What’s up with the leg?
The classic dog urination position for dogs is with one leg held up in the air. That position can mostly be seen performed by male dogs rather than female ones. Apparently, the leg in the air is not necessary for a dog to be able to pee.
The reason for the frequent use of the position lies in the way dogs communicate with each other. Originated from wolves, dogs are genetically built to live in a pack, which requires sending and receiving signals and messages from one another. Pack animals mark their packs’ territories with urine, letting other animals know who rules that specific area. When a dog lifts a leg, it can direct its urine a little higher so it’s the same hight as another dog’s nose. This way, other dogs can more easily detect the pheromones in the urine and know whose territory they are approaching.
What about the females?
Female dogs might also lift their legs when they pee, but marking territory is not the only reason why they do that. When a female dog is ready to have a puppy, male dogs will know about it through the pheromones in her urine. Lifting a leg and pointing the pee higher would help female dogs with finding a proper father for their puppies. Spayed females will often stop lifting their legs to pee after going through the procedure.
Apart from reproduction and territory marking, leg-lifting is also a way to communicate dominance. Submissive dogs will probably lift their legs less than dominant ones. Just like they used to do in their ancestral wolfpack! Also, older dogs tend to have joint problems. This makes it hard for them to lift a leg, making them squat whenever they need to use the doggie-loo, just like females.