The Evolution of the Multicoloured Face of Mandrills: Insights from the Perceptual Space of Colour Vision

Julien P Renoult,H Martin Schaefer,Bettina Sallé,Marie J E Charpentier,Daniel Osorio

doi:10.1371/journal.pone.0029117

Abstract

Multicomponent signals consist of several traits that are perceived as a whole. Although many animals rely on multicomponent signals to communicate, the selective pressures shaping these signals are still poorly understood. Previous work has mainly investigated the evolution of multicomponent signals by studying each trait individually, which may not accurately reflect the selective pressures exerted by the holistic perception of signal receivers. Here, we study the design of the multicoloured face of an Old World primate, the mandrill (Mandrillus sphinx), in relation to two aspects of signalling that are expected to be selected by receivers: conspicuousness and information. Using reflectance data on the blue and red colours of the faces of 34 males and a new method of hue vectorisation in a perceptual space of colour vision, we show that the blue hue maximises contrasts to both the red hue and the foliage background colouration, thereby increasing the conspicuousness of the whole display. We further show that although blue saturation, red saturation and the contrast between blue and red colours are all correlated with dominance, dominance is most accurately indicated by the blue-red contrast. Taken together our results suggest that the evolution of blue and red facial colours in male mandrills are not independent and are likely driven by the holistic perception of conspecifics. In this view, we propose that the multicoloured face of mandrills acts as a multicomponent signal. Last, we show that information accuracy increases with the conspicuousness of the whole display, indicating that both aspects of signalling can evolve in concert.

Highlights

It is becoming increasingly clear that animals frequently communicate by complex displays [1,2,3]
Such displays are often termed multicomponent signals because information conveyed by the whole display may be different or more accurate than information associated to the individual traits that make up the display [9]
When including foliage background colouration in the vectorisation procedure, half of the male mandrill faces show blue hues matching with the predicted range of hues that concomitantly maximise hue disparity against both the red facial hues and the foliage background

Summary

Introduction

It is becoming increasingly clear that animals frequently communicate by complex displays [1,2,3]. There is growing evidence, that complex displays can be perceived as a whole [4,5,6,7,8]. Such displays are often termed multicomponent signals because information conveyed by the whole display may be different or more accurate than information associated to the individual traits (named components hereafter) that make up the display [9]. The evolution of components in a multicomponent signal is expected to be mutually dependent and driven by the holistic perception of the display by receivers. Little is known on how the holistic perception of receivers effectively shapes the design of multicomponent signals

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