No one really knows for sure why dogs love to roll in stinky things, but people who study animal behavior have some pretty good idea. Some experts believe that dogs like to mark themselves with their territory. A dog wearing a bit of woodchuck carcass or horse poop on his neck and shoulders is a lot like a man wearing a big gold chain around his neck. It says something about him and where he lives, something like, ‘I am a dog of means; I own the territory with all this nice stuff.
It is hard for people to understand how anyone, even a dog, could rate the value of his territory according to its riches of cow pies. This is one of those situations that illustrates how completely different dogs and people are. People appreciate things that are clean and fresh, while dogs like things that are old and smelly.
There may be a good reason for their off-putting tastes. Since the beginning of their existence, dogs have spent their lives scrounging for food. It is possible that even the hint of a good meal triggers a sense of elation. Out of necessity, they may have developed a unique appreciation for anything that is remotely edible. A week-old carcass certainly qualifies. So does a fish washed up on shore. Even the presence of deer or cow dung suggests that there is a potential meal somewhere in the neighborhood.
Then again, there may be a simpler reason why dogs enjoy coating themselves with horrid things, one that has nothing to do with survival and everything to do with taste. Other experts believe that they roll in dung, carcasses, and pond scum simply because they like the smell. Not just a little, but enough to want to carry it around with them, just as people enjoy dabbing themselves with their favorite perfume or cologne.
Smell is a primal sense and it is hard to account for who likes what. Just as some people enjoy the smell of cheese, dogs may revel in smells that most of us find objectionable. It is hard to criticize their tastes, because they have millions more scent receptors than we do. Our own senses of smell are barely functional compared to theirs. Therefore, It is possible that they detect pleasing odors of which people are completely unaware of .