How do male dogs know when females are in heat?

Answer by  Gabriel (2146)

Its all about the pheromones. When the female goes into heat, her body starts to smell differently to other dogs. The males react and nature takes it course. It occurs during ovulation.

Answer by  worker6721 (49)

when female dogs are in heat, their hormones spur their bodily glands to release a chemical called pherimone that male dogs can smell and detect with their own hormones.

Answer by  CarolynOsborne (2804)

Dogs in heat emit a different set of hormones and therefore scents than dogs that are not in heat. Since dogs' noses are enormously more sensitive than those of humans, male dogs can detect these scents very easily. As a matter of fact, they seem to be able to detect these from pretty far away.