Science Puzzle
Why Are Flamingos Pink?
Flamingo chicks hatch with fluffy grey feathers and stay greyish for their first couple of years. Adults in the wild are a brilliant pink. Yet flamingos kept in zoos in the past often faded until they were almost white, even though they were healthy and well looked after.
What makes a wild adult flamingo pink?
The Answer
Their food. Flamingos are pink because of the pigments in what they eat.
Wild flamingos feed by sweeping their upside-down beaks through salty lakes and lagoons, filtering out algae and tiny animals such as brine shrimp. These are full of carotenoids: orange, red and yellow pigments, the same family of chemicals that colours carrots and tomatoes. A flamingo can't make carotenoids itself. Its liver turns the ones it eats into pink and red pigments, which end up in its new feathers, skin and even its egg yolks.
Chicks are grey because they haven't had time to build up the pigment. The zoo flamingos faded because, as their old feathers fell out, the new ones grew in without colour: their diet had all the nutrition they needed but none of the pigment. Zoos now add carotenoids to their food, and their flamingos stay pink.
Salmon work the same way. Wild salmon get their pink flesh from shrimp-like creatures they eat, and farmed salmon are given the pigment in their feed.
The principle: Pigments from food. Some animals can't make certain colours themselves and take carotenoid pigments from their diet, so their colour depends on what they eat.