where does a male dog enter a female dog
Canine reproduction Male canines are the only animals that have a locking bulbus glandis or "bulb", a spherical area of erectile tissue at the base of the penis. During copulation, and only after the male's penis is fully inside the female's vagina, the bulbus glandis becomes engorged with blood.[9] In coyotes, when the female's vagina subsequently contracts, the penis becomes locked inside the female.[10] This is known as "tying" or "knotting". While characteristic of mating in most canids, the copulatory tie has been reported to be absent[11] or very brief (less than one minute)[12] in the African wild dog, possibly due to the abundance of large predators in its environment.[13]
Sexual selection Sexual selection is a mode of natural selection where members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (intrasexual selection). These two forms of selection mean that some individuals have better reproductive success than others within a population, either from being more attractive or preferring more attractive partners to produce offspring.[1][2] For instance in the breeding season sexual selection in frogs occurs with the males first gathering at the water's edge and making their mating calls: croaking. The females then arrive and choose the males with the deepest croaks and best territories. Generalizing, males benefit from frequent mating and monopolizing access to a group of fertile females. Females have a limited number of offspring they can have and they maximize the return on the energy they invest in reproduction.