Carotenoids buffer the acute phase response on fever, sickness behavior, and rapid bill color change in zebra finches

Abstract

Carotenoids are finite resources that animals can allocate to selfmaintenance, attractiveness or reproduction. Here we test how carotenoids affect the acute phase response (APR), an intense rapid systemic response characterized by fever, sickness behavior and production of acute phase proteins, which serves to reduce pathogen persistence. We conducted a 2×2 factorial design experiment in captive adult male and female zebra finches (Taeniopygia guttata) to determine the effects of carotenoid supplementation on the intensity of the APR. We measured changes in feeding rate, activity level and body temperature of the birds. We found that, relative to unsupplemented controls, carotenoidsupplemented birds exhibited less severe reductions in feeding and activity, smaller increases in body temperature and lower circulating levels of haptoglobin (an acute phase protein) 24 h after inducing an APR. Among supplemented individuals, those with higher blood carotenoid levels exhibited a lower reduction in activity rate after 24 h. Forty-eight hours after APR induction, birds exhibited a significant decrease in plasma carotenoid levels and a decrease in bill hue, with less reduction in hue in carotenoid-supplemented individuals. These results demonstrate that carotenoids can alleviate several important behavioral and physiological effects of an APR and that bill color can change rapidly following induction of the costly APR immune defense. In particular, immune activation may have caused birds to preferentially draw down carotenoids from the bloodstream, ostensibly for use in health. Rapid bill color changes over a 48-h period support growing evidence that bills may serve as short-term signals of health and condition.

Categorical colour perception occurs in both signalling and non-signalling colour ranges in a songbird

“…Previous studies have shown the categorical perception of behaviourally or ecologically important stimuli, for example, in discriminating between different speech phonemes [11] or birdsong note types [4], predators versus conspecifics [3], or potential mates [2,8], but studies have not compared the perception of similar stimuli across different functional contexts. Male zebra finch beak colours range from light orange to dark red [13], and females show a mating preference for males having redder beaks [43,44], a preference thought to be driven by the fact that the expression of carotenoid-based red coloration correlates positively with variation in cell-mediated immunity in this species [13,45,46]. The sharper category boundary observed in the orange -red colour range may therefore be the result of selection on communicative function in the context of mate choice.…”

The potential utility of carotenoid‐based coloration as a biomonitor of environmental change

“…2000), Complete Freund's Adjuvant (George et al . 2017) or lipopolysaccharide of Escherichia coli (Alonso‐Álvarez et al . 2004)) or by comparing the immune defences of individuals with bright and dull ornaments (Dunn et al .…”

Testosterone, signal coloration, and signal color perception in male zebra finch contests

“…Previous studies have linked the orange to red color continuum of male zebra finch bills with immune function (Blount et al, 2003;deKogel & Prijs, 1996;George et al, 2017;McGraw & Ardia, 2003; but see Birkhead et al, 1998), suggesting that bill color may reflect individual quality and, by extension, competitive ability. However, although one behavioral study has supported the role of carotenoidbased colors in aggressive signaling (Ardia et al, 2010), others have found no evidence of a signaling function (Bolund et al, 2007;Burley & Coopersmith, 1987;Etman et al, 2001).…”