Seasons
A bitch’s season (or heat) is when she becomes fertile and able to get pregnant. It usually happens twice a year, lasts about 2–3 weeks, and often starts between 6–12 months old (depending on breed and size).
The 4 Stages
Pro-oestrus (days 1–7/10):
Vulva swells
Bloody discharge
Male dogs will be very interested, but she won’t usually accept them yet
Oestrus (days 7–17):
Discharge becomes lighter/straw-coloured
She may “stand” for a male and move her tail aside (flagging)
Most fertile time is usually around days 10–14, but it can vary
This is when pregnancy is most likely
Dioestrus (about 2 months):
No longer fertile
Hormones settle, but her body may act as if she’s pregnant (false pregnancy is common)
Anoestrus (several months):
Resting phase before the next season
Key Things to Watch Out For
Even if bleeding slows or stops, she can still be fertile — assume risk of pregnancy for the full 3 weeks.
Male dogs will try very hard to reach her, so keep her securely supervised indoors and in the garden.
Some bitches get more clingy, restless, or off their food. Others may get irritable, and it’s quite common for bitches (even spayed bitches) to fight with each other during a season.
Use care on walks — Use fully enclosed private fields where possible
