If you own an unspayed female dog, understanding her reproductive cycle isn’t optional — it’s essential for her welfare. Being “on heat” (in oestrus) is a normal physiological process, but it comes with physical and behavioural changes that require attentive management. Here’s what to expect and how to handle it responsibly.
What “On Heat” Actually Means
The oestrous cycle is the period during which a female dog is reproductively active and capable of conception. It’s controlled by hormonal fluctuations — primarily oestrogen and progesterone — that trigger physical changes signalling fertility to male dogs.
Most dogs first come into heat between 6 and 12 months of age, though larger breeds may not cycle until 18–24 months. After the first cycle, most dogs cycle every 6–8 months — typically twice a year. The complete cycle has four stages:
- Proestrus (7–10 days): Vulval swelling and bloody discharge appear. Not yet fertile — males may show interest but females typically reject advances at this stage.
- Oestrus (5–9 days): Discharge lightens or becomes straw-coloured. This is the fertile window. The female will accept mating.
- Dioestrus (10–140 days): Progesterone dominates regardless of whether mating occurred. This is when phantom pregnancy symptoms may appear in some dogs.
- Anestrus: A period of reproductive inactivity between cycles.
Physical Signs to Watch For
The signs of heat are fairly consistent across breeds, though intensity varies:
- Swollen, enlarged vulva
- Bloody or straw-coloured vaginal discharge
- Increased urination — scent marking to attract males
- Frequent licking of the genital area
- Subtle changes in nipple appearance
Some dogs show minimal discharge; others are considerably messier. Keep a note of each cycle’s timing and duration. Irregular cycles — particularly in older dogs — can indicate thyroid dysfunction or other hormonal conditions worth investigating with your vet.
Behavioural Changes During Heat
Hormonal fluctuations affect behaviour significantly. Common changes include:
- Restlessness and increased vocalisation — howling is partly driven by this hormonal state
- Increased affection toward people, or conversely, increased agitation and irritability
- “Flagging” — the female holds her tail to one side to signal receptivity when touched near the hindquarters
- Attempts to escape — intact females in oestrus will actively seek out males. Fence integrity matters more during this window than at any other time of year.
- Appetite fluctuations — some dogs eat less during peak oestrus
Male dogs can detect a female in heat from considerable distances. If there are intact males in the neighbourhood, be aware that they may wait outside your property — and that a determined male will attempt to access a fence or gate that would ordinarily stop him.
Managing a Dog on Heat
Containment
An in-season dog should not be left unattended in an outdoor area, even briefly. During oestrus especially, keep her on-lead in all public spaces — dog parks, trails, and off-lead areas are off the table for this period. One unsupervised encounter is enough for conception.
Hygiene
Dog hygiene pants and “in-heat nappies” are available from most SA pet stores and manage discharge effectively indoors. Wash bedding frequently during the proestrus and oestrus stages. Some owners find it practical to confine the dog to easy-clean areas during peak discharge days.
Exercise
Don’t stop exercising your dog during heat — she still needs physical activity and mental stimulation. Maintain lead control at all times and be prepared for male dogs approaching quickly. An intact male responding to a female in oestrus is operating on strong biological drive — obedience training alone may not override it reliably.
The Case for Spaying
Unless you’re actively planning to breed your dog responsibly, spaying (ovariohysterectomy) is the most practical decision for most dog owners in South Africa. The benefits are substantial:
- Eliminates the management burden of heat cycles entirely
- Prevents pyometra — a life-threatening uterine infection that’s most common in older intact females and carries significant surgical risk
- Significantly reduces the risk of mammary tumours if performed before the second heat
- Contributes to responsible pet ownership in a country where dog overpopulation remains a serious welfare concern
The SPCA and most South African vets recommend spaying before the first heat (around 6 months) for most breeds. For large and giant breeds, timing is more nuanced — early spaying may affect musculoskeletal development. Discuss the right timing with your vet based on your dog’s breed and size.
When to Contact Your Vet
Most heat cycles are uncomplicated and require no veterinary intervention. Contact your vet if:
- The cycle lasts longer than four weeks without resolving
- Discharge becomes foul-smelling, thick, or purulent — this can indicate pyometra or infection, both of which are emergencies
- Your dog appears lethargic, is off her food, or shows signs of abdominal discomfort
- You suspect unintended mating occurred — options exist if you act within 48–72 hours
Staying current with dog vaccinations is important year-round, but particularly relevant around heat cycles when hormonal changes can affect immune function. It’s also worth revisiting your dog’s allergy history with your vet at this stage, as some dogs show increased skin sensitivity during hormonal fluctuations.
