If you’re a human being and eat too many carrots, your skin may turn a lovely shade of yellow-orange, from a build-up of pigments called carotenoids. Physicians call the condition “carotenemia.”
If you’re a sea otter who eats a steady diet of purple sea urchins, your teeth and even your bones may turn lavender, mauve, lilac, amethyst….stained that color by plum-crimson pigments in your preferred food. Veterinarians call it “echinochrome staining.” (This link has very cool pictures of what it looks like on otter teeth and skulls.)
Carotenoids and echinochrome are different bio-pigments, and the staining process works differently, but carotenemia and echinochrome staining are colorful examples of how, whether land mammal or marine mammal, sometimes we are what we eat.
Update, October 10, 2012: More interesting information on biopigments. When tree frogs don’t get enough carotenoids in their diets, their colors can fade, as shown in these dramatic photos from issue 5, 2011 of Zooquaria, the quarterly magazine of European Association of Zoos and Aquaria (EAZA). Coloration, for many animals, is a crucial way they defend themselves (through camouflage or by appearing more fearsome). It’s also a key part of reproduction for many animals. Bright colors can signal health and desirability to mates; if they don’t get the proper biopigments, they miss out on mating opportunities.
Sea Otter photo: By Mike Baird from Morro Bay, USA via Wikimedia Commons; Carrot photo: public domain via Wikimedia Commons; Frog photos: Victoria Ogilvy, http://www.eaza.net/activities/Documents/NutritionDocs/ZA_NutritionIssue5.pdf