Estrus, or ‘heat’ simply refers to the stage of a female dog’s reproductive cycle in which she can become pregnant.
During estrus, oestrogen levels rapidly rise and fall as mature eggs are released from the ovaries, leading to female dogs becoming more receptive to mating with males.
A dog in this stage of her cycle is commonly said to be in heat.
When do dogs first come into heat?
A dog’s first estrus tends to occur sometime between six months and 24 months old.
However, this can occur sooner in smaller breeds and much later in larger ones.
How often do dogs go into heat?
Most female dogs usually come into heat around twice per year (every six months), although it really does vary between breeds and individual dogs.
Smaller dog breeds can have a heat cycle of up to three times in a year while a bigger breed may come into heat just once every 12 months.
For younger dogs only just reaching puberty, cycles may be more irregular and it can take up to two years for a dog to develop a regular cycle.
There is no ‘mating season’ for dogs and so their cycle can come at any time of year.
How long do dogs stay in heat?
On average, a dog will stay in heat for 10 to 14 days, although this can be shorter or longer depending on the individual dog.
Although there is a point of the cycle where she is most fertile, she can become pregnant at any stage of estrus.
How to tell if your dog is in heat?
The first signs of estrus in your dog are a swelling of the vulva and a bloody vaginal discharge. However, this discharge may not be noticeable until a few days into their cycle and so it’s more likely you’ll spot changes in your dog’s behaviour at first.
Female dogs can appear more alert and nervous than usual when in heat due to hormonal changes and they may act differently with other dogs. A dog in heat will also likely try and initiate sex with male dogs when they approach by lifting their hindquarters and tensing the rear legs.
They will also begin to urinate more frequently, as increased pheromones in the urine can act as a reproductive marker which can attract other dogs.
How can I stop my dog going into heat?
The only way to stop your dog going into heat is to get it spayed, which helps protect against accidental pregnancy.
Research suggests that spaying dogs can also help increase lifespan by ridding them of diseases of the reproductive system.