The four stages of the canine estrous cycle
Every heat cycle follows the same four-stage pattern. Understanding each stage — and knowing exactly what to record — is the foundation of accurate cycle prediction. For a deep dive into the biology, see our complete heat cycle guide. This article focuses on the practical tracking side.
| Stage | Duration | Key Signs | What to Record |
|---|---|---|---|
| Proestrus | 7–10 days | Bloody discharge, vulvar swelling, attracts males but refuses mating | First day of discharge (Day 1 of cycle) |
| Estrus | 5–14 days | Discharge lightens to straw color, standing behavior, flagging tail | First day of standing heat, discharge color change |
| Diestrus | 60–90 days | Discharge stops, vulva returns to normal, refuses males | Date discharge stopped |
| Anestrus | 4–5 months | No reproductive activity, resting phase | Total cycle length (proestrus Day 1 to next proestrus Day 1) |
Why accurate tracking matters
A dam's cycle length is more consistent than you might expect — but only if you have enough data. Most bitches cycle every 6–7 months, but individual variation ranges from 4 to 12 months. The key insight is that your bitch's cycle length tends to be consistent across seasons once she is mature. If her first three cycles were 6.5, 6, and 7 months apart, you can predict the next one with reasonable confidence.
Without tracking, you are guessing. With 3+ tracked cycles, you can predict the next heat within a 2–3 week window — enough time to schedule progesterone testing, arrange stud travel, and prepare for breeding. Use our Heat Cycle Tracker to log every cycle and get automatic predictions.
What to record every cycle
At minimum, record these data points for every cycle:
- Day 1 of proestrus — the first day you notice bloody vulvar discharge. This is the anchor date for the entire cycle.
- First day of estrus — when discharge lightens and the bitch begins showing standing behavior (flagging tail, allowing approach).
- Duration of estrus — how many days the bitch is in standing heat.
- Last day of discharge — when all discharge has stopped.
- Any unusual observations — split heats, false pregnancies, changes in intensity or duration.
If you are also doing progesterone testing for breeding, record those values alongside the cycle dates. This creates a powerful dataset for timing future breedings — see our progesterone testing protocol for details.
How to calculate the next predicted cycle
The simplest approach: average the intervals between your tracked cycles. If you have three cycle start dates — January 5, July 10, and January 20 — the intervals are 186 days and 194 days, averaging 190 days (~6.3 months). Add 190 days to January 20 to predict the next cycle around late July.
With more data, the prediction tightens. After 4–5 tracked cycles, most breeders can predict the next heat within a 2-week window. The Heat Cycle Tracker calculates this automatically and shows a predicted range.
Signs your dam is approaching heat
In the weeks before proestrus, watch for these early indicators:
- Behavioral changes — increased restlessness, clinginess, or nesting behavior
- Vulvar changes — slight swelling days before discharge appears
- Attracting males — intact males in the area may show increased interest even before visible discharge
- Appetite changes — some bitches eat more or less in the days before proestrus
- Urination frequency — more frequent urination, especially marking behavior
When tracking reveals irregularity
Not all cycle patterns are normal. Tracking makes it possible to identify problems that might otherwise go unnoticed:
Short cycles (under 4 months)
Cycles shorter than 4 months may indicate insufficient luteal phase or premature ovarian activity. This can reduce fertility because the uterine lining may not have fully recovered from the previous cycle. Consult a reproductive veterinarian if cycles are consistently under 4 months.
Split heats
A split heat occurs when a bitch shows signs of proestrus (discharge, vulvar swelling) but then stops — only to resume a full heat cycle 2–6 weeks later. This is more common in young bitches and is usually not a fertility problem, but it makes timing confusing. Track both episodes and note which one progressed to full estrus.
Silent heats
Some bitches ovulate with minimal or no visible signs — no discharge, no swelling. These “silent heats” are more common in certain breeds and in older bitches. If you suspect silent heats, progesterone testing can confirm ovulation is occurring even without visible signs.
Building a cycle history
The most valuable breeding tool is a multi-season cycle history. After 3–5 tracked cycles, you will know your bitch's typical pattern — cycle length, proestrus duration, estrus duration, and any quirks. This data makes breeding planning dramatically easier and reduces the chance of missing the fertile window.
Start tracking today with the Heat Cycle Tracker. When the predicted heat approaches, schedule progesterone testing to pinpoint the exact breeding window. After a successful breeding, calculate your due date with the Whelping Date Calculator.
Related Tools
Sources: Concannon PW. Reproductive cycles of the domestic bitch. Animal Reproduction Science (2011) 124:200–210; Feldman EC, Nelson RW. Canine and Feline Endocrinology (4th ed.). Saunders; Linde-Forsberg C. BSAVA Manual of Canine and Feline Reproduction and Neonatology; Johnston SD, Root Kustritz MV, Olson PNS. Canine and Feline Theriogenology. Saunders; Merck Veterinary Manual (Estrous Cycle; Progesterone Testing). Progesterone-based ovulation timing is the gold standard for AI and stud-fee management — see the progesterone testing protocol guide for ng/mL ranges. This article is for educational purposes and does not replace professional veterinary care.
Heat cycle tracking FAQs
1At what age should I start tracking my dog's heat cycles?
Start with her very first season. Small breeds often have their first heat around 6–7 months, medium breeds around 7–9 months, and large or giant breeds anywhere from 12 to 24 months — with a normal range from as early as 4 months to over 2 years. Record that first cycle even though early seasons are frequently irregular; you need two to three logged cycles before predictions become trustworthy.
2How many cycles do I need to track before I can predict the next heat?
Plan on two to three complete cycles before trusting a prediction, with tighter accuracy after four or five. A bitch's cycle can take up to two years to settle into a regular rhythm, so never base a breeding plan on a single early season. The average interestrous interval is about seven months (a normal range of 4–13 months per the Merck Veterinary Manual), but most bitches stay consistent with themselves once mature.
3How often do dogs come into heat?
Most bitches cycle roughly every 6–7 months — about twice a year. Small breeds may cycle three times a year, while many giant breeds and certain breeds such as the Basenji and Tibetan Mastiff cycle only once a year. Rather than assuming the average, track the gap between Day 1 of consecutive seasons to learn your own dog's true frequency.
4I missed Day 1 of proestrus — is my tracking ruined?
No. Estimate Day 1 from the first day you noticed bleeding or vulvar swelling and label it as approximate. From there, lean on the estrus transition (discharge lightening to a straw color, standing and flagging) and, if you intend to breed, on progesterone testing — those events are anchored to ovulation rather than to the day you happened to spot the first discharge.
5Can date tracking alone tell me the exact day to breed?
No, and this is the most important limit to understand. Tracking predicts the window in which to start progesterone testing; it cannot pinpoint ovulation, which varies from cycle to cycle and dog to dog. Only serial progesterone testing — ideally paired with vaginal cytology — identifies the LH surge and the fertile days. Use your cycle history to know when to begin testing, then let progesterone tell you when to breed.
6What's the difference between a split heat and a silent heat?
In a split heat, a bitch begins proestrus (discharge and swelling), stops for several days to a few weeks, then resumes and completes a normal cycle — common in young bitches as their reproductive system matures. In a silent heat, she ovulates with little or no visible discharge or swelling, so the season is easy to miss entirely; this is more common in small breeds and some individuals. Log both episodes of a split heat, and use progesterone testing to confirm ovulation if you suspect a silent one.
7Do female dogs in the same household synchronize their heat cycles?
Despite the popular belief, there is no solid scientific evidence that cohoused bitches truly synchronize their cycles. Apparent overlap is usually coincidence, or one female's presence and pheromones nudging another's behavior — not precise hormonal synchronization. Track each bitch independently, and never assume that one female coming into season means the others are fertile too.
8Does spaying stop the cycle, and should I keep tracking afterward?
A standard spay removes the ovaries, so a spayed bitch no longer cycles and there is nothing left to track. If a spayed dog later shows heat-like signs — swelling, discharge, or male attraction — that is abnormal and may indicate retained ovarian tissue (ovarian remnant syndrome), which warrants a veterinary exam.
9Which cycle patterns mean I should call the vet?
Bring your tracking log to the vet if intervals are consistently under 4 months or over 12 months, if a mature bitch has repeated split heats, if you suspect silent heats, or if you see any discharge outside the expected window. Foul-smelling discharge with lethargy, fever, or excessive thirst is an emergency — it can signal pyometra, a life-threatening uterine infection. A reproductive workup plus a thyroid panel is the usual starting point for persistently irregular cycles.