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A grassland bird eavesdrops on prairie dog calls to keep itself safe from predators

Prairie dogs are the Paul Reveres of the Great Plains: They bark to alert neighbors to the presence of predators, with separate calls for dangers coming by land or by air.

"Prairie dogs are on the menu for just about every predator you can think of"— golden eagles, red-tailed hawks, foxes, badgers, even large snakes—said Andy Boyce, a research ecologist in Montana at the Smithsonian's National Zoo and Conservation Biology Institute.

Those predators will also snack on grassland nesting birds like the long-billed curlew.

To protect themselves, the curlews eavesdrop on the alarms coming from prairie dog colonies, according to research Thursday in the journal Animal Behavior.

Previous research has shown birds frequently eavesdrop on other bird species to glean information about potential food sources or approaching danger, said Georgetown University ornithologist Emily Williams, who was not involved in the study. But, so far, scientists have documented only a few instances of birds eavesdropping on mammals.

"That doesn't necessarily mean it's rare in the wild," she said, "it just means we haven't studied it yet."

Prairie dogs live in large colonies with a series of burrows that may stretch for miles underground. When they hear one each other's barks, they either stand alert watching or dive into their burrows to avoid approaching talons and claws.

"Those little barks are very loud—they can carry quite a long way," said co-author Andrew Dreelin, who also works for the Smithsonian.

The long-billed curlew nests in short-grass prairie and incubates eggs on a ground nest. When one hears the prairie dog alarm, she responds by pressing her head, beak and belly close to the ground.

In this crouched position, the birds "rely on the incredible camouflage of their feathers to become essentially invisible on the Plains," Dreelin said.

To test just how alert the birds were to prairie dog chatter, researchers created a fake predator by strapping a taxidermied badger onto a small remote-controlled vehicle. They sent this badger rolling over the prairie of north-central Montana toward curlew nests—sometimes in silence and sometimes while playing recorded prairie dog barks.

When the barks were played, curlews ducked into the grass quickly, hiding when the badger was around 160 feet (49 meters) away. Without the barks, the remote-controlled badger got within about 52 feet (16 meters) of the nests before the curlews appeared to sense danger.

"You have a much higher chance of avoiding predation if you go into that cryptic posture sooner—and the birds do when they hear prairie dogs barking," said co-author Holly Jones, a conservation biologist at Northern Illinois University.

Prairie dogs are often thought of as "environmental engineers," she said, because they construct extensive burrows and nibble down prairie grass, keeping short-grass ecosystems intact.

"But now we are realizing they are also shaping the ecosystems by producing and spreading information," she said.