A positive correlation has been found between the number of males attempting to mate and the length of time they show interest in the female. 9, 26, 28, 62 Free-ranging dogs tend to show the most elaborate courtship behaviors. Some show apparent indifference, and some give varied amounts of attention. When in contact with estrous females, males display a lot of individual variation in behavior. Apparently the odor can travel great distances, because dogs have been found at the home of an estrous female over 5 miles from the fenced yard where they usually stay. Premating (courtship) behavior begins when the male first picks up the scent of an estrous bitch. 9, 27 They may, however, occasionally show a preference for certain bitches, and they are more likely to reject individual females that are dominant or females of other breeds if their contact has been limited to one or two breeds. Male dogs are considered to be promiscuous breeders and receptive to an estrous bitch at any time of the year. 8, 38 The male sexually dimorphic behaviors in dogs include interest in estrous vaginal secretions, mounting, pelvic thrusting, ejaculation, urine marking, roaming, and intermale aggression. Dogs castrated at birth and injected with testosterone as adults will show more masculine behavior than either intact or neutered females but less than dogs castrated after sexual maturity. 42 Removal of the gonads shifts the dimorphism somewhat toward the opposite sex. 1 The distinction between maleness and femaleness is blurred, not absolute. 45, 46 It also has been shown that testosterone is necessary to produce interest in the vaginal secretions of estrus. 38, 44 Other male traits tend to be dominance over owners, aggression to dogs, territorial defense, destructiveness, playfulness, general activity, and snapping at children. Essentially all intact males show sexual mounting, thrusting, and raised-leg urination, but 40% of intact females also show mounting and thrusting, and 5% show raised-leg urination. Part of the “female brain” remains in all males as well, so they can show varying amounts of behavior typically associated with females. As has already been mentioned, neonatal female puppies have low levels of testosterone, so it is not surprising that females occasionally show behaviors that are typically considered masculine. The development of male behaviors at puberty is the expression of sexual dimorphism. 76 Light deprivation may slow down maturation of the gonads, 55 as might other physical, environmental, and breed factors. 76 All characteristics of the fluid part of the ejaculate are comparable with those of adults by 45 weeks of age. 76 Early ejaculates have large numbers of abnormal spermatozoa, but these numbers soon decrease. 27 In studies of Beagles, the first ejaculation occurred around 33 weeks of age. 9 In wolves puberty occurs at about 2 years. Puberty in dogs comes at 6 to 18 months, occurring slightly later in males than in females. If puppies are deprived of opportunities to include these behaviors in play, their adult mating behaviors are adversely affected. As with most adult behaviors that occur in puppies, these behaviors are abbreviated and out of context-a part of juvenile play. 9, 14, 28, 52 Instead of being sexual, however, these behaviors represent play. Early castrated puppies show no interest in estrous females unless they receive testosterone injections.īehaviors such as mounting, pelvic clasps, and thrusts can appear in puppies as young as 3 to 6 weeks. This interest continued for at least 20 months. 6 During the time of injections, these tiny puppies showed a preference for estrous females. 45 Puppies experimentally castrated during the first few days postpartum and then injected with testosterone for 3 months developed almost the same as noncastrated puppies. 38, 76 These levels do not explain the sexual differences, so it is assumed that the surge occurs prenatally. 44, 48 Thereafter, levels gradually fall and do not rise again until puberty. The exact time of this perinatal testosterone surge in male puppies is not well studied, 38 but it is known that at birth and for the first 20 days of life, testosterone levels in male puppies are approximately 2 mg/ml versus 0.1 mg/ml in the females. This is called “the organizational effect of the hormone.” 53 Without the testosterone influence at this time, the brain remains feminine regardless of which gonads are present. In males of most species, there is a surge of testosterone within a few days of birth that is responsible for masculinizing the brain, including those areas responsible for the male behaviors.
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