Mutually honest? Physiological ‘qualities’ signalled by colour ornaments in monomorphic king penguins

Abstract

International audienceMate choice is expected to be important for the fitness of both sexes for species in which successful reproductionrelies strongly on shared and substantial parental investment by males and females. Reciprocal selection maythen favour the evolution of morphological signals providing mutual information on the condition/quality oftentative partners. However, because males and females often have differing physiological constraints, it isunclear which proximate physiological pathways guarantee the honesty of male and female signals in similarlyornamented species. We used the monomorphic king penguin (Aptenodytes patagonicus) as a model to investigatethe physiological qualities signalled by colour and morphological ornaments known to be under sexual selection(coloration of the beak spots and size of auricular feather patches). In both sexes of this slow-breeding seabird, weinvestigated the links between ornaments and multiple indices of individual quality; including body condition,immunity, stress and energy status. In both sexes, individual innate immunity, resting metabolic rate, and theability to mount a stress response in answer to an acute disturbance (capture) were similarly signalled by variousaspects of beak coloration or auricular patch size. However, we also reveal interesting and contrastingrelationships between males and females in how ornaments may signal individual quality. Body condition andoxidative stress status were signalled by beak coloration, although in opposite directions for the sexes. Over anexhaustive set of physiological variables, several suggestive patterns indicated the conveyance of honestinformation about mate quality in this monomorphic species. However, sex-specific patterns suggested thatmonomorphic ornaments may signal different information concerning body mass and oxidative balance of malesand females, at least in king penguins

Beak color dynamically signals changes in fasting status and parasite loads in king penguins

“…Repeatability of the color measurements were high (between 0.70 and 0.91) and are given in Supplementary Material ESM 1. Correlations between those spectral parameters are presented in Figure 1a (see also Viblanc et al 2016). Briefly, the correlations between UV and YO color parameters were very low, consistent with the fact that those colors in the king penguin are produced by 2 different mechanisms (structural for the UV and pigmentary for YO colors; see Dresp et al 2005).…”

“…Previous studies have found that higher beak UV brightness is associated with greater mating prospects (Nolan et al 2010) and different body condition in males and females (Dobson et al 2008;Viblanc et al 2016). Higher beak UV hue is negatively related with hormonal stress responses and oxidative damages in females ).…”

“…In addition to pigmented ornaments, structural colors such as ultraviolet (UV) may also provide information on individual quality. For instance, inter-individual variation in integument UV coloration has been linked to inter-individual variation in body condition in several species (Bize et al 2006;Jacot and Kempenaers 2007;Dobson et al 2008;Viblanc et al 2016). However, because of the structural nature of UV colors, it is unclear whether this trait is labile and reflects intra-individual changes in condition over short to long time periods.…”

“…Further, beak UV is associated with indices of condition. Beak UV brightness was positively correlated to body condition in breeding males, but negatively correlated in breeding females (Dobson et al 2008;Viblanc et al 2016). Beak UV hue is negatively related to total oxidative damage in breeding females but not in males, and is negatively related to individuals' responsiveness to acute stress in both sexes .…”

Sex identification in King Penguins Aptenodytes patagonicus through morphological and acoustic cues

“…) but, recently, differences in flipper length between female and male King Penguins (Viblanc et al . ) and ornamentation size (Dobson et al . , Viblanc et al .…”