The Impact of male reproductive skew on kin structure and sociality in multi‐male groups

Patterns of within‐group relatedness are expected to affect the prospects for cooperation among group members through kin selection. It has long been established that dispersal patterns determine the availability of kin and there is ample evidence of matrilineal kin biases in social behavior across primate species. However, in 1979, Jeanne Altmann¹ suggested that mating patterns also influence the structure of within‐group relatedness; high male reproductive skew and the frequent replacement of breeding males leads to relatively high levels of paternal relatedness and age‐structured paternal sibships within groups. As a consequence of frequent replacement of breeding males, relatedness among offspring of a given female will be reduced to the half‐ rather than full‐sibling level. Depending on the number of sires and degree of relatedness among mothers, members of the same birth cohort may be as closely related as maternal siblings. If animals are able to recognize their paternal kin and exhibit biases in favor of them, this may influence the distribution of cooperation and the intensity of competition within groups of primates. Here, I summarize the evidence that serves as the basis for Altmann's predictions and review evidence regarding whether or not the availability of paternal kin also leads to paternal kin bias among primates.     

Familiarity breeds progeny: sociality increases reproductive success in adult male ring-tailed coatis (Nasua nasua)

The ring-tailed coati (Nasua nasua) is the only coati species in which social groups contain an adult male year round, although most males live solitarily. We compared reproductive success of group living and solitary adult male coatis to determine the degree to which sociality affects reproductive success. Coati mating is highly seasonal and groups of female coatis come into oestrus during the same 1-2 week period. During the mating season, solitary adult males followed groups and fought with the group living male. This aggression was presumably to gain access to receptive females. We expected that high reproductive synchrony would make it difficult or impossible for the one group living male to monopolize and defend the group of oestrous females. However, we found that group living males sired between 67-91% of the offspring in their groups. This reproductive monopolization is much higher than other species of mammals with comparably short mating seasons. Clearly, living in a group greatly enhanced a male's reproductive success. At the same time, at least 50% of coati litters contained offspring sired by extra-group males (usually only one offspring per litter); thus, resident males could not prevent extra-group matings. The resident male's reproductive advantage may reflect female preference for a resident male strong enough to fend off competing males.     

Orangutan diet,range, and activity at Tanjung Puting,Central Borneo

Previously, wild orangutan feeding and ranging behaviors have been described only from populations in hilly or mountainous regions. The Tanjung Puting study focuses on an orangutan population in a swampy lowland area near sea level. Tanjung Puting also differs from other areas in the virtual absence of large figs, which are significant orangutan food sources elsewhere. During a 4-year period and 6804 hr of observation, focal orangutans were recorded in 11,338 foraging bouts accounting for 3805 hr. Composition and phenology of the forest habitat were documented. The orangutans were predominantly frugivorous, with fruit-eating accounting for 61% of the foraging time. However, the overall variety in their diet was remarkable; 317 different food types have been identified, including fungus, insects, and honey. Orang-utans were strongly opportunistic foragers, with the composition of their diet varying markedly from month to month. During most months orangutans fed on a complex mix of fruit, leaves, bark, insects, and small vines. During some months fruit was not the major component of the diet. All orangutans foraged in both the dry-ground mixed dipterocarp forest and the peatswamp forest habitats found in their ranges. Adult males and females utilized different proportions of certain resources in their diets. Prime adult males also ranged further per day and spent more time on the ground than prime adult females. At Tanjung Puting contact with other orangutans usually increased a focal orangutan’s day length, day range, and amount of time spent moving. This suggests that foraging alone maximized each orangutan’s foraging returns by minimizing the day range traveled. Orangutan solitariness is the result of a large body size and of a predominantly frugivorous and opportunistic diet.     

草地螟雄蛾生殖系统的形态和结构

针对目前关于草地螟Loxostege sticticalis L.雄成虫生殖系统结构和功能的研究相对缺乏的状况,本文利用光镜和扫描电镜系统研究了草地螟雄蛾的内外生殖器官及相关结构。草地螟雄蛾内外生殖器官集中于腹部第5¹0腹节;内生殖器官位于510腹节;内生殖器官位于5⁸腹节内腔中,由睾丸(testes)、贮精囊(seminal vesicle)、输精管(vas deferens)、附腺(accessory gland)和射精管(ejaculatory ducts)组成;外生殖器官为腹部第9、10腹节的特化结构,包括抱握器(harpes)、背兜(tegumen)、基腹弧(vinculum)、钩形突(uncus)、颚形突(gnathos)、阳茎囊(aedeagal caecum)和阳茎(phallus)。外生殖器中抱握器的端刺(furcella)方向为雄蛾区别于其它种类的一个重要形态学特征。该研究首次明确了草地螟雄蛾的生殖系统结构,并为锥额野螟蛾属中种间分类提供更多的科学依据。     

Factors affecting social behavior and reproductive success of male rhesus monkeys

This paper reviews aspects of life history that influence the reproductive success of male rhesus monkeys. Recent theories propose that there is some optimum level of inbreeding for each population and that behaviors related to group transfer by males are the result of selection pressure toward such an optimum. Group changing by males is clearly linked to the effects of testosterone at sexual maturation. A male’s maternal genealogical rank is not consistently related to the age at which it leaves the natal group, but social interactions within the natal group may influence the age of departure. Choice of the new group is influenced by the operational sex ratio and the presence of maternal relatives. Rank in the new group is positively correlated with seniority. Seniority, in turn, is influenced by the rank of the male’s natal group, his mother’s genealogical rank, and the presence of male siblings in the new group. Much of this effect is due to the high mortality of males born to females and/or groups of low rank. Most studies show a positive association between male reproductive success and rank. Males from high-ranking groups and/or maternal genealogies that join groups containing brothers tend to remain in those groups longer, attain a higher rank, and probably achieve higher levels of reproduction than other males.     

The association between rank and reproductive success of male rhesus monkeys

The paternity of 202 of 220 offspring of rhesus monkeys housed in six separate half-acre field cages at the California Primate Research Center was determined by genetic marker techniques. Reproductive success of the adult males was statistically significantly correlated (r = 0.76, P <0.0005) with rank. Marked systematic changes in reproductive success were, however, observed for two adult males during the three years covered by this study. Based upon these results and those of another study, it is argued that changes in rank position typically follow, rather than precede, changes in reproductive success.     

Drifting behaviour as an alternative reproductive strategy for social insect workers

Restricted reproduction is traditionally posited as the defining feature of eusocial insect workers. The discovery of worker reproduction in foreign colonies challenges this view and suggests that workers’ potential to pursue selfish interests may be higher than previously believed. However, whether such reproductive behaviour truly relies on a reproductive decision is still unknown. Workers’ reproductive decisions thus need to be investigated to assess the extent of workers’ reproductive options. Here, we show in the bumblebee Bombus terrestris that drifting is a distinct strategy by which fertile workers circumvent competition in their nest and reproduce in foreign colonies. By monitoring workers’ movements between colonies, we show that drifting is a remarkably dynamic behaviour, widely expressed by both fertile and infertile workers. We demonstrate that a high fertility is, however, central in determining the propensity of workers to enter foreign colonies as well as their subsequent reproduction in host colonies. Moreover, our study shows that the drifting of fertile workers reflects complex decision-making processes associated with in-nest reproductive competition. This novel finding therefore adds to our modern conception of cooperation by showing the previously overlooked importance of alternative strategies which enable workers to assert their reproductive interests.     

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.     

Social and seasonal influences on reproductive biology in male moustached tamarins (Saguinus mystax)

In several primate taxa there is evidence that the social and physical environment can exert a significant effect on reproductive behavior and biology. In this paper we examine social and physiological factors influencing group composition and reproduction in free-ranging moustached tamarin monkeys (Saguinus mystax mystax). This species is characterized by cooperative care of the young and a breeding system that includes both polyandrous and polygyandrous matings. Body measurements collected on adult males residing in multimale groups indicate marked within-group differences in testes volume. In 12 of 17 groups examined, testes volume of at least two resident adult males differed by 21–174%. Among these males, testes volume was not correlated with either body weight or adult age class. We also examine whether factors such as time of year had an effect on reproductive condition. An analysis of body measurements of 128 adult male and 127 adult female moustached tamarins, wild-trapped and released in northeastern Peru, indicates cyclic changes in genital size. For males, mean monthly testes volume in July (712 mm³) was twice that recorded in June (351 mm³). Females exhibited a similar pattern. Although endocrine information on intra- and intersexual social effects on fertility are unavailable for S. mystax, given the high degree of social cooperation and lack of overt aggression among adult male group members, we offer the possibility that resident male moustached tamarins compete for access to the groups' lone breeding female through socially induced reproductive suppression and sperm competition. © 1996 Wiley-Liss, Inc.     

Anopheles culicifacies: effects of age on the male reproductive system and mating ability of virgin adult mosquitoes

Abstract. Under controlled laboratory conditions of 28–30^oC and 16:8 L:D photoperiod, an attempt was made to develop an age-grading technique for Anopheles culicifacies males. Mating activity was maximal when females were 5–12 days old and males were 5–7 days old. The numbers of total and mature spermatocysts declined significantly with age, and the proportion of the testes occupied by the sperm reservoir increased as virgin males grew older. Mating resulted in the loss of spermatozoa and accessory gland substance from the reproductive system. Loss of mating ability of older virgin males seemed to be age-related, because the reproductive system contained ample supplies of accessory gland substance and spermatozoa. Morphological changes of the reproductive system, due to mating and age, were used to infer the age and reproductive history of unknown males in a laboratory evaluation.     

Nuclear binding sites for juvenile hormone III in the male accessory reproductive glands of Melanoplus sanguinipes

Summary

We have identified a potential nuclear juvenile hormone (JH) receptor in the long hyaline tubules (LHT), part of the male accessory reproductive gland (MARG) of M. sanguinipes. The MARG was incubated in vitro with [³H]JH III, and the distribution of the [³H]JH III among the cellular fractions of the LHT was determined. Some 37±4% of the radioactivity was associated with the crude nuclear pellet, while the cytosolic, microsomal and mitochondrial fractions contained 30±3%, 23±2% and 10±1%, respectively. The bound JH III was measured in nuclear extracts of LHT from males up to 15 days post-eclosion. These results revealed that JH binding increased in an age-dependent manner up to day 7, then levelled off to day 12, to increase again on day 14. The nuclear-binding component in the LHT had a very strong affinity for JH III, with a K_D value of 0.8 nM. Our observations are considered in relation to the potential site and mode of action of JH.     

Brief report: Infant-killing and infant disappearance following male takeovers in a group of free-ranging howling monkeys (Alouatta palliata) in Costa Rica

Events surrounding an infant-killing following a male takeover are described for a group of free-ranging howling monkeys in Costa Rica, and additional evidence is presented for infant disappearances following three previous male takeovers. Infant-killing is best interpreted in this context as a male reproductive strategy, as infant-killing did effectively shorten the interbirth interval, and only infants of high-ranking females died or disappeared following a male takeover. Due to the exclusive access of the dominant male to high-ranking estrous females, an incoming male who had lived as a peripheral male before taking over the group would run little risk of eliminating his own offspring in the course of killing the offspring of high-ranking females.     

Semen quality and reproductive endocrine function with regard to blood cadmium in Croatian male subjects

In 123 Croatian men with no occupational exposure to metals, the influence of cadmium on reproductive parameters was examined after adjusting for age, smoking, alcohol, and biomarkers of lead, copper, zinc, and selenium. The following variables were measured: blood cadmium (BCd), blood lead (BPb), activity of -aminolevulinic acid dehydratase (ALAD), erythrocyte protoporphyrin, serum copper (SCu), serum zinc (SZn), serum selenium (SSe), activity of glutathione peroxidase (GPx) in blood, testis size, semen quality (including sperm concentration, motility, viability, and morphology), indicators in seminal fluid (the lactate dehydrogenase isoenzyme LDH-C₄, fructose, zinc, acid phosphatase, and citric acid), and hormones in serum (follicle-stimulating hormone – FSH, luteinizing hormone, prolactin, testosterone, and estradiol). The median and range BCd values were 2.94 (0.49-11.93) g/L in 61 smokers and 0.59 (0.20-3.71) g/L in 62 nonsmokers (p<0.0001). Smoking habits (cigarettes/day) highly significantly correlated with BCd (p<0.0001). After adjusting for potential confounding variables by multiple regression, BCd was significantly associated with a decrease in testis size (p<0.03) and an increase in serum estradiol (p<0.005), FSH (p<0.03), and testosterone (p<0.04). Smoking was significantly associated with a decrease in serum prolactin (p<0.006) and LDH-C₄ in seminal fluid (p<0.03). Several reproductive parameters were significantly associated with BPb and ALAD, biomarkers of lead, and/or with SCu, SZn, SSe, and GPx. The necessity of controlling for various metals, and other potential confounders when assessing the influence of a particular metal on reproductive function in men, is emphasized.     

Lowered female reproductive effort as an indicator for increased male production and sexuality in Daphnia (Crustacea: Cladocera)

Summary

The relationship between environmental factors, sex ratio, mode of reproduction, and female reproductive effort was examined in the cyclically parthenogenetic Daphnia magna. Female reproductive effort was found to decline before a significant production of males and sexual eggs takes place. Unlike factors such as crowding, poor nourishment, low (sometimes high) temperature and short or long day length, lowered reproductive effort is not a cue but rather an indicator of the selective advantage that would accrue from a changed sex ratio and mode of reproduction. The mechanism of the complex system of environmental sex determination in Daphnia is reviewed, and the adaptivity of ESD is discussed.     

Dimorphic ergatoid males and their reproductive behavior in the ponerine antHypoponera bondroiti

Summary We studied the reproductive behavior of the ponerine antHypoponera bondroiti from Okinawa, Japan. This species has dimorphic wingless ergatoid males (major and minor), dimorphic reproductive females (alate queens and wingless reproductive intercastes), and workers. Workers have neither ovarioles nor spermatheca. Major ergatoid males are the largest colony members. Two major males fought one another in the nest until one disappeared, leaving the other to occupy the nest chambers where queens emerge and mate. Minor ergatoid males also fought one another, although they seemed to be less pugnacious, resulting in occasional cohabitation of multiple minor males in the same nest chamber. Major males never attacked minor ones, allowing them to coexist in the same nest chamber. Minor males seemed to mimic females. Both major and minor males mated with both alate queens and intercastes within the nest. After mating, some alate queens shed their wings and remained in the nest, while the others left the nest for dispersal in the laboratory. Intercastes remained in the nest.     

Factors affecting life and death in Serengeti cheetahs: environment, age, and sociality

We examined environmental and social factors affecting reproductivesuccess across a 20-year data set of individually known cheetahson the Serengeti Plains of Tanzania. Because cheetahs are seeninfrequently and are not amenable to mark–recapture techniques,we devised a model to estimate time of death for individualsthat disappeared from our records. We found that males had markedlylower survival than females. Recruitment was negatively affectedby rainfall but positively affected by numbers of Thomson'sgazelles, the cheetahs' chief prey. There was a negative associationbetween recruitment and numbers of lions, demonstrating thatthe high rates of predation observed in previous studies haveimplications for the dynamics of cheetah populations. Recruitmentwas related to mother's age, peaking when she reached 6–7years. Sociality affected survival in two ways. First, adolescentsliving in temporary sibling groups had higher survival thansingletons, particularly males with sisters. Second, adult malesliving in coalitions had higher survival than singletons inperiods when other coalitions were numerous, yet they had lowersurvival when other coalitions were rare. These results corroborateobservations of enhanced prey capture by female adolescentsand antipredator benefits for adolescents in groups, as wellas competitive advantages for adult males in groups. Furthermore,our findings stress the importance of interactions between environmentaland social factors in affecting reproductive success in mammals.     

Effects of delayed mating and male mating history on longevity and reproductive performance of the rice stem borer, Chilo suppressalis (Walker) (Lep., Pyralidae)

Abstract:  The mating potential, effects of delayed mating and male mating history on longevity and reproductive performance of female rice stem borer (RSB), Chilo suppressalis , were investigated under laboratory conditions. Given the opportunity, RSB males copulated an average of 2.7 times, while females generally mated only once. Females were more severely affected by mating delay than males in terms of female longevity and reproductive performance. With increasing age at mating, females' longevity increased, while oviposition period, fecundity and egg fertility decreased. Mean fecundity and egg fertility of females mated 1 and 7 days after emergence were 251.3% and 99.2%, and 96.2% and 75.5% respectively. Both were reduced significantly when female mating was delayed beyond 4 days after emergence. However, irrespective of the first mating age and different mating history of the males, the results indicated that both did not result in a significant difference in the quality of their contributions to female longevity and reproductive performance. The results obtained in this study are discussed in relation to the potential effect on pheromone control of RSB.     

The morphology and reproductive status of female Schistosoma mansoni following separation from male worms

Popiel I., Cioli D. and Erasmus D. A. 1984. The morphology and reproductive status of female Schistosoma mansoni following separation from male worms. International Journal for Parasitology14: 183–190. Sexually mature females of Schistosoma mansoni were separated from their male partners and surgically transferred to Nile rats (Arvicanthis niloticus). Over a period of 35 days there was a significant decrease in size of these worms and regression of the reproductive system took place. Electron microscope observations of the vitelline gland and ovary provided details of and a time scale for the regressive changes which took the form of a cessation of cell differentiation and turnover, together with extensive cell death. Survival of cells within these organs was restricted to the undifferentiated cells and by day 35 the worms resembled immature females. It is concluded that regression of the female reproductive system was the result of discontinued male stimulation.The nature and implications of the obligatory relationship between male and female S. mansoni are discussed.