Detection of conspicuous and cryptic food by marmosets (Callithrix jacchus): An evaluation of the importance of color and shape cues

Abstract

Since 19th century, the adaptive function of color vision for object identification has fascinated science. Countless articles uncovered the advantages of trichromacy (i.e., color vision expressed by most humans) in detecting yellowish/reddish targets against a background of mature green leaves. Unfortunately, the same attention was not offered to achromatic visual information, that had their physiological foundations much more explored than their possible adaptive function. So far, mostly because of studies conducted in humans, we know that achromatic cues might also play an important role in object identification, particularly when camouflage is involved. For instance, dichromacy (i.e., color vision expressed by many colorblind humans), favors the detection of camouflaged targets by exploitation of shape cues. The present study sought to evaluate the relative importance of color and shape cues on the detection of food targets by female and male marmosets (Callithrix jacchus). Animals were observed with respect to their foraging behavior and the number of food targets captured. We confirmed that females are advantageous in detecting conspicuous food against a green background and revealed that females and males rely on shape cues to segregate cryptic food. Unexpectedly, males outperformed females in cryptic food foraging. Camouflage improved males' (but not females') performance.