Male dogs use pheromones in urine to mark their territory.
Pheromones are natural aphrodisiacs.
Male dogs use natural aphrodisiacs in urine to mark their territory.
What do male dogs use in urine to mark their territory?

Natural aphrodisiacs
competing for resources
Tails
Urine  cleaner
Something coming from a gland
Chemical energy
an area swollen with pus
Chew toys