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Photo courtesy of Heather Dawson, AKC Breeder of Merit


Humans take years to develop. Dogs, in our eyes, mature almost overnight. One morning you have an adorable, leggy puppy on your hands, and the next your puppy is starting to act like a teenager, complete with mood swings and behavioral changes.

Sexual maturity is an important part of this process, and it is something that we need to understand if we want to be responsible dog owners. Here is what you need to know about sexual maturity in puppies to keep your puppy healthy.

When Do Puppies Reach Sexual Maturity?

Puppies have to grow up sometime. Sexual maturity in puppies typically occurs between 6-to-9 months of age, although certain giant breeds may take longer. Sexual maturity in puppies can happen before your puppy is fully grown, which can be dangerous for females and is why the AKC recommends waiting until after your female’s first heat to breed her. Sexual maturity is largely size- and breed-dependent, so talk to your vet and breeder about your puppy.

What to Expect as Your Puppy Sexually Matures

lab puppy

We all know what happens to humans when we hit puberty. Dogs get to skip the acne and facial hair, but they do experience significant hormonal changes that can alter their behavior. The changes are different for male and female puppies.

Sexually mature female dogs typically go into heat twice a year. The most noticeable change during this time occurs at the start of their heat, called proestrus. The bitch’s vulva will swell, and she will develop a vaginal discharge for a period of 7-to-10 days, a bit like a human period. Your puppy can become pregnant during her first heat, so be sure to keep a close eye on her if you decide not to spay.

Male dogs do not go into heat like females. They are sexually active year-round, but they are most fertile after 12-to-15 months of age, once they are fully physically mature. Males can start to mark as they become sexually mature, which many owners consider an undesirable trait. They also develop a tendency to mount, and sexually mature male dogs may also roam, which requires owners to take extra precautions when it comes to containing their intact dogs.

Spaying and Neutering

The most important decision you need to make as your puppy reaches sexual maturity involve spaying and neutering. Unless you plan on breeding or showing your dog, veterinarians recommend spaying and neutering. This prevents future health problems and eliminates unwanted puppies. Talk to your vet and breeder about the best time to spay or neuter your dog and plan accordingly. If you decide you do want to breed your puppy after he matures, make sure you do your research, as this decision comes with a lot of responsibility.

Learn more about responsible breeding practices.

Understanding when sexual maturity in puppies takes place, and what it means for your dog, will help you become a more responsible dog owner. This knowledge allows you to make decisions regarding your dog’s health. Plus, knowing the science behind sexual maturity in puppies will help you understand your puppy’s changing and sometimes confusing behavior.
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