When a female dog is in heat, she releases a pheromone called Methyl p-hydroxybenzoate that has shown to sexually arouse male dogs that pick up that scent. That's by design, of course — but it can stir up a lot of chaos for you and your canine companion. If an intact male dog catches the scent of a nearby female in heat, she will become his entire focus. Male dogs may stop eating, increase their marking, become increasingly aggressive and obsess over tracking down the female dog in heat throughout the duration of her cycle.