Which adult male savanna baboons form coalitions?

We investigated the mechanism of alliance formation among adult male savanna baboons by comparing the characteristics of males that formed coalitions frequently with males that never or seldom took part in coalitions. We observed three groups: two of Papio cynocephalus cynocephalusin Amboseli National Park, Kenya, and one of P. c. anubisin the vicinity of Gilgil, Kenya. We considered four hypotheses: (1) Males must be familiar with each other, (2) males must have an affinitive bond, (3) males must have more than average experience, and (4) the combined fighting ability of the coalition partners relative to the fighting ability of their opponent determines the likelihood that a coalition is formed. We conclude that relative fighting ability forms the key factor in coalition formation. High- ranking males do not form coalitions often, since they hardly need them. Low- ranking males rarefy form coalitions, since they cannot form effective coalitions among themselves. Affinity (“friendship”) may play a role as an additional factor. The relation of coalition formation with age and period of residence, which was found in several studies, can be explained largely by the correlation between these parameters and fighting ability.     

Massacre of the innocents in Cardiocondyla thoracica: Manipulation by adult ant males incites workers to kill their immature rivals

Wingless males of the ant genus Cardiocondyla exhibit a remarkable range of intrasexual competition, from mutual tolerance among males in the colonies of some species to regular lethal fighting in the nests of others. Here, we describe male–male antagonism in Cardiocondyla thoracica (Smith, 1859) from Northern Australia. Males appear to widely ignore adult competitors, but grab defenseless, young rivals during or immediately after emergence and daub them with hindgut secretion. This fluid elicits fatal worker aggression against the besmeared individual. Besmearing and subsequent worker aggression is known from other species of Cardiocondyla but is usually directed towards adult contenders, whereas males kill freshly eclosing males by biting or dismembering. The behavior of C. thoracica males thus constitutes a novel nuance of rival elimination.     

The mating system of a bee fly (Diptera: Bombyliidae). II. Factors affecting male territorial and mating success

Males of an undescribed bombyliidfly (Comptosia sp.)occupy traditional territories on a Southeast Queensland hilltop, to which females come solely for the purpose of mating. Territorial fights between males involve aerial collisions during which modified spines on the wing margins produce scars on the bodies of opponents. Territory owners and mating males are not different in size or age from the remainder of the male population. Although residency is related to fighting success, the strength of the effect is ambiguous. Consequently, our data do not appear to fit predictions from game theoretical models for fighting protocol. Hilltop males lacked the extensive population variation typically found in territorial species, and thus, the presumed advantages of traits such as large size may be suppressed. Hilltop males were larger than males at a nonhilltop, resource-based mating site and the possibility of alternative mating tactics is discussed.     

Kin structure and colony male reproduction in the hornet<Emphasis Type="Italic"> Vespa crabro</Emphasis> (Hymenoptera: Vespidae)

We estimated queen mating frequency, genetic relatedness among workers, and worker reproduction in Vespa crabro flavofasciata using microsatellite DNA markers. Of 20 colonies examined, 15 contained queens inseminated by a single male, 3 colonies contained queens inseminated by two males, and 2 colonies contained queens inseminated by three males. The genetic relatedness among workers was estimated to be 0.73±0.003 (mean±SE). For this high relatedness, kin selection theory predicts a potential conflict between queens and workers over male production. To verify whether males are derived from queens or workers, 260 males from 13 colonies were genotyped at four microsatellite loci. We found that all of the males were derived from the queens. This finding was further supported by the fact that only 33 of 2,990 workers dissected had developed ovaries. These workers belonged to 2 of the 20 colonies. There was no relationship between queen mating frequency and worker reproduction, and no workers produced male offspring in any of the colonies. These results suggest that male production dominated by queens in V. crabro flavofasciata is possibly due to worker policing.     

Diet does not affect intercolonial fighting in Leptothoracine ants

Summary An experiment examined the effects of diet on brood rearing in colonies ofLeptothorax ambiguus andL. longispinosus and on fighting between colonies of the two species. Colonies fedDrosophila and honey reared more pupae than colonies fed the Bhatkar and Whitcomb (1970) diet. However, diet had no effect on intercolonial fighting.     

Sons of low-ranking female rhesus macaques can attain high dominance rank in their natal groups

Five adult and subadult sons of middle- and low-ranking female rhesus macaques (Macaca mulatta) were observed to hold high dominance rank in their natal groups during a 12-month study at Cayo Santiago, Puerto Rico. Three of these males also experienced high mating success during at least one mating season. These findings contrast with all previously published accounts of rank acquisition by natal male rhesus macaques in provisioned colonies, and they present a challenge to the hypothesis that natal transfer functions to increase male access to fertile females.     

Six weeks in the life of a reproducing army ant colony: male parentage and colony behaviour

The army ant Eciton burchellii is one of the most conspicuous ant species in New World tropical forests, but studies of colony life histories have been hampered by the nomadic lifestyle of these ants, which alternate between a nomadic phase when the colony relocates frequently, and a statary phase when the colony remains at a fixed site. Here we report on a colony from Venezuela that we studied continuously for six weeks, from the time that the queen produced a reproductive brood until the adult reproductives emerged and the colony entered the next cycle. Our findings support the contention that reproductive larvae develop faster than worker larvae, and that the nomadic phases of colonies with reproductive broods are significantly shorter than those of colonies with worker broods. This strongly suggests that the onset of pupation is linked to the onset of the statary phase. We used microsatellite genotyping to accurately identify male and queen larvae and we describe how they can be distinguished morphologically. Using the same genetic markers, we determined the parentage of 81 males produced by this colony. Only one of the males had a genotype that could not be directly derived from the observed queen genotype, but this mismatch is most probably due to a single mutation at one of the microsatellite loci, rather than this male being a worker son. We therefore conclude that this colony provides no evidence that workers lay eggs that develop into adult males in the presence of the queen, confirming the results of an earlier study on male parentage in an Old World army ant. Received 16 November 2006; revised 15 January 2007; accepted 16 January 2007.     

The function of male aggressive displays towards females in mountain gorillas

In groups ofGorilla g. beringei, male aggression towards females regularly takes the form of male display. This paper examines male display towards females in two Karisoke study groups (Group 5 and Group BM) in 1989, a period when none of the females were new immigrants. Results are based on 259 hr of focal observations and 121 hr ofad libitum observations on male behaviors towards females. The goal is to see if the data are compatible with four non-mutually exclusive hypotheses to explain male displays towards females: (1) demonstration of male fighting abilities to influence female long term residence decision; (2) decrease potential competitive inequities between females; (3) provision to females of an occasion to confirm their subordinance to a male; and (4) short term influence on mating. First, male-female proximity was tested against proportion of male displays, to rule out the possibility that males display towards females simply because they happen to be close by. There was no association between proximity and male display. Dominant males were responsible for a higher proportion of displays than subordinate males. This is consistent with the idea that males display to demonstrate their fighting abilities, or their qualities as protector, since dominant males are the ones offering long term protection against infanticide and predators. Females that were in a position to transfer did not receive a higher proportion of male display, however. Long term resident dominant females received a higher proportion of displays from the dominant males, which is consistent with the idea that males attempt to decrease potential competitive inequities between females. There was an association between female appeasement reactions and male displays, which suggests that males display to create occasions for the females to confirm their subordinance to them. Estrous females did not receive a higher proportion of male displays, and there was no association between male display and copulation, suggesting that male displays are not a form of courtship aggression aimed at influencing mating in the short term.     

THE EVOLUTION OF ALTERNATIVE REPRODUCTIVE TACTICS IN MALE CARDIOCONDYLA ANTS

Alternative reproductive tactics are often associated with discontinuous variation in morphology but may evolve independent from each other. Based on life‐history data and a phylogeny we examine how male morphology and reproductive behavior are linked in the evolution of the ant genus Cardiocondyla. Wingless Cardiocondyla males engage in lethal fighting for access to female sexuals, whereas winged males disperse and mate away from the nest. This basic pattern shows considerable variation across species. A phylogeny based on ～3 kbp sequence data shows that male diphenism and lethal fighting are ancestral traits tightly linked in evolution. Winged males were lost convergently in several species groups, apparently in response to the low probability of encountering female sexuals in nests without a resident fighter male. An early dichotomy separates two clades with alternative male morphologies and fighting behavior, but phenotype and fighting strategy are not correlated with the presence of winged males.     

Observations on the social waspRopalidia montana from peninsular India

Four colonies ofRopalidia montana collected in August in the Nilgiri Hills of southern India had adult populations of 32,000-61,000. Queens represented 0·46–1·40% of the populations. All colonies contained males, but in widely varying proportions (1·47–27·00%). The large adult populations and the fact that the nests were largely filled with brood in all stages of development indicate that the colonies were in a stage of active growth in this season. In December, however, colonies have been reported to have smaller adult populations and little brood. Thus brood production appears to be seasonal in southern India. Predation by the hornetVespa tropica was observed in 4 of 31 active colonies.Ropalidia montana adults were defenseless in the face of these depredations, which appear to continue at a low level for days or weeks on a given nest.     

Male parentage and queen mating frequency in the bumblebee <Emphasis Type="Italic">Bombus ignitus</Emphasis> (Hymenoptera: bombinae)

Kin selection theory predicts conflict between queens and workers in the social insect colony with respect to male production. This conflict arises from the haplodiploid system of sex determination in Hymenoptera that creates relatedness asymmetries in which workers are more closely related to the sons of other workers than to those of the queen. In annual hymenopteran societies that are headed by a single queen, the mating frequency of the queen is the only factor that affects the colony kin structure. Therefore, we examined the mating structure of queens and the parentage of males in a monogynous bumblebee, Bombus ignitus, using DNA microsatellites. In the seven colonies that were studied, B. ignitus queens mated once, thereby leading to the prediction of conflict between the queen and workers regarding male production. In each of the five queen-right colonies, the majority of the males (95%) were produced by the colony’s queen. In contrast, workers produced approximately 47% of all the males in two queenless colonies. These results suggest that male production in B. ignitus is a conflict between queen and workers.     

Agonistic Displays and the Benefits of Fighting in the Field Cricket, Gryllus bimaculatus

Fighting is often composed of discrete agonistic displays. Few studies have partitioned fighting behavior into its component agonistic displays and evaluated the relationships between the frequency of the displays and the potential benefits of fighting, particularly mating success. In this study, we quantified the frequency of male field cricket, Gryllus bimaculatus, agonistic displays. The displays were quantified under three social environments which varied in the potential benefits of fighting: males with other males only, males with other males and female scents, and males with other males and females. We found that (1) the presence of females elicited an increase in agonistic displays characteristic of intermediate levels of escalation, (2) female scents did not produce a similar increase in the frequency of agonistic displays, and (3) in the presence of females, the frequency of agonistic displays was positively correlated with mating success. Aggressive stridulation, an energetically low-cost display, was more strongly associated with mating success than were more costly displays. The results are discussed in the context of the evolutionary theory of aggression and in the context of cricket mating systems.     

Effects of female body size and age and male mating status on male combat in Anastatus disparis (Hymenoptera: Eupelmidae)

1. Aggressive behaviour is widely exhibited by animals to acquire important resources and usually shows a dangerous or nondangerous pattern. Dangerous fighting patterns are usually characterized by fights ending with contestants being severely injured or killed. Resource value is an important nonstrategic factor influencing fighting behaviour. Studies of many species addressing nondangerous fighting behaviour have shown that when resource values change, organisms usually adjust their fighting behaviour accordingly. Only a few species show dangerous fighting patterns. Thus, few relevant studies have addressed how variation in resource value affects aggression with a dangerous fighting pattern. 2. Here, an egg parasitoid wasp, Anastatus disparis, which exhibits a dangerous fighting pattern to acquire mating opportunities, was used as an experimental model to study the adjustment of fighting behaviour resulting from a change in resource value. 3. Our results show that the female properties of body size and age affect their objective resource value and that males increased their fighting intensity for relatively large and young females. However, male mating status in A. disparis may not influence the subjective value of mate resources, and fighting intensity did not significantly differ between mated and virgin males. In addition, the number of times a male had previously mated had no significant effect. These results suggest that mating opportunities are important for both virgin and mated males, resulting in neither of them showing any adjustment in fighting for mating opportunities. 4. Generally, A. disparis males with extreme fighting patterns adjust their fighting behaviour according to the variation in resource value, which avoids the meaningless costs of injury and death.     

Forceps Size Does Not Determine Fighting Success in European Earwigs

Male European earwigs (Forficula auricularia) possess substantially larger forceps than females and use these forceps to batter rivals in intrasexual contests to determine dominance. Although previous investigations have shown that male fighting and mating success increases with forceps size, it is not clear that sexual selection acts directly on forceps size per se; increased forceps size may be a correlated response to selection for some other trait. We experimentally reduced forceps length of males and paired them with unmanipulated males in staged encounters. Although apparent (postmanipulation) forceps length did not affect contest outcomes, original (premanipulation) forceps length did: males with longer original forceps won more contests. These results suggest that weapon size itself does not determine success in contests between male European earwigs. Thus, sexual selection may operate on forceps size in some other context or may act on some other trait that covaries with forceps size.     

Fate of ousted male residents of one-male bisexual troops of Hanuman langurs (Presbytis entellus) at Jodhpur,Rajasthan, India

Little is known about the fate of adult male residents after they are ousted from bisexual one-male troops of Hanuman langurs (Presbytis entellus) in the course of adult male replacements. In a long term study at Jodhpur, Rajasthan, it was possible to reconstruct partial life histories of several ousted residents. One resident was killed during the male change. Ousted residents did not regain residency despite their continued invasions into bisexual troops. It is assumed that the males' chances to take over and to defend a troop are restricted to an age of 9–14 years, when the males are in prime physical condition. One male became solitary for some months while trying to regain residency of his old troop, before joining some “alien” males. As a rule, males are likely to rejoin their own male bands if they are ousted after short periods of residency. If the residency exceeds 3 months then the ongoing structural change in the former band may prevent their reintegration. However, in such cases, ousted residents which belonged to the same band may reunite and mingle with another male band which lacks prime males. Weaned sons may follow their fathers after ousting. In the case of numerous weaned offspring, fathers and sons may together form at least temporary new male bands.     

Fighting between two females for a male in the hoolock gibbon

I observed fighting between two adult females for an adult male in a group of hoolock gibbons (Hylobates hoolock)during fieldwork conducted between November 1988 and December 1990 at Lawachara in the West Bhanugach Reserve Forest, Sylhet, Bangladesh. I discuss the history of the episodes and the consequences of fighting.     

Honesty of agonistic signalling and effects of size and motivation asymmetry in contests

Game theoretical models predict that the main function of fighting behaviour is to assess the relative fighting ability of opponents. The sequential assessment game has often been used to investigate contests, while honest signalling theory has received much less attention. With the wolf spider Hygrolycosa rubrofasciata we investigated whether male agonistic signalling can reveal honest information about fighting ability, and how size and motivation asymmetries affect male fighting behaviour. We also determined whether male–male competition affects the courtship behaviour of the males. We found that agonistic drumming activity is an honest indicator of male fighting ability, and that relative size asymmetry and motivation to fight both contribute to the fighting ability. We also found that male–male competition decreases the courtship drumming rate of subdominant males, suggesting that male–male competition limits the opportunities for female choice. We conclude that sequential assessment and honest signalling may both be used in settling contests, and that they may be used simultaneously. Received: 10 December 1998 / Received in revised form: 23 June 1999 / Accepted: 5 July 1999     

Ownership-dependent mating tactics of minor males of the beetle <Emphasis Type="Italic">Librodor japonicus</Emphasis> (Nitidulidae) with intra-sexual dimorphism of mandibles

Intra-sexual dimorphism is found in the weapons of many male beetles. Different behavioral tactics to access females between major and minor males, which adopt fighting and alternative tactics, respectively, are thought to maintain the male dimorphism. In these species major males have enlarged weapons that they use in fights with rival males. Minor males also have small weapons in some of these species, and it is unclear why these males possess weapons. We examined the hypothesis that minor males might adopt a fighting tactic when their status was relatively high in comparison with that of other males (e.g., ownership of a territory). We observed the behavioral tactics of major and minor males of the beetle Librodor japonicus, whose males have a dimorphism of their mandibles. Major males fought for resources, whereas minor males adopted two status-dependent tactics, fighting and sneaking, to access females, depending on their ownership of a sap site. We suggest that ownership status-dependent mating tactics in minor males may maintain the intra-sexual dimorphism in this beetle.     

Control of male production in the swarm‐founding wasp,Polybioides tabidus

In social insect colonies, male production may involve conflicts over the sex ratio, worker vs. queen reproduction, and each queen's contribution to the males when there are multiple queens. We examined male production in the swarm‐founding, multiple‐queened wasp, Polybioides tabidus, for which previous work suggested worker control of the sex ratios. We found that queens produced the males in accord with the collective worker preference. We also found that diploid males were produced, but only in association with haploid males. Simulations show they should have been produced in other colonies as well and their absence indicates that they were killed in some of these other colonies. The pattern of their removal indicates that P. tabidus cannot distinguish diploid from haploid males, and that haploid males would have been removed from these colonies too. This provides evidence that the workers are able to manipulate male production when collective preferences dictate.     

Territoriality and fighting in a colonial thrips, Hoplothrips pedicularius, and sexual dimorphism in Thysanoptera

ABSTRACT.

• 1 Hoplothrips pedicularius (Haliday) (Thysanoptera: Phlaeothripidae), a tubuliferan thrips in which males possess greatly enlarged forelegs, lives in colonies on Stereum fungus.
• 2 Females oviposit onto communal egg masses, and males fight by grasping and stabbing with their forelegs in territorial defence of oviposition areas. Prolonged escalated fights occur between males who are of similar size.
• 3 Larger males usually win fights and become dominant at the oviposition area. Dominant males secure 80% of matings, and mate most frequently during oviposition periods, with an ovipositing female.
• 4 Smaller, subordinate males avoid fights and attempt to 'sneak’copulations. However, they occasionally challenge the dominant male. Challenges tend to follow copulations by the subordinate male and occur more frequently between males who are of similar size.
• 5 Subordinate males who eventually leave the oviposition area are larger than those who remain, have frequently challenged the dominant male, and have more frequently been stabbed.
• 6 Sexual dimorphism in thrips is associated with gregariousness, claustral habitats, female-biased sex ratios, and male winglessness. In thrips genera in which males exhibit foreleg armature, males are larger relative to females. The ecological circumstances promoting sexual dimorphism and male fighting in spatially-structured populations are discussed.