Characteristics of the motor and genital copulatory responses of the male hamster

The temporal and dynamic characteristics (duration, frequency, rhythmicity, and vigor) of pelvic thrusting displayed by 17 male golden hamsters during their copulatory behavioral responses: mounts, intromissions, ejaculations, and long intromissions, as well as their temporal correlation with the genital contacts established by intravaginal penile insertion, were studied by an accelerometric and polygraphic technique. Pelvic thrusting in all copulatory behavioral responses appeared as series or trains of rhythmical, synchronic, vigorous movements. The various pelvic thrusting trains lasted around 1 s on average, but those of mounts were significantly longer than the trains displayed in the other behavioral responses. The frequencies of pelvic thrusting were similar in all responses (around 15 thrusts per s) excepting mounts which had lower values. In intromission, ejaculation, and long intromission responses, when penile insertion occurred, pelvic thrusting either was interrupted or showed changes in its characteristics: penile insertion was related to a period without thrusting in intromissions, to a series of intravaginal thrusting of higher frequency (16.4 thrusts per s) and lower vigor in ejaculations, and to a prolonged period of 6 to 25 s of slow intravaginal pelvic thrusting (1–2 thrusts per s) in long intromissions. Penile insertion lasted longer in ejaculations than in intromissions and it was significantly shorter in both of these responses than in long intromissions. These results provide information about some dynamic aspects of sexual behavior in hamsters, as well as a temporal correlation between the motor and genital components of this behavior.     

Correlation of in vivo testicle and seminal vesicle size with post mortem dimensions in bulls

This study was conducted to quantify the relationships between in vivo measurements of testicular and seminal vesicle size and post mortem size of these organs in 30 Santa Gertrudis bulls. The in vivo measurements of testicles were obtained by transrectal ultrasonography and palpation per rectum, while scrotal circumference was measured by scrotal tape. Linear post mortem dimensions were obtained by direct measurements of the excised organs. Volume was assessed by water displacement while the testicles were weighed. Seminal vesicle length, determined by palpation, had the highest correlation with post mortem measurements (r = 0.70; P = 0.0001). Accurate estimation of the thickness of the vesicles (1.47 vs 1.55 cm for in vivo and post mortem, respectively) was performed by ultrasonograph. Of all seminal vesicle linear measurements, width had the highest correlations with volume measured by water displacement (r = 0.67; P = 0.0001 and r = 0.38; P = 0.04 for post mortem and in vivo, respectively). Testicular diameter was accurately measured by ultrasonography (5.54 vs 4.58 cm in vivo and post mortem, respectively) and was highly correlated (range r = 0.84 to 0.89; P = 0.0001) with post mortem measurements of testicular volume, weight and circumference. The correlation between scrotal circumference and diameter of the testicle was 0.75 (P = 0.0001). The correlations of testicular diameter measured by ultrasound with the post mortem measurements of testicular weight and circumference were similar to the correlations between scrotal circumference and those 2 post mortem measurements. We conclude that palpation of vesicle length is highly correlated with volume of the seminal vesicle in situ. Individual linear measurements do not seem to be an accurate predictor of the relativ size of the seminal vesicle. Furthermore, ultrasonography does not seem to be a more accurate measure of testicular size than scrotal circumference for evaluation of breeding soundness.     

Study of pharmacological activation of the male sexual behavior

The model of sexual exhaustion of male rats was used in the study. The specific aim was to compare the effects of cocaine on the mount latency, number of mounts, intromissions and ejaculations during the entire copulatory cycle with the same indices during the first 30 min of observation (the latter is most frequently used in laboratory settings). Experiments consisted of four 3-day test periods. On days 1 and 2, male rats were allowed to interact with receptive females until the satiation criterion was reached (30 min without mounts). On day 3, male rats were injected with cocaine (5, 10, or 30 mg/kg, i.p.) or its vehicle 15 min prior to testing. Cocaine administration in a dose-dependent way increased the total number of mounts and ejaculations during the entire observation session but not during the initial 30-min period. The mount latency was unaffected by cocaine treatment. The results suggest that the expression of the stimulating effects of cocaine on sexual behavior depends on the duration of the observation period.     

Crowding or ACTH treatment of pregnant mice affects adult copulatory behavior of male offspring

Sexual behavior of male offspring from female mice chronically crowded during Days 12-17 of pregnancy was investigated. In an 80-min test pairing with a sexually experienced female primed with estradiol and progesterone injections, males from crowded mothers displayed poorer copulation than controls: mount and intromission latencies were longer, number of mounts and intromissions lower, and ejaculations within the test period were abolished. Daily injections of 500 micrograms testosterone propionate improved copulatory vigor in offspring from crowded mothers. A second series of experiments investigated the effects of ACTH treatment of females during the same period of pregnancy. A low dose rate (1 IU injected daily) had little effect but male offspring from females injected daily with 8 IU displayed longer intromission latency and fewer mounts and intromissions than controls. Daily injections of 500 micrograms testosterone propionate improved copulatory vigor, although mount frequency remained depressed. The similarity of the effects on male offspring copulation of crowding their mothers during pregnancy or ACTH treatment during pregnancy suggest mediation by similar mechanisms, implicating involvement of maternal pituitary-adrenocortical secretions during pregnancy in the production of these behavioral deficits. Postnatal influences were minimized by fostering all litters at birth to untreated dams.     

Developmental expression of penile reflexes and copulatory behavior in male rats.

First, pubertal development of the penile reflexes, e.g., erections, cups and flips in Wistar-Imamichi male rats was investigated following sheath retraction. Second, the penile reflexes and copulatory behavior in the above males were compared between 10 and 44 weeks of age. The penile reflexes in Wistar-Imamichi rats began to appear from day 26, and all males displayed full components of the reflexes on day 47. The occurrence rates and mean numbers of erections, cups and flips in aged adults were significantly low, compared with the young adults. Also, in the observation of copulatory behavior the occurrence rate of ejaculations, and mean numbers of intromissions and ejaculations in aged adults were significantly lower than that in young adults. These results of the present study may suggest that the decrease of copulatory behavior in male rats with age results from the dysfunction of the penile reflexes with age.     

Copulatory patterns of primates as viewed in broad mammalian perspective

The goals of this review are to classify the patterns of copulatory behavior displayed by various species of primates, to compare them to the patterns of nonprimate mammalian species, and to search for correlates of the various patterns. Copulatory patterns are classified in relation to the presence or absence of four defining attributes: a lock, thrusting during intromissions, multiple intromissions, and multiple ejaculations. Literature on copulation in 67 primate species is reviewed, and a tentative classification is proposed for 33 primate species. Although neither social organization nor genital morphology provides a fully satisfactory relationship, there are indications that variations in copulatory behavior are related to variations in genital morphology.     

Copulatory Behavior as Courtship Communication

In the copulatory behavior of many species of rodents, mounting patterns with ejaculation are preceded by mounts with nonejaculatory intromissions. Although not directly related to insemination, these intromissions have generally been treated as “copulatory” behavior. If we treat these nonejaculatory intromissions as courtship communication in the tactile modality, new relationships become apparent. Within the context of classical ethology, intromissions can be considered in relation to both proximate dynamics and ultimate effects. Within the sociobiological/behavioral-ecological context, intromissions can be viewed in relation to manipulation, female assessment and choice, and honesty of communication. The intromissions synchronize, persuade, and orient at the same time as they manipulate the partner.     

Sexual behavior and pregnancy rate of Bos indicus bulls

To study sexual behavior and pregnancy rate of Zebu bulls, 9 Brahman and 6 Nelore bulls were first examined for libido and serving capacity, semen characteristics and scrotal circumference, a week before being placed, individually, into a group of 16 estrus-syncronized heifers to observe mating activity. Scores for libido (0 to 10) and for serving capacity (based on the number of services per period) were assigned for each bull over a 15-min period. Estrus was synchronized with Norgestomet (3 mg, s.c. implant and 3 mg, i.m.) and estradiol valerate (5 mg, i.m.). The implants remained in place for 10 d, then 40 h after their removal a bull was placed with the heifers. Four Brahman and 6 Nelore bulls were monitored for 2 h while the remaining 5 Brahman bulls were observed for 30 h. Number of services and mounts per bull, the hour at which each event took place, and the identification of the heifers serviced were recorded. Pregnancy was diagnosed by transrectal palpation 50 to 60 d after mating. Mean libido score (+/- SEM) of the 15 bulls was 6.4 +/- 0.5, and mean serving capacity was 0.53 +/- 0.19; both of these measures were correlated with age (r = 0.78, P < 0.01, and r = 0.56, P < 0.05, respectively). In the 2-h trials, the number of mounts was correlated with the libido score (r = 0.73, P < 0.05), and the number of services was correlated with age (r = 0.76, P < 0.05) and with libido and serving capacity score (r = 0.91 and 0.92, P < 0.01). In the 30-h trials, the mean (+/- SEM) number of mounts and of services per bull was 74.4 +/- 21.1 and 14.6 +/- 0.5, respectively. The mount-to-service ratio and percentage of serving efficiency were 5.1 +/- 1.4, and 19.8 +/- 4%, respectively. Libido score was correlated with the mount-to-service ratio (r = -0.86, P < 0.10) and with serving efficiency (r = 0.84, P < 0.10). The percentage of heifers serviced, of those serviced 2 or more times and of those pregnant was 55 +/- 5.3; 47.1 +/- 6.4, and 59.2 +/- 5.8, respectively. Pregnancy rate was not correlated with any trait (P > 0.10). It was concluded that libido and the serving capacity test seem to indicate the mating potential of Zebu bulls over a relatively short period of time (e.g. 30 hours), in which resultant pregnancy rates are comparable to those of European bulls.     

Previous sexual experience alters the display of paced mating behavior in female rats

The present study tested whether the display of paced mating behavior in female rats over four weekly tests is affected by sexual experience and whether test parameters, i.e., ending the test based on time or number of stimulations received, influence behavioral changes. In Experiment 1A rats with nonpaced sexual experience returned to the male more quickly overall compared to sexually naïve rats in a 30-min test of paced mating behavior. In Experiment 1B, rats received four weekly 30-min tests with one, different, male rat partner each week. Over the four tests, rats returned to the male significantly more quickly after intromissions, but significantly more slowly after ejaculations. Experiment 2A tested whether sexual experience would influence paced mating behavior in tests with a 15-intromission end criterion and the male replaced after ejaculation. Rats tested weekly under 15-intromission test conditions returned to the male significantly more quickly after intromissions, but no behavioral change was observed after ejaculations. When those same rats were given a 30-min test of paced mating behavior (Experiment 2B), they returned to the male significantly more slowly after ejaculations. Collectively, these data show that sexual experience influences the display of paced mating behavior in female rats and that the test parameters interact with sexual experience to influence the nature of the changes. Sexual experience may facilitate behaviors that promote reproductive success in female rats.     

Effect of prostaglandin F2 alpha on libido, seminal quantity and quality of buffalo bulls

Four mature Murrah buffalo bulls on a regular semen collection schedule of twice a day, two days per week, were injected with 30 mg prostaglandin F2 alpha THAM salt(PGF) intramuscularly 30 minutes prior to each alternate first ejaculation for six weeks. Effects of PGF on time to initial false mount on the decoy, time to ejaculation after two false mounts (reaction time), seminal volume, sperm concentration, total sperm output, motility of fresh and thawed semen and the semen doses obtained per collection were evaluated. Treatment caused significant (P < 0.01) reduction in the time to first false mount and the reaction time for the first ejaculations but had no effect (P > 0.05) on these for the second ejaculations. Values for other quantitative and qualitative parameters did not differ (P > 0.05) due to PGF treatment. It is concluded that PGF at the dosage and frequency of administration used may be of some value in improving libido in low-libido bulls but does not alter the reproductive capacity of buffalo bulls.     

Short-latency effect of testosterone on copulatory behaviour and ejaculation in sexually experienced intact male rats

The effect of a single injection of testosterone on the number of stimuli required to trigger ejaculation and on copulatory behaviour was investigated in sexually experienced intact male rats. An intraperitoneal injection of 100 microgram free testosterone 1 h before testing facilitated the copulatory behaviour and decreased the number of mounts and intromissions needed for ejaculation; the latter effect was obtained in a test in which a constant interval was kept between each intromission.     

Seminal transferrin and spermatogenic capability in the bull

The objective of this study was to determine the relationship between seminal transferrin and sperm output in ejaculates from mature dairy bulls. Caudal sperm reserves in mature Holstein bulls (n = 15) were depleted by 8 successive ejaculations during a 50-70-min period (depletion phase). Bulls were then ejaculated 6 times per week for a period of 4 weeks (6X phase). Weekly sperm output (WSO) and weekly transferrin output (WTfO) were the sums of sperm and transferrin levels in 6 ejaculates taken in 1 week of the study. Mean WSO ranged from 20.7 billion to 39.6 billion and mean WTfO ranged from 334 micrograms to 1872 micrograms among the bulls. Regression analysis of sperm and transferrin levels in ejaculates collected during the depletion phase indicated that approximately 40% of seminal transferrin was not related to sperm output and probably was from accessory fluids. A relationship between total seminal transferrin and total sperm in ejaculate was observed (p less than 0.01, r = 0.54). This relationship was stronger when the transferrin was corrected for accessory fluid contribution (p less than 0.01, r = 0.65). The relationship between WSO and WTfO corrected for accessory fluid transferrin contribution (cWTfO) was significant (p less than 0.01, r = 0.64). The relationship between WSO and cWTfO can be interpreted to reflect the relationship between actual testicular sperm production and transferrin from testicular or epididymal origin.     

Effect of pineal indoles and testosterone on sex behavior

The possible action of melatonin and 5-methoxytryptophol, two pineal indoles, upon castrated male rat sexual behaviour with three testosterone dose levels was studied. Both indoles reduced the number of mounts and intromissions. 5-Methoxytryptophol, in addition, decreased the number of ejaculations. The sexual actions of the pineal indoles are prevented by the administration of high testosterone dose levels (500 micrograms/day).     

Sexual behavior during successive ejaculations in bonnet and pigtail macaques

During tests of sexual behavior which permitted multiple ejaculations, male bonnet and pigtail macaques were found to differ on a number of traditionally defined behavioral parameters. Although pigtail tests were terminated by a more stringent criterion, they were longer in duration and more ejaculations were recorded than in the bonnet tests. Pigtail males required relatively more intromissions for initial ejaculations and somewhat fewer on successive ejaculations. Bonnets, on the other hand, generally ejaculated on the first mount of a test and then exhibited increased numbers of intromissions to successive ejaculations. Although both species exhibited increases in successive postejaculatory intervals, the changes were more gradual for the pigtails.     

Sperm competition and diversity in rodent copulatory behaviour

The copulatory behaviour of male mammals is characterized by striking diversity in patterns of copulatory stimulation and ejaculation frequency. We conducted comparative analyses of rodents to investigate the potential influence of sperm competition in the evolution of copulatory behaviour. We found that increasing sperm competition is associated with faster rates of stimulation and earlier ejaculation among species in which males perform multiple intromissions prior to ejaculation, but with no overall change in the number of intromissions per ejaculation. Increasing sperm competition is also associated with a higher frequency of repeated ejaculations with the same female, and with shorter refractory periods between repeated copulations. Increasing sperm competition level thus appears to select for male ability to ejaculate more rapidly and more frequently with each female mated. As prolonged copulations are known to reduce female remating rates, these findings indicate that males may experience opposing selection pressures on copulatory behaviour with respect to offensive and defensive aspects of sperm competition. We conclude that sperm competition is likely to be an important selection pressure explaining diversity in mammalian copulatory behaviour.     

Group mating among Norway rats II. The social dynamics of copulation: Competition,cooperation, and mate choice

The social interactions within groups of Norway rats (Rattus norvegicus) had a strong impact on the individual pattern of copulation which, in turn, affects sperm precedence and the probability of implantation in this species. Males alternated uninterrupted ejaculatory series, augmenting each others' copulatory investment. Females took turns mating after receiving an intromission, collectively potentiating the males' copulatory behaviour; increasing the number of oestrous females increased the number of intromissions and ejaculations achieved by each male but did not affect the amount of copulation experienced by each female. These turn-taking patterns within each sex provided the opportunity to change partners and permitted the emergence of different sex-typical patterns of copulation. Furthermore, the dominant male contributed more intromissions and tended to give each female more ejaculations than the subordinates did. Dominant males were also more likely to inhibit the subordinates' sperm transport. Females competed among themselves for the opportunity to mate with a male as he approached ejaculation and were likely to protect more of the dominant male's sperm transport than the subordinate male's.     

Heterosexual interactions of pairs of laboratory-housed stumptail macaques (Macaca arctoides) under continuous observation with closed-circuit video recording

Female-male interaction of heterosexual pairs of stumptail macaques, housed together continuously, was studied 24 hr per day using closed-circuit video recording. Two pairs were studied for approximately 2 months each. Although no generalizations can be made from such a small sample, no aspect of behavioral interaction varied significantly with the stage of the menstrual cycle of the female partner. Copulation occurred regularly but only during the daylight hours. Both pairs showed several peak ejaculation days (5–21 ejaculations/day), which were distributed throughout the entire menstrual cycle. In general, the highest number of ejaculations was observed to occur when the animals were put together either for the first time or following a separation of a few days. In one pair the female became pregnant, and from the fifth week of pregnancy onward there was a gradual increase in male aggression, coinciding with a decrease in male sexual and grooming behavior. In a second study eight different pairs were observed during the first day together and male copulatory behavior was studied. Two patterns of copulatory behavior could be discerned: pairs displaying a high number of ejaculations (19–38) and pairs displaying a low number of ejaculations (4–8). With regard to the interejaculatory interval (IEI), the male stumptail appeared to be unique. In contrast to what has been reported for other mammals, i.e., a steady increase in IEI with subsequent ejaculations, the stumptail showed increasing IEIs only during the first three to four, as well as between the last, ejaculations; in between, the IEI remained relatively constant. The maximum number of consecutive ejaculations observed was 38, displayed during a 10-hr time period (mean (± SEM)IEI, 12.9 ± 3.5 min).     

Bull-bull mounts in Holstein bulls: a survey of its incidence,possible causes,and consequences in Uruguayan bull’ breeders

Bulls frequently display male-male mounts, with consequences in the incidence of injuries, and possibly affecting the reproductive performance of the bulls. This behavior is known as the “buller syndrome” when appears in steers, with several individuals mounting one or a few penmates. The study aimed to collect information on the incidence of bull-bull mounts, the possible associated factors, the productive consequences, and management applied by distributing a survey to Holstein bull breeders in Uruguay. A survey was applied and responded by most Holstein breeders in Uruguay (30/33). Nineteen of the 30 breeders observed mounting behavior among bulls, and 15 of them considered it as a relevant problem. The breeders that observed the behavior had a greater number of bulls than those that did not observe it (P = 0.002). All of them observed that mounts were persistently directed towards the same individual (considering a specific period, while it remained in the group). Of these, 11 (58%) considered that this stopped only when the “buller” bull was removed from the group, mentioning that the behavior was frequently redirected to another individual. The mounts between bulls are a major problem in the breeding of Holstein bulls, with important consequences on weight gain and animal health, reproductive problems such as low libido and seminal quality, and even provoking the death of animals. Although not all breeders reported the existence of the problem, those with the bigger herds did. While some management and/or environmental conditions seem to influence (higher density, regrouping, managements that involve movement of animals, and spring) the incidence of bull-bull mounts, there are no standardized managements to avoid this behavior. Considering that most breeders were interested in including practices to minimize this problem if available, it would be essential to understand better the causes and predisposing factors to decrease its negative impacts.     

Gonadal hormones masculinize and defeminize reproductive behaviors during puberty in the male Syrian hamster

Three experiments were conducted to test whether testicular hormones secreted during puberty masculinize and defeminize the expression of adult reproductive behavior. Experiment 1 tested the hypothesis that gonadal hormones during puberty masculinize behavioral responses to testosterone (T) in adulthood. Male hamsters were castrated either before puberty (noTduringP) or after puberty (TduringP). All males were implanted with a 2.5-mg T pellet 6 weeks following castration and tested once for masculine reproductive behavior 7 days after the onset of T replacement. TduringP males displayed significantly more mounts, intromissions, and ejaculations than noTduringP males. Experiment 2 tested the hypothesis that gonadal hormones during puberty defeminize behavioral responses to estrogen (EB) and progesterone (P). Eight weeks following castration, noTduringP and TduringP males were primed with EB and P and tested for lordosis behavior with a stud male. Behavioral responses of males were compared to that of ovariectomized (OVX) and hormone primed females. NoTduringP males and OVX females displayed significantly shorter lordosis latencies than TduringP males. Experiment 3 investigated whether prolonged T treatment or sexual experience could reverse the deficits in masculine behavior caused by the absence of T during puberty. Extending the T treatment from 7 to 17 days did not ameliorate the deficits in masculine behavior caused by absence of T during puberty. Similarly, when the level of sexual experience was increased from one to three tests, the deficits in masculine behavior persisted. These studies demonstrate that gonadal hormones during puberty further masculinize and defeminize neural circuits and behavioral responsiveness to steroid hormones in adulthood.     

Sexual behavior of donkey jacks: influence of ejaculatory frequency and season

The courtship of 5 jacks was evaluated weekly for 12 mo. The characteristics of sexual behavior were recorded before the collection of 2 ejaculates, at 4-h intervals, into an artificial vagina in the presence of a female in either natural or induced estrus. The maximum time given to the jack to perform the ejaculatory mount was 1 h. If the jacks did not ejaculate, another attempt was made the following week. At the time of collection, the male and female remained free in a paddock (20 m2). The data presented in this study is based on results in which the first and second ejaculates occurred successively. Statistical analysis was done by a 2 x 2 factorial design in randomized blocks. The mean +/- SEM of sexual behavior characteristics for the first and second ejaculate were, respectively: time until first mount = 0.7 +/- 0.2 and 0.9 +/- 0.2 min; time until first erection = 11.9 +/- 1.1 and 11.6 +/- 1.1 min; time until ejaculation = 15.0 +/- 1.2 and 13.6 +/- 1.2 min; frequency of partial exposure of penis = 3.4 +/- 0.4 and 3.2 +/- 0.4; frequency of total exposure of penis = 1.0 + 0.2 and 1.1 +/- 0.2; frequency of flehmen responses = 6.6 +/- 0.5 and 4.6 +/-0.5; frequency of erections = 1.3 +/- 0.1 and 1.2 +/- 0.1; frequency of retreats away from the female = 1.8 +/- 0.2 and 1.0 +/- 0.2; frequency of mounts with erection but without ejaculation = 0.3 +/- 0.1 and 0.1 +/- 0.1; frequency of mounts without erection = 2.0 +/-0.1 and 1.2 +/- 0.1 ; and frequency of pelvic copulatory movements = 4.8 +/- 0.4 and 4.4 +/- 0.4. Individual differences were observed (P<0.05) for partial and total exposure, flehmen responses, mounts without erection and pelvic copulatory movements. The variables flehmen responses, retreats away from the female and mounts without erection showed significant differences (P<0.05) between ejaculates. Seasonal effects on sexual behavior characteristics were not found. However, a monthly effect was noted for flehmen responses, partial exposure of the penis, mounts without erection, retreats away from the female and pelvic copulatory movements when the 2 ejaculates were combined.