Effect of Isolation on the Recognition of Context-Specific Alarm Calls in a Captive Vervet Monkey (Chlorocebus pygeryhrus)

Abstract

In contrast to many animal signals that share limited information, context-specific signals communicate referential and/or situational information that is consistently interpreted by a group. Wild Vervet monkeys (Chlorocebus pygerythrus) use context-specific alarm calls to communicate predator type (e.g., eagle, leopard, snake), which causes receivers to respond in predator-specific ways. Captive Vervets use and respond to context-specific alarm calls, though these calls can be applied to novel stimuli such as when eagle calls signal an airplane, another flying entity. Context-specific calls may require a social structure to be produced and understood, where isolated individuals may not understand the information contained within calls. This experiment evaluated the response of a socially-isolated captive Vervet monkey to the context-specific calls that he presumably heard for the first time during the study. The subject, Ross, was exposed to three types of Vervet monkey predator-specific alarm calls, a Vervet monkey social signal, and a control signal (i.e., European Starling). Ross showed behavioral differences after the Vervet calls, suggesting he could recognize conspecific vocalizations. Ross demonstrated an ability to recognize the “alarm” nature of alarm calls with increased scanning behavior displayed after the calls. However, Ross was unable to distinguish between the predator type that the calls communicated. He failed to show the predator-specific responses to alarm calls. Ross’ inability to recognize the information communicated within predator-specific alarm calls suggests the importance of social learning in understanding the context-specific nature of these signals. The overall interpretation of the results should be treated with caution because the study was based on the response of a single animal who lived in an extraordinary situation of social isolation.