For some puppies, nothing says "hello" quite like humping the leg of a new acquaintance. That's inevitably followed by either an apology on the part of the puppy's owner or a remark about pups being pups. Humping is a natural activity on the part of both male and female puppies. That said, so is eliminating, but owners should set the boundaries, and humping is a good habit to break.
Just as you suspected, the primary reason puppies hump is because it gives them a pleasurable feeling. It's the equivalent of puppy masturbation. Also known as mounting, humping isn't relegated only to people. Puppies may masturbate their beds, toys and litter mates.
Humping and stress
Humping isn't always related to sex. Many puppies and dogs hump in response to stress, according to the American Kennel Club. When young dogs are excited or scared, it's common for them to mount their person, their bed or another item in the vicinity. If you've noticed an excessive amount of humping at the dog park, there's a reason for that. Between the stress of strange dogs and the desire to play, the park is a humping haven.
Humping is often a dominance display when it comes to other dogs, and that makes it dangerous. If the other dog won't put up with it, a nasty fight may ensue. A dominant puppy may try to mount almost any dog he meets, just to prove his point. This is a practice you must nip in the bud with proper training and socialization.
Less frequently, humping may indicate a medical problem. Urinary tract infections and the resulting discomfort may cause puppies to hump to gain temporary relief. Dogs suffering from compulsive disorders or anxiety may hump because of their emotional condition. Have your vet thoroughly examine your pet if you suspect medical issues play a role in her humping.
Stopping the behavior
Most dog owners aren't fond of humping behavior, yet may inadvertently encourage it. For example, if your puppy humps your leg for attention and you immediately pick him up — primarily to stop the humping — what you've taught him is that humping gets him what he wants. Even scolding him is a form of reward, because you are paying attention to him. As Whole Dog Journal points out, laughing at his antics is a form of negative reinforcement.
So, what to do when your puppy starts humping your leg? Get up and ignore him. When no attention is paid to him, he will get the idea that mounting isn't getting him the recognition he desires. It's also important to start this type of "training" as soon as possible because once a puppy starts humping, it is harder to break him of it.
Minimizing his behavior may require some tough love. If he starts humping a guest, banish him to another part of the house or put him in his crate. Train your puppy to perform some basic obedience behaviors, such as sitting. When he starts to hump, distract him and have him sit instead.
Observe when your puppy starts humping if he isn't doing it all the time. Once you have figured out the triggers, you can either avoid them or ensure your puppy isn't involved. For example, if guests arriving bring out the humping instinct in your dog, put him away before answering the dog and seating your company.
While neutered dogs may hump, they are far less likely to than intact animals. That's especially true of male dogs, who tend to hump much more than their female counterparts. Once neutered, much of the sexual element of humping is gone or greatly diminished. It's the rare dog whose humping isn't reduced by at least half once his testicles are gone.