DOMINY, N.J.*; LUCAS, P.W.; SUPARDI NOOR, N.; University of Chicago; University of Hong Kong; Forest Research Institute of Malaysia: Primate Sensory Ecology: A study of Fruits, Fingers, and Form

Sensory processing is a central subject in primate evolution. However, few studies have considered how primates discern edible targets from their environment. Because the nutritional parameters of foods vary with respect to odor, color, texture, and taste, the sensation and perception of such cues is relevant to primate survival and reproductive success. In fruits, for example, color and sugar concentrations may change during development. Sugars, in turn, are decomposed by yeast to produce ethanol, a volatile compound to which primate olfaction is acutely sensitive. Accordingly, for highly frugivorous primates, odor and color may be pertinent cues because they operate at greater distances than other sensory modalities. Here we report on the sensory properties of 238 fruits (N = 193 species) from Singapore, Kibale Forest, Uganda, and Pasoh Forest, Malaysia. Results show that fruits evince a variety of spectral changes during development. Collectively, color was a poor predictor of sucrose, fructose, or glucose content. However, the elastic modulus of fruit flesh was a strong predictor of sugar content and ethanol, which ranged from 0.5 – 48%. Furthermore, some fruits provoked palpation by chimpanzees. The deliberation of this behavior implies a cognitive link between texture and food quality. Accordingly, the olfactory and haptic senses appear to be well tuned for discriminating edible fruits. The importance of trichromatic color vision is less clear.