Andrew Dreelin slowly drove a remote-control car with a taxidermied badger aboard through sagebrush and cactus. The Badger-inator creeped along toward a long-billed curlew on its nest in the middle of central Montana’s prairie dog country.
Dreelin, a research fellow at the Smithsonian Conservation Biology Institute, then played a recording of prairie dogs panic chirping while a colleague watched the female long-billed curlew. Moments later, the curlew flattened her neck to the ground and disappeared almost completely.
The test was over. Dreelin turned the Badger-inator around and drove it back.
Dreelin and colleague Andy Boyce were trying to answer a fundamental question that had plagued them both for years: Why do birds seem to disproportionately nest in prairie dog colonies that draw everything from hawks and eagles to coyotes and badgers?
The answer, they found, is pretty simple: Birds appear to use prairie dog colonies as their very own home-alert security systems.
“Prairie dogs are food for grassland species, and they physically modify the vegetation structure and engineer burrows,” said Boyce, a research scientist with the Smithsonian’s Migratory Bird Center. “But our work points to a whole other dimension. They are a keystone information producer, which isa relatively new fourth dimension of their keystone impacts.”
Eavesdropping to Survive
Long-billed curlews aren’t the only ones who use surrounding wildlife to their advantage.
Red-breasted nuthatches listen to the sophisticated alarm call systems of the black-capped chickadees. They even seem to understand the chickadee’s nuanced vocalizations that explain variation in size and risk of potential predators, according to a 2007 paper. And a 2013 paper showed that burrowing owls also likely listen in on prairie dog calls, becoming more alert when researchers played prairie dog calls as opposed to cattle mooing or an airplane overhead.
Different species of mammal also listen to each other. A 2008 paper showed that eastern chipmunks changed their foraging behavior based more on the frantic chattering of the eastern tufted titmouse than on the presence of the actual hawk.
“So rodents can give the information but also receive the information,” said Courtney Duchardt, a University of Arizona range and wildlife professor who has studied prairie dogs and mountain plovers for well over a decade. “Based on what I know about other bird species and research around this, it makes sense if you’re living in an area and getting information not to ignore that information. Across the animal’s world we’re finding more and more who do this.”
For Boyce and Dreelin, long-billed curlews and prairie dogs were the perfect place to find more examples. Boyce has studied long-billed curlews for years. Their nests are tricky to find, but not impossible. They also generally only nest once a year, giving researchers a (relatively) easy research subject.
Working with some local remote-control car enthusiasts and a taxidermied badger, Dreelin and a team came up with a plan.
Race Car Badger
First, Dreelin and Boyce needed a credible threat, which came in the form of a donated taxidermied badger. Dreelin then stripped down a remote-control car and strapped the badger aboard. He reached out to some local RC car folks for technical help, including how to keep the badger’s body from blocking a signal from reaching the car’s antennae.
“He had to get the RC car enthusiast to teach him how to do the opposite of what every RC car person wants to do,” Boyce said, “which is make their car go faster.”
The study consisted of two trials, both on curlew nests near prairie dog colonies but not in them. The researchers realized that even hiding in a blind, prairie dogs would see the researchers and sound the alarm, so they had to avoid currently occupied colonies.
In the first trial, he drove the Badger-inator, as he began calling it, toward the long-billed curlew nest, noted the distance when she put her head down to hide, then measured the distance. A few days later, he ran the second trial, this time driving the Badger-inator while playing prairie dog alarms recorded from nearby prairie dog colonies.
“When they had an early warning with the alarm calls, they started hiding triple the distance away,” he said.
He ran tests—one with the calls and one without—on 14 nests and consistently found the same result.
Save the Prairie Dogs, Save the Birds
Boyce and Dreelin both admit they’re not prairie dog people. They’re bird people. But they also realize that many of the bird species they study are in steep decline, and part of the answer to their survival may lie in prairie dogs, one of the West’s most maligned creatures.
Prairie dogs once covered much of the western half of North America, but after over a century of being gassed, trapped, shot and otherwise persecuted, black-tailed prairie dogs now occupy only about 2 percent.
There’s a reason prairie dogs are considered a keystone species, though. Dozens of animals in the West depend on them, including bison, burrowing owls, black-footed ferrets and swift foxes.
And because of their alarm calls, researchers realize, numerous grassland bird species like long-billed curlews also depend on chattering rodents.
“Predators are a big limiting factor for prairie bird species,” Boyce said. “By not persecuting prairie dogs, we could help conserve grassland bird populations.”
Boyce and Dreelin next hope to document nest survival in long-billed curlews, to see if their ability to eavesdrop within prairie dog colonies actually lead to more chicks and stronger populations.
From there, they want to begin similar measurements in songbirds like the chestnut-collared longspurs to understand the full picture of prairie dogs as home alert systems.
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