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Heat

The Chihuahua Heat Cycle

Overview
 
Owners of female dogs are understandably concerned about the Chihuahua heat cycle. Unless a female is spayed (more ahead) the dog will enter in and out of heat. 

There will be physical and sometimes behavioral changes. Heat, also known estrous (not be be confused with estrus - a certain part of the cycle) is the is the stage in a female's reproductive cycle during which time:
  • Eggs are released from the ovaries
  • She becomes receptive to mating
  • If there is no pairing, a tie is not made and no pregnancy occurs, the uterus will shed its lining, which produces varying levels of blood and tissue that are expelled from the vulva.
When Heat Starts for a Chihuahua

With toy breed dogs, the first heat season begins rather early in the puppy stage. It is considered normal for a Chihuahua to enter into her first heat between the age of 4 months old and 7 months old. Therefore, without spaying, a puppy is able to become pregnant. 

When a female dog does have her first heat cycle, this means that she has entered puberty. If a Chihuahua does not enter her first cycle by the age of 12 months, it is suggested to have her evaluated by the veterinarian.
Female Chihuahua pink hat
How Long Heat Lasts For

This varies for each dog and there are several stages to the heat cycle. In general, a Chihuahua will remain in the estrus phase of heat (the time when there is active bleeding) anywhere from 5 days to 3 weeks.

You may not notice that it has begun until several days - or even a week - into the cycle. In addition, a female will not be receptive to a male for the entire cycle.

There are 4 stages to be aware of:

1) Proestrus - This is the beginning of the heat cycle. It will last approximately 1 week, but can vary between 5 days and 8 days. During this stage, the female's body is preparing for a possible pregnancy; though she will not yet be receptive to a male. 
Estrogen levels peak in this stage then drop as the dog enters into stage 2. It is at this time that the dog's vulva will begin to swell. There may be some preliminary discharge that is reddish brown.

2) Estrus - While this has a similar name to 'estrous' (Which refers to the entire heat cycle), estrus is the 2nd stage. This is also known as 'Standing Heat'. This lasts for 5 days to 3 weeks. Progesterone levels rise while estrogen falls. The vulva will be fully swollen and discharge will flow. It will range from pink to red.

During this phase of the Chihuahua heat cycle, the female is very receptive to males. She may actively seek out a mate. It is common for the female to flag a male (life her tail).

Eggs drop during this time and for each dog the timing of this is different. In general, it will happen between days 10 and 15 (counting day 1 as the day that blood first appeared) and it is only during this time that a mate will be successful. 

3) Diestrus - As hormone levels begin to stabilize, the discharge of blood will slow and then stop. Regardless of whether a female has been paired with a male (or has even had any contact with a male dog), she may show nesting behavior

With nesting, the Chihuahua may seek out toys and stuffed animals to 'mother', often hiding them in a safe spot to guard over and protect. During this phase, she will no longer be receptive to a male and a tie will not be successful.

4) Anestrus - This is the resting phase that occurs between heats. While it will not be noticeable owners, unless she is spayed, a Chihuahua's body is preparing for the next heat. 
Female Chihuahua heat cycle
How Often a Chihuahua Enters Heat

Toy breed dogs will have a heat cycle roughly 2 times per year. It may take be several cycles before a young female falls into a regular pattern. Usually by the age of 2 years old, a Chihuahua's heat will become very predictable.

Unlike humans who enter menopause, an un-spayed female will generally have her heat cycle for her entire life. Though for seniors over 8 years old, the time in-between estrus will lengthen and discharge may be lighter. 

Signs and Symptoms of Heat

Swollen vulva - This begins at the start of the first stage (proestrus) and will gradually increase until it peaks during the standing heat phase. The size of the vulva may swell up to 3 times its normal size.

Raised Teats - Previously recessed teats may protrude from the belly, become harder and sometimes develop a darker color.
Discharge - This may begin as a reddish-brown. As the heat cycle progresses, it usually transitions to a pinkish-red. The first heat may produce a clear to pink discharge. For toy breeds dogs, the flow is rather light and may go unnoticed for some. For others, the flow will be heavier and the use of a canine doggie-diaper will come in handy. 

Flagging - When the female is receptive to the male during the Estrus phase, she will be flirty with males and raise her tail to them.

Nesting - As the heat cycle ends, even if a female has had no contact with any males dogs, she may show nesting behavior. During this time, she may behave in a mothering way to toys (most often soft stuffed animals). It is important to allow her to carry out these activities as they are harmless and brought about by hormonal changes.

It is suggested to not touch what she may consider her impromptu 'litter'. As she enters the anestrus stage (resting period between heats), this behavior will go away. Though, it is normal for dogs to have favorite toys and be protective of what they consider to be their belongings.

Mood Swings and Behavioral Changes - There can be some mood swings when a female is experiencing heat. As the uterus contracts, there may be some cramping that causes a dog to retreat. There may be some minor whimpering as well. 

During the estrus phase, she may appear to be moody; sometimes acting reserved or sometimes behaving agitated or anxious. This type of moodiness is temporary and a dog's normal disposition will soon return.

A dog in heat may have such strong urges to mate that she may try to runaway, even if she has never previously shown such behavior. During this time, owners should be very aware when opening doors that lead outside. As always, keep your Chihuahua on leash whenever outside.

Males dogs will know that a female is in heat and can actually sense this from up to 3 miles away. Each time that a female in heat urinates, she leaves behind traces of blood that send out very strong signals to all un-fixed males in the area.
It is best to keep daily walks close by the home and stay away from dog parks or other areas where there may be other dogs. When taking your Chihuahua outside for bathroom duties, scan the area first for any stray dogs that may have ventured there. 

Split Heat

For toy breeds like the Chihuahua, it is not uncommon for the very first heat to be a split heat. When this happens, the vulva will appear swollen and there will be some discharge but the dog will not ovulate and the cycle will seemingly be done. Then, 1 to 3 weeks later, her body will release eggs (ovulate) and the heat cycle will finish.

Silent Heat

This refers to when a female canine experiences hormonal changes yet there are no physical signs and there is no bleeding. This is not normally a health issue or any major concern. Since the Chihuahua is so tiny and often there is very little discharge, some females will lick the area clean which causes an owner to believe that a silent heat occurred.
two female Chihuahuas
Clara Su & Ruby Ru (3 & 4 years old) 
Photo courtesy of owners Lori & Harry Scatton 
Spaying

There are both pros and cons regarding this, though spaying a female does have more advantages than just stopping the heat cycle to prevent unplanned pregnancy. It eliminates the possibility of uterine or ovarian cancer and decreases her odds of developing mammary cancer by a vast degree. It also reduces the stress and strain that the body endures during each heat. Finally, spaying can calm behaviors; females in heat are known to try and run away to find a mate and are often more territorial at home. 

A possible risk is an increased chance of developing urinary incontinence; studies show that this occurs with roughly 20% of spayed females, sometimes soon afterward or in some cases, many years later. There are inconclusive studies showing possible links to increased rate of cancer; much more research needs to go into this. 

Still, most veterinarians recommend having a female dog spayed even before the first season.

If an owner does not intend to breed their female, spaying is strongly recommended. 
Hygiene During Heat

While the discharge may seem so minor that the need for a doggie diaper is not needed, it must be remembered that over the course of weeks, that discharge will accumulate. It will end up on bedding, furniture, carpeting and any other areas that the Chihuahua rests or sleeps. This can cause unsanitary conditions for both you and your dog. Also, when it dries, it is harder to clean.  For these reasons, it is always recommended to place a canine diaper on a dog in heat, which can be taken off when she needs to go to the bathroom. Many owners choose to place a cute pair of panties on top of that, however that is optional. This way, the discharge is contained. 

You will want to replace this at least every morning and every evening with a new one as long as the active stage of heat is occurring. In between bath times, the vaginal area can be wiped with quality canine wipes so that the dried discharge does not stick to fur and cause twisted clumping of hairs which can pull at the skin and cause discomfort. 
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