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When Do Dogs Go Into Heat?

Adrienne is a certified dog trainer and former veterinarian assistant who partners with some of the best veterinarians worldwide.

Canine heat cycle stages: when does a dog go into heat?

Canine heat cycle stages: when does a dog go into heat?

When Will My Dog Get Their First Heat Cycle?

The heat cycle, better known as the estrus cycle, typically occurs when a female dog reaches 6 months of age. However, there are many variants, depending on the breed of the dog and its level of development. It is not unheard of for large breed dogs such as Saint Bernards and mastiffs to go into heat at one year of age or even as late as 18 months.

The heat cycle in dogs is divided into three different phases, which when combined together, is an average of about 21 days.


The first phase is called proestrus. This phase is characterized by vaginal swelling and vaginal bleeding. At this stage, male dogs will appear interested; however, the female dog will not allow them to mount. This stage usually lasts an average of 7 to 10 days.


The following stage is called estrus. At this point, the female is actually fertile. The pink-red bloody discharge at this point is replaced by a straw-colored discharge. The female dog will appear more interested in the male, and after some flirting, will keep her tail to the side and allow the male to mount. Should you witness a "tie" where the male and female are stuck together to each other, the chances of pregnancy are pretty high. This phase lasts an average of 4 to 13 days.


The last stage is the final and it is called diestrus. Even though the male will still attempt to mount, the female is no longer interested and is no longer fertile. This concludes the estrous cycle.


This is the period of time between the end of the last cycle and proestrus.

How Often Do Heat Cycles Occur in Dogs?

Heat cycles usually occur twice a year or once a year. However, in some cases, the dog's heat may go unnoticed. This may occur because the dog may tend to clean herself up quite a bit by licking away the vaginal discharge. Even though not that common, some dogs may go through what is called a "silent heat." In this scenario, the dog exhibits subtle symptoms which the owner will not notice. However, male dogs may be great detectors of such silent heats and may confirm them by observing their behavior.

What If My Dog Doesn't Go Into Heat?

However, should your female dog appear not to go in heat for some time, it may be helpful to report to your vet to rule out some conditions that may suppress the heat cycle, such as hypothyroidism, diabetes mellitus, cancer, Cushing's disease, and Addison disease.

When Is My Dog Most Fertile?

If you are considering breeding your dog, the estrus phase is when you want her to mate. If you are not planning to breed, the estrus phase is when you want to keep her safely inside far from male dogs. Males can detect females in heat from many miles away. So do not be surprised if you may find some male dogs waiting behind your door.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.


Setemstraight on May 25, 2012:

Hey there! This is a very interesting subject, and I, too, wish there were more actual research done on it because all too often, a theory is propounded, and then, without any real research or proof, it is repeated until it becomes Gospel truth, and we all live our lives or make decisions around it. Later, the theory is proved false perhaps (or perhaps not,) but by then, like I said, we've all lived our lives and altered our behavior because of it!

You mention air scenting, and that is a very interesting topic. I would suppose,maybe, that on a clear day, with a good wind blowing directly from the female to the male in an unbroken line, in an open field (no houses, wooden or vinyl fences, trees, etc., to block the scent,) then perhaps the male would be able to smell the in-cycle female from a further distance, but certainly not from the astronomical distances we've all been told.

I have a book at home (circa 1969 - yes 1969! LOL,) that advises dog owners who do not wish to breed their females during a certain heat cycle to not let her off the premises so she does not leave her scent around. This would prevent tracking and trailing right to her front doorstep! My friend with the chihuahua had no problems because her dog never left house or fenced yard. Her little dog didn't leave a scent trail behind in the neighborhood. The dog lived for 15 years. I don't know at what age a female dog stops having heat cycles as I've never had an unspayed female dog. I now own an intact male, and I can say that I've never had a problem with him in the four years that I've had him and I know for a fact that there is at least one unspayed female living only afew blocks away.

This brings me to another aspect of this: is it possible that this theory had its origin from people who believe that every dog should be "fixed" so as to stop all breeding? I don't know. I mean, if a person truly believes that a male dog can detect a female dog in heat from five miles away and will go to heroic lengths to escape to get to her, then that person would certainly opt to neuter their dog as soon as possible. Right? If I believed it, I would neuter my dog too. I don't neuter him because I don't believe this theory, have seen no evidence of it, and, after doing a lot of research, came to the conclusion, that, at least in his case, neutering would bring about more health risks than it would prevent, and of course, I am 100 percent committed to not allowing him to procreate! (But that's another topic altogether.)

Gotta go. Have a great day!

Adrienne Farricelli (author) on May 25, 2012:

Setemstraight, it is not that I do not agree with you, it is that there appears to not be any updated studies on this. You talk about tracking, and it is true that dogs track. Of course, a female in heat will not be kept for a whole week indoors so every time she is walked and allowed to pee it will give a trail for male dogs to follow! So I see that now you agree now about the ability to "track down: a female in heat. However, let's remember that dogs do not ONLY track. Yes, it is common to see the the picture of blood hounds following a trail but dogs also follow smells through air. Air-scent dogs pick up a scent carried in air and look for its origin, in other words the point of greatest concentration, it looks like an air scent dog can detect the presence of humans up to 1/2 mile away. I a heading out right now but will be back later and will do more research on this because it is quite interesting. Now, it would be ideal if there were studies done on the possibility a dog can "air scent" a female in heat that has not left any track and kept in the home all the time. I think if in the home, the male dog cannot track her down or air scent (indeed many people say they have good results from closing all windows)but when kept in the yard I think it may be possible but not sure on the mile radius. I will get back to this later.

Setemstraight on May 24, 2012:

Wow, it's been a long time since I've been on this site. Didn't know anyone responded to my post! I would like to respond also.

You said, "I have seen dogs work for search and rescue and if they can perceive the presence of a human beings (and yes, even up to two miles away) and track them down with success, the same can be done with a female dog in heat."

Yes, they can follow a track for two and many, many more than two miles, but the BEGINNING of the track isn't two miles away -- it's right under their noses! My point is this: if the female dog urinates in the neighborhood and walks around and then goes home, you can bet the bank that any male dog that happened to walk by and smell where she walked and where she urinated can and will TRACK her scent right to her front door! However, if he is two miles away (or even a block away) from anywhere that she was, he cannot smell her and make a "bee line" straight to her home. Even a bloodhound can't do that!

Look at this website:

These people have actually done an experiment and proved that male dogs cannot smell a female in heat from miles away. All they do is follow a trail that she leaves behind,and if she walked ten miles that day, then they follow that trail for ten miles, but the beginning of the scent trail is still right under their noses or in close proximity thereof! They aren't smelling her from two, five, or ten miles away! They may be TRACKING her from this distance, but the beginning of the trail was virtually right under their noses. Therefore, if you can keep your female home during her cycle, males in their yards a mile away will be totally oblivious to it. In fact, males two houses away will be totally oblivious to it. Only those males that live right next door to her and meet at the fence line will know. (And then look out!)

There are a lot of myths and misinformation that abound but I haven't seen any research proving that I'm wrong. I have seen experiments, which I posted above, proving I'm right.

Now, let's talk coyotes hanging about when FiFi is in season. If the coyote came into the area where the dog in heat left her scent, then of course, he is going to be hanging about, but only if he happens to wander to the area (by chance.) He didn't smell it from a mile away! And, of course, if others see him there, they'll come to investigate also to see what's going on - perhaps he has food that they'll like to get a piece of.

This reminds me of people who think that if they accidentally drop a piece of hot dog on their kitchen floors, ants will smell it from outside and they will be raided. They might be, but not because the ant smelled it from outside, but because an ant aimlessly wandered into their kitchen (by chance) looking for food, found the hot dog and followed its own trail back to notify the others to come help bring it home! Same with the coyotes. If they happen to be wandering around and pick up the scent, they'll stick around, but prove to me that they picked up the scent two miles away! Can't be done because it's not true.

Hunting dogs, also, don't pick up the scent of the animal three miles away from where they're standing. They pick up the scent and then follow it for three miles.

And, read Alexandra Semyonova's book, The 100 Silliest Things People Say About Dogs (2009 - available on Amazon.) Dogs are not wolves any more than we are chimps and they do not have dominance hierarchies or ranks. This author has done extensive, ongoing research on dogs.

In closing, I want to thank you for this opportunity to participate in this discussion with you. We may not agree, but it's always good to share differing views. Thank you.

jason amos on December 14, 2010:

hi i am looking 4 a huscy

Setemstraight on October 24, 2010:

Male dogs cannot detect female dogs in heat from many miles away. This is a myth according to the late Dr. Leon F. Whitney in his 1971 book entitled, "Pets." In this book Dr. Whitney states that he conducted studies into this matter and the males could not detect that the female was receptive from three feet away!!!!

Also, I know a lady who had a chihuahua that she never spayed from puppyhood until the dog died of natural old age. The dog lived in the house and went out into the fenced backyard to do her business. In all the years she had the dog, she was never once bothered by male dogs camping on her lawn when this female was in heat. How could this be if the males can detect it from miles away? The lady lives in the suburbs of a very large city. There were many male dogs living in the neighborhood - no doubt on the same block!

There are so many urban legends and falsehoods that persist about dogs. I would like for someone to produce the research that proves males can detect females in heat from many miles away. Dr. Whitney conducted research and says they can't. Until someone with actual research comes along to prove him wrong, I'm with the good Doctor.

lily on April 29, 2009:

haha thanks i hav a female puppy and a male dog i want to breed