Canine conspecific coprophagy, the tendency or predisposition of some dogs to eat their own faeces or those of other dogs, seems paradoxical because dogs typically show an aversion to conspecific faeces. In an attempt to resolve this paradox, we set out to determine the factors associated with the occurrence of this behaviour and to evaluate the efficacy of 11 products marketed for treating coprophagy as well as behaviour modification procedures. Because a large sample of dogs was needed to address these issues, two web-based surveys were utilized. One, intended to compare coprophagic dogs and non-coprophagic dogs, yielded 1552 returns. The other, yielding 1475 usable returns, specifically recruited owners of coprophagic dogs to gather information about the characteristics of coprophagy and treatment success. The findings revealed that 16% of dogs sampled engaged in frequent conspecific coprophagy, defined as having been seen eating stools at least six times. No evidence was found relating the coprophagy to diet or the dog's age. Coprophagic dogs were as easily house trained as non-coprophagic dogs, suggesting a normal aversion to faeces. Coprophagic dogs were more likely to be reported as greedy eaters than non-coprophagic dogs. The reported success rate of the commercial products and behaviour modification approaches was close to zero, indicating that the behaviour is not readily changed. The coprophagy was overwhelmingly directed at fresh stools, defined as being no more than 2 days old. A hypothesis is offered that coprophagy reflects a tendency inherited from the ancestral wolf to keep the den area free of faecal-borne intestinal parasites that might be deposited in the den resting area and would typically have parasite ova that are not initially infective, but could develop infective larvae after 2 days. An evolved parasite defence strategy to consume fresh faeces in the rest area would be adaptive.