When it occurs in puppies, coprophagia is generally considered part of the process of exploring the world around them. Most will be satisfied with a sniff, but a few will want, like human children, to put everything in their mouths. One bizarre fact: Dogs will rarely eat soft, poorly formed stools or diarrhea. They appear to be attracted most to hard stools. Frozen ones, in particular, are gulped down with relish. There is a reason why dog owners have coined the term, "poopsicle."
In his study, Hart made some other observations about why dogs eat poop:
Coprophagia was more common in multi-dog households. In single-dog homes, only 20 percent of dogs had the habit, while in homes with three dogs, that rose to 33 percent.
Poop eaters are no harder to house train than any other dogs.
Females are more likely to eat poop, and intact males were least likely.
92 percent of poop eaters want fresh stuff, only one to two days old.
85 percent of poop eaters will not eat their own feces, only that of other dogs.
Greedy eaters—dogs who steal food off tables—tend to also be poop eaters.
In many cases, dogs start to eat their own poop because of some kind of environmental stress or behavioral triggers, including:
Isolation: Studies have shown that dogs who are kept alone in kennels or basements are more likely to eat poop than those dogs who live close to their people.
Restrictive confinement: Spending too much time confined in a small spaces can cause the problem. It's not unusual to see coprophagia in dogs rescued from crowded shelters.
Anxiety: often a result of a person using punishment or harsh methods during housetraining. According to this theory, dogs may eliminate and then eat their own poop to get rid of the evidence, but then they are punished more. It becomes a vicious cycle.
Attention-seeking: Dogs eat their own poop to get a reaction from their humans, which they inevitably will. So if you see your dog doing this, don't overreact.
Inappropriate association with real food: Dogs who are fed in close proximity to their feces may make a connection between the odors of food and those of poop and will be unable to tell the difference.
Scenting it on their mothers: Lindsay writes that in some cases, puppies will get confused by sniffing fecal odors on their mother's breath after she has cleaned them. Also, sometimes mothers may regurgitate food that is mixed with puppy fecal matter. He calls this an "appetitive inoculation," which may set a puppy up to develop this bad habit.
Living with a sick or elderly dog: Sometimes a healthy dog will consume stools from a weaker canine member of the household, especially in cases of fecal incontinence. Scientists hypothesize that this may be related to the instinct to protect the pack from predators.