Why bright orange feathers and red hair raise melanoma risks in birds and humans

A bright orange hue in birds and humans comes from pheomelanin, a pigment made from the amino acid cysteine. But this colouration carries risks as well as benefits. New research shows how it affects health, mating choices, and survival in animals—including an unexpected link to melanoma in both birds and people.

Pheomelanin gives feathers and hair their reddish-orange tones. In zebra finches, only males develop these colours, forming orange cheek patches and brownish-red plumage. Females lack these markings entirely and do not produce the pigment.

The pigment plays a dual role. On one hand, it helps remove excess cysteine from cells, preventing damage. Males benefit from this protective effect, while females—without pheomelanin—remain more vulnerable. Yet producing pheomelanin may also come at a cost. In Eurasian nuthatches, females prefer males with less intense orange plumage, possibly because brighter males father nestlings in poorer condition. Beyond mating, pheomelanin has darker implications. In birds, its synthesis is tied to a higher melanoma risk and a reduced ability to handle environmental stress. Similarly, ginger-haired humans face an increased melanoma risk, regardless of sun exposure. The exact reasons remain unclear, but oxidative stress during migration, diet, and pollutants may influence cysteine levels in birds. Still, direct links to melanoma development need more study. For now, one thing is certain: the same pigment that attracts mates and shields cells can also leave animals—and humans—more susceptible to disease.

Pheomelanin’s effects stretch from appearance to health, shaping both survival and reproduction. Birds with bright orange feathers may struggle with stress or disease, while humans with red hair face higher cancer risks. The pigment’s costs and benefits depend on cysteine levels, but many questions about its long-term impact remain unanswered.