When we walk in the wild, we often see this situation: dogs see something like a tree trunk or a utility pole and like to sniff around, then they lift one hind leg and urinate on the tree trunk.

　　Why is that? It turns out they are marking their "territory"! There is their own scent in the dog’s urine, called scent hormones. Dogs use the smell of this scent hormone to mark their area of influence.

　　Children probably all like snow, right? After snowfalls they can have snowball fights and build snowmen. Actually, dogs also become unusually active after snow; they run around in the snow and urinate everywhere.

　　Do dogs like to play in the snow? Not exactly. It turns out that snow can cover the dog urine and eliminate the dog’s scent. Once it snows, the territory boundaries marked by urine disappear, which means their territory may be taken over by others of the same species. Therefore, after every snowfall, they have to work hard to re-establish their territory.

　　The concentration of scent hormones is generally only one in several million, and only members of the same species can detect it by smell. Not only dogs have scent hormones, but other animals do as well.