The color of animal waste provides direct insight into diet and physiological processes. Most mammal feces are brown, resulting from stercobilin, a bile breakdown product processed in the liver. Herbivores often produce greenish waste due to the high chlorophyll content of their diet. This general color consistency makes any deviation, such as the idea of purple feces, a fascinating topic.
The Myth of Purple Poop
No known animal naturally or consistently produces purple feces as a normal biological function. The digestive systems of most animals are designed to break down and absorb nutrients, leaving behind waste colored by bile pigments and undigested solids. The misconception stems from observations of wild animals consuming large quantities of highly pigmented foods, such as dark berries or fruits.
Anecdotal reports often center on animals like badgers, foxes, or bears, whose droppings can appear black, dark brown, or occasionally purplish after a seasonal feast. For example, the feces of water voles have been noted to sometimes display a purple hue depending on their forage. These temporary color shifts are simply a direct reflection of the pigments ingested, not a feature of the animal’s inherent biology.
How Diet Creates Temporary Coloration
The temporary purple or dark reddish-blue staining is primarily caused by plant compounds called anthocyanins. These are water-soluble flavonoid pigments found abundantly in dark-colored produce, such as blackberries, elderberries, and chokeberries. Unlike many other nutrients, anthocyanins have limited absorption in the small intestine of most mammals.
This means a significant portion of the pigment travels through the digestive tract largely intact. Because they are not fully metabolized, these intense pigments stain the fecal matter as it passes through the colon. When high concentrations of these pigmented fruits are consumed, the undigested anthocyanins are simply excreted, resulting in the striking, transient coloration.
Natural Causes of Unusual Feces Colors
While a consistent purple color is not natural, other unusual colors in animal feces are common and act as important biological indicators. The standard brown hue in mammals comes from the breakdown of hemoglobin in old red blood cells, which the liver converts into bilirubin and then excretes as bile.
If bile production is obstructed, feces can become pale, white, or clay-colored, often signaling a problem with the liver, gallbladder, or pancreas. In birds and reptiles, the white component of their droppings, known as guano, is uric acid, which is how they excrete nitrogenous waste instead of liquid urine.
Feces can also turn green, which may indicate the animal has ingested a high volume of plant matter, or that waste is moving too quickly through the digestive system. A black, tarry appearance suggests the presence of digested blood from bleeding in the upper gastrointestinal tract, while bright red indicates fresh blood from the lower tract. These variations provide a visible assessment of the animal’s recent diet and overall health.