dog season



The reproductive biology of female dogs is quite different to female humans. Dogs are only sexually receptive once or twice a year. The most common time between ‘seasons’ is 7 months, but some individuals have shorter or longer intervals. Dogs can have their first season from 6-18 months of age.

Dogs are not ready to mate when their season starts, which allows owners to plan mating, or plan on how to prevent mating! When your dog is in season you must avoid exercising her where there may be male dogs off lead and she should never be left unsupervised. If your dog is mated accidentally, call your vet for advice.


Your dog may show changes in behaviour before her season. She may become clingy or aloof, more friendly with other dogs or less tolerant of them. Other dogs might start to show more interest in her.

The first day of her season is when you first see a pink or red discharge at the vulva. The vulva then swells significantly. Some bitches show abdominal discomfort in the first week of their season.

After 7-10 days the discharge becomes more straw coloured and the vulva less swollen. This is when your dog is approaching her fertile period. Mating at this point usually results in pregnancy because healthy dog sperm can survive up to 7 days in the female.

After 3-4 weeks your dogs will no longer be of interest to males and her vulva will reduce in size. If it is her first season her vulva will not return to its prepubertal size.


Dates and Behaviour

Most dogs will conceive if mated between day 10 and 14 from the first day of their season. If she allows the dog to mate she is probably in her fertile window. Experienced stud dogs will also show less interest in a female dog if she is not around ovulation.

However, using these methods gives little indication of when puppies will be born. Pregnancy, if counted from mating, can appear to be as short as 58 days or as long as 69 days.

Ovulation Prediction

A test that can predict when a dog ovulates gives the breeder more information on when to mate the dog, but also when to expect puppies. The eggs are not ready to be fertilised until 2 days after ovulation and stay ready for up to 48hours. Dogs are pregnant for 63 days from ovulation (plus or minus one day).

Ovulation tests offered to breeders include blood progesterone testing, vaginal cytology, ovulation pads, and ferning.

Vaginal cytology can be accurate if it is performed by an experience person and repeated every 2 days from the start of the season until after mating.

Progesterone testing requires a blood sample to be taken by a vet (fertility clinics can run tests but only vets can take blood by law). The most accurate results are gained by testeing every 2 days from day 8 or 9 of the season until ovulation occurs. Single tests can be difficult to interpret in some cases.

Saliva ferning gives an indication of oestrogen levels but is not accurate enough on its own.

Other tests such as ovulation pads, vaginal pH, and electric conductivity are not scientifically validated and should be avoided.

Puppy Prediction

Puppies should arrive 62-64 days after ovulation, regardless of mating date. Large litters tend to arrive early, and small litters slightly later. If puppies have not arrive by day 65 from ovulation seek veterinary advice.

If the date of ovulation is unknown and a breeder is worried the puppies are late, or where a caesarian may be needed because there is only one big puppy, progesterone tests can be used to predict when it is safe to remove the puppies.

Progesterone drops sharply just before birth so progesterone is low the puppies need to be delivered. If it is still high the puppies can stay inside a bit longer. In very rare cases the drop doesn’t happen which is why knowing the true due date is so important.


Chosing to breed a litter of puppies should not be done lightly. Breeding and raising puppies correctly is expensive, time consuming, and it can be both a joyful time and a time of heartbreak. Speak to your vet and to experienced mentors before deciding to breed your dog.