Abstract:
Howler monkeys (platyrrhini) have evolved routine trichromatic color vision in-
dependently from catarrhines, which presents an opportunity to test hypotheses
concerning the adaptive value of distinguishing reddish from greenish hues. A
longstanding hypothesis posits that trichromacy aids in the efficient detection of
reddish‐ripe fruits, which could be an advantage for the detection of the nutritional
content of the fruit, such as sugars. In the present study, we assessed fruit visual
conspicuity and selection based on color and sucrose content by wild mantled
howler monkeys (Alouatta palliata) on Agaltepec Island, Mexico. We used colorimetry
to classify dietary fruits as cryptic (greenish) or conspicuous (reddish) against their
background leaves. Species‐specific color models indicate that trichromatic howler
monkeys should be more efficient in discriminating the conspicuous ripe fruits from
leaves compared to detecting cryptic ripe fruits from leaves. We found howler
monkeys consume more cryptic fruits compared to conspicuous fruits, and that they
consume more unripe fruits than ripe fruits. The consumption (acceptance) of fruit
was independent of sucrose content, and thus this disaccharide may not play an
essential role in mantled howler food selection. Our findings suggest that routine
trichromatic color vision may aid in the detection and discrimination of con-
spicuously colored fruits, but that the final decision whether to accept or reject a
fruit probably involves the use of other senses in addition to vision.
