Prairie dogs bark to alert each other to the presence of predators, with different cries depending on whether the threat is airborne or approaching by land.
But their warnings also seem to help a vulnerable grassland bird.
Curlews have figured out that if they eavesdrop on alarms from US prairie dog colonies they may get a jump on predators coming for them, too, according to research published on Thursday in the journal Animal Behavior.
“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. Such animals also gladly snack on grassland nesting birds such as the long-billed curlew, so the birds have adapted.
Previous research has shown birds frequently eavesdrop on other bird species to glean information about food sources or 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, a type of ground squirrel, live in large colonies with a series of burrows that may stretch for miles underground, especially on the vast US plains. When they hear each other’s barks, they either stand alert watching or dive into their burrows.
“Those little barks are very loud; they can carry quite a long way,” said research 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.
Researchers created a fake predator by strapping a taxidermy badger on to a remote-controlled vehicle, rolling it 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 about 160ft away. Without the barks, the remote-controlled badger got within about 52ft of the nests before the curlews appeared to sense the danger themselves.