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Puppies, hormones, health, and behavior

Your puppy will start gradually becoming a little man or little woman somewhere in its adolescent stage, between 5 and 9 months. Sex hormones don’t just appear one day (although it may seem that way), the progressively increase over certain time periods.

Hormonal behaviors can include mounting (“humping”) in both males and females, roaming (more for males), urine marking, moodiness, clinginess, selective hearing or other change in behavior. By six months of age both females and males can be fertile, sometimes earlier for some males. You may also notice adult dogs treating your teen differently and they may act more aggressively toward your dog.

We recommend spay and neuter between 6 and 9 months, so your dog has time to benefit from some of the more positive hormonal changes but not so late as for those changes or behaviors to become problematic.

Testosterone in males starts rising at about 4 or 5 months, peaks at 10 months, and then settles to adult levels at about 18 months.

Females can experience their first estrus (heat cycle) at 5 or 6 months, with 8 or 9 being more of an average. If you don’t want to deal with a heat cycle or a fertile female, then consider spay at the earlier end of the 6-9 month window.

Shelter surrenders are most likely to happen in this time period because of the hormonal influence on behavior. So when your little darling becomes teenzilla, schedule an appointment with your vet to discuss spay/neuter.

Dr Jennifer Cattet has a great article on this stage, and rather than trying to repeat all of her good advice for surviving puppy teenhood, here’s the link.

Signs of estrus (heat cycle)

First heat cycles don’t always occur by 6 months, but that’s when you should be ready for one. They will have some light bleeding and her vulva will swell. Your first sign may just be a few drops of blood on the floor. Once you realize that no one is injured, you’ll be able to realize it’s her heat cycle.

We do NOT recommend spaying during a heat cycle. A dog can be spayed during this time, but is much more prone to bleeding and complications, so unless you have a compelling reason to spay during a heat cycle, we suggest waiting it out.

During her cycle you will want two pairs of sanitary pants. Some take panty liners, which makes it easier to keep her clean. You can get utilitarian pants almost anywhere online. Some etsy shops have cute pants that look like little dresses. Be sure she doesn’t chew on her pants or panty liners, and use bitter apple if necessary. You can also use huggies pull ups and cut a hole for her tail. Again, make sure she doesn’t chew them or you risk an obstruction.

Do not leave the pants on at night. She needs a chance to breathe and she’s more likely to try to chew the pants at night anyway.

Some girls are very clean and she may have a heat cycle you don’t even notice. First cycles tend to be light. The only sign may be a little extra licking and a little more affection. There’s also something called a “silent heat,” where there’s no swelling or bleeding. In either case, she can still get pregnant, so between 6 months of age and her spay, it’s important to be vigilant and not expose her to any intact males.

Her cycle should last about 21 days, and assume she’s fertile for all 21 days and not let her anywhere near an intact male. All of her outdoor activities must be carefully supervised. Intact males are tenacious and can jump or dig into your yard before you realize. Females in season are more likely to get loose and go looking for a boyfriend, so even if she’s usually 100 percent reliable off leash, keep her leashed for her entire cycle.

False pregnancies

False pregnancies occur fairly often in dogs. False pregnancies occur about two months after her heat cycle. She may act like she’s having a litter, carry her toys around like puppies, and even produce milk. She thinks this is really happening, so be thoughtful and support her while she passes through her false pregnancy.


Pyometria is a uterine infection that can happen after an estrus cycle.

If you notice any vaginal discharge or pus after your dog’s heat cycle, she may have a pyometria. Fever and increased thirst are also signs.

A pyometria is serious and life threatening and should be considered a veterinary emergency. If you suspect one, do not wait until the weekend is over or until a clinic opens in the morning. Call your veterinary emergency clinic and ask to talk to a vet tech to determine if you need to bring her in.

Pyometria happens as a result of hormonal changes and is not the fault of you, your dog, or your environment.

Unwanted breedings

If, despite your best efforts, a male manages to breed your female, do NOT try to separate them. Mating causes a physical “tie” between the male and female and separating them can cause pain and physical damage and can also cause you to be bitten by a scared dog in pain.

The tie will end itself after 15-45 minutes. Help the male lift his leg over the female so they are standing tail-to-tail (if the male hasn't’ already done this himself) and try to keep them still so they don’t pull on each other. Ideally, you can have two people, one holding each dog.

Please see the rolled up newspaper protocolfor appropriate punishment, then call us and seek your vet when you can think straight.

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