Finding out your dog eats poop is one of the most disgusting discoveries a dog owner can make, and most owners can't look at their dog in the same light, or let their dog lick their face, after seeing them snacking on a turd.
Some studies say dogs eat poop out of boredom, others say dogs who have an enzyme deficiency, pancreatic sufficiency or parasites are more likely to be a poop eater, but a new study shows there more be a more ancient reason:
Since their poop has a high chance of containing intestinal parasites, wolves poop far from their dens. But if a sick wolf doesn't quite make it out of the den in time, they might do their business too close to home. A healthier wolf might eat this poop, but the parasite eggs wouldn't have hatched within the first day or two of the feces being dropped. Thus, the healthy wolf would carry the risk of infection away from the den, depositing the eggs they had consumed away in their own, subsequent bowel movements at an appropriate distance before the eggs had the chance to hatch into larvae and transmit the parasite to the pack.
Domestic dogs may just be enacting this behavior instinctively—only for them, there isn't as much danger of them picking up a parasite at home.