Noise pollution doesn't just annoy your neighbors or keep you from sleeping. It's just possible that, when we make too much noise, we alter the balance between predators and prey in an ecosystem. And these toads show us how.

Spadefoot toads are masters at staying alive. They have to be. They're toads that live in the desert. Native to Arizona, these animals can stay buried in sand, not moving, eating, or drinking for multiple years at a time. Half a decade of living as a dried-out mummy has no effect on the toad, which pops back to life with a little water and a few hours of work.

It then crawls out into a newly-awakened desert, replete with things that want to eat it. To stay alive in this environment, it needs another form of protection, a kind of acoustic camouflage which Dr. Bernie Krause terms a "biophony." Biophonies are the aggregate sounds made by non-human animals, and they can serve many purposes.

Spadefoot toads have a lot to get done during their short trips to the surface of the desert. They need to find water, in the form of a pond deep enough to house tadpoles for the duration of their aquatic life. To make tadpoles they need to find other spadefoot toads. And they need to allure these other toads in order to get them to mate. To do so, spadefoot make mating calls. These calls expose them to more than just their mates. Predators come down to the ponds, and a loudly croaking toad is an easy meal.

Hundreds of loudly croaking toads are another matter. When these toads get together, they croak in a kind of synchronicity. The toads themselves are able to tell the difference between individuals, but to humans and to predators the group sounds like a confusing chorus, an all-encompassing sound that is hard to resolve into individual croaks.


The toads aren't on autopilot. In order to maintain this synchronicity, they need to be able to keep in contact with each other. When a loud noise, like a jet engine, disrupts their ability to hear each other, they fall out of sync and quiet down. Once they're quiet, each individual that tries to get a chorus going exposes itself to predators. It can take half an hour, during which the braver toads become snacks, to get back in sync with each other.

Video: Arizona Game and Fish Department

[Via The Great Animal Orchestra.]