You have email; your dog has p-mail. He can read reams of information by smelling an invisible dried splash on a fire hydrant or a desiccated lump in a clump of grass. The world is an ever-changing canine community bulletin board, and it keeps his walks interesting. Let him sniff.
It's not that your dog sniffs just at potty time; it may be that potty time is the only time he's outside to sniff. Maybe he's looking for a clean spot, or even an especially dirty one. If you let him, he'll sniff all the time to find out who's been here, how many, how old, what's been on the menu, breeding condition -- your dog can glean "data" such as these and more by sniffing what other dogs have left behind. Once he has gathered the information, he leaves his own comments by making a deposit near or on top of the old news. He does that in his own yard to fend off trespassers or even in the house to establish dominance. In neutral territory he's advertising his presence and making social contact.
Love -- or at least sex -- is precisely the sort of social contact an intact dog has in mind. A bitch in heat secretes powerful pheromones in her urine that create the olfactory equivalent of flashing neon signs everywhere she "goes" -- and she will go frequently. If she's looking for love in all the wrong places, keep her on home territory and on a leash or you'll be followed by a comet tail of suitors and serenaded every night she's specially fragrant.
Sometimes dogs sniff to look casual and nonthreatening in the presence of a tense or aggressive dog, according to author and certified professional trainer Jolanta Benal. This behavior is a suggestion from one dog to a tense-postured one, "Hey, I'm cool. Don't mind me, I'm just sniffin'. See? Don't want no trouble, man. Be serene."
Smells that disgust us can be entrancing to a dog; some that we enjoy, they find offensive. Citrus is an attractive aroma to humans, for instance, but dogs tend to shy away from it. If your dog gets into your houseplants or flowerbeds, try spreading lemon, lime, orange or grapefruit rinds on the soil and see if he backs off. The citronella essence we spray to repel mosquitoes will often do the same for dogs. The pungency of red pepper also can be discouraging.
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