Individual variation in perfume blending in male greater sac-winged bats

Male greater sac-winged bats, Saccopteryx bilineata, use hovering flights to court females in their harem territory. While hovering, males fan a fragrant perfume from sac-like organs in the wing membrane towards the females. Each afternoon, males renew the perfumes of their wing sacs during a stereotypical and time-consuming behavioural sequence, which includes blending secretions from genital and gular glands. I investigated whether male perfume-blending behaviour varies between the mating and the nonmating season, and whether successful males, those with large harems, have different patterns of perfume blending than less successful males. I measured variation in perfume-blending behaviour in 21 adult males. The pattern of perfume blending was not significantly different between the mating and the nonmating season. However, the time at which perfume blending began and terminated differed between seasons. During the mating season, males spent about the same time cleaning their wing sacs during phase I of perfume blending, irrespective of the number of females in their harem. During phase II, males with large harems spent significantly less time refilling and blending perfume than males with small harems. In addition, males with large harems took up fewer droplets of secretion from the genital region. Overall, male-male interactions were rare during perfume blending, and the decrease in duration in phase II was not attributable to more disturbance in large harems. There was also no evidence that males prevented each other from transferring secretions into their wing sacs. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Intracolonial social distance, signaling modality and association choice in the greater sac-winged bat (Saccopteryx bilineata)

Understanding patterns and motivations for social spacing greatly illuminates the structure and internal dynamics of given groups or social systems. The highly social, polygynous greater sac-winged bat, Saccopteryx bilineata, represents an excellent model for social spacing analysis, since the choice of individual roost-sites within a day-roost constitutes an enduring, often repeated decision about relative proximity to conspecifics. Day-roost colonies consist of one or multiple harem groups, each with several females and a single male. Additionally, non-harem males without females may be present. A social-distance–time-budget metric revealed that harem males, females, and non-harem males differed significantly in their respective spatial associations while roosting. Harem males and females were most closely associated, with harem males located at the center of harems instead of at the borders. Non-harem males associated significantly closer with one another than with harem females that they were trying to access. The signaling modality mediating social interactions depended on the respective social distances between communicating bats. Our results suggest a concentric social organization based around harem males, which may select roost sites in closest possible proximity to females to enhance courtship signal strength. This constitutes an interesting deviation from the normative form of harem maintenance, patrolling borders, in mammals.     

Female-biased dispersal and patrilocal kin groups in a mammal with resource-defence polygyny

In most mammals, dispersal rates are higher in males than in females. Using behavioural and genetic data of individually marked bats, we show that this general pattern is reversed in the greater sac-winged bat (Saccopteryx bilineata). Dispersal is significantly female biased and male philopatry in combination with rare male immigration causes a patrilineal colony structure. Female dispersal helps avoid father-daughter inbreeding, as male tenure exceeds female age at first breeding in this bat species. Furthermore, our data suggest that females may engage in extra-harem copulations to mate with genetically dissimilar males, and thus avoid their male descendants as mating partners. Acquaintance with the natal colony might facilitate territory takeover since male sac-winged bats queue for harem access. Given the virtual absence of male immigration and the possible lower reproductive success of dispersing males, we argue that enhancing the likelihood of settlement of male descendants could be adaptive despite local mate competition. We conclude that resource defence by males is important in promoting male philopatry, and argue that the potential overlap of male tenure and female first conception is the driving force for females to disperse.     

Testosterone is associated with harem maintenance ability in free-ranging grey-headed flying-foxes,Pteropus poliocephalus

Males of many vertebrate species aggressively defend their reproductive interests by monopolizing females, and the ‘challenge hypothesis’ predicts that testosterone levels in reproductive contexts rise to facilitate males'' competitive behaviours necessary for meeting social challenges. The hypothesis is successful in explaining patterns of testosterone secretion in many avian species, but remains comparatively unexplored in mammals. ‘Circulating plasma testosterone levels (T)’ were studied in relation to harem maintenance in grey-headed flying-foxes, Pteropus poliocephalus. In this species, harems provide mating opportunities and so a male''s ability to maintain a harem is likely to correlate with his fitness. We hypothesized that if T reflect a male''s ability to withstand challenges from competitors, then T should be linked to successful harem maintenance. To test this, we temporarily removed males from their territories prior to and during the short mating period, recording their harem sizes both before removal and after reintroduction. Most males successfully reclaimed their territory and a harem, but during the mating period, males with higher T had harems closer to their original size, and males with lower T suffered reduction in harem size. Our findings highlight the role of T in harem maintenance in a major mammalian taxon with complex forms of social organization.     

Subordinate Males in Harem Groups of Jamaican Fruit‐Eating Bats (Artibeus jamaicensis): Satellites or Sneaks?

In the caves of Yucatan, Mexico, the Jamaican fruit‐eating bat, Artibeus jamaicensis, forms harems consisting of four to 18 females and a dominant male that defends the group against foreign males. Large groups (>14 females) contain an additional subordinate male. In theory, subordinate males can associate with harem groups either as satellites, if they provide at least some benefits to the dominant male, or as sneaks, if they only impose costs on the dominant male. We assessed the costs and benefits of subordinate males in three removal experiments. In the first experiment, when a dominant male was removed from its group, its role was occupied by the subordinate male (in large groups) or by a foreign male (in small groups). Former subordinate males took less time to gain control of the harems and stayed longer with the groups than foreign males. In the second experiment, when a subordinate male was removed, the rate of visitation by foreign males and the number of agonistic displays by the dominant male both increased. In the third experiment, when the number of females in large groups was reduced, subordinate males spent less time with their groups and the rate of visitation by foreign males increased. However, the frequency of agonistic displays by dominant males towards subordinate males did not change. Dominant males invest large amounts of energy in defending the harems, but obtain direct and immediate benefits from the presence of subordinate males in the form of access to a larger number of females, and suffer no obvious costs. Subordinate males apparently invest little energy in defending the harems, obtain no obvious immediate benefit, but gain long‐term benefits by having priority access to vacant positions left by dominant males. Subordinate males in harem groups of the Jamaican fruit‐eating bat can be considered satellites because their presence brings immediate benefits to the dominant males.     

Genetic mating system and the significance of harem associations in the bat Saccopteryx bilineata

We analysed the polygynous mating system of the bat Saccopteryx bilineata using behaviour observations and genetic data on 11 microsatellite DNA loci. Basic social units in S. bilineata are harem groups that consist of single males and up to eight females. Colonies comprise several harem groups, and the composition of colonies and harems is often stable over several reproductive seasons. The combination of parentage exclusion and likelihood-based parentage assignment in this study produced detailed parentage information for a large colony of S. bilineata. Reproduction occurred mostly within the colony (17% extra-colony paternity), but social associations in harems within the colony did not represent reproductive units (70% extra-harem paternity). The latter finding was consistent over three reproductive seasons. Spatial association of the roosting sites of males and females could not explain parentage patterns in the colony. Even though intra-harem paternity was less frequent than expected, it contributed significantly to reproduction of harem males. On average, the number of offspring sired by a male with females in his harem territory increased significantly with harem size, which corresponds to the higher energetic investment that is related to the maintenance of large harems. However, extra-harem paternity was not correlated with a male's harem size or intra-harem reproductive success. This suggests that individual preferences of females rather than male traits associated with the ability to defend large harems are most likely to cause the detected differences between social association and genetic mating system.     

The dynamics of male harem dominance in southern elephant seals (Mirounga leonina) at the South Shetland Islands

Breeding chronology, harem structure and changes in male harem dominance were studied at Stranger Point, Isla 25 de Mayo/King George Island, principally by extensive field census work during the 2003 breeding season. Males were individually identified and their size estimated by using a photogrammetric method. Peak female haul out for the population occurred on 31 October, when a total of 276 females were observed along 7 km of coastline, distributed in ten harems with a median size of 16 females. Overall sex ratio and harem sex ratio for the breeding population were 1:6.7 and 1:10.6, respectively. A total of 33 males were identified associated with harems. Male size conferred an advantage in terms of dominance hierarchy, since dominant males (4.91±0.15 m) were significantly longer than subordinate males (4.63±0.19 m). Harems were dominated by an average of 4.5 (range 2–7) different males during the breeding season. Elephant seals at Stranger Point breed in very low density aggregations. The main breeding events in this population occurred later than at other breeding sites, which agrees with previous observations in the area. Male movement among harems suggests that differences in mating success among males could be achieved through their different behaviours.     

Effect of female group size on harem male roosting behavior of the Indian short-nosed fruit bat <Emphasis Type="Italic">Cynopterus sphinx</Emphasis>

Mate guarding has been known to incur costs and cause constraints for harem males in many polygynous species. However, the effect of female group size on the harem male’s time budget in bats has received very limited attention. The Indian short-nosed fruit bat, Cynopterus sphinx, exhibits resource defense polygyny, in which tent roosting males construct tents and defend multiple female bats. We studied the effect of female group size on three aspects of harem male behavior: social grooming by reciprocal licking, tent maintenance, and tent guarding in the mast tree Polyalthia longifolia. In the process of reciprocal licking, all the bats in the harem were drenched in saliva before emergence, and this activity was positively and significantly correlated with female group size. Once females departed for foraging, harem males remained in their respective tents at night-time between intermittent foraging bouts and engaged in tent maintenance and tent guarding. Time invested by harem male bats in tent maintenance and tent guarding were positively and significantly correlated with female group size. Harem males extended their presence in tent by utilizing tents as feeding roosts. Female group size also influenced the emergence time of harem male bats, where males with largest group emerged later than did the smallest group. Likewise, harem male with the smallest group had more time available for foraging than the male with the largest group. Findings of this study suggest that having a larger harem may indeed be costly for the males by reducing their foraging time.     

Pairs and Harems in a Cichlid Fish,Lamprologus brichardi1

L. brichardi is a substrate brooding cichlid with facultative polygamy. The social organization was studied in the field for a 6-week period. The mating structure was examined in detail in the laboratory. Two types of social groupings are described:

• 1 Aggregations of sexually mature but nonterritorial fish, also frequently visited by territory holders in the vicinity.
• 2 Reproductive units (families) mainly consisting of the reproducing pair members and offspring from several broods. All family members defend a common territory around the shelter site. Occasionally a male has access to two females each with a separate territory (harem).

The factors influencing mating structure were investigated in the laboratory:

• 1 Females select breeding sites rather than partners.
• 2 Without competitors for breeding sites, and with an equal or nearly equal sex ratio, harems were established nearly as often as pairs.
• 3 Young males are physically able to mate and form a harem; but they are usually prevented from doing so by more competitive (larger) males.
• 4 Competition for breeding sites is not a prime influence on harem formation, although it is of great importance in determining the composition and size of the breeding population.
• 5 Just as many pairs as harems were formed with and without predators, even though, with predators, no young survived.
• 6 In L. brichardi the formation of harems is not predominantly determined by the distribution of suitable spawning sites. The monopolization of females is only slightly influenced by the distance between their territories.
• 7 In L. brichardi it is not necessary for harem formation that the male is bigger than the female.
• 8 Behavioural protocols and data on growth rates, as well as spawning intervals, did reveal any consistent difference between pairs and harmes.

Of the variables tested, male competition for females was therefore the sole determinant of who should mate.     

Harem size and oviposition behaviour in a polygynous bark beetle

Abstract. 1. Harem polygyny can have fitness benefits and costs on females. In bark beetles of the genus Ips the latter may include within‐harem competition between larvae. However, earlier competition between females for male care and mating opportunities may also influence oviposition behaviour. There has been relatively little investigation into the relationship between harem size and initial egg output. The present study investigated this relationship in the bark beetle Ips grandicollis. 2. The measure of egg output used was the number of eggs in the gallery with the most eggs in each harem. Mean (±SE) harem size of 242 observed harems was 3.25 ± 0.10. A curvilinear relationship was found between egg output and harem size, with females in smaller harems (one to four females) laying more eggs with increased harem size. However, females in larger harems (five to seven females) laid fewer eggs as harem size increased. The optimal harem size (in terms of number of eggs laid) was close to four females. 3. We found no evidence from a behavioural assay that females could preferentially choose unmated males over mated males with harems of two females. Additionally, the distribution of harem sizes suggests that females distribute themselves among males randomly. 4. The results suggest that harem size has effects on female reproduction that extend beyond larval competition and influence patterns of oviposition. The mechanism that determines why egg laying is greatest at intermediate levels is unknown. There is no evidence that smaller harems belong to lower quality males, but females may adjust egg‐laying behaviour in large harems as a result of reduced male attendance or anticipated larval competition.     

Reconstruction of Parentage in a Band of Captive Hamadryas Baboons

The male leaders of free-ranging harem groups of hamadryas baboons are believed to mate exclusively with the female members of their harems, which typically contain no more than 2–3 females. Using no-parent parentage exclusion analysis (PEA) we identified the paternity of 25 offspring born in a captive band of hamadryas baboons (Papio hamadryas hamadryas) containing five adult males, each with a stable harem of about five females. Nine of 13 microsatellite (SSR) loci known to be highly polymorphic in rhesus macaques (Macaca mulatta) were successful in identifying the sires of all but two offspring without knowledge of the dams' genotypes, and we were able to determine the sires of all offspring when the dams' genotypes were considered. Mating success of the males ranged between 2 and 7 offspring and bore no clear relationship to the males' ages, ranks or the number of females in their harems. The males sired 7 of the 25 offspring with females outside their own harems, with higher-ranking males exhibiting greater success monopolizing access to females in their harem than lower-ranking males did. More surprisingly, the females assigned as the dams of 14 of the 25 offspring could be unequivocally excluded from parentage. The identity of the true dam could be determined for each of these 14 offspring using single-parent PEA and was uncorrelated with the ranks of these offsprings' sires and whether the offspring were born to dams outside the sires' harem groups. The combined effect of this extraharem mating and kidnapping was that only 12 of the 25 offspring were raised within their sires' harem groups. A second group of hamadryas baboons of identical structure exhibited the same high incidences of infant kidnapping and mating outside the harem group. It is unclear whether these behaviors provide an adaptive advantage or represent aberrant behavior resulting from captivity or other circumstances.     

Mate choice or harassment avoidance? A question of female control at the lek

Recent studies on the reproductive behavior of fallow deer,Dama dama, propose that harassment from nonterritorial maleshas a major influence on female movements and mate selection,leading ultimately to the evolution of lek mating in this species.In order to support this statement, one must demonstrate thatfemale movements between lek and isolated territories, and amonglek males, lead to a reduction in levels of harassment. We arguethat current evidence in favor of this view is inconclusive.A quantification of the total harassment costs experienced byfemales in lek and isolated territories has never been made.In addition, female movements within the lek may actually leadto higher levels of disruption and harassment: The rate at whichfemales join male territories increases with harem size (thenumber of females present in the territory), even though haremsare disrupted increasingly with size due to a higher frequencyof intrusions by nonterritorial males. Females also join maleterritories at a higher rate while these males are engaged incopulatory sequences, but copulatory sequences are again associatedwith high levels of disruption and harem instability. In theabove studies it is argued that females are nonselective intheir mating preferences. This assessment is based on the findingthat males that adopt different reproductive strategies do notdiffer in their mating rates. Here mating rate is measured asthe number of copulations received per female-hour. There area number of reasons, however, why females exhibiting matingpreferences might remain longer with preferred males, and sothe above preference measure cannot be used to exclude the possibilitythat females are selective. More research is required to identifythe major factors influencing patterns of mate selection andthe evolution of leks in this species. We suggest a number offield tests that may help to identify these factors.     

To lek or not to lek: mating strategies of male fallow deer

We studied the mating system of fallow deer (Dama dama) for6 years in central Italy. Males in this population could defendterritories that were either single, clumped in leks, or satelliteto leks. The most highly successful males in our study werein leks. When we considered all males, there were no significantdifferences in average copulatory success according to territorytype because many lek males did not achieve any copulations,which were seen in only a few lek territories. The variancein copulatory success, however, was much greater for leks thanelsewhere. Single territories were occupied for shorter timesduring the rut than lek territories. Fighting among males wasmore frequent in the lek, even when we excluded highly successfullek males from the analysis. Chases of nonterritorial malesand harem size were correlated with the number of copulationsachieved by individual males, but did not vary according toterritory type. Copulatory success of some individuals increasedwith age, but there were no age differences among males holdingdifferent types of territories. Satellite males switched tolek territoriality in the course of one rut, but switches fromsingle territory to lek territory were rare. We suggest thatmales in single territories are inferior competitors that selecta low-risk, lowbenefit strategy, whereas those in lek territorieswhere no copulations were seen may be attempting to establishthemselves on the lek to increase their copulatory success infuture years.     

Temporal and Spatial Distribution of Male Scent Marks in the Polygynous Greater Sac-Winged Bat

Scent marks are relatively long-lived signals that can be perceived by conspecifics when the producer is absent. Therefore, it is often not obvious to whom the signal is directed. In daytime roosts of the polygynous greater sac-winged bat, males scent mark territories with facial gland secretions. Territories are a valuable resource for males, as they offer exclusive courtship opportunities, which results in increased male reproductive success and, consequently, increased male–male competition over territories. The information encoded in male scent marks could, therefore, be either directed at females as part of an olfactory courtship display or at male competitors as part of territorial behaviour. We expected territorial males to scent mark in the morning, shortly before females return to the territory and close to female roosting sites, if scent marks are directed at females as part of the courtship display. And we expected harem males to scent mark at the territory boundaries, where male–male encounters are most likely to occur, if scent marks are directed at male competitors. We found that males marked more frequently in the afternoon, at a time when all females have already left the territory, and harem males marked at the territory boundaries and not inside their territory in the area where females roost. At boundaries males fan volatiles from specialised wing sacs towards competitors outside the territory. Scent marking of male Saccopteryx bilineata might therefore be congruent with the assessment-hypothesis, which states that scent marks offer intruders the possibility to make an olfactory assessment of the territory owner without direct physical interaction. Thus, scent marks of male S. bilineata are most likely influenced by male–male competition and not by female choice.     

Reversed Sex Change in The Haremic Protogynous Hawkfish Cirrhitichthys falco in Natural Conditions

Bi‐directional sex change has recently been reported in a range of reef fishes, including haremic species that were earlier thought to be protogynous (female to male). However, the occurrence of this phenomenon and the social conditions driving the reversion of males to females (reversed sex change) have been poorly documented under natural conditions. Reversed sex change is predicted to occur in low‐density populations where facultative monogamy is common. However, few studies have evaluated this over a long period in such populations. We documented the occurrence of bi‐directional sex change during a 3‐yr demographic survey of a population characterised by small harem sizes in haremic hawkfish Cirrhitichthys falco. New males were derived following a change in sex of functional females (secondary males; n = 3) and juveniles always matured first as females (n = 3). Thus, C. falco exhibited a typical protogynous sexual pattern, consistent with a range of haremic fish species. We observed reversed sex change in two males. In both cases, all the females disappeared from their harems and the neighbouring males expanded their territories to encompass the territories of the sex changers. However, bachelor males did not always revert to females. A dominant male experienced bachelor status twice but regained mating opportunities following the immigration of a female into his territory or by taking a female from a neighbouring harem. Thus, we conclude that bachelor males use reversed sex change as a facultative tactic to regain reproductive status in a haremic mating system. In addition, we discuss the influence of harem size upon occurrence of reversed sex change.     

Transition of nonharem male to harem male status in the short-nosed fruit bat Cynopterus sphinx

The short-nosed fruit bat Cynopterus sphinx is known to exhibit resource defence polygyny as its primary mating strategy. Tent construction by harem males to recruit females represents a heavy investment of time and effort, which is not done by nonharem males. The previously unobserved mode of harem formation by the solitary males was studied using mark-recapture and radio-telemetry. In our observation, the solitary males roosting near to harems started recruiting females by occupying the tent abandoned by the harems. This result suggests that the transition of nonharem male to harem male status possibly by a previously unobserved mode and the female recruitment is associated with resource (roost). It implies that the solitary males are actively involving in female recruitment and also presumably mating.     

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.     

Red deer females collect on male clumps at mating areas

Mating strategies in mammalian herbivores are adapted to thedispersion of females, and female dispersion is mainly determinedby resource dispersion, although it is frequently unclear whetherfemales may also be influenced by the location of males. Inthe red deer (Cervus elaphus) the distribution of females beforethe rut predicts the places were males should establish territoriesand even their relative success. However, the number of femalesusing the mating areas in Doñana increases during therut. We observed 20 areas of meadows, used by grazing femalesbefore the rut. At the onset of the rut, the number of females increasedin some of these areas and decreased in others, and the opposite patternwas found after the rutting period. Changes in the vegetationat mating and nonmating areas could not account for the changesin female distribution; even some of the highest quality meadowswere vacated by females during rut. In selecting the matingareas, females avoided isolated small meadows within the scrubarea and preferred larger meadows where a number of neighboringrutting males could be found. Females also avoided those areas heavilyused by fallow deer (Dama dama), a competing sympatric species.We found that females suffered less sexual harassment when inlarger harems and when their harem was surrounded by other harems.Our results, together with those in the literature about thispopulation, indicate that red deer females collect during theearly rut in mating areas containing several rutting males,although once there they may select particular sites based on availabilityof food rather than based on the presence of a particular male. Byjoining harems in large meadows they are less harassed, andat the same time they probably increase their chances of matingwith highly competitive males. The results from Doñanasupport the idea that harassment avoidance may lead to femalemovements to areas with male territories without lek breedingor female comparison of male phenotypes and may bring an insightinto those factors leading to clumps of male territories andleks.     

Male foraging avoidance in female feeding territories in a harem polygynous cichlid in Lake Tanganyika

We studied foraging site partitioning between the sexes in Neolamprologus tetracanthus, a shrimp-eating Tanganyikan cichlid with harem-polygyny. Females maintained small territories against heterospecific food competitors within large territories of males, foraging exclusively at the inner side of their own territories (foraging areas). Males fed as frequently as females in their own territories, but mostly outside female foraging areas, although they frequently entered female territories and repelled food competitors from the territories. Soon after removal of the resident females, however, harem males, as well as many food competitors, invaded the vacant territories and intensively devoured prey of female foraging areas. This indicates that although female foraging areas appear to contain more food than outside the areas, harem males refrained from foraging there when the resident females were present. We suggest that harem males will attempt to keep female foraging areas in good condition, whereby they may get females to reside in male territories and/or promote female gonadal maturation.     

One-male harems and female social dynamics in Guinea baboons

Little is known about the mating system and social organization of Guinea baboons. This study investigated whether Guinea baboons have a harem-based mating system similar to that of hamadryas and gelada baboons and whether one-male mating units also correspond to social units. Ten adult females in a captive multi-male multi-female group of Guinea baboons were focally observed 2 h per week for 12 weeks, and all observed copulations within the group were recorded. Some males copulated with a single female while others had harems of 2-4 females. All females copulated with a single male except 1 female that switched harems early in the study. The focal females had higher rates of social interaction with their harem members, especially their harem male, than with individuals outside the harem. Females appeared to be subordinate to the harem male but little or no physical aggression or herding behavior from the male was observed. Variation in female social interactions within the harem was not accounted for by their sexual interactions with the male or their genetic relatedness with the females. Females, however, appeared to maintain social relationships with their female relatives in other harems. Taken together, the results of this study show that both mating and affiliative interactions in Guinea baboons are concentrated within one-male units and that the social dynamics within and between these units share some similarities as well as differences with those of hamadryas and gelada baboons.