Puppies are absolutely adorable whether they're purebred or complete mutts. However, just like all baby mammals, puppies only come about as a result of their parents engaging in sexual intercourse. Canines (including wolves, foxes, jackals, and dogs) are unique in how they mate since before the act is over, the two dogs get stuck together in what's known as a copulatory tie that lasts for five to 40 minutes after the male dog ejaculates.
Why dogs get stuck together
There are actually multiple things happening when dogs get stuck together while mating, but to understand the full process, you first need to know more about the erectile tissue of the penis. All mammals have two types of erectile tissue: one stiffens the penis, and the other fills the penis glans and makes the organ swell.
In most mammals, these tissues are both activated at the same time, but in dogs, the penis is stiffened before intercourse begins, and the penis doesn't begin to really swell until the two dogs start mating. In fact, male dogs have long bones in their penis, so they have very little penis-swelling tissue, and their penises do not grow much until after sex begins.
Once the male has mounted the female and enters her, the glans tissue begins to expand, particularly around the base in an area called the bulbus glandis. As the male ejaculates, the penis starts expanding dramatically. When the bulbus glandis expands, it becomes very stiff and grows three times as wide and twice as thick as when flaccid. At the same time this is happening, the female's vaginal muscles start tightening and squeeze down on the penis.
The male dog will usually dismount during the tie, leaving the two dogs locked together butt to butt. They will remain in place until the male's penis deflates, and the female's vaginal muscles relax.
Evolutionary benefits of ties
Why dogs remain tied together, and why they do it in this position is still a mystery, but there are some theories. For example, while the male has already ejaculated sperm into the female, scientists speculate that during the tie, the male does ejaculate a small amount of prostate fluid, which may help push his sperm further into the female, increasing the likelihood of her getting pregnant.
The tie may also help prevent other dogs from mating with the female until the male's sperm has a chance to enter the egg. As for why they face outward from one another, this could be a defensive tactic that allows them to survey all 360 degrees of their surroundings.
How to help stuck dogs
If you come outside to see your dog tied together with another, do not try to help. While female dogs sometimes will start crying, whimpering, or even growling or barking, it's important to realize that this process is totally natural.
Unfortunately, separating them is not part of the natural process and can actually hurt both dogs and cause them unnecessary stress. After a while, the dog penis will return to its normal size, and the female's vagina will relax, and the two dogs will be able to go their separate ways.
Even if you are upset because you did not want the dogs to breed together, you should not try to break them up, as the male has already ejaculated. If the female is going to get pregnant, there's nothing you can do to stop it at this point, and attempting to separate the dogs will only risk hurting them.