Have you ever been able to tell from the tone of someone’s voice and context clues that you’re in grave danger, even if you don’t quite understand what they said to you? Something as complex as being able to tell from tone and context clues what’s going on may seem specific to just humans, however, West African Diana monkeys can do just that! Male Campbell’s monkey alarm calls were played along with crowned eagle and leopard vocalizations in order to test whether Diana monkeys would react to the alarm calls as well as being able to distinguish the predator from the alarm call.
Dr. Klaus Zuberbühler located wild Diana monkey groups within a 50km^2 radius of Taï National Park, Côte d’Ivoire between June 1996 and February 1999. A speaker was placed in the close vicinity and their vocalizations were recorded before and while 15 second recordings of shrieks of crowned eagles or leopard growls were played. Two experiments were carried out The first was to determine whether the Diana monkeys respond to the Campbell’s calls in general. Their responses to both the Campbell’s alarm calls and to the predators vocalizations were both recorded and compared to each other. The second experiment answered whether Diana monkeys understood which predators the Campbell’s monkeys alarm calls warned of. When alarm calls for the predator are understood, they’ll react more weakly when the predator’s vocalization is played. The strength of their alarm calls in response to the predator vocalizations after being presented with Campbell’s alarm calls were analyzed in order to come to a conclusion. In the first experiment, when presented with both eagle alarm calls and eagle vocalizations, the Diana monkeys gave eagle alarm calls and alert calls but no leopard calls. When presented with leopard alarm calls and vocalizations, they gave leopard alarm calls and alert calls but no eagle calls. In the second experiment, after hearing Campbell’s monkeys eagle alarm calls, Diana monkey’s weakly reacted to eagle vocalizations. When leopard vocalizations were played after eagle alarm calls they reacted strongly. When leopard vocalizations were played after leopard alarm calls they reacted weakly. And lastly, when eagle vocalizations were played after leopard alarm calls, they reacted strongly.
The experiment provided excellent data in order to prove the initial hypothesis that Diana monkeys understand and respond to Campbell’s monkeys alarm calls. In the first experiment, the fact that Diana monkeys responded nearly as strongly to the alarm calls as to the predator vocalizations meant that they do respond to Campbell’s monkey alarm calls. The second experiment showed very well that they are able to understand the meaning of the alarm calls and react accordingly. This experiment helps to show us that it isn’t just humans that possess the cognitive competence to understand the meaning in vocalization. This study and more help to open up our understanding of other animals and their capabilities in interacting with each other as it’s easy to forget that animals are also capable of some pretty incredible and complex things.
References
Zuberbuhler, K. (2000). Interspecies semantic communication in two forest primates. Proceedings of the Royal Society B: Biological Sciences, 267(1444), 713-718. doi:10.1098/rspb.2000.1061
Selena Lomeli
November 12, 2018 — 9:59 pm
This is a very intriguing article. It made me think about our discussion on alarm calls. I wonder how the ability for Diana monkeys to understand the alarm calls of Campbell’s monkeys came about.
Josephine Brodie
November 13, 2018 — 4:44 pm
I really enjoyed your article, the into was very captivating and you used easy to understand language throughout. I especially liked how your conclusion tied in your introduction and got the readers thinking.