It's estimated that over a million puppies are born each day. That number isn't as surprising when you take into account three factors. First, there are more than 900 million total dogs in the world; second, female dogs can get pregnant at just six months of age; and third, one female dog plus her babies can have more than 67,000 puppies over six years. However, the latter two are only possible for dogs who aren't spayed and can thus go into heat. Here are some more facts about dog heat cycles and spaying:
1. Dogs go into heat every 6-12 months.
The canine estrus cycle, more commonly known as a dog's heat cycle, happens just once or twice a year.
2. Puppies go into heat.
Most female dogs will go into heat for the first time as puppies, around the age of 6 months.
3. Dog heat cycles up to 4 weeks.
The heat cycle typically lasts for three to four weeks, which means they are fertile during that entire time. Because of this, it's recommended you keep your dog away from intact males until after the four weeks to avoid impregnation. In other words, no doggie day care or visits to the dog park for females in heat.
4. Bleeding occurs for the first 2 weeks of the heat cycle.
Although the heat cycle lasts three to four weeks, dogs usually only bleed for the first two. This means that even if a female isn't bleeding, she is still fertile. In addition, females in heat don't bleed a large amount and some don't bleed much at all.
5. Dogs in heat know when they are fertile.
Interestingly, female dogs know when they're fertile, as they often become more flirtatious. On the flip side, they also know when they're not ready to breed yet. Females can be a little cranky right in the beginning of heat if they feel it's not quite the right time to breed.
6. Puppies can be spayed at 8 weeks old.
7. Spayed dogs live longer lives.
Research has shown that altered dogs live longer on average, with spayed female dog having around 23% longer lifespans. There are a few factors that contribute to this. First, spayed dogs tend to roam less, reducing accidents out in the world (like fights with animals or being struck by a car). Second, spayed dogs are less likely to develop certain reproductive system cancers and illnesses.
8. Females spayed before their first heat are typically healthier.
Furthermore, medical evidence shows that females spayed before their first heat cycle tend to be healthier. This is in part because of the aforementioned fact that spaying a female at a young age decreases her risk of developing cancers (like mammary and uterine cancer), and illnesses (like pyrometra, a fatal uterine infection). Most dog shelters and adoption programs spay females before their first heat.
9. Spaying can alter a dog's behavior.
Spaying can change some behaviors of unaltered dogs. These behaviors include roaming or wandering, excessive urination, howling, mounting and certain destructive behaviors. They will not, however, become fat and lazy, which is a common misconception.
10. Spaying can also alter a dog's temperament.
Spaying can also improve a dog's temperament. They become less aggressive and focused on their mating drives, often resulting in more attention for their owners. All that being said, spaying will not alter your dog's personality or instincts.
BONUS: Spaying is cost-effective.
Spaying and neutering is a one-time cost that is relatively low, especially taking into account the benefits of the surgery and comparing to the alternative. Unaltered dogs can lead to higher costs later, from caring for a litter of puppies to a dog with related health complications (like cancer or pyometra). In addition, unaltered dogs can be destructive around the house or get into fights with other dogs, both of which can become costly.