Eat too many carrots and your skin might turn orange, thanks to a group of pigments called carotenoids. Orange skin may not look intimidating to you, but to wild Andean condors, that flash of color in their competitors’ eyes and skin may help them dominate at dinnertime.
Andean condors rely largely on a diet of decaying flesh, but a recent PLOS ONE study suggests that these birds also eat the fresh and partially digested vegetable material in the intestines of carcasses. Condors eat in groups with a strict pecking order, where adult males rank the highest and juvenile females the lowest. Feeding frenzies often lead to conflicts over meals, and this is when the reds, oranges, and yellows of carotenoid pigments may help a young bird signal its dominance in the group. The bare skin of a young condor can turn from pale pink, yellow or dull grey to a vibrant red, orange, or yellow in seconds during these displays.
The researchers investigated how Andean condors and American black vultures acquire these pigments through diet, and what potential biological and environmental factors contribute to the pigments’ biological absorption. They compared pigment concentrations in blood samples from wild condors, black vultures, and captive condors, the latter fed a diet strictly of mammal flesh. The researchers found that captive condors generally had low levels of carotenoids compared to the wild birds, and that the wild condors in particular had a carotenoid concentration about three times higher than that of the wild American black vultures, despite their similar diets. In addition, the wild condors had a high percentage of vegetal matter in their droppings.
These results indicate that wild condors feeding on entire carcasses, including semi-digested vegetal matter, are better able to access the pigments needed for their fast-changing, colorful displays of dominance during a feeding frenzy than the captive condors.
While this research may not inspire us to eat carrots so we turn a dominating shade of orange, it may provide a pivotal foundation for understanding the role carotenoids play in the endangered Andean condors’ diet.
Citation: Blanco G, Hornero-Méndez D, Lambertucci SA, Bautista LM, Wiemeyer G, et al. (2013) Need and Seek for Dietary Micronutrients: Endogenous Regulation, External Signalling and Food Sources of Carotenoids in New World Vultures. PLoS ONE 8(6): e65562. Do i:10.1371/journal.pone.0065562