Abstract # 183:

Scheduled for Monday, September 21, 2009 08:00 AM-08:10 AM: Session 17 (Shell Room) Oral Presentation


S. F. Etting and L. A. Isbell
Department of Anthropology, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA

The Snake Detection theory hypothesizes that variation among primates in their evolutionary histories with snakes has led to differences in snake-detection abilities across taxa. Old World anthropoids have coexisted with constricting and venomous snakes throughout their evolutionary history and are predicted to detect snakes from farthest away, whereas Malagasy prosimians, having only co-existed with constricting snakes, are predicted to be less effective detectors. New World primates are predicted to be intermediate since constricting snakes were in the New World when platyrrhines arrived while venomous snakes appeared there only more recently. We tested these predictions in a comparative study that involved presenting three models (snake, toy bear, and rope) to captive populations of rhesus macaques (Macaca mulatta), squirrel monkeys (Saimiri sciureus), and black-and-white ruffed lemurs (Varecia variegata) at decreasing distances, from 15 m to 1.5 m. Scan samples were conducted to record numbers of animals in the viewing area and proportion of animals gazing at the models. We fit latent-state models to the data in order to reveal underlying changes in behavior associated with detection. Analyses indicate reactions to the snake, but not the control models, began at 4.5 m in rhesus macaques and 1.5 m in squirrel monkeys. Black-and-white ruffed lemurs never responded to the models. These findings support the premise that variation in evolutionary history with snakes is reflected in differential detection ability.