Swollen vulva and vaginal bleeding are obvious signs that a dog is in heat. The dog parent has to buy some doggie diapers. These special diapers would be very necessary especially if the carpet is off white or the seats are covered with light colored materials. Bleeding while in heat can be rather messy. Fortunately, cat owners do not have to deal with this concern as cats don’t bleed when in heat.
Although non-bleeding during the estrus cycle is advantageous to the cat’s owners, some cat parents can’t help but wonder why. Cats, after all have the same reproductive system as other mammals. Cats, like dogs, have two oval shaped ovaries connected to the two long and thin fallopian tubes that are situated on either side of the uterus. The ovary releases the progesterone and the estrogen sex hormones. The uterine walls have vascular and glandular linings. The muscular substance is called myometrium and the inner lining is known as endometrium. In a process called ovulation, an egg will be released by one of the ovaries. The egg will travel through the fallopian tube to the uterus. Before ovulation, the hormone estrogen released by the ovaries will stimulate the uterus to prepare for the possible pregnancy. The uterus will thicken its walls by building up the lining with extra blood and tissues. If the egg was fertilized by a sperm it would attach to the uterus’ cushiony walls.
Cats do not bleed when in heat because these animals belong to the species where there is a significant difference in reproductive system functioning. In humans, in dogs and in other mammals, the endomitrium is shed in a process called menstruation if the egg released during the ovulation is not fertilized. The thickened lining of the uterus made up of blood and tissue as well as the unfertilized egg will be excreted out of the body through the vagina. This is what causes dogs to bleed when in heat. In some animals, the endomitrium will be reabsorbed if conception did not occur during the estrous cycle. As the blood and tissue that thickened the walls of the uterus are reabsorbed or soaked up by the uterine walls, no bleeding will occur. This specific condition occurs in cats.
Bleeding will not occur when cats are in heat because these animals are induced ovulators. A cat’s reproductive process is very interesting. A female cat would not ovulate if it is not mated or if manual stimulation does not take place. A female cat in heat would be receptive to the attention of a male cat. The female cat would take up the mating position – the tail is raised, the forelegs are bent and the hind legs are raised to expose the vulva to accommodate the entry of the male cat’s penis. The tom will bite the female cat at the scruff of the neck to ensure its cooperation. Scientists though believe that the biting is another way by which the female is stimulated to ovulate. A cat’s penis is barbed and withdrawal from the vagina will make the female cat scream. The barbs in the cat’s penis would stimulate the female cat to ovulate.
Cats are polyestrus animals. They can go into heat several times a year. A cat owner would then be thankful that the pet does not bleed when in heat. Otherwise, the owner would need to make the pet wear specialized diapers or face the task of cleaning the mess that results from the pet’s bloody discharge.