Book Description

Animals that live in social groups have the opportunity to learn from one another. Given the possibility of transmitting a learned behavior across generations or groups, the term "cultural transmission" is commonly used as a synonym for observational learning in animal behavior. Cultural transmission appears to be important in distinguishing predators from non-predators as well as in knowing how to react when a predator is encountered. Mobbing is a conspicuous anti-predator behavior, whereby potential prey initiate an encounter with a predator. Mobbing has been observed in many bird species, and mammal species, including primates such as marmosets and tamarins. The adaptive significance of mobbing behavior remains unclear, but mobbing responses can be modified by experience. The cultural transmission of enemy recognition hypothesis states that an individual learns to fear an object after witnessing others mob it, and in tum will avoid it or mob it in the future. I tested the cultural transmission hypothesis in three family groups of Geoffroy's marmosets (Callithrix geo.ffroyi). In two experiments using non-threatening novel stimuli and predator models I tested the hypothesis that marmosets will learn to react with alarm calls to a previously non-threatening stimulus by perceiving other marmosets' mobbing behavior and/or calls to what appears to be that stimulus. The first experiment consisted of trials in which one group served as a "tutor" while another group served as a "student". The student group could hear but not see the tutor group during tutoring. Contrary to predictions, the marmosets in experiment 1 failed to learn to react with alarm calls to a previously non-threatening stimulus. It is possible that the procedure and stimuli were unrealistic to the marmosets and failed to convince them that the stimulus warranted concern. In the second experiment, groupmates tutored each other and mobbing could be both seen and heard by the students. Once again, however, the students failed to acquire fear of the novel stimulus. Alarm vocalizations increased after tutoring in only one of five trials in experiment 2. However, a pattern of increased proximity to the novel stimulus after tutoring was found. This suggests that the marmosets learned not to fear the novel stimulus, but to investigate it. My data argue against the hypothesis that the function of mobbing in marmosets is to teach others to be afraid. Rather, mobbing may communicate a more general message that the object is something that warrants attention and careful assessment.