University of Arizona researcher Allie Burnett knows more about the elusive Harris’ antelope ground squirrel than practically anyone in the world.
“They’re not chipmunks,” Burnett often corrects people.
At Burnett's study site in the UA Santa Rita Experimental Range, a blur of stripes ripped through the desert dust and she thought, “Was that a zebra-tailed lizard, or was that an antelope squirrel?”
As a speedy creature and the size of a stick of butter, the antelope squirrel is not easy to locate and study.
“If I had known that beforehand, maybe I wouldn’t have chased them around the desert for two years,” Burnett joked.
A graduated master's (now Ph.D.) student at the UA, Burnett has published the first part of her study on the Harris’ antelope squirrel in the respected "Animal Behaviour" journal. The culmination of much time and effort, her research uncovers a rich and unexpected complexity in the squirrel’s communication network. Despite it being a difficult study in part because antelope squirrels are solitary, or “asocial,” Burnett proved she was up for the task.
“To be effective in doing animal behavior research, you really have to be patient and observant. [Burnett] is both of those things,” said John Koprowski, a retired professor at the UA School of Natural Resources and the Environment. Koprowski is Burnett’s research advisor on the project and gloats at the fact that she is not only “incredibly hardworking but also quite clever.”
Burnett recalled waking up before the sun, as early as 3 a.m., to drive down with her research assistant from Tucson to her experimental site an hour away in the Santa Rita Mountains.
“It’s nice getting up in the morning,” said Alexis Blair, the research assistant who worked with Burnett nearly every day during the 2-year project. “The whole desert kind of comes to life.”
Once at the site, the first step was bed check, or “burrow check,” to see if the squirrels had stayed in the same burrow throughout the night. They rarely did.
“What are you guys doing in the middle of the night? Could you guys not sleep?” Burnett remembered thinking.
Next, Burnett and Blair would listen to the squirrels to produce their alarm calls. Loud, sharp and high-pitched, they are easy to mistake as a bird’s call. Intrigued by larger questions of communication evolution, Burnett didn’t just listen but tested her new theory.
The standard school of thought in this research field has always been linear. As squirrels become more social, their communication becomes more complex, according to Burnett. But what about for solitary species?
“Is it the sociality that came first, or is it the communication complexity that came first?” Burnett asked. “No one’s looked at that before.”
Researchers look to squirrels to understand how systems like language evolve. By uniquely studying the antelope squirrel, an asocial and non-hibernating species, Burnett can test if alarm calls are only a social thing. If so, then antelope squirrels should stop their yelling in the non-breeding season when their offspring aren’t around. We have a “beautiful, elegant test case,” Burnett said.
What Burnett found was a surprise to both her and her advisor: the antelope squirrel’s alarm calls serve two functions. The call warns offspring and acts as a predator deterrent. Now that this asocial squirrel has learned to make noise to scare a predator, the offspring will hear that call. Could it be that fear from predators is what triggers communication to evolve?
“Now, you are creating this snowball effect where increased communication complexity increases sociality, and they feed into each other and bam humans!” Burnett said. She added, however, that “none of this is confirmed.”
“It’s a great hypothesis,” said Dan Blumstein, a renowned expert in complex animal communication at the University of California, Los Angeles. But antelope squirrels are just the first test case needed to answer bigger questions. Blumstein believes a comparative study should be set up that looks into lots of species — those that call, those that don’t call and their degree of socialization.
In the meantime, a lot more can still be learned from the antelope squirrels themselves. In a continued study, Burnett found that not only do antelope squirrel calls serve different functions, but each call is diverse and layered in complexity.
About a thousand calls, from a hundred different squirrels, have been recorded by Burnett, according to her own estimates. Sometimes she’ll hear a “chip plus trill” or “trill plus chirp.” Burnett explained that similar to how the tone of voice in human language layers information and how the arrangement of words can change the meaning of a sentence, a squirrel’s “repertoire” of calls could all potentially mean different things.
Once a “forgotten species” of the Sonoran Desert, according to Burnett, the small and solitary antelope squirrel has proven it can unlock new ideas around communication evolution – you just need to be able to spot them first.
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