Chromaticity as a signal of ripeness in fruits taken by primates

We have measured the reflectance spectra of many samples of fruit eaten by chimpanzees and three frugivorous monkey species. If the fruit are plotted in a colour space appropriate for catarrhine primates, several distinct rip ening patterns are evident. The degree of ripeness of many species would be discernible by dichromatic primates, but for most fruit a trichromatic con sumer would be at an advantage. However, by calculating which set of possib le photopigments would maximise the chromatic distance between samples of e ach fruit species, we show that the spectral positions of the primate long- (L) and middle-wavelength (M) cone pigments are not optimised for this tas k.