Data from: How chimpanzees integrate sensory information to select figs

Figs are keystone resources that sustain chimpanzees when preferred fruits
are scarce. Many figs retain a green(ish) colour throughout development, a
pattern that causes chimpanzees to evaluate edibility on the basis of
achromatic accessory cues. Such behaviour is conspicuous because it
entails a succession of discrete sensory assessments, including the
deliberate palpation of individual figs, a task that requires advanced
visuomotor control. These actions are strongly suggestive of
domain-specific information processing and decision-making, and they call
attention to a potential selective force on the origin of advanced manual
prehension and digital dexterity during primate evolution. To explore this
concept, we report on the foraging behaviours of chimpanzees and the
spectral, chemical and mechanical properties of figs, with cutting tests
revealing ease of fracture in the mouth. By integrating the ability of
different sensory cues to predict fructose content in a Bayesian updating
framework, we quantified the amount of information gained when a
chimpanzee successively observes, palpates and bites the green figs of
Ficus sansibarica. We found that the cue eliciting ingestion was not
colour or size, but fig mechanics (including toughness estimates from
wedge tests), which relays higher-quality information on fructose
concentrations than colour vision. This result explains why chimpanzees
evaluate green figs by palpation and dental incision, actions that could
explain the adaptive origins of advanced manual prehension.