Keep ‘Em Separated: Synopsis to a Dog’s Heat Cycle

On April Fool’s, Athena started her second heat. Let’s get down to the nitty gritty and talk about dog heat cycles and the difficulties of keeping intact dogs apart.

A dog’s heat cycle is characterized by three distinctive phases. The first sign of her heat is the swelling and licking of her vulva. It is at this point that her heat has begun. She is in the proestrus stage and soon begins to bleed. This will make her interesting to other dogs, but typically she will not be receptive, and no mating will occur. Thorin starts to show some level of interest in Athena. He licks and nibbles on her ears, is more interested in smelling her, covering her pee, and may even hump her. Athena combats his advances and they can be together with supervision. Athena wears a diaper in the house, and typically becomes a bit clingier and eats a little less. This stage lasts about a week, until there is a spike in her estrogen and luteinizing hormones which marks the approach of ovulation.

Once this has occurred, she has entered the estrus stage of her heat and soon ovulates. Vulvar discharge changes from blood to a yellow or pink colored fluid and she becomes receptive to a male’s interest and will flag them. She will allow them to mount (called standing heat) and pregnancy is possible; though some females can become aggressive during their heat! Males near her are now in a breeding frenzy and will constantly whine and try to get to her. At this point intact dogs must be kept separated. It would be best to send one of the dogs to another location – either a trusted friend’s house, or day care facility. Males around a female in estrus are exceptionally stressed – shaking, not eating, constantly whining, and inconsolable.

Unfortunately, Thorin and Athena are a bonded pair and become even more intolerable if they are not able to see each other. We had tried keeping them in crates, in separate rooms, on separate floors of the house, but this meant constant howling from the two of them. Thorin can, fortunately, be contained in an impact crate and is kept in a far end of a room where he can just barely see Athena’s crate when we are away. Windows are kept open to allow fresh air, we use automatic air freshener cans to hopefully mask some of her scent, and have cameras set up to check on them when we are at work. We are extremely fortunate that this separation method works for us – there are plenty of stories of dogs escaping crates, destroying rooms, and mating through crates. Thorin isn’t interested in anything except Athena for this week, and it is a very stressful time for him. Even when out walking him, he constantly checks behind us and whines to go back home. The dogs absolutely cannot be allowed any sort of open contact with one another, else puppies show up in two months. It is a grueling task to keep two intact dogs separated during estrus. This phase can’t end soon enough, and poor Thorin suffers the most.

After her ovulation and breeding window has passed, she will no longer stand for males  - Thorin and Athena can finally be together again! She enters diestrus where she has one last hormonal peak for progesterone. This stage can last up to two months and ends with her vulva returning to normal. At the end of this stage, Athena exhibits some nesting behavior. She collects any stuffed toys around the house, brings them to her favorite dog bed, and cuddles with them. She typically whines some and acts needier for attention and love. These false pregnancy symptoms last around a week for us but does not occur in all dogs. If the dog was bred during estrus, she would whelp at this point.

In general, the frequency of heat cycles can be related to a dog’s size. Smaller dogs have more frequent heats, and giant breeds may only have one heat a year. Athena (thus far) cycles every six months. This tends to be the most common timing for tams. However, some cycle every four months, and some just once a year. The technical term for their off cycle (the time in between heats) is anestrus. 

Of course, all dogs are individuals and will exhibit unique signs and symptoms during their heat. Similarly, the length of time spent in each stage can widely vary. We recommend keeping a heat journal to record your experiences so that you can understand the general trend for your female. Additionally, there are a couple of anomalies that can occur related to her heat cycle. We do not have experience with these firsthand, but it is good to understand what they entail.

A silent heat occurs when there is a lack of signs while a female enters her heat. This can be a mix of factors including the female meticulously cleaning herself or not bleeding much (called a dry heat). If the female in an assertive or aggressive dog, males may not be so tempted to show their interest. It is important to note that during a silent heat, a dog is in heat and therefore ovulates and can become pregnant. Even if signs are not present, getting her tested for progesterone or LH levels, will indicate that she truly is in heat.  

A skipped, or missed heat altogether, could point to medical issues. If a dog has truly skipped their cycle, they should get checked by a vet to make sure there isn’t an underlying problem. The same is true of prolonged heats that include vulvar swelling for more than 21 days.  

A split heat happens when a dog enters proestrus and does not continue to the estrus phase. It could take up to three months before her heat returns and she ovulates. This is usually found in younger females and can occur due to the lack of luteinizing hormones to prompt ovulation.

It is also important to understand the potential threat of pyometra with an intact female. Pyometra (pyo) is an infection of the uterus due to bacteria-attracting cysts from the over thickening of the uterus lining. It is typically seen in intact females, as the uterus lining can build up from many estrus cycles not resulting in pregnancy. Pyo is life threatening and symptoms include pus discharge, discomfort, lethargy, increased thirst, vomiting, frequent urination and lack of appetite. Pyo typically develops a few months after estrus and is most common in older, intact dogs. 

For those who are interested in keeping their female intact for breeding, we highly recommend doing additional research regarding heat cycles. And for those crazy enough to have both sexes intact, we wish you quick heats and no accidental matings! 


Reference Links:
FAQ Summary https://www.vetwest.com.au/pet-library/reproduction-in-dogs
General Summary https://www.animalwised.com/dog-heat-cycle-stages-and-symptoms-808.html
Cytology During Heat https://www.eastcentralvet.com/canine-estrous-cycle.pml