Though it may be unsettling to humans, the act of eating feces — or coprophagia — is a common behavior among dogs. But why do dogs eat poop?
In some cases, coprophagia is the result of a health condition that alters a dog's appetite, such as diabetes, Cushing's syndrome or hyperthyroidism.
It could also arise due to nutrient deficiencies.
For example, a 1981 study in the American Journal of Veterinary Research found that dogs develop coprophagia if they're fed a diet that's deficient in thiamine (vitamin B1). But such deficiencies are unlikely to occur very often under normal, nonlaboratory circumstances.
Other studies have shown that chronic pancreatic deficiency, malabsorption syndrome (when nutrients aren't absorbed properly) and starvation can lead to canine coprophagia. In these cases, a large amount of undigested food may wind up in the stool — a dog may eat its own feces because of the enhanced nutritional value in its stool and its increased appetite from malabsorption.
However, these diseases must be in their advanced stages before a dog will resort to coprophagia, according to a 1988 article in the Canadian Veterinary Journal.
Most of the time, dogs with coprophagia are well nourished and don't appear to have any underlying health issues. The exact reason why these healthy canines develop a taste for poop is unclear.
One hypothesis states that coprophagia is a normal scavenging behavior — a holdover from dogs' evolutionary history.
Another possible explanation proposes that coprophagia is a behavior learned during puppyhood. A mother dog licks her pups' genital and anal areas to stimulate urination and defecation, and then consumes the excrement to keep the den clean.
Some pups learn this behavior from their mothers or siblings, but most of them stop doing it by the time they're weaned. Those that carry on the behavior into adulthood may have acquired a taste for feces.
Alternatively, it may be that dogs eat feces out of boredom, to get attention or because they're anxious.
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