh trill, often compared to a jackhammer, a riveting gun, or a very loud alarm clock, and a single call can last from about 20 seconds to nearly a minute before he pauses for breath. At a breeding pool with many males calling at once, the combined sound is genuinely uncomfortable at close range and carries a long way across open country. The purpose is the same as any frog chorus, to attract females and to space out rival males, but this species has pushed call duration and volume unusually far.
Is the Great Plains toad a spadefoot?
No, though it shares some habits with them. It is a true toad, in the same genus as the American and Fowler's toads, with dry warty skin, large parotoid poison glands behind the eyes, and a horizontal pupil. Spadefoots are a separate family with vertical, cat-like pupils, smoother skin, no large parotoid glands, and a single hard black spade on each hind foot. What the Great Plains toad has in common with spadefoots is the dry-country lifestyle, spending long periods burrowed backwards into the soil and emerging to breed explosively after rain, but it reaches that lifestyle as a toad rather than a spadefoot.
Where and when might you encounter one?
Across the plains and the arid south-west, on warm nights during the rainy season, especially after a heavy thunderstorm. That is when Great Plains toads leave their burrows and move to flooded fields, roadside ditches, stock ponds, playa lakes, and temporary pools to feed and, if conditions are right, to breed. Away from those brief windows they are underground and effectively invisible. During the day, even in the breeding season, they stay buried or hidden, so a spring or summer night drive along wet prairie roads after rain is the classic way to find them, often alongside spadefoots and other toads.
Are Great Plains toads good for farms and gardens?
Generally yes. Their diet is dominated by ants and beetles and includes cutworms and other caterpillars that damage crops and garden plants, so a resident toad population provides free pest control. They ask little in return, needing only some undisturbed soil to burrow into and access to shallow water for a few nights of breeding after summer rain. The main ways people harm them are by removing those breeding pools through drainage or changed irrigation, by heavy tillage and pesticide use, and by road traffic during breeding migrations. Leaving rough margins, a shallow seasonal pond, and some cover helps keep them around.