Feces
Feces (or faeces; sg.: faex) are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine.[1][2] Feces contain a relatively small amount of metabolic waste products such as bacterially altered bilirubin, and dead epithelial cells from the lining of the gut.[1]
This article is about feces in general. For specifically human feces, see Human feces.
Feces are discharged through the anus or cloaca during defecation.
Feces can be used as fertilizer or soil conditioner in agriculture. They can also be burned as fuel or dried and used for construction. Some medicinal uses have been found. In the case of human feces, fecal transplants or fecal bacteriotherapy are in use. Urine and feces together are called excreta.
Ecology
After an animal has digested eaten material, the remains of that material are discharged from its body as waste. Although it is lower in energy than the food from which it is derived, feces may retain a large amount of energy, often 50% of that of the original food.[8] This means that of all food eaten, a significant amount of energy remains for the decomposers of ecosystems.
Many organisms feed on feces, from bacteria to fungi to insects such as dung beetles, who can sense odors from long distances.[9] Some may specialize in feces, while others may eat other foods. Feces serve not only as a basic food, but also as a supplement to the usual diet of some animals. This process is known as coprophagia, and occurs in various animal species such as young elephants eating the feces of their mothers to gain essential gut flora, or by other animals such as dogs, rabbits, and monkeys.
Feces and urine, which reflect ultraviolet light, are important to raptors such as kestrels, who can see the near ultraviolet and thus find their prey by their middens and territorial markers.[10]
Seeds also may be found in feces. Animals who eat fruit are known as frugivores. An advantage for a plant in having fruit is that animals will eat the fruit and unknowingly disperse the seed in doing so. This mode of seed dispersal is highly successful, as seeds dispersed around the base of a plant are unlikely to succeed and often are subject to heavy predation. Provided the seed can withstand the pathway through the digestive system, it is not only likely to be far away from the parent plant, but is even provided with its own fertilizer.
Organisms that subsist on dead organic matter or detritus are known as detritivores, and play an important role in ecosystems by recycling organic matter back into a simpler form that plants and other autotrophs may absorb once again. This cycling of matter is known as the biogeochemical cycle. To maintain nutrients in soil it is therefore important that feces returns to the area from which they came, which is not always the case in human society where food may be transported from rural areas to urban populations and then feces disposed of into a river or sea.