Harem Holders Research Articles

Determinants of Harem Size in a Polygynous Primate: Reproductive Success and Social Benefits.

Simple SummaryThe size of primate ‘harems’ varies considerably, both inter- and intra-specifically. Previous studies have shown that females prefer high-quality males and that high-quality males are superior in inter-male competition, leading to them having a larger harem size. Based on eleven years of observations of Yunnan snub-nosed monkeys (Rhinopithecus bieti), we documented longitudinal stability in the distribution of harem sizes between 2010 and 2020. These demographic properties are the outcome of male and female social investment decisions that affect their reproductive performance and success. Male reproductive success was positively related to harem size, while constraints on individual social benefits and social investments limited harem size. Our findings advance our understanding of the socioecological determinants of harem size variation in polygynous primates.We used long-term data on the variation in harem size in Yunnan snub-nosed monkeys to research the effects of harem size on reproductive success and the ratio of grooming received to given (RGRG). The results suggest that harem holders derive reproductive benefits commensurate with harem size, whereas the females’ reproductive success is unaffected by harem size. Males of larger harems groomed less and had higher RGRG than males of smaller harems. In the case of females, grooming given increased, and RGRG decreased with an increase in harem size. The males’ reproductive success seems to be a driver of harem size maximization. From the females’ perspective, dwindling social benefits appear to set the upper limit for harem enlargement. We also showed that males of monogamous units (‘single-female harems’) invested more into grooming their female, presumably to prevent unit disintegration and loss of mating privileges.

Male Scent Gland Signals Mating Status in Greater Spear-Nosed Bats, Phyllostomus hastatus.

Chemical signals are ubiquitous, but often overlooked as potentially important for conveying information relevant for sexual selection. The male greater spear-nosed bat, Phyllostomus hastatus, possesses a sexually dimorphic gland on the chest that produces an odoriferous secretion. Here, we investigate the potential for this glandular secretion to act as a sexually selected olfactory signal by examining gland activity in and out of the mating season and determining if variation in its chemical composition reflects variation in male mating status or attributes of the individual. Based on gas chromatography-mass spectrometry (GC-MS) measurements of samples collected from wild bats roosting in caves in Trinidad, West Indies, we find that males that defend and roost with groups of females (harem holders) have significantly different chemical profiles from males found roosting in all male groups (bachelors). Additionally, profiles differed significantly among individuals. Taken together, these results suggest that this chemical signal has the potential to communicate both mating status and individual identity and thus could be used to mediate interactions among individuals within this harem-based social mating system.

Alternative reproductive tactics and reproductive success in male Carollia perspicillata (Seba's short-tailed bat).

The use of alternative reproductive tactics (ARTs) is widespread in animals. Males of some species may change tactics depending on age, body condition and social environment. Many bat species are polygynous where a fraction of males only have access to fertile females. For polygynous bats, knowledge of the reproductive success of males using different ARTs is scarce, and it remains unclear how age of males is related to switching decisions between social statuses. We studied a large captive population of Carollia perspicillata, where males are either harem holders, bachelors or peripheral males. Using a multistate procedure, we modelled the age-related switches in reproductive tactics and in survival probability. From the model, we calculated the reproductive success and the frequencies of males displaying different reproductive tactics. As in mammals, the switch between social statuses is often related to age, we predicted that the transition probability of bachelor and peripheral males to harem status would increase with age. We show, however, that social status transition towards a harem holding position was not related to age. Reproductive success changed with age and social status. Harem males had a significantly higher reproductive success than bachelor males except between a short period from 3.8 to 4.4years of age where success was similar, and a significantly higher reproductive success than peripheral males between 2.6 and 4.4years of age. Harem males showed a clear decrease in the probability of maintaining social status with age, which suggests that senescence reduces resource holding potential.

Scent‐marking behaviour by stallions: an assessment of function in a reintroduced population of Przewalski horses (Equus ferus przewalskii)

AbstractScent marking is a common form of intraspecific communication in mammal species, and using faeces or urine is a cost‐effective way of signalling competitive ability and resource holding power. Marking is ritually performed by male equids, and here we assess the function of male scent‐marking behaviour in a recently introduced population of Przewalski horses Equus ferus przewalskii in Mongolia. Two forms of scent marking were observed: defecation on stud piles formed from repeated dunging in the same place, and overmarking of faeces and urine of mares. Stud piles were marked with dung by the harem holder and sniffed before and after dung was deposited. They were not found specifically at the periphery of harem ranges but occurred for the most part along routes used by the horses, and were more common in the core parts of harem ranges or where harem ranges overlapped. Thus, rather than being used to defend range boundaries, stud piles were placed predominantly where they would be encountered by male intruders. Mare excreta were covered with urine by the stallion, but were only sniffed before they were marked, not after. These marks appear to advertise to the mare and other, intruding stallions that the harem holder was the mare's consort and that the interloper should not risk trying to steal the mare or sneak a mating. Thus, the two forms of marking by harem holders appear to combine as first and second lines of defence of paternity rights in male intrasexual competition.

Relatedness and site fidelity at the southern elephant seal, Mirounga leonina, breeding colony in the Falkland Islands

Southern elephant seals are highly gregarious during the breeding season, and both sexes show fidelity to the colony. We used microsatellite DNA analysis to assess kinship among seals in the main colony on the Falkland Islands. Specifically, we investigated whether females tend to cluster with close kin and avoid mating with male kin. We also tested expectations for kinship patterns based on sex differences in site fidelity and philopatry. Relatedness within a harem was significantly greater than between harems for only two of seven harems and was not related to harem size. Some long-term associations of female kin were found within harems, including associations of up to 5 years, but kinship among these females was not significantly higher on average than among dyads of other returning females. There was no pattern suggesting that females tended to choose harems with harem holders that were either more or less related to them than alternative harem holders. Overall, pairwise comparisons of females showed significantly greater kinship than pairwise comparisons of males, consistent with previous studies suggesting greater male dispersal.

Extreme polygyny among southern elephant seals on Sea Lion Island, Falkland Islands

Elephant seals are known from long-term behavioral studies to be highly polygynous and to show high variance in reproductive success among males. However, genetic studies have determined that the level of polygyny varies between the closely related northern and southern elephant seals. In the present study, we investigate paternal success at the Sea Lion Island southern elephant seal colony in the Falkland Islands by using both behavioral measures and genetic markers. We find that the average success of harem holding males at Sea Lion Island is significantly higher than both the northern species and the nearby southern elephant seal population at Punta Delgada. We compare genetic paternity with various behavioral indices of male mating success, and we find that the behavioral measures provide a good estimate of the variance in male reproductive success. Only 28.2% of males achieved paternities, and among these, harem holders accounted for 89.6%. We discuss the implications of our results in the context of the demographic and physical environment. Specifically, a comparatively high variance in resource holding potential among males, differences in male social behavior, and a small tidal cycle limiting peripheral male access during female departure from the harem at this colony may be important factors leading to the comparatively high variance in male reproductive success at Sea Lion Island.

Queuing for harem access in colonies of the greater sac-winged bat

Colonies of the greater sac-winged bat, Saccopteryx bilineata, consist of nonterritorial males and males that defend harem territories in which females roost. The traits of nonterritorial males that define their success in harem take-overs are so far unknown. We predicted that the time nonterritorial males spent in the colony and their proximity to harems would be important factors. We temporarily removed harem holders from a colony of 60 greater sac-winged bats on consecutive days and observed which of the nonterritorial males took over the harem. To test for consistency of results, we repeated the experiments in some of the territories. In a second set of experiments, we removed both the harem holder and the corresponding usurper from the first experiment. On average, usurping males preferred territories with a large harem over territories with a small harem and they belonged to groups of males who spent the daytime near the corresponding harems. Usurpers in the second experiment were present in the colony for a shorter time than usurpers in the first experiment. Overall, the results support the hypothesis that nonterritorial males form overlapping peripheral groups for harems and that they live in a hierarchy according to their tenure in the group. Group membership and hierarchy seemed to be the factors that determined whether a male occupied a vacant harem. Hence, instead of floating, the pattern of harem succession in greater sac-winged bats is best described by queuing of nonterritorial males for access to a harem. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.

Age– and density–dependent reproductive effort in male red deer

Reproductive effort in female ungulates originates from gestation and lactation and has been studied extensively; however, no comparable studies of reproductive effort in males (due to fighting for access to mates) have, to our knowledge, previously been reported. Here, we report on weight loss of male red deer during the annual mating season--a direct measure of male reproductive effort (or somatic reproductive costs). The 'terminal investment' hypothesis predicts that reproductive effort should increase with age, given that costs remain stable. We also propose the 'mating strategy-effort' hypothesis, which predicts that reproductive effort peaks in prime-aged males, since they are most often the harem holders. Consistent with the mating strategy-effort hypothesis, relative weight loss during the rutting season peaked at prime age and was lower in younger and senescent males. Weight loss during the rut was relatively smaller as density increased and more so for older males. This is probably primarily due to males (particularly senescent males) starting their rut in poorer condition at high density. The pattern of reproductive effort in males with regard to age and density therefore differs markedly from the pattern reported for females.

Differential energy budget and monopolization potential of harem holders and bachelors in Hanuman langurs (Semnopithecus entellus): preliminary results.

The demographic structure in the Hanuman langur (Semnopithecus entellus) population of Jodhpur is extreme, in that some single males monopolize harems with, on average, 25 adult females. It has been proposed that extratroop males, which live in all-male bands, inhabit low-quality habitats and suffer from reduced food provisioning and longer daily travel distances. To compare the resulting energetic consequences for harem holders and bachelors, I estimated their gross energy intake and daily energetic expenditures. This analysis revealed no clear-cut differences between the two classes of males in time spent feeding on provisioned food, daily path length, gross energy intake, and energy expenditure. Due to the small sample size and other limitations of the study design, the hypothesis under investigation can not be evaluated conclusively. The preliminary results suggest, however, that energy budgets of harem holders and bachelors do not differ markedly. The importance of direct ecological pressures to males for our understanding of variation in group composition is highlighted.

EXTRA-HAREM PATERNITY IN THE WHITE-LINED BAT SACCOPTERYX BILINEATA (EMBALLONURIDAE)

AbstractWe studied the paternity in a colony of the harem-polygynous white-lined bat Saccopteryx bilineata by microsatellite typing and compared the data with group composition and stability. Although we recorded a high stability for harem groups, neither spatial proximity of males to harem females nor harem ownership allowed us to predict the paternity of the next year's harem offspring. Eight out of 28 juveniles were fathered by holders of the harem in which they were born, while the other 20 represent Extra-Harem-Young (EHY). 50% of EHY were fathered by males from outside the colony and 50% by other harem holders or peripheral males of the colony. On average, reproductive success of harem holders (1.2 offspring/year) was higher compared with peripheral males (0.4 offspring/year). Harem size seemed not to influence reproductive success of harem holders. Although maintaining of a territory seems to be costly for a harem male, his ability to control the females of his harem may be restricted; instead female Saccopteryx bilineata appear to have a high potential for female choice.

Wanderers Between Harems and Bachelor Bands: Male Hanuman Langurs (Presbytis Entellus) At Jodhpur in Rajasthan

Abstract 1. Life-histories of individually identified males of an Asian colobine monkey, the Hanuman langur, were followed in order to understand mechanisms and functions of social processes associated with the formation of male bands, especially the degree of cooperation and competition among males. 2. The monkeys belonged to a geographically isolated population which is subject of a field-study in Rajasthan, India, spanning more than 15 years. The population consists of 27-29 one-male / multi-female troops ('harems'; average 39 members, home ranges up to 1.3 km2) and 12-14 all-male bands (average 12 members, moving ranges up to 20 km2). Females are highly philopatric, whereas males transfer from bisexual troops into male bands. Harem holder residencies average 27 months (range 3 days to more than 74 months). No male achieved residency in more than one troop, suggesting that residency is associated with a distinct peak in a given male's resource holding potential. The proportion of infants sired by extra-troop males is minimal. The dispersal pattern of langur males seem to reflect a long-lasting effort to achieve reproduction. This goal is tied to the necessity to rise through the ranks of a male band to the top of its dominance hierarchy, because only the highest ranking males can replace current harem holders during male band invasions into the home range of bisexual troops. 3. The age-class composition of seven male bands with a mean membership of 3-25 individuals was studied in detail. The longitudinal fluctuation in membership was less pronounced than the differences between bands. This reflects ecological conditions in the moving range of a given band which determine a ceiling in the number of members. The bands contained 27% juveniles, 23% subadults, 13% young adults, 30% prime adults and 9% old males. At any given time, in each band lived at least one individual who was of at least young adult age. Immatures often followed elder males during daily travels, but not

Temporal Relationships, Transitions and Structure of the Behavioural Repertoire in Male Apennine Chamois During the Rut

AbstractThe reproductive behaviour of adult male Apennine chamois was studied during 4 rutting seasons in the Abruzzo National Park, Central Italy. The analysis of temporal relationships between behaviour patterns in male-male and male-female repertoires has allowed to group together the patterns functionally associated. Courtship activities were much more predictable and fixed than behaviours in male-male interactions. Qualitative and quantitative variations of the main behaviour patterns have been evaluated throughout the rut. November 8-12 marked the start of the intense phase of the rut. Two of the 3 species-specific courtship behaviours appeared in the peak of the rut (November 23-27). Older males grouped and successfully defended larger harems, containing a greater number of prime females. Males herded females mainly by the Head Down threat, in both the still and moving postures. The aggressive connotation of the Snort, an usually assumed "alarm" call, has been here discussed in the harem formation context. The courtship sequence has been described. The function of female reactive urination was evaluated in this context. A harem holder did not only have to prevent females from leaving, but he had also to deal with male competitors. Usually long agonistic interactions occurred before a Rush or a Chase ended up the contest between 2 males. The Neck Up has been presented here as an effective posture to display the "Attention Guiding Adaptations" present in the body morphology of adult male chamois. Direct correlations were found between the age (i.e. the dominance) of an intruder and the distance at which it was pursued away by the harem holder, as well as the Marking/Horning activity of the latter. The frequency of utterance of the Rut Call built up 60% of all behaviour patterns recorded (N = 8059). It was also used often (36.3 % ; N = 102) to initiate a contest as a vocal dominance display. Harem holders showed a positive correlation of call frequency to the harem females with the rut progression. The last 2 aspects suggest a strong similarity of function to what found for the red deer in assessing the contenders' ranks and in enhancing the oestrus of females. The comparison of male rutting behaviour in Apennine chamois with that reported for other Rupicapra taxa indicated a close affinity with the Pyrenees subspecies and detectable differences with the northeastern chamois.

MORPHOLOGY AND BIOLOGY OF REPTILES

tion. Since nine-banded armadillos are born in litters of genetically identical quadruplets, there is no genetic variation within families. Therefore, there can be no selection within families as a result of interactions between sibs. The hypothetical evolution of strong sib altruism in the nine-banded armadillo would have to occur by selection at the family level operating upon the between family variation for the appropriate behaviors. Dawkins' misconception of the role of population structure in the evolution of social behaviors stems from his confusion of the effect of selection with the process of selection. He reasons as follows (chapter 3): Because evolution consists of changes in gene frequency and because genes persist unchanged longer than chromosomes, genomes, or gene pools, the gene must therefore be the unit of selection. Since genes reside on the chromosomes of individuals, all forces which affect gene frequencies can be reduced to increments or decrements in the fitness of individuals as a matter of mathematical convenience. This reductionist approach (employed by Hamilton in his mathematical formulation of kinship theory), however, does not mean that all selective changes can be attributed strictly to selection at the genic level. The differential proliferation of the various units of population structure can be the actual mechanism of gene frequency change. And, it is the variance between the units of population structure which determines the relative rates of gene frequency change caused by selection at any level. These aspects of population structure are of special interest in the study of the evolution of social behaviors because population structure per se can permit the evolution of traits which would be selected against in randomly mating and mixing populations. In addition to these shortcomings, many of Dawkins' arguments approach circularity as, for example, his discussion of why some male elephant seals win and hold harems. Harem holders tend to win these fights against would-be usurpers, if only for the obvious reason that that is why they are harem holders. Usurpers do not often win fights, because if they were capable of winning they would have done so before! (p. 173). In short, usurpers do not often win fights, because usurpers do not often win fights. I do not believe that arguments of this type can assist the average layperson in understanding the process of evolution by natural selection. Instead, I fear that arguments of this nature will add more anecdotes to that body of misconceptions known as the common wisdom.