The human menstruation cycle occurs monthly but for canines it occurs twice a year usually in the spring and autumn and lasts for around three weeks. During this time the bitch becomes pregnant if she copulates with a dog.
Author’s note: For the purposes of this article we will use the generic ‘dog’ to signify ‘bitch’.
Your dog’s first period of oestrus can happen at any stage in the first year of her life. Its timing is determined by her breed and size; small dogs tend to menstruate at a younger age than big dogs.
A dog’s oestrus can be a messy affair but it could equally pass without you even knowing, especially if you do not know what to look for.
Four stages of the canine oestrus cycle:
Your dog’s appetite increases and she becomes more tolerant of male dogs. There may be moments of listlessness and nervousness. An increasing volume of oestrogen in your dog’s blood causes an oedema (swelling) of the vulvar lips. You may notice some bloody discharge from the vulva.
The pinnacle of her cycle lasts for about 6 - 11 days. Should you dog copulate during oestrus she will more than likely fall pregnant. She may exhibit flagging, which is when she raises her tail and holds it to one side.
This stage sees the preparation of the structures of her uterus for pregnancy. However, if your dog has not copulated during her oestrus ‘period’ these quickly degenerate.
Here is a stage of relative inactivity of your dog’s reproductive organs. Her uterus and ovaries return to a normal state. Anoestrus can last for between 60 and 200 days. Following anoestrus the cycle begins again.
How do I know if my dog is ‘in heat’?
The longer time you take to get to know your dog the more chance you have of noticing the changes which take place at each stage of her oestrus cycle. One of the most obvious pointers to her being 'in heat' is her behaviour around male dogs.
Here are some of the other common symptoms of the dog ‘period’:
Behaviour changes: She may become agitated, clingy or exhibit nesting behaviour. She may also be intolerant to heat.
Vulvar swelling and shape changes: The vulva becomes enlarged during pro-oestrus but softens and wrinkles during oestrus.
Bleeding and discharge: A bloody discharge from a dog is usually the first sign of being in heat. Discharge consistency and colour varies during the cycle; it can range from bloody to straw-coloured and can be heavy, light or non-existent.
Hygiene: Your dog will want to keep her genitals clean, and will do so by licking them. However, some dogs are physically incapable of reaching their hind quarters.
Excessive urinating: Frequent urination is your dog's way to let other dogs know she is in heat. It is an instinctive behaviour and should not be discouraged.
Pyometra is an infection of an unaltered dog’s womb. It can be potentially life-threatening and if diagnosed requires urgent surgery. The infection can be caused either by hormone changes or contamination of the dog’s womb by E. coli, or both. The symptoms of a pyometric infection follow.
- Season lasts longer than usual
- Your dog seems unwell and does not eat
- Your dog drinks far more than she usually does
- Your dog’s belly is swollen, and she begins to vomit
Pyometra develops four to six weeks from the completion of her oestrus cycle. The only cure for an advanced pyometra is the removal of the dog’s uterus and ovaries.
How to look after your dog when she is on heat
If you are aware of what to look out for throughout your dog’s menstrual cycle, you are well-placed to help her through any problems she may encounter.
Here is a list of advisories for owners of unaltered bitches:
Do not leave her alone outdoors when she is in oestrus. Male dogs will become aggressive and make determined efforts to reach her.
During your dog's ‘period’, have her confined to a room that can be easily cleaned and restrict her access to rooms with carpets and rugs. Oestrus can last up to 24 days so make sure she is comfortable and happy during that time.
If you have her confined to a crate let her out to exercise and interact with the family as much as possible. Oestrus does not warrant a strict quarantine.
Her behaviour towards other animals may seem aggressive and domineering; she may even behave in the same fashion around you. This is caused by the fluctuation of hormones in her body.
Importantly, through your dog's period be tolerant of her and do not berate her. It's a tough time for a dog and she will need a good deal of support and patience. If you do not intend to let your dog breed, you should consider having her spayed. Spaying completely eliminates the behaviours and unpleasant physical symptoms of oestrus but it is also thought to protect your dog from some cancers.