Lizards, birds, and fish flaunt bright colors, but most mammals stick to more muted tones like browns and blacks. Why is that? There are a few reasons behind this lack of vibrant hues in mammals.
Firstly, mammals largely rely on one pigment, melanin, to produce their colors. Evolutionary biologist Matthew Shawkey explains that while other animals can create a wide array of colors through pigments or structural changes in their skin, mammals use melanin almost exclusively. This limits the diversity of colors in their fur and skin. For example, zebras and pandas have white patches where melanin is absent.
The structure of mammal fur also plays a role. Unlike feathers and scales, mammal hair lacks the complexity needed to reflect colors in a vibrant way. Some mammals, like the mandrill, may have bright colors on bare skin, but not on their fur. Sloths occasionally appear green due to algae, but that color comes not from their fur but from the organisms living on it.
Historically, when mammals evolved, they faced threats from dinosaurs and adapted to a primarily nocturnal lifestyle. Researchers believe that darker coloring helped them blend into the night. In a 2025 study, Shawkey’s team analyzed ancient mammal pigments and found all were dull shades of brown or gray, aligning with this theory.
Even after the dinosaurs vanished, most mammals maintained their muted palettes. A reason for this may be that many mammals, including most modern species, have limited color vision. They primarily see shades of blue and green, making bright colors less crucial for communication or camouflage.
Interestingly, while most mammals lack vibrant colors, they do employ patterns for signaling. Animals like skunks use their black and white markings to warn predators, while the African wild dog’s unique patterns help them communicate while hunting. Tigers, fascinatingly, may look orange to humans but appear green to many of their prey, allowing them to camouflage effectively.
However, recent studies show some exceptions. Some mammals can fluoresce under UV light, revealing colors that humans can’t see but that may be visible to other animals. Additionally, scientists have discovered iridescence in certain species like the African groove-toothed rat. This discovery points to the idea that there are still surprises about mammalian coloration waiting to be uncovered.
As Jessica Dobson, an evolutionary biologist, noted, “When you start looking, mammals are more colorful than we give them credit for.” This expanding understanding could reshape how we view the animal kingdom’s color diversity.
