Why does the dog sometimes hug our leg?

More than one dog owner confirmed, with extreme embarrassment, that there can be feeling between the dog and the owner’s legs, with its pelvic movement of the animal, as if it were mating.
The dog goes through, during its existence, a particular phase of socialization, during which it decides what it wants to be. This critical period begins at the age of four weeks and continues until the twelfth week: any living being who shares this time with the dog, becomes in its eyes a member of its species.

In the case of puppies, this phase is generally spent together with animals of two different species. Men and dogs. The puppies become so mentally hybrid, in very close relationship both with humans and with their four-legged counterparts.

All in nature

As long as one remains in the realm of simple daily activities, this ambiguity does not create problems. As the puppy considers itself adopted by the herd of humans. But when we start talking about sex, this solidarity, this promiscuity stops abruptly. Luckily for the human being, the sexual attraction of the dog is determined and conveyed in the right direction by some factors of innate education. A female in heat produces a particular smell of sexual attraction that attracts males even at great distances. Since men cannot perceive these emissions, domestic dogs consider the man a member of the social group devoid of sexual drive.

Everything should then proceed in the most consistent way, but unfortunately meeting a female dog in heat is a rare event in a domestic dog life. In the animal, a certain level of sexual frustration increases, so that even the cat of the house can suddenly become attractive. At that point, the dog will try to mate with anything (object or animal) that stands still as long as necessary for the purpose: cats, other male dogs, cushions. The human legs are “targets” that the dog can easily reach and which it can easily cling to.
In such a situation, the most correct behaviour is to be compassionate, rather than angry. Gentle rejection of such proposals is all that is really needed, not harsh punishment.

Instinct

Note that the considerations on the sexual interest of the dog towards the cat are not meaningless. Frustrated dogs really try to mate with their feline companions. But only if they’re cats that grew up with them. The proximity with a cat in the critical period of the development supplements a dog code of recognition as if the feline belongs to its same species. The cohabitation with men, dogs, and cats, in a period between the 4th and the 12th week, leads the puppy to cuddle with three different species for life.

Of course, this recognition system has a drawback. The absence of contact with an animal species in the aforementioned period teaches the puppy that this species is different, and therefore potentially it represents a source of danger. If a puppy is removed from its mother before it opened its eyes and also its ears, it will be able to develop a relationship of attachment to man, but it will be uncomfortable with other dogs, not recognizing them as members of its species.
Likewise, if a puppy lives with its mother until the twelfth week without any approach with a human being, it will never be an easily tame and treatable dog by man. No confirmation therefore that the domestic dog is such for genetic information.