The first heat cycle in dogs usually occurs between the ages of six and ten months, however this varies from dog to dog. Small dog breeds, according to veterinarian Margaret V. Root Kustritz in her book The Dog Breeder’s Guide to Successful Breeding and Health Management, have an earlier heat cycle than huge or giant dog breeds.
The 4 Phases of the Canine Heat Cycle
The heat cycle of a dog is divided into four stages: pro-estrus, estrus, diestrus, and anaestrus. You can identify if your dog is approaching the estrus cycle and when you should take extra precautions by becoming familiar with these phases.
Physical changes occur during proestrus in preparation for ovulation. This period lasts an average of nine days, although it can last up to seventeen days. Swelling and firming of the vulva, as well as the exudation of a bloody discharge, are physical indications of pro-estrus.
At this stage of heat, male dogs are already showing interest in female dogs. They will analyze the female’s urine and be drawn to her by her pheromone production. According to Margaret V. Root Kustritz, some males may urinate over the urine generated by a dam in heat to mask the smell from any possible competing males. In general, a female in proestrus will accept the presence of males and their examinations, but she will not allow mounting at this time.
2. The menstrual cycle
Because your dog will eventually allow mounting during this period, it is also known as “standing heat.” This stage usually lasts nine days on average, but no generalizations can be established. The vulva will appear mushy at this time, and the crimson exudation will be replaced by a straw-colored discharge. When stimulated, she may indulge in “flagging,” which is the act of tugging the tail to the side.
If she is with a male, a female in heat may engage in solicitation behavior such as licking the male, displaying the rump and then running away, playful mounting, and more. Females are at their most fertile during this time, therefore dog owners must exercise extreme caution in keeping them contained.
During this period, the female dog usually loses interest in the male, however the male may stay around for a while. In most other species, the production of progesterone secretions stops if the animal is not pregnant.
However, regardless of pregnancy, progesterone emissions remain for additional 60 days in dogs, making it difficult to detect early pregnancy. During this period, the female’s estrus symptoms usually fade away, and she can return to her normal routine.
This is a period of inactivity in the reproductive system during which the reproductive organs ultimately rest. While this phase, which lasts between 100 and 150 days, appears to be inert, the pituitary gland and ovaries of the dog are already preparing for the next heat cycle. During this time, male canines should be uninterested in females.