If you own an unspayed female dog, the first question almost everyone asks is how long is a dog on heat. The short answer is roughly two to four weeks, with about three weeks being typical. The longer answer matters more, because the fertile window sits inside that period rather than spanning all of it, and knowing which days are which is the difference between managing a season calmly and ending up with an unplanned litter.
How Long Is a Dog on Heat?
Most owners use “on heat” to mean the visible bleeding and swelling phase, which lasts around two to four weeks. Within that, the dog is only actually fertile for part of the time. The full reproductive cycle runs in four stages:
- Proestrus, roughly 9 days (range 3 to 17): the vulva swells and a bloody discharge appears. Males take interest, but the female will usually refuse them. She is not yet fertile.
- Oestrus, roughly 9 days (range 3 to 21): discharge lightens to a straw or pink colour. This is the fertile window, and she will accept mating.
- Dioestrus, around 60 to 90 days: the cycle closes down and progesterone dominates whether or not mating happened, which is why phantom pregnancies occur.
- Anoestrus, about 4 to 5 months: reproductive rest before the next season.
Most dogs have their first season between 6 and 12 months, though large and giant breeds often wait until 18 to 24 months. After that, most cycle roughly every six months. Some breeds are slower, and a dog that cycles only once a year is not necessarily abnormal. The stages of the canine reproductive cycle are well documented if you want the underlying physiology.
Physical Signs to Watch For
The signs are fairly consistent across breeds, though intensity varies a great deal between individuals:
- A swollen, visibly enlarged vulva.
- Bloody discharge early on, lightening to straw coloured as she becomes fertile.
- Increased urination, which is scent marking aimed at attracting males.
- Frequent licking of the genital area, sometimes the only obvious sign in a fastidious dog.
Some dogs bleed heavily and others barely at all, so a “silent” season is easy to miss in a dog that grooms herself well. Keep a written note of the start date and length of each cycle. Irregular or absent cycles, particularly in an older dog, can point to thyroid or other hormonal problems worth raising with your vet.
Behavioural Changes During a Season
Hormonal shifts change behaviour noticeably, and most of what owners report falls into a few patterns:
- Restlessness and more vocalising than usual, which is one of several hormonal drivers behind why dogs howl.
- Either increased clinginess or increased irritability, depending on the dog.
- Flagging, where she moves her tail to one side when touched near the hindquarters. This signals receptivity and usually means she has entered the fertile phase.
- Determined escape attempts. An intact female in oestrus will actively go looking for males, and fence integrity matters more in these three weeks than at any other time.
Male dogs detect a female in season from a considerable distance, and intact males may camp outside your property for days. A determined male will get over, under or through a gate that would normally hold him, so check the perimeter before the season starts rather than after.
Managing a Dog on Heat
Containment
Do not leave an in-season dog unattended outdoors, even briefly. Keep her on a lead in every public space for the full three to four weeks. Dog parks, off-lead trails and beaches are off the table for this period, because one unsupervised encounter of under a minute is enough for conception. This is a period where reliable lead training earns its keep.
Hygiene
Dog hygiene pants, sold as season pants or in-heat nappies, are available from most South African pet retailers and handle discharge well indoors. Wash bedding often through proestrus and early oestrus. Many owners find it simplest to keep the dog to hard-floored rooms during the heaviest days.
Exercise
Do not stop exercising her. She still needs the physical outlet and the mental stimulation, and a bored, hormonal dog is harder to live with. Walk at quieter times, keep her on lead throughout, and expect approaches from off-lead males. A male responding to a female in oestrus is driven by something stronger than his recall, so positive reinforcement training should be treated as management support here, not as a substitute for a lead.
The Case for Spaying
Unless you are planning a properly considered breeding, spaying is the practical choice for most owners. It removes the management burden entirely, prevents pyometra (a life threatening uterine infection that is common in older intact females and carries real surgical risk), and substantially lowers mammary tumour risk when done early. It also matters at a national level: dog overpopulation is a serious welfare problem in South Africa, and organisations such as the NSPCA deal with the consequences daily.
Traditional advice is to spay before the first season at around six months. For large and giant breeds this is genuinely contested, because early spaying may affect joint and skeletal development, and many vets now prefer to wait. Discuss timing with your vet against your dog’s breed and size rather than applying one rule to every dog. If you are still choosing a breed, our overview of popular dog breeds in South Africa is a useful starting point, and keeping vaccinations current is part of the same routine care.
When to Contact Your Vet
Most seasons pass without any need for veterinary help. Call your vet if:
- Bleeding continues beyond about four weeks without settling.
- Discharge turns thick, foul smelling or purulent, which can indicate pyometra. This is an emergency.
- She becomes lethargic, goes off her food, drinks excessively or shows abdominal discomfort.
- You think an unplanned mating happened. Options exist, but they are time limited, so ring the same day rather than waiting to see.
