"Can Daisy come out and play?" Image Courtesy Pat Koven

Whether you are planning on breeding your dog or having her spayed, if you’ve never gone through it before, it’s good to know what to expect if she goes into season. This is known medically as estrus, and known colloquially as being “in heat”.

If you are planning on breeding, this is a subject that is best discussed with your veterinarian beforehand. This article is written with the non-breeder in mind.

Let’s assume you’ve brought your female puppy home and planned on having her spayed, but for one reason or another, the first window of opportunity was missed, and she has gone into her first season.

Dogs usually reach this milestone around six months of age. Smaller breeds may experience estrus sooner, and larger breeds may have a delay in their first season until they are a month or so older, but if you do want to have your female dog spayed before her first estrus, think about making the appointment before her six-month birthday.

Dogs go into season roughly twice a year, every six to seven months.

The estrous cycle has four stages. You won’t be expected to remember the medical terms for them, so let’s think of them as beginning, middle, end, and resting time.

Proestrus: (beginning) What You Can Expect Your Dog to Experience: 

•  Swollen vulva
•  Bloody vaginal discharge
•  Licking
•  May be more affectionate and clingier with her people
•  May be attracting the neighborhood male dogs, but she won’t be interested in them yet
•  Urinating more frequently
•  More vocal than usual
•  May be grumpy toward other dogs
•  If approached by a male dog, may sit down or become aggressive
•  May lose her appetite.

The vaginal discharge varies from dog to dog but can be heavy and bright red. If you have never experienced a female in season, this discharge can be alarming. 

Some dogs will keep themselves quite clean during this time, and some dogs won’t. Be prepared to keep her in an area that is easy for you to clean. Doggy diapers are available, but keep in mind diapers won’t keep her from being bred. Dogs determined to fall in love will find a way, and a paper barrier is not going to stop them.

This stage usually lasts seven to 10 days but can last up to four weeks. She will go into the estrus stage next:

Estrus: (middle) What You Can Expect Your Dog to Experience: 

•  Increased licking of the vaginal area
•  She is now interested in male dogs, turning to them and presenting herself
•  She may hold her tail to the side
•  She is ovulating and is fertile at this time
•  Vaginal discharge becomes lighter
•  Wants to go outside frequently

Pheromones from a female dog in season can be detected by male dogs from a long distance. Prepare for the onslaught if there are loose dogs in your neighborhood. When taking her out, make sure you have her on a strong leash and would be able to handle her should a male dog approach her. Doggy social gathering places like dog parks are not a great idea at this time.

Your sweet little girl may be very eager to make new friends. She has suddenly become very popular, and she likes it. To prevent accidental breeding, keep her on a leash when away from home, and don’t leave her in the yard alone even if she’s fenced in. Even if a male dog can’t get in, females have been known to dig out or jump a fence during this time. Don’t let her surprise you or take a chance on losing her.

The estrus stage lasts about nine days but can be as long as three weeks. 

Diestrus: (end, thank goodness!) What You Can Expect Your Dog to Experience: 

If your female was bred during her heat, this is the gestational period (pregnancy). Canine gestation lasts approximately 58 to 63 days. If you suspect that she might be pregnant, consult with your veterinarian as soon as possible.

•  She will no longer be interested in mating, whether she is bred or not
•  The vaginal discharge is, for the most part, disappearing
•  The vulva may still be slightly swollen
•  She is gradually going back to the dog you knew before all this

Diestrus lasts about two months. Your girl will be going through all kinds of hormonal changes during this time, but you probably won’t know it. If you are interested in the medical terms and technical bits, read Veterinary Partner’s article The Canine Estrous Cycle: Being in Heat.

Anestrus (let’s take a break)

The final stage is anestrus. This is the resting time between breeding cycles and lasts about six months until your female goes into her next proestrus cycle.

Avoiding estrus can be medically important, as dogs that have gone through one or more estrous cycles have a greatly increased risk of mammary (breast) cancer, and older female dogs who are not spayed often get life-threatening uterine infections known as pyometra. Spending a small amount for a spay surgery at the right time can help save your dog – and save you thousands of dollars on complex and dangerous medical expenses.

If you plan on having her spayed, remember you have about six months. It may be a good idea to call your veterinary clinic and make your girl’s appointment in plenty of time.