The cliche understanding is that dogs mark their territory with pee. At times I’ve been on walks with family and friends with half a dozen dogs. There have been occasions where they form a line just to pee in the same spot.
So how does the ownership work? Is it like a co-op? Last one to pee wins?
It’s not really ownership, per se. It’s really more like planting a flag to say “I was here”. They’re leaving their scent behind to let other outsider dogs know that they are around the area, like a calling card. Sometimes the pheromones in the urine can let other dogs know if they are in estrus, so it has a useful social/mating component to it.