Although they don’t have language the way humans do, animals can clearly communicate with each other (otherwise, why would they make sounds at all?). We usually view animals’ vocalizations as reflexive (a yelp in response to pain) or very general (a threatening growl), but research in the past few decades has shown that animal vocalizations can be remarkably specific.
Some of the most specific communication has been found in the alarm calls of prairie dogs. Prairie dogs live in burrows in the ground, making them vulnerable to predators, so it’s very important for them to be able to communicate the presence of a predator to the rest of the colony. Moreover, because different predators have different attack strategies (a hawk would attack from the air, whereas a dog would attack from land), it’s also important for prairie dogs to communicate what kind of predator is nearby so the most appropriate escape response can be made.
Researchers have found that prairie dogs do indeed make different alarm calls depending on the species of predator spotted. However, just because a prairie dog makes a predator-specific alarm call doesn’t mean that other prairie dogs interpret it as such; it’s possible that prairie dogs can make distinctions between predators when giving alarm calls yet not respond to these distinctions when hearing other prairie dogs’ alarm calls. They could rely on other cues, such as the behavior of the prairie dog that made the alarm call or the predator itself, to make the appropriate escape response.
In order to test whether prairie dogs can distinguish between different types of predator calls, researchers ran a playback experiment. First researchers recorded alarm calls made by prairie dogs in response to seeing different types of predators. They later played back these calls in the absence of a predator and looked at the prairie dogs’ responses.
If the prairie dogs truly understand that different types of calls are associated with different types of predators, then they will respond appropriately based on the predator. The researchers found that the prairie dogs did just this. When they heard an alarm call to a hawk, they immediately ran into their burrows, the typical response to a hawk predator. When they heard an alarm call to a dog, they became alert but didn’t immediately enter their burrows, just as they would respond to the presence of a dog.
These results demonstrate something very important about prairie dog alarm calls: these calls are referential, meaning that they refer to an object (or in this case, animal), rather than being reflexive. This is significant because, until the last few decades or so, it was thought that the referential nature of human language was one of the characteristics that set it apart from other animal communication.
Further research on prairie dog alarm calls has shown just how specific they can be. Multiple studies have shown that prairie dogs have different alarm calls for different humans, and for the same human wearing different colored shirts, suggesting that prairie dogs can encode color and shape information into their calls. Researchers have also found regional differences between calls, where the acoustic differences between calls for the same predator are greater between colonies that are geographically farther away.
And prairie dogs aren’t the only species with specific vocalizations: vervet monkeys, Diana monkeys, Campbell’s monkeys, ground squirrels, and chickens (to name just a few) have all demonstrated different alarm calls for different types of predators.
So if these vocalizations are so specific and referential, do they count as language? It’s definitely a contested issue (as you would expect). Few scientists would argue that these vocalizations are the same type of language as that of humans. However, these vocalizations suggest that the cognitive structures involved in human language may have evolved earlier than we previously thought. And they’ve certainly made scientists rethink what exactly a “language” is!
Here’s an interesting video about prairie dog alarm calls by Con Slobodchikoff, who has done nearly all of the research out there on prairie dog vocalizations. And here’s a video with Robert Seyfarth (who, along with Dorothy Cheney, has done an incredible amount of research on vervet vocalizations) about whether such specific vocalizations count as language. Finally, here’s a video of vervet alarm calls in action!
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