When a female dog reaches puberty, their reproductive cycle starts. In dogs, the official term is ‘oestrus’ but you will often hear it called being 'in season' or 'in heat'.
How long is a dog in season?
It usually lasts around two to three weeks. Your dog might not show signs that she is in season this whole time. However, she can become pregnant any time during a season and for a few days afterwards.
How often do dogs come into season?
If she's unneutered, most female dogs come into heat twice a year, but this can depend on her breed and size. Some dogs have have longer or shorter cycles and they should be regular by the time they're an adult.
When do dogs get their first season?
When dogs have their first season will depend on their breed, but the average is around six months old. Some smaller breeds can start earlier than larger breeds, and some larger breeds won't start until later (around 18 months old).
Most owners choose to neuter (or spay) their dog. This involves a vet removing both of your dog's ovaries, and usually the uterus. This means she will be unable to become pregnant and will no longer have seasons.
Signs a dog might be in season
You will know your female dog is in season when you see her vulva is swollen or she has a bloody vaginal discharge. You may also notice her urinating and cleaning that area more often than usual. However, some dogs do not show any obvious signs.
Her behaviour might also change, such as becoming more clingy, distant or stressed. She might also be more or less friendly with other dogs, or become defensive if another dog pays attention to her rear end. Or she might mount furniture, people or other dogs.
Male dogs in the home and out on walks will become very interested in your female dog during this time as her urine (wee) contains pheromones and hormones that let dogs know she is in season.
What to do if your dog is in season
You'll need to:
- avoid areas where she'll be approached by dogs off lead
- take her for walks at less busy times of day to avoid unwanted attention
- be prepared to keep her on a lead in public areas
- make sure any unneutered male dogs are separated from her if they live together (even if the dogs are related)
- avoid potentially stressful events, such as a staying in kennels, visits to busy places or neutering (unless it's an emergency)
- try to keep things consistent, predictable and safe for your dog
- monitor for any symptoms of complications during or after her seasons (eg pyometra or pseudopregnancy)