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When rain falls and water is plentiful, the sex lives of plains spadefoot toads are pretty, well, plain. Females prowl ponds for the suitor with the most winsome call; they pair off to couple, churning out legions of eggs that will hatch into, as genetics might predict, more plains spadefoot toads.

But when the weather gets drier and deep ponds more scant, as they often do in the North American deserts where spadefoots live, this narrative acquires a twist. Female plains spadefoot toads start seeking out not the duckish quacks of their own species but the baritone trills of the Mexican spadefoot toad.

When Karin Pfennig, a behavioral ecologist at the University of North Carolina at Chapel Hill, first noticed the behavior some two decades ago, “I thought it had to be a mistake,” she told me.

The Atlantic