Your dog's behavior can be interesting, complicated, endearing and surprising. It can also be somewhat repugnant – especially the habit of eating feces. Although not the favorite topic of dog owners, stool eating, or coprophagia, is a universal canine behavior.
At some point in a dog's life he's likely to sample the feces of cats, hoofed animals, (notably horses and deer), rabbits, and other dogs. He may even indulge in eating his own stool.
Why would your dog be compelled to engage in such a revolting habit? Because he's driven by the forces of nature. Coprophagia happens to be a normal behavior for dogs and has evolutionary underpinnings. Back in the days when our dogs' ancestors lived in cramped dens the living space quickly became soiled with waste from puppies – an ideal environment for transmission of parasites and other disease carriers. The mother and other adults ingested stool to keep the den clean. From this we know that dogs, in a primitive sense, are "programmed" to seek and eat stool in some situations.
For a different reason, as an omnivore, your dog may also be attracted to the stool of deer, horses, rabbits and other animals for the nutrients and vegetable matter they contain. Of course, these nutrients are adequately supplied by commercial dog foods and are no longer needed from other sources, particularly one so disgusting. But, your dog may not be interested in such nutritional trivia, especially while running through fields in search of bounty.
Evolutionary behavior notwithstanding, however, it's still upsetting when your own cocker spaniel sweeps the yard in search of "snacks." Equally annoying is a raid on the cat's litter box. As many of us who live with both dogs and cats can attest, cat stool seems particularly attractive to dogs for some unknown reason.
Eating feces can develop into a problem when it becomes habitual. The behavior is most commonly observed in puppies and juvenile dogs, and is often associated with the dog spending long periods of time alone with little stimulation. Coprophagia is especially likely in caged puppies (such as those in pet stores), puppies or dogs kept in crates for long periods, and in dogs that spend long days in a fenced yard. The problem is often resolved when dogs are properly supervised.
Prevention is the Best Medicine
What can you do about this less-than-desirable habit? The most effective remedy is prevention. Your dog is less likely to ingest feces if you supervise him more closely. Use a leash when walking him and clean feces from the yard (or litter box) daily. If your dog spends a great number of hours outdoors and the stool eating is troublesome, consider keeping him indoors when he is alone.
If you prefer to correct the behavior, there are a few options. Unfortunately, most commercial remedies are ineffective. These typically involve adding some substance to your dog's diet (for dogs that eat their own stool) to make the stool taste strange. Some "home remedies" include sprinkling meat tenderizer or crushed breath mints on the food. Alternatively, you can try "doctoring" the dog's feces with a spicy hot sauce in hopes of rendering the stool aversive. This solution requires the dog to sample the stool for it to be effective and it is less practical than simple avoidance.
In addition, you can try leaving your dog's feces in the yard and covering them with a nontoxic chemical but this is unlikely to fool your dog. He is likely to avoid the trap, but not necessarily to learn a lesson. Should your dog's chosen smorgasbord be the litter box, you can effectively restrict access to the room that it is in by installing a hook-and-eye mechanism on the door and propping it just wide enough so the cat (but not the dog) can come and go freely.
In most cases, one or other of these efforts will probably help resolve the problem. But if your dog's habit persists in spite of your efforts, or if it seems compulsive in any way, consult your veterinarian for evaluation of your dog's health and for help with a behavior modification plan.