Movement and reproductive behavior of solitary male redtail guenons (Cercopithecus ascanius)

Adult male redtail guenons (Cercopithecus ascanius) live as resident males in heterosexual groups or as nonresident males outside groups. Data are reported here on movement and temporary intrusions by nonresident males in heterosexual groups. These data further elucidate the reproductive strategies of this class of individual. Observations of three radiocollared males provided data on the details of their movement relative to groups. Regular sampling of three heterosexual groups provided data on patterns of nonresident males' intrusions. During peak mating months, nonresident males formed loose affiliations with groups. The males affiliated with one group at a time, with each affiliation lasting several weeks. Nonresident male intrusions in groups were unevenly distributed and were not correlated with the number of potentially fertile females in each group. Estimates of male density indicate that there were about two nonresident males per group, which suggests an adult sex ratio of three females per male within the study area. Nonresident male redtail guenons apparently do not spread their reproductive efforts over several groups at once, but instead each male tends to direct his attention toward the group offering the best opportunity for reproductive payoffs. Factors that determine which groups they attempt to infiltrate may include the characteristics of resident males, female choice, or both, but the number of fertile females probably has no effect. The male low density and female-biased sex ratio among adults should facilitate resident males' attempts to monopolize fertilizations in groups; however, resident males were unable to prevent copulations by nonresident males even when only one nonresident was intruding in a group.     

Male-male Interactions in Heterosexual and All-male Wild Mountain Gorilla Groups

Variation in male dispersal and behavior patterns are components of intraspecific differences in social systems. A comparison of male behavior in different social settings can be useful for determining which behavioral mechanisms contribute to variability in social systems. Two heterosexual multimale groups and one all-male group of mountain gorillas (Gorilla gorilla beringei) were observed for over 1100 h at the Karisoke Research Centre, Rwanda. Data on proximity patterns, dominance relationships, aggression, agonistic interventions, affiliation, and homosexual behavior were compared among the males in these groups to examine the influence of female presence, sex ratio, group size, and kinship on male—male interactions. Males in the all-male group stayed closer together, affiliated more, exhibited more homosexual behavior, and were more aggressive toward each other than males in heterosexual groups. However, the males in heterosexual groups showed more wounding and more consistent dominance relationships. Kinship did not influence male-male relationships in the all-male group. The males in the heterosexual groups rarely interacted with one another; they may actively avoid close proximity to reduce aggression. Results suggest that the variable social system of mountain gorillas may be more strongly influenced by demographic factors, male-female social relationships, and male-male competition for mates than by any benefits of male-male relationships.     

Testing multiple hypotheses for the maintenance of male homosexual copulatory behaviour in flour beetles

Diverse animal groups exhibit homosexual interactions, yet the evolutionary maintenance of such behaviours remains enigmatic as they do not directly increase reproductive success by generating progeny. Here, we use Tribolium castaneum flour beetles, which exhibit frequent male homosexual copulations, to empirically test several hypotheses for the maintenance of such behaviours: (1) establishing social dominance; (2) practice for future heterosexual encounters; and (3) indirect sperm translocation. We found no evidence that Tribolium males use homosexual copulations either to establish dominance or to practice behaviours that increase their subsequent heterosexual reproductive performance. Our results provide limited support for the hypothesis of indirect sperm translocation: when males from two genetic strains mated with females immediately following a homosexual copulation, females produced progeny sired not only by the directly mating male, but also by that male’s homosexual partner. However, this phenomenon was detected in only 7% of homosexual pairs, and in each case such indirectly sired progeny accounted for < 0.5% of females’ total progeny. Direct observations indicated that mounting males often released spermatophores during homosexual copulations. These observations suggest that homosexual copulations may be a behavioural mechanism that allows males to expel older, potentially low‐quality sperm. Additional work is needed to test this new hypothesis, and to determine whether sperm release during homosexual copulations occurs in other groups.     

Plasticity in the mating system of the longnose filefish,Oxymonacanthus longirostris, in relation to mate availability

The mating system of the longnose filefish,Oxymonacanthus longirostris, was examined on coral reefs of Okinawa, Japan. This species has been shown previously to be monogamous. Fish were usually found swimming together in heterosexual pairs with the male and female sharing the same feeding territory. However, both monogamous and polygynous (bigamous) males were found in the present study. Polygynous males, which were larger than monogamous males, visited and stayed several minutes in turn with each female within the territories. Although most males were monogamous in the early breeding season, over 20% of males mated polygynously in the late breeding season. The adult sex ratio in the former was unbiased, but became slightly female-biased toward the end of the breeding season because of the higher disappearance rate of males. The higher disappearance rate may be due mainly to a higher mortality rate of males resulting from a greater deterioration of physical condition during the breeding season. Thus, the mating system varied with the change of the adult sex ratio. Plasticity in the mating system of this species may be the outcome of male mating tactic depending on local mate availability.     

Effects of group composition on agonistic behavior of captive pigtail macaques,Macaca nemestrina

We surveyed agonistic behaviors of 20 captive groups of pigtail macaques (Macaca nemestrina) housed under identical spatial conditions. Fifteen groups contained one male each; the other five groups contained no adult males. Groups included six to twelve adult females, some of which had infants with them. We found no relationship between social density of groups and incidence of agonistic behavior, but significantly more contact aggression (grab, hit, push, bite) and noncontact aggression (chase, open-mouth “threat,” bark vocalization) occurred among females in groups containing no males than in those containing one male each. Apparently, males played an important role in the inhibition of intragroup conflict. We also found that females in groups containing males exhibited less noncontact aggression if infants were present than if no infants resided in their groups. Thus, competition of females over infants must not have been an important constituent of intragroup conflict under the conditions of this survey.     

Longevity costs of same‐sex interactions: first evidence from a parasitic wasp

Costs of sexual interactions play a key role in life‐history evolution. Although the costs of reproduction have been investigated in both sexes of many insects, the costs of same‐sex interactions have been examined in few species. In parasitic wasps, very little has been reported about the longevity costs of heterosexual interactions, and nothing is known about longevity costs of same‐sex interactions. In this study, the effects of heterosexual and homosexual activities on longevity were evaluated in Psyttalia concolor (Hymenoptera: Braconidae), a synovigenic koinobiont larval‐pupal endoparasitoid of tephritid flies. When compared with individually housed virgin wasps, male longevity was strongly reduced both in males kept with females, and in males kept with other males. When females were kept with males, their longevity was reduced compared with the virgin females and females kept with other females. Overall, the costs of male–female interactions were considerable in both sexes of P. concolor, while same‐sex activities were found to be costly only among males, suggesting that they may have implications for the evolution of the P. concolor mating system.     

Gonadal hormones and sexual behavior in groups of adult talapoin monkeys (Miopithecus talapoin).

Three heterosexual groups of six to eight monkeys were studied; all females were ovariectomized, whereas males were either intact or castrated. Aggressive hierarchies were evident in all groups, with females generally outranking males. When females were treated with estradiol, all males looked more frequently at the latters' sexual skin swellings, but only one male who was both dominant and intact copulated with them. Thus, either castration or low rank resulted in decreased levels of sexual behavior in male talapoins. The sexual behavior of dominant castrated males was restored by testosterone therapy, whereas subordinate castrates never copulated, even after large doses of testosterone, though penile erections and ejaculatory reflex (during masturbation) were restored. Following removal of a dominant male, the sexual behavior of the next male in rank was restored, provided he was not castrated and untreated. In contrast to males, female talapoins showed no consistent correlation between their rank and sexual activity. Estradiol therapy was without overall effect upon the frequency of female mounting behavior, though some females mounted and presented to one another more often. Estradiol treatment also caused females to present to males more frequently, but only to those that were sexually active (i.e., who mounted females).     

Fraternal birth order and the maternal immune hypothesis of male homosexuality

In men, sexual orientation correlates with an individual's number of older brothers, each additional older brother increasing the odds of homosexuality by approximately 33%. It has been hypothesized that this fraternal birth order effect reflects the progressive immunization of some mothers to Y-linked minor histocompatibility antigens (H-Y antigens) by each succeeding male fetus and the concomitantly increasing effects of such maternal immunization on the future sexual orientation of each succeeding male fetus. According to this hypothesis, anti-H-Y antibodies produced by the mother pass through the placental barrier to the fetus and affect aspects of sexual differentiation in the fetal brain. This explanation is consistent with a variety of evidence, including the apparent irrelevance of older sisters to the sexual orientation of later born males, the probable involvement of H-Y antigen in the development of sex-typical traits, and the detrimental effects of immunization of female mice to H-Y antigen on the reproductive performance of subsequent male offspring. The maternal immune hypothesis might also explain the recent finding that heterosexual males with older brothers weigh less at birth than heterosexual males with older sisters and homosexual males with older brothers weigh even less than heterosexual males with older brothers.     

Long-term study of the social dynamics of patas monkeys (<Emphasis Type="Italic">Erythrocebus patas</Emphasis>): group male supplanting and changes to the multi-male situation

Data on social changes in patas monkey (Erythrocebus patas) groups were collected to clarify the general characteristics of male supplantation and to evaluate the overall role of supplanting in patas society. Seven patas groups were observed in Kala Maloue National Park, Northern Cameroon for 11 years. Analysis of this data revealed that social change, such as male supplanting, was restricted to the mating season. Male supplanting occurred in the course of outsider males seeking to gain access to estrous females within the heterosexual group and supplanting was inevitably followed by a multi-male situation arising in the group. Many cases of multi-male invasion were preceded by the supplanting of resident males and the multi-male situation arose due to a temporary absence of serious aggression towards invader males by the new resident males. Notably, an all-male group was found only once and it did not contribute to the supplanting of resident males in the one-male group. Electronic Publication     

Homosexual incest avoidance among females in captive Japanese macaques

This paper reports a systematic pattern of homosexual incest avoidance among females in a captive group of Japanese macaques (Macaca fuscata) culled from the Arashiyama-West troop known for its high rates of female homosexuality. The study group included three matrilines and two generations. Between eight and 11 females were sexually active over four consecutive mating seasons, and all engaged in both heterosexual and homosexual activity. While all females performed homosexual acts with almost all possible non-kin partners, they systematically avoided homosexual interactions with their mother, daughters, and sisters. This pattern could not be explained either in terms of kin not being simultaneously in estrus, kin avoiding affiliative interactions in general, or non-kin utilizing the tension-reducing effect of estrus to affiliate exclusively with each other. In contrast to homosexual females, heterosexual pairs of relatives (brother-sister, mother-son) were sometimes incestuous. Assuming that female homosexuality expresses the reproductive strategy of females unconstrained by male influence, the present results point to the strong tendency of females to avoid incest and suggest that males are primarily responsible for the reported exceptions to incest avoidance.     

Male reproductive strategies in black and gold howler monkeys (Alouatta caraya)

Behavioral and demographic factors such as group size, social structure, dispersal patterns, and mating systems affect male reproductive success. In the present study, we analyze the relationship between social structure, genetic relatedness of adult males and offspring paternity in one population of Alouatta caraya inhabiting a continuous forest in Northern Argentina. After 14 months of behavioral studies and genotyping 11 microsatellites, we found that dominant or central males achieved greater mating success and fathered all the offspring conceived during our study in two multimale–multifemale groups (both including three adult males). Although skewed toward the dominant males, females copulated with almost all resident males and with extra group males. We found significantly fewer agonistic interactions between adult males in the group with fewer females and where males were more genetically related to each other (average relatedness r = 0.237; 0.015 int/ind/hr vs. r = 0.02; 0.029 int/ind/hr). Paternity was also analyzed in two other neighboring groups which also showed strong skew to one male over a 2‐year period. These results reveal that even though female black and gold howlers mate with many males, infants are typically fathered by one dominant male. Am. J. Primatol. 76:43–55, 2014. © 2013 The Authors. American Journal of Primatology Published by Wiley Periodicals, Inc.     

Schistosoma mansoni: Adult worm chemoattraction,with and without barriers

Heterosexual and homosexual chemoattraction studies were done with 8- to 12-week-old Schistosoma mansoni adults in linear chambers containing Earle's saline, in the absence and presence of both perforated and unperforated dialysis sac chimney barriers. In the absence of barriers attraction was seen in all heterosexual and homosexual combinations. After 90 min of observation at 37 C, organisms maintained at 4 or 37 C for at least 1 hr prior to the assay showed heterosexual attraction similar to those used immediately after perfusion. There was significantly more heterosexual attraction between worms from same than different pairs. In the presence of perforated barriers the greatest attraction was heterosexual, with males moving toward females; heterosexual attraction with females moving toward males was approximately equal to homosexual female attraction, and male homosexual attraction was not seen. In the presence of unperforated barriers the greatest attraction of females toward males occurred during the first 0.5 hr; within 3 to 4 hr females were no longer significantly attracted to males. However, after 0.5 hr males were more significantly attracted to females in unperforated than perforated chimneys. These studies demonstrate that adult schistosomes attract each other in vitro, and that there is a chemical basis for this attraction.     

Homosexual Mating Displays in Penguins

More than 50 yr ago, field studies recorded the same‐sex pairs (and trios) of penguins displaying to each other during the mating season, using behavior patterns typical of heterosexual mating displays. Such observations led to a hypothesis that due to a lack of sex recognition pairing occurs at random with respect to sex, an idea countered by the argument that sex recognition is highly accurate. No quantification of same‐sex mating displays has tested the frequency of such displays in penguins or tested the hypothesis of random display partners with respect to sex. During their mating season, we studied displaying and paired king penguins, Apenodytes patagonicus, at Kerguelen Island and sexed them using a DNA marker, to quantify any occurrence of this behavior. Indeed, same‐sex courtship displays were common (28.3% of 53 displaying pairs), the great majority of which were between males. Some homosexually displaying males eventually paired with females, but such males were significantly slower in heterosexual pairing than males that did not display homosexually. In two extraordinary cases, same‐sex pairs learned each other’s calls, an essential step in the pairing process. The frequency of such pairs was much lower than among displaying couples, significantly so for males. Finally, the frequency of homosexually displaying pairs was significantly lower than expected from random assortment of displaying birds, for both males and females. We examined possible explanations for same‐sex display and its biological significance. A population sex‐ratio bias in favor of males and high concentration of male sex hormones may help to explain non‐reproductive homosexually displaying pairs.     

Sex roles in the ghost moth Hepialus humuli (L.) and a review of mating in the Hepialidae (Lepidoptera)

Recently it has been found that female Lepidoptera belonging to diverse families actively court their males, rather than play a merely passive role. Male and female Hepialus humuli have been reported to come together in three different ways: (1) females are attracted to groups or ‘leks’ of white, hovering males by visual stimuli; (2) females are attracted to the males by olfactory-substances produced on the hind-tibial brushes of the males; (3) males are attracted to sedentary females by olfactory stimuli. During my study I observed H. humili males flying on a total of 21 nights in two different parts of England. The males hovered in groups for about 20 min each evening, starting and stopping their flights in synchrony. Timing depended on light intensity, northern moths flying later in the summer evenings than southern moths. I observed a total of 18 matings. Normally, a female from outside a male lek flew into the group and up to one of the males. This male then usually followed her to a settling position, where mating took place. In a few cases females touched males; in one case a female struck a male in the air so that both fell to the ground and were copulating when examined. Photographs of hovering males show that their hind tibial brushes are fully everted in flight. The organs are folded against the body when the moth is mating, at rest or dead. Whilst hovering, the males are apparently emitting pheromones which function as primary attractants, rather than as the aphrodisiacs of many other lepidopteran males. The mating behaviour of hepialids is reviewed. It is concluded that all studied hepialids which have male brush organs (some Hepialus and Oncopera, Sthenopis, Zenophassus) exhibit similar flight and mating behaviour: males hover, sit or loop back and forth on the spot in leks; females fly into male aggregations and mate there (although some published observations suggest otherwise). In contrast, hepialids such as Fraus, Oxycanus and other Hepialus that lack male brush organs have mating behaviour in which the males are the active partner, a more standard lepidopteran method. In view of the controversies surrounding mating in hepialids, future systematic and behavioural work on Hepialidae throughout the world will be worthwhile.     

Mating system of an exceptional primate, the olive colobus (Procolobus verus)

In the olive colobus (Procolobus verus), many groups have multiple males and the males have large testes. This indicates that even though this species lives in small groups, single males do not monopolize the groups. We investigated the strategies employed by males to secure their mating success, and sought to determine whether the lack of male monopolization was a result of female mating strategies, as indicated by the exaggerated sexual swellings of the females. Four study groups were monitored for demographic changes, and group composition was determined in six additional groups in Taï National Park, Ivory Coast, between 1994 and 1999. Social behavior was recorded by scan and focal sampling in the study groups. The almost permanent association of olive colobus with Diana monkeys (Cercopithecus diana) in effect provided males a resource at which they could expect females to visit and sometimes even permanently join them, as well as protection from predators. As alternative strategies for obtaining females, one male took over the group of another male and one male immigrated into a bisexual group. Within bi‐male groups, dominant males mated most frequently and males defended their groups during intergroup interactions. Lone females that visited groups or solitary males had a swelling more often than expected, and generally mated with the males they visited. Females had long receptive periods, several consecutive receptive cycles, and some overlap in receptive periods within groups. Females mated with extragroup males, and during infertile periods. We concluded that the males used the Diana monkeys for safety reasons and to obtain mating partners, and that female reproductive biology and behavior prevented the monopolization of groups of females by single males. Our data were inconclusive as regards the benefits to females of avoiding monopolization by males. Am. J. Primatol. 62:261–273, 2004. © 2004 Wiley‐Liss, Inc.     

Agonistic Behaviour and Sexual Conflict in Atypical Reproductive Groups: The Case of Bearded Vulture Gypaetus barbatus Polyandrous Trios

Social behaviour in species forced to form atypical breeding coalitions is poorly documented. The saturation of optimum territories in the Bearded vulture Gypaetus barbatus population in the Pyrenees has led floating males to settle in already occupied territories, thereby forming polyandrous trios. We examined the patterns of intrasexual aggression in five trios (nine reproductive events in total) during courtship. Alpha males initiated 82% of agonistic encounters that were mainly aimed at preventing or disrupting copulations. During the fertile period in recently formed groups, intrasexual aggression had a negative influence on the frequency of heterosexual copulations, which may be a contributing factor to the lower productivity of polyandrous trios. Females rejected a higher proportion of beta male- than alpha male-initiated copulations, and rejected copulations with both alpha and beta males more often when the other male was present close by. These results indicate that alpha males cannot effectively prevent all copulation attempts by beta males and that females avoid harassment by minimizing sexual activity when both males are present. Aggression between males decreased with time, occurring less often in established than in recent trios, despite the fact that the frequency of heterosexual copulations – the cause of conflicts – was similar. The frequency of homosexual interactions tended to increase in established trios, suggesting that this behaviour may help to regulate aggression within these groups, although no significant relationship between homosexual interactions and aggression was found. In summary, reproductive conflicts in trios seem to be unavoidable, although they tend to decrease if the group is maintained. This suggests that, for birds in these groups, the maintenance of a quality territory is more important than solving sexual conflicts.     

Lack of effects on male fertility from a quadrivalent HPV vaccine in Sprague‐Dawley rats

BACKGROUND: Human papillomavirus (HPV) infection is one of the most common sexually transmitted diseases in both men and women. A recently developed quadrivalent HPV vaccine, Gardasil^®, has been shown to be highly effective in the prevention of several HPV‐mediated diseases. The objective of the present study was to evaluate the potential effects of the vaccine on male fertility including reproductive performance, sperm evaluations, and histology of the testes. In addition, anti‐HPV antibodies were measured during the study. METHODS: Group 1 (30 male rats) received the full human dose of vaccine (0.5 mL, ～200‐fold excess based on body weight) by intramuscular injection at 6 weeks, 3 weeks, and 3 days prior to cohabitation. Group 2 males received only 1 dose at 3 days prior to cohabitation. Additional groups (20 male rats each) were administered PBS or Merck Aluminum Adjuvant similarly to Group 1. Ten males in the vaccine‐treated groups were bled for immunogenicity assays after each dose. Twenty males per group were mated to untreated female rats. Cesarean sections were performed on Gestation Day 15 or 16. Cohabited males were necropsied and sperm count and motility were evaluated. RESULTS: There were no unscheduled deaths during the study and no evidence of toxicity in vaccine‐treated male rats. The vaccine induced a specific antibody response to the 4 HPV types after each injection. There were no effects on the cesarean‐section parameters of females or reproductive parameters of the cohabited male rats, including histomorphology of testes and epididymis, sperm count, and sperm motility. CONCLUSIONS: These results demonstrate that this quadrivalent HPV vaccine had no detectable adverse effects on routine measures of male fertility in rats. Birth Defects Res (Part B) 89:376–381, 2010. © 2010 Wiley‐Liss, Inc.     

A one‐locus model of androdioecy with two homomorphic self‐incompatibility groups: expected vs. observed male frequencies

Androdioecy, the occurrence of males and hermaphrodites in a single population, is a rare breeding system because the conditions for maintenance of males are restrictive. In the androdioecious shrub Phillyrea angustifolia, high male frequencies are observed in some populations. The species has a sporophytic self‐incompatibility (SI) system with two self‐incompatibility groups, which ensures that two groups of hermaphrodites can each mate only with the other group, whereas males can fertilize hermaphrodites of both groups. Here, we analyse a population genetic model to investigate the dynamics of such an androdioecious species, assuming that self‐incompatibility and sex phenotypes are determined by a single locus. Our model confirms a previous prediction that a slight reproductive advantage of males relative to hermaphrodites allows the maintenance of males at high equilibrium frequencies. The model predicts different equilibria between hermaphrodites of the two SI groups and males, depending on the male advantage, the initial composition of the population and the population size, whose effect is studied through stochastic simulations. Although the model can generate high male frequencies, observed frequencies are considerably higher than the model predicts. We finally discuss how this model may help explain the large male frequency variation observed in other androdioecious species of Oleaceae: some species show only androdioecious populations, as P. angustifolia, whereas others show populations either completely hermaphrodite or androdioecious.     

Rank,relationships, and responses to intruders among adult male vervet monkeys

We examined the influences of dyadic relationships among captive adult male vervet monkeys (Cercopithecus aethiops sabaeus) on behavior directed toward caged “intruder” males placed inside subjects' enclosures. Subjects were all 9 adult male residents from three stable social groups, each of which contained 3 adult males, at least 3 adult females, and their immature offspring. Every male was observed in two 3-hour sessions, each time with one of the 2 other adult males from his group. Observation sessions consisted of six consecutive 30-min stages in which group composition and the presence of the intruder were manipulated. All groups exhibited a stable, linear male dominance hierarchy prior to and throughout the study. In each group, there was one pair of males, when together, in which each member exhibited higher rates of intruder-directed approach and aggressive behaviors than when either animal was paired with the third male of his social group. Such pairs were also distinguished by high levels of within-pair agonistic interactions. The higher-ranking member of each dyad was the most aggressive male toward the intruder in his social group, although only one of these animals was the dominant male of his group. Mutual facilitation of aggression against intruding males is interpreted as cooperative behavior benefitting both males by increasing the likelihood of repelling a potential competitor for resident females. Such cooperation provides further evidence in nonhuman primates for cohesive male-male dyads between animals whose social interactions are characterized by agonism. © 1993 Wiley-Liss, Inc.     

The Function of Male Agonistic Displays in Ursine Colobus Monkeys (Colobus vellerosus): Male Competition,Female Mate Choice or Sexual Coercion?

Male agonistic displays may allow males to assess competitors, females to assess mates, or could be directed at cycling females to sexually coerce them. We analysed the display output of 26 male ursine colobus monkeys (Colobus vellerosus) in four groups over 13‐mo at the Boabeng‐Fiema Monkey Sanctuary, Ghana. Display indices (including three behaviours, loud calls, stiff‐legs, and jump‐displays) were calculated for males in each group. Males vary in their expression of these behaviours suggesting they are sexually selected signals. We investigated the target of displays and whether display indices varied in relation to male dominance rank, eviction of other males, copulation rate, and proceptive behaviours received from females, to assess the primary function of these behaviours. Male displays decreased in vigour over time and were targeted to other groups and males. High‐ranking males displayed more than low‐ranking males. Alpha male display indices correlated with the number of other males evicted from the group. Display rates were generally higher when cycling females were present in the group. However, neither male display index nor rank correlated with copulation rates. Alpha and non‐alpha males gave cycling females equal rates of sexual solicitations; likewise cycling females showed no difference in the rates of proceptive behaviours directed towards alpha and non‐alpha males. Females mated promiscuously and did not seem to base mating decisions on male display output, although data on female hormones is needed to determine if they mate with strongly displaying males more in the periovulatory period. The male–male competition hypothesis received the greatest support, with some support for the female mate choice hypothesis. Although behaviours that appeared sexually coercive were observed, the function of male displays did not seem to be sexual coercion. Displays were rarely directed at females and males that displayed more did not have greater mating success.