As readers of my blog know, I like squirrels. I professed my love for them in a previous post. In this post, I want to go into greater depth on one of the most socially complex squirrels, the prairie dog. There are 5 species of prairie dogs in North America, although most detailed studies have been conducted on only two species, the Black-tailed Prairie Dog that inhabits short-grass prairie from Canada to Mexico east of the Rockies, to as far west as southeastern Arizona; and Gunnison’s Prairie Dogs, centered around the four-corners region of the southwest. Prairie dogs have a rather complex alarm calling system that allows them to transmit information on their predators. Detailed information, like whether it’s a terrestrial or aerial predator and whether it’s moving fast or slow. As someone interested in animal communication, I’ve been looking for opportunities to record prairie dogs.
One of my first potential opportunities came last summer, when I was on my way from Carson City to Tucson, via Panguitch, Utah. As I was driving between Great Basin National Park and Panguitch, I passed through a small valley where off on one side of the highway I saw the characteristic mounds and short vegetation of a prairie dog town. I found a small dirt road and eased off the highway. I stepped out of the car, expecting to see roly-poly squirrels darting to their burrows and hear their squeaky alarm calls. But I saw no squirrels, and the only sound I heard was the whisper of the wind though a few small bushes.
I walked out to a few nearby mounds, looking for sign. I almost fell in a badger hole, with fresh tracks leading in and out. Lizards darted into the prairie dog holes, but I found no tracks or scat of prairie dogs. This was a prairie dog ghost town. This area of Utah is home to the Utah Prairie Dog, listed as a federally threatened species. Although numbers have been increasing during the last couple of decades, it is still vulnerable to plague and poisoning. Plaque is caused by a bacterium carried by fleas – the bacterium is not native to North America, so prairie dogs seem very susceptible to it. I don’t know what killed the prairie dogs that used to live in the town I was looking at. The vegetation was just beginning to recover, and the burrows were still intact, so the demise of the colony wasn’t too long ago.
Black-tailed prairie dogs used to be found in southeastern Arizona, although there is little consensus as to whether they were here before the huge influx of cattle that arrived in the late 1800’s. They were shot and poisoned out of the area by the 1950’s, and just a few years ago, Arizona Game & Fish released some into Las Cienegas National Conservation Area, south of Tucson. So that is where I went to try to record prairie dogs.
Because these are new releases and the animals are carefully monitored, the colonies are easily accessible by road. In early April, I found one of the colonies, and parked outside of the barbed-wire fence that surrounded the 5-10 acre plot. The minute I opened the car door, they started alarm calling and running to their burrows. I entered their enclosure through a walk-in gate and placed my microphone between a couple of burrows. I turned the recorder on and went back to my car, which I hoped sufficed for a blind. I watched the prairie dogs as the recorder ran, for almost 40 minutes. Soon after I got back to the car, prairie dogs at the far side of the colony started emerging from their burrows, and calling while they scanned the area. This lasted for about 10 minutes, growing ever quieter as some quit calling and started foraging on grass near their burrows. Just then the prairie dogs in the burrow closest to the mic emerged and started calling loudly, presumably in response to this strange object in their midst. But they settled down, and their calling became much softer for the next few minutes. Then the entire colony was very quiet, as some animals were busy foraging, and others were interacting with each other. They did not seem to react to several ravens flying over the colony.
After a few minutes of this peace and quiet, a loud, wheezy alarm call went out, and all of the prairie dogs dived for their burrows and disappeared. A Swainson’s hawk flew over the far side of the colony and then flew on toward Cienega Creek. The prairie dogs stayed hidden for several more minutes, before carefully raising their heads out of their burrows. It took several minutes more before they came out and started foraging again. When I finally emerged from my car to retrieve the mic, the prairie dogs started alarm calling again. Below is an example of some of the calls; can you hear the difference between the alarms for strange object, hawk, and person?
According to studies conducted on Gunnison’s Prairie Dogs, they not only produce different alarm calls for different types of predators, but also change their calls based on individual characteristics of the predators. For instance, they found that not only did prairie dogs have different calls for different human researchers, but they had different calls for researchers in different colors of clothing! Why would prairie dogs have developed such an ability? The primary researcher on this work, Dr. Con Slobodchikoff, hypothesizes that relaying information on individual predators (not just species of predators) allows the prairie dogs to adjust their responses for individuals that might have different hunting strategies. For example, they might need to respond differently to a particular coyote that likes to hunt by lying in wait outside of a prairie dog burrow than to one who tends to hunt by coursing through the entire colony. Also included in the alarm calls was information on the location of the predator, and the direction and speed it was traveling. Many years of detailed experiments with Gunnison’s Prairie Dogs have led Dr. Slobodchikoff to conclude that their categorization of predators implies a sophisticated cognitive function, with the alarm calls themselves representing a primitive grammar. And alarm calls are not their only vocalization.
Prairie dogs are considered ecosystem engineers because of the profound effect their have on the environments in and around their colonies. Because they like wide open spaces in order to detect predators and see each other, they mow down shrub and tree seedlings to keep them from establishing. Their constant grazing keeps the grass green longer (like mowing your lawn), which attracts and provides food for pronghorn, deer, and bison. Their burrows provide living quarters for burrowing owls, box turtles, snakes and mountain plovers. And prairie dogs are important prey for black-footed ferrets, swift foxes, hawks, eagles, coyotes, snakes, and badgers. Their extensive burrow systems even effect the water dynamics of the soil.
Prairie dog hunting is allowed in just about every state where they are present. They are not killed to be eaten, but rather for the pleasure of “varmint-hunting.” The internet hunting sites are full of sage comments such as, “Yes. Yes. They are like carnival side show targets. . .Except they blow up like they swallowed TNT, and give me the giggles when they get hit!” Ranchers and farmers tend to have little tolerance of prairie dogs, which compete with their cows and can consume some crops. Reports of horses and cows breaking their legs in prairie dog burrows appear to be greatly over exaggerated. In some areas, population control may be warranted, but people who like to plink away at prairie dogs just to watch them explode in a spray of blood are psychopaths and should not be encouraged.
It’s not just individual species that make up ecosystems, but the relationships among them. Intricate webs of genes and interactions that sustain soils, grasslands, forests, streams and oceans; webs that are easily torn apart, severely damaging ecosystems. Prairie dogs seem to epitomize our schizophrenic attitude toward wildlife: vilified by ranchers, deified by environmentalists, but recognized as invaluable components of prairie ecosystems by ecologists, and as examples of complex animal communication systems by cognitive scientists.
You can learn a lot by listening to prairie dogs, if you are willing to take the time.
References:
Slobodchikoff, C.N. 2012. Chasing Doctor Doolittle: learning the language of animals. St. Martins Press.
Recorded using Sony PCM-M10 and Audio-Technica AT2022 mic with Felmicamps SK3.5 preamp. Recording subject to amplification and equalization.