The four stages of a female dog's heat cycle, explained

When we talk about the canine “season cycle", we’re not talking about the weather. We’re talking about the female reproductive cycle, also known as the “oestrous cycle” or the “heat cycle”.

Knowing the ins and outs of your dog’s season cycle can help you prevent an unwanted pregnancy and understand why they may be acting a bit odd.

There are four phases, by the way: Proestrus, Oestrus, Doiestrus, and Anoestrus. We discuss what these science-y terms mean below.

Key takeaways - heat stages in dogs

• A dog's heat cycle lasts roughly six months, but they're only in season for two to four weeks during this time.

• Dogs usually have two seasons a year.

• Small breed dogs can get their first season at roughly six months, but bigger breeds can take longer to reach maturity. For example, giant breeds can take two years.

• Phases of dog heat can vary depending on a dog's breed and size.

At a glance - the stages of a female dog's heat cycle

What the four stages mean

1. Proestrus (the prologue) - days one to nine

Proestrus is when a female dog’s body starts to prepare for the possibility of pregnancy. Hormone levels begin to shift, and her ovaries start to mature eggs. You'll likely notice some physical signs, too, like bleeding.

As with menstruation in humans, this is a natural bodily process and nothing to be alarmed about. Don’t be surprised to see male dogs in the vicinity starting to gather around her, though she won’t be willing to mate during this phase.

You'll likely notice behavioural changes, too. She may become more clingy or affectionate with you or she might become a tad more irritable or anxious. Each dog is different, and these shifts can vary widely.

The timeline of proestrus varies from dog to dog. While some might breeze through it in a swift three days, others could stretch it out for as long as 17 days. But the majority of dogs average around nine days.

It’s a good idea to keep an eye on your dog’s diet and exercise during proestrus. Hormonal changes can affect her appetite and energy levels; some dogs may eat less or seem less interested in physical activity, while others may exhibit the opposite behaviour.

2. Oestrus (fertile territory) - days 5-15

Oestrus, not to be confused with “eostrous” in “eostrous cycle”, is the centrepiece of the canine reproductive cycle, when your dog is fertile and capable of conceiving puppies.

Oestrus can last anywhere from three to 21 days, though about a week is usual.

During oestrus, your dog’s oestrogen levels drop, and her progesterone levels begin to rise. These hormonal changes prepare her body for possible pregnancy. While you won't be able to see these internal adjustments, they profoundly influence her receptiveness to male dogs and her overall behaviour.

Not surprisingly, your pup’s behaviour toward male dogs may seem more playful or affectionate during oestrus. If puppies aren't in your plans, now’s the time to be extra vigilant. Keep her on a lead during walks, and carefully supervise any interaction with male dogs.

Nutrition is also crucial during this period. Since your dog’s body is going through a lot, you'll want to make sure she's eating a balanced diet rich in the nutrients she needs. Again, don't be surprised if her appetite changes: hormonal fluctuations can do that. Keep her well fed, but avoid overfeeding; excessive weight can lead to complications, whether she becomes pregnant or not.

Finally, remember to exercise her. While you may have to adjust your walking routes or avoid the dog park to prevent unwanted attention, she still needs her daily dose of physical activity.

3. Dioestrus (calming down) - days 60–90

Think of this as the cool-down phase after oestrus.

Dioestrus can last anywhere from two to three months. Hormone levels will taper off and eventually return to their baseline. If you've been on high alert during oestrus to avoid an unwanted pregnancy, you can finally let your guard down a bit.

Now here's the peculiar part: Whether or not your dog has mated and become pregnant, her body essentially behaves as if she's expecting. No matter what, she'll be producing hormones like progesterone to support a possible pregnancy. This hormonal shift can result in some fascinating and, at times, confusing behaviours.

For instance, you might notice your dog engaging in phantom pregnancy symptoms. These can range from mild nesting behaviour to more advanced symptoms like milk production. If your dog is struggling with their symptoms your vet can prescribe medication to help with this.

Dioestrus is also an important time for bodily healing. You should notice any bleeding or discharge start to disappear, and your pup’s mood and energy levels will start to normalise.

As always, maintain a balanced diet and exercise. This is especially important if your dog has mated and there’s a chance she’s become pregnant.

4. Anoestrus (time off) - until next season

So you've weathered the storms of proestrus, oestrus, and dioestrus. Say hello to anoestrus, the dormant phase of your dog's reproductive cycle.

Anoestrus lasts around four to five months, offering a breather for both you and your pup. No more male admirers lurking around, and no more watching your dog like a hawk during walks.

Oestrogen and progesterone levels will have both normalised at this point and your dog will likely be less prone to mood swings or irritability. This is a fantastic time to focus on your pup’s general well-being.

Even If your dog became a fussy eater during earlier phases in her heat cycle, she may get back to her regular eating habits during anoestrus.

With hormones at a steady level, it's also a good time to schedule any elective surgeries or procedures, like spaying. The risks associated with these surgeries can often decrease during anoestrus.

Remember: a balanced diet is essential year-round, not just during the reproductive phases. Physical activity should also remain consistent.

Dog seasons: how long does it last?

So, as you can see above, the actual heat cycle lasts months. But what about the bit that's the most worrying part for many pet parents: your dog's season?

A dog's season will typically last between two and four weeks, though it can last longer in rare cases.

How many seasons does a dog have a year?

A dog usually has a season twice a year (every six months). But the number of seasons can vary depending on a dog's breed and size.

For example, some dogs may cycle every four months and others every eight months. Once your dog reaches adulthood her cycles should be regular, although it’s not always possible to predict the exact day when her season will start.

When do puppies have their first season?

Small breed dogs typically have their first season at around six months, but bigger breeds, like Great Danes, can be eighteen months or older.

Puppy in season symptoms can be split between behavioural and physical changes:

Behaviour

• Attracting males: Male dogs show a high interest in her.

• Mood shifts: She may become very clingy, nervous, restless, or grumpy.

• Mounting: She might hump toys, furniture, or other pets.

• Nesting: She gathers toys and bedding into her sleeping spot

• Tail flagging: She moves her tail to one side if touched or near male dogs.

Physical changes

• Frequent licking: The puppy cleans her back end much more than usual.

• More weeing: She needs to urinate more often to spread scent markers.

• Swollen teats: Her nipples may grow a little larger.

• Swollen vulva: The outer genital area becomes large and prominent.

• Vaginal discharge: Red, pink, yellow, or bloody fluid leaks from the area.

Handling unplanned and planned pregnancies in dogs

Breeding your dog should always be a well-thought-out process, not an accident. Nonetheless, accidents do happen. Give your vet a call to discuss options if your dog is accidentally mated, as you don’t have to proceed with the pregnancy.

If you decide to go ahead, or if the pregnancy is planned, and your fur baby is expecting some fur babies of her own, it’s time to take some important steps.

Start by taking your expectant dog mum to the vet. They'll offer personalised advice and help you make sure your dog is healthy and ready for motherhood. Meanwhile, provide your dog a balanced diet , the correct anti-parasite treatment, and just the right amount of exercise so both she and her future puppies are in tip-top shape.

As the due date approaches, make a cosy space for the big arrival. And be sure to schedule postpartum check-ups for the proud mom and her new puppies.

If you’re not planning on expanding your fur family permanently, you have some options:

• Adoption: The classic choice. There are many loving homes out there, just looking to adopt a puppy. If you go this route, socialise the puppies well and make sure they're up-to-date on their vaccines and vet checkups before they go to their new homes.

• Friends and family: Sometimes the perfect home is closer than you think. Your extended network might just contain the perfect pet parents, saving you the search.

• Rescue organisations: You can try approaching rehoming centres or charities such as the Dog's Trust or Blue Cross who may be able to help. You can also find rescue centres via the Association of Cats and Dogs Homes.

Should you spay your dog?

Choosing whether or not to spay a female dog is ultimately a personal decision.

In terms of safety, the main thing to keep in mind is to NEVER spay during active heat (the Oestrus stage). This can increase the risk of surgical complications, and most vets will avoid this time.

If you’re planning to breed your dog, the decision is a pretty simple one. But if you’re not, you should seriously consider it. The vast majority of vets recommend it, though the right time to do it may vary by breed.

Spaying carries a number of health benefits for female dogs, including a reduced risk of mammary, uterine, and ovarian cancers, as well as eliminating the risk of the life-threatening uterine infection pyometra. One study found that spayed dogs live about 26% longer than dogs who aren’t spayed.

Worried about your dog changing after a spay? Many of these could be positive. When you eliminate the intense hormonal fluctuations caused by your dog’s heat cycle, you’re also likely to eliminate some unwanted behaviours. In some cases, paying your dog can reduce things like marking, howling, excessive barking, or even running away in search of a mate.

Finally, keep in mind that rescue organisations only have so much space and can be under a lot of pressure. If you can avoid adding to that pressure through responsible pet parenting, it can only be a good thing.

When shouldn't a dog be spayed?

• While in heat (season): A dog shouldn’t be spayed when they’re in season, so during the Proestrus or Oestrus stage. Aonestrus is the safest stage. Hormonal changes like this make blood vessels larger, which increases surgical risk.

• Too early in puppyhood: A vet will never perform surgery before three months of age as it causes complications.

• During illness: Dogs who are unwell or have weight issues (under or over) shouldn’t be spayed.

Frequently asked questions

Do dogs go through menopause?

No, dogs never go through menopause. But you may notice that their seasons get less frequent as they age.

When’s the safest time to spay a dog after her heat cycle?

It’s safest during the mid-Anoestrus stage, which is two to three months after her season completely ends.

How do I know when my dog's heat cycle is fully over?

You’ll know when the cycle is fully over once all vaginal discharge stops and she no longer accepts male dogs. It’s usually three to four weeks from the start of her bleeding.

Do male dogs go into heat?

No. They’re fertile year-around once they reach sexual maturity (around six months of age onwards).

Can my dog get pregnant on her first day of bleeding?

It’s very unlikely, but not impossible.

What are the warning signs of Pyometra after a heat cycle?

Warning signs include:

• Foul-smelling discharge

• Loss of appetite

• Increased thirst and peeing

• Severe lethargy

• Swollen abdomen