Nesting Birds Eavesdrop on Prairie Dog Alarm Calls to Keep Their Eggs Safe From Grassland Predators
New research suggests long-billed curlews keep an ear out for warnings from prairie dogs in order to hide from predators and protect their nests
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Prairie dogs are chatty creatures. The animals have a variety of calls to alert each other to the presence of predators, each of them distinct based on the nature of the threat. Now, researchers from the Smithsonian’s National Zoo and Conservation Biology Institute (NZCBI) have discovered that birds known as long-billed curlews also listen in on the calls to keep themselves safe.
Their findings were published in the journal Animal Behaviour last week.
Black-tailed prairie dogs are burrowing squirrels that live in large colonies throughout the Great Plains. They’re vulnerable as prey to lots of animals—like hawks, eagles, foxes, snakes and badgers—which come at them from different angles. That’s why prairie dogs developed calls that differ based on whether a predator is approaching from the ground or the air, and they even vary based on the predator’s color. When prairie dogs hear each other’s barks, they either stand alert or hide underground.
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It’s not just prairie dogs that hear these calls. The rodents share their habitat with other species, including large shorebirds called long-billed curlews, which breed in the grasslands. But areas with lots of prairie dogs might seem like a counter-intuitive place for a bird to build a nest, since they can be prime locations for other animals to look for a meal.
“Lots of birds live on or around prairie dog towns, even though they are magnets for predators, so we suspected birds would have ways to mitigate that risk to better enjoy the benefits,” says Andrew Dreelin, the study’s lead author and a research fellow with NZCBI’s Migratory Bird Center and Great Plains Science Program, in a statement. “With this study, we are getting to see an underappreciated behavioral benefit.”
“This brings us one step closer to understanding the complex relationship between prairie dogs and grassland birds,” he adds.
Dreelin and his colleagues wondered if the curlews could also take advantage of the prairie dogs’ alarm system. To find out, they created a remote-controlled taxidermy badger nicknamed the “Badger-inator” to test how the birds react to prairie dog alarms near their nests. As the Badger-inator rolled around Montana’s prairies, it occasionally played recordings of prairie dog barks and other times moved in relative silence.
The researchers found that when the barks played, incubating female curlews quickly crouched in the grass to camouflage themselves and protect their nests. Without the barks, the birds sensed the danger from the Badger-inator much later—and the pseudo-predator could get about 70 feet closer to them, on average, before they reacted.
“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,” explains Holly Jones, a study co-author and conservation biologist at Northern Illinois University, to Christina Larson at the Associated Press.
Non-incubating male curlews didn’t have the same response to the fake badger, according to the study. Male curlews will often make alarm calls when faced with a predator, but instead of fleeing, they will sometimes mob the animal. They were about equally likely to perform this behavior regardless of whether Badger-inator emitted prairie dog calls—but they only mobbed the simulated predator about a quarter of the time. One possible explanation for this is that an obvious reaction might draw attention to their nests and leave their eggs more at risk of predation.
“We know that prairie dogs are keystone species because of the way they physically alter the environment and create homes for other plants and animals,” says Andy Boyce, the study’s senior author and a research ecologist at NZCBI, in a statement. “What we hadn’t realized until now is that in addition to being homebuilders, they might also be acting as home-security systems.”
Birds sometimes pay attention to the calls of other bird species to get information about nearby predators or food sources—but so far, scientists haven’t found many instances of birds listening in on mammals, as Georgetown University ornithologist Emily Williams, who was not involved in the study, tells the AP.
“That doesn’t necessarily mean it’s rare in the wild,” she adds, “it just means we haven’t studied it yet.”
