So if animals could talk, what on earth would they talk about? What is important for them to say? A lot of what animals talk about centers on warning each other about danger from a potential predator using alarm calls. Some of the best research we have on animal communication comes from work on alarm calls. At its most fundamental level the research on birds, mammals and primates reveals that call structure differs depending on the type of predator that is presenting a threat. Depending on the species, the calls could represent two categories: predators in the air and predators on the ground. For some species, however, things get more specific and each call can represent a specific type of predator. Meaning they have a ‘word’ for each threat. For example, vervet monkeys (Chlorocebus pygerythrus) have a word (alarm call) for an eagle, a leopard, and a snake. The well-studied Diana monkey (Cercopithecus Diana) not only assigns a word for each predator, but the order of the sounds conveys a particular meaning. Diana monkeys also are multilingual, in that they comprehend the alarm calls and syntax structure of other primates they share the forest with (e.g. Campell’s monkey). There are similar findings for other species of primate (e.g., Putty-nosed monkey). Unlike the great ape language studies of the 1970’s (e.g., Koko the gorilla, Washoe the chimpanzee) that used human sign language, these studies are based on natural populations that use communication to cooperate and gather important information about their surroundings. Though in all fairness, recent studies have highlighted how wild populations of great apes (gorillas, chimpanzees, bonobos, and orangutans) all use hand signals as a form of communication).
At this point you might be thinking that primates having words, syntax, and grammar is not so amazing. After all, they are usually highly social, live in groups, and have larger brains than many other species. But what about squirrels? Yes, squirrels, or prairie dogs (Cynomys spp.) to be more specific. Prairie dogs are highly social ground squirrels that make their home in the grasslands of North America. There are five species of prairie dog and all are under threat of extinction. Prairie dogs have a large vocabulary when it comes to predators, probably because they are low on the proverbial food chain. Foxes, coyotes, badgers, weasels, ferrets, eagles, hawks and snakes, to name of few, hunt them! Studies on Gunnison’s prairie dogs (Cynomys gunnisoni) in particular, provide evidence that information relating to an individual predator’s size, shape, color, direction, and speed of travel is incorporated into an alarm call. The components of each alarm call representing size, shape, color, direction and speed of travel also vary consistently within the structure of the call, which implies an order or sequence to the structure of a call remarkably similar to the word order, or syntax, found in language. Prairie dogs don’t just give calls to predators either. They have calls for non-predators like elk, antelope, porcupines, and even cows!
It would seem that semantics (words), syntax (structure, order), and grammar (rules for syntax) may be common features of animal communication systems. The absence of a vocal apparatus that prevents the mechanical production of some sounds is insufficient evidence for the lack of language in animals. As a more detailed understanding of how animals communicate is revealed, language as a defining feature of being human may go the way of tools. Until Jane Goodall’s research on chimpanzees, the definition of man included ‘the making and using of tools’. Since her groundbreaking research showing that chimpanzees make, modify, and use natural tools, we have discovered that even birds make tools. So next time you are out in nature and hear birds chirping, monkeys howling, or prairie dogs barking, remember, they may be talking about you!
References:
Arnold, K. and Zuberbühler, K. 2008 Menaingful call combinations in a non-human primate. Current Biology 18: R202-R203.
Gyger, M., Marler, P., Pickert, R. 1987. Semantics of an avian alarm call system: the male domestic fowl. Behaviour, 102, 15-40.
Greene, E. & Meagher, T. 1998. Red squirrels, Tamiasciurus hudsonicus, produce predator-class specific alarm calls. Animal Behaviour, 55, 511-518.
Owings, D. & Virginia, R. 1978. Alarm calls of California ground squirrels. Zeitschrift für Tierpsychologie, 46, 58-70.
Pereira, M. & Macedonia, J. 1991. Ringtailed lemur anti-predator class, not response urgency. Animal Behaviour ,41, 543-544.
Placer, J. and Slobodchikoff, C.N. 2000. A fuzzy-neural system for identification of species- specific alarm calls of Gunnison’s prairie dogs. Behavioural Processes, 1-9.
Seyfarth, R.M., Cheyney, D.L. 1980. The ontogeny of vervet monkey alarm calling behavior: A preliminary report. Zeitschrift für Tierpsychologie., 54, 37-56.
Slobodchikoff, C. and Kiriazis, J. 1991. Semantic information distinguishing individual predators in the alarm calls of Gunnison’s prairie dogs. Animal Behaviour, 42, 713- 719.
Slobodchikoff, C., Ackers, S., Van Ert, M. 1998. Geographic variation in alarm calls of Gunnison’s prairie dogs. Journal of Mammalogy, 79, 1265-1272.
Slobodchikoff, C.N., Paseka, A. and Verdolin, J.L. 2009. Information content of alarm calls: Prairie dog alarm calls encode information about predator colors. Animal Cognition, 12:435-439.
Zuberbühler, K. 2000. Referential labeling in Diana monkeys. Animal Behaviour, 59, 917-927.
Zuberbühler, K. 2002. A syntactic rule in forest monkey communication. Animal Behaviour, 63: 293-299.
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