Regulation of reproduction in the neotropical ponerine ant,Pachycondyla villosa

Workers in queenless groups of the antPachycondyla villosa engage in antennal boxing and biting and by these interactions establish social dominance hierarchies, in which several high-ranking individuals may lay eggs. We observed egg cannibalism by dominant workers. The presence of larvae negatively effects the number of worker-produced eggs in queenless colony fragments in two ways. First, larvae feed on the eggs, and second, workers lay fewer eggs when larvae are present. In queenright colonies, workers lay eggs at a low rate, which are eaten by the queen or fed to the brood, but apparently they do not compete aggressively for egg-laying.     

Changes in the dominance rank and reproductive behaviour of male bonnet macaques (Macaca radiata)

The dominance rank of male bonnet macaques influenced their associations and sexual interactions with cycling and conceiving females. Only high-ranking males formed exclusive associations with high-ranking females, and high-ranking males copulated with these females more often than did other males. Changes in male dominance rank were directly related to changes in male mating behaviour, as males who rose in rank spent increasing amounts of time in exclusive proximity to conceiving high-ranking females, and males whose ranks declined spent decreasing amounts of time in proximity to such females. The year of the study in which dominance relationships were most stable was also the year in which the top-ranking male most successfully monopolized access to conceiving high-ranking females.     

Dominance hierarchy and reproductive conflicts among subordinates in a monogynous queenless ant

In insect societies lacking morphologically specialized breedersand helpers, reproduction is often restricted to behaviorallydominant individuals. Such societies occur in about 100 speciesof ants that have secondarily lost the queen caste. All females,who are morphologically workers, can potentially mate and layeggs but only a few do so, and we demonstrate in Dinoponeraquadriceps that this is regulated by a dominance hierarchy.Six types of agonistic interactions allowed the ranking of 5-10workers in the hierarchy (n = 15 colonies). In particular, alphaand beta had characteristic behavioral profiles and were easily recognized.Only alpha mated, and workers ranking beta to delta sometimes producedunfertilized, male-destined eggs. Natural replacements (n = 19)and experimental removals (n = 15) of alpha demonstrated that betawas the individual most likely to replace alpha, although gammaand more rarely delta sometimes did, and we discuss the conflictthat occurs among high-ranking individuals over who should replacealpha. After such replacements, the new alpha behaved more aggressivelythan the overthrown alpha. Newly emerged workers tended to reachhigh ranks and displaced older high-ranking individuals downthe hierarchy. Low-ranking subordinates often prevented high-rankingindividuals from replacing alpha by biting and holding theirappendages (worker policing), which is consistent with the patternof relatedness associated with monogyny and monandry in D. quadriceps. Weinvestigated the relative importance of chemical communicationand dominance interactions to regulate reproduction. Alpha,beta, and sterile workers have different signatures of cuticularhydrocarbons, and these may provide honest information whichunderpins worker policing by low-ranking individuals.     

Effects of spatial proximity and alliances on dominance relations among female ring-tailed lemurs (Lemur catta) at Berenty Reserve, Madagascar

In the present study, we describe a change in the dominance rank of the top-ranking female in a wild troop of ring-tailed lemurs (Lemur catta) at Berenty Reserve, Madagascar. After the top-ranking female fell to the bottom-ranking position, she was able to outrank a low-ranking female with the support of her adult daughter or an unrelated high-ranking female. These results indicate that, as in cercopithecine monkeys such as macaques and baboons, close proximity and alliances influence dominance relations among adult females in a wild troop of ring-tailed lemurs.     

Worker dominance and policing in the ant Temnothorax unifasciatus

In many species of eusocial Hymenoptera, conflict about the production of males is resolved through “policing.” Recent studies in wasps and the ant Temnothorax unifasciatus suggest that in these species policing workers are dominant themselves and selfishly increase their own chances of later becoming fertile. Policing may therefore to some extent be associated with dominance and selfishness, and dominance and policing behaviour are indeed difficult to distinguish and often not mutually exclusive. Moreover, selfish policing requires that workers form rank orders already in the presence of the queen. Here, we try to allocate aggressiveness by workers towards policing and/or dominance behaviour and investigate whether hierarchies based on subtle, non-aggressive interactions exist in queenright colonies of the ant T. unifasciatus. We either split colonies into a queenright and queenless halve or temporarily removed the queen from complete colonies, which in both cases allows a few dominant workers to lay eggs in the queenless colony. Reunification of colony halves and return of the queen to orphaned colonies led to aggression against those workers that had become fertile during the absence of the queen. Dominant workers in reunited, split colonies were more severely attacked than those in orphaned colonies after return of the queen. Furthermore, we observed that workers, which later became dominant egg layers under queenless conditions, have more contact with the queen than other workers. Both results corroborate the existence of rank relationships among workers in queenright colonies and show that results from policing experiments may be affected by the disturbance of pre-existing hierarchies through colony splitting.     

Social relations among females in pre- and postemergence colonies of a subtropical paper wasp,Parapolybia varia (Hymenoptera: Vespidae)

In southern Taiwan, most colonies (13 out of 14) ofParapolybia varia were founded by multiple females. Several females were present at the founding and increased up to 25 about one week after it. Observations on 2 pre-emergence colonies (in a total of 21 h) and those on 4 postemergence colonies (in 62 h) revealed the following facts: In the pre-emergence period, the top-ranking female dominated all others like a despot. Some females attending from the founding also dominated other females who joined later. Interactions among females gradually decreased in frequency after the founding and became milder. The top-dominant rarely left the nest and monopolized most of ovipositions by physically disturbing the subordinates' attempts to oviposit. Differential oophagy was not observed even when the subordinates succeeded in laying (6 cases). After the emergence of workers, the subordinate associates gradually disappeared and the colonies became monogynous (one egg-layer or queen per colony). Monogyny was also confirmed in October on 3 big colonies which had already produced reproductive forms. Eighty-six percent of females (n=50) taken from nests of early stage containing nothing or eggs alone were inseminated and 66% of them had well developed ovaries, while 90% of those (n=20) from more developed nests containing mature larvae and/or pupae were inseminated and only 25% had developed ovaries. This suggests that the ovaries of the subordinates had possibly, though not completely, degenerated through dominance interactions. Social biology ofParapolybia wasps in Taiwan. II. Based on part of a thesis presented to Hokkaido University in partial fulfillment of the Doctoral degree.     

Morphology and reproductive behaviour of intercastes in the ponerine antPachycondyla obscuricornis

Summary Queens are usually the functional reproductives inPachycondyla obscuricornis, but none were found in one colony collected near Brasilia. In this colony, three adults differed morphologically from workers; although wingless, their thorax was more or less like that of winged queens (scutum and scutellum distinct; metanotum larger than that of workers). Another 11 such individuals were found by opening cocoons. We consider that these are intercastes (sensu Peeters, 1991). Two adult intercastes were mated and laid eggs. In contrast, all the workers were virgin, but some laid distinct trophic eggs which were fed to the two reproductives. Following experimental removal of the intercastes, dominance interactions began among the workers, and reproductive eggs were then laid. Intercastes with a reproductive function have not been reported previously in the Ponerinae. They are distinct from ergatoid queens (permanently wingless reproductive caste) or gamergates (mated egglaying workers).     

Allofeeding in Arabian Babblers (Turdoides squamiceps)

Allofeeding is a common social display among adult Arabian babblers (Turdoides squamiceps). The sociology and rates of allofeeding were studied with a tame population of babblers at the Shezaf Nature Reserve in the Rift Valley, Israel. Allofeeding rate varies with the season and food availability. Experimental supplementation to the whole group or to certain individuals greatly increased the rate of allofeeding, but it did not change the social order of the interactions. The interactions were almost always unidirectional: the donor allofed an individual lower in rank. Most of the few exceptions were reciprocal allofeeding among pairs of low-ranking individuals, correlated with a change in dominance between a young male and a young female. Higher-ranking individuals sometimes interfered with allofeedings by lower-ranking ones, and receivers frequently refused to accept the food offered. Allofeeding may therefore be considered as a display of dominance. However, as dominance rank rarely changes, except in very young birds, we suggest that allofeeding interactions display the prestige of the donors, that is, the degree of dominance of one individual over the other.Electronic Supplementary Material Supplementary material is available for this article at .     

Social interactions between an inquiline ant, <Emphasis Type="Italic">Ectatomma parasiticum</Emphasis>, and its host, <Emphasis Type="Italic">Ectatomma tuberculatum</Emphasis> (Formicidae,Ectatomminae)

Inquilines, workerless social parasites, frequently show advanced adaptations to their parasitic life style that indicate a long co-evolutionary history with their host. Ectatomma parasiticum, the first inquiline described in the poneromorph group, usurps established colonies of E. tuberculatum and produces only sexuals. In laboratory colonies, parasites were specifically attacked by the host workers, showing a failure in their social integration. Social interactions were frequent between parasites and their hosts, especially antennation, interpreted as attempts to promote colonial odor transfer. Inquilines destroyed eggs laid by the other queens (67 out of 209 eggs laid), including conspecific parasites, which is unusual. Such partial integration into the host colony and potential parasite virulence argue for a recent evolution of social parasitism in E. tuberculatum.     

The unusual social organization of the antPachycondyla tridentata (Formicidae,ponerinae)

Colonies of the ponerine antPachycondyla tridentata from Malaysia occur with and without queens. In a total of 7 colonies we found more than 80% of the workers to be mated, irrespective of the presence or absence of queens. This is a hitherto unknown social organisation in ants. Queens and workers competed equally for reproduction. In the colonies investigated several ants were laying eggs. Behavioral observations revealed persistent dominance interactions between colony members. A few ants, but not necessarily a queen, occupied top positions. Removal of the most dominant ants led to a new hierarchy in which subordinate ants with developed ovaries were attacked significantly more frequently than non-reproductive ants. On the average, callows were more aggressive than older subordinate ants, displacing most of the older laying workers in one colony. Nestmate recognition tests revealed that non-reproductive ants were much more aggressive towards foreign ants than were ants with developed ovaries.     

Symmetrical patterns in non-agonistic social interactions found in unprovisioned Japanese macaques

Non-agonistic social interactions in an unprovisioned troop of Japanese macaques (Macaca fuscata yakui) were analyzed with the spacing between individuals, leading-following interactions, and exchange of social grooming. The most frequent interactions were found between kin-related females. Unrelated females stayed with one another rather frequently, but rarely exchanged social behaviors. Interactions between males and females were infrequent though they were occasionaly observed between high-ranking males and high-ranking females. Very frequent exchange of grooming was observed between males, and even high-ranking males exchanged grooming more frequently with males than with females. Most non-agonistic social interactions in the study troop were based on bidirectional exchange of social behaviors, in which no clear tendency relevant to dominance or sex was found; while in provisioned Japanese macaque troops, associations between males and females, between unrelated females, and between males were formed mainly be subordinates' active roles in associative behaviors. This seems relevant to the idea that dominance grealty influence social life in provisioned troops. The present study provides guidelines for interspecific comparison of social interaction patterns of macaque species.     

Male-female Parental Roles in Sarotherodon galilaeus (Pisces: Cichlidae)

Sarotherodon galilaeus is a predominantly biparental, sexually monomorphic mouthbrooder. 15 spawnings of pairs in the weight range 150–450 g were observed in aquaria. Only clutches of females larger than 320 g were reared jointly; with those of smaller females, the first fish to pick up eggs brooded alone, while the comparatively few eggs left for the second fish were invariably eaten. The latency after which eggs were picked up increased with the duration of spawning and indirectly with fish size. This increase was larger in males than in females, so large males started to collect eggs later than their mates. In small pairs (female weight < 200 g), by contrast, the male would pick up eggs first and carry them alone. This is the case in a smaller congeneric species, S. melanotheron, indicating that the apportioning of broodcare is based on a unitary, size-dependent mechanism among Sarotherodon. Yet picking-up order was not entirely determined by these equations. Some fish did not show any reaction towards the eggs and occasionally males became care-givers despite expected longer latency, seemingly because of aggressive dominance.     

Agonistic and Affiliative Relationships of Adult Female Howlers (Alouatta palliata) in Costa Rica Over a 4-Year Period

We observed 12 adult female mantled howlers (Alouatta palliata), which have been part of Group 2 at Hacienda La Pacifica, Guanacaste Province, Costa Rica, via focal animal sampling during portions of July and August of 1988 and 1990–1992 (7–9 females/year, 955.3 hr of observation). We used agonistic interactions and time in proximity (<1 m) as indices of social relationships. The rate of female–female agonistic interactions was 0.38/hr (yearly range: 0.24 to 0.51/hr). Yearly dominance hierarchies, based on outcomes of dyadic agonistic interactions, varied in linearity between 60.7 and 94.6%. Adult females spent 7.10% of their time in proximity to another adult female (yearly range: 1.04–15.64%) and 4.95% of their time in proximity to an adult male (yearly range: 2.27–7.51%). Using yearly dominance ranks, we tested proximity patterns for differences based on rank and presence of dependent offspring. In 3 of the 4 years, high-ranking females spent significantly greater proportions of their time in proximity with other females than did low-ranking females. Time in proximity with the 3 or 4 adult males was not associated with rank. Having a dependent infant was not related to the proportion of time in proximity to females or males, and females, especially top-ranking ones, spent more time in proximity to females with dependent infants than to females without infants. These results show that social relationships in mantled howler groups are dynamic and generally support predictions made by von Schaik (1989) regarding scramble-type, female competitors. We also discuss the roles of immigrations, infants, and male relationships in the patterning of social relationships.     

Dominance Interactions Regulate Worker Mating in the Polygynous Ponerine Ant Gnamptogenys menadensis

In queenless ants, workers compete aggressively to be reproductives instead of sterile helpers. To limit the number of reproductives, either mating or egg-laying by mated workers can be regulated. In Gnamptogenys menadensis , all mated workers reproduce, and field data presented here indicate that mating is not random. We removed gamergates experimentally (n=16 groups) to induce mating and gamergate replacement. Virgin workers engaged in agonistic interactions, allowing us to classify them into two groups: dominants performed antennal boxing and biting, while subordinates did not. However, a few subordinates cooperated to immobilize individual dominant workers. This effectively reduced the number of dominants because immobilized dominants became subordinates. Six to 12 wks after the removal of reproductives, between one and eight dominants per colony started to perform 'sexual calling' outside the nest entrance. Sixteen (out of 33) dominants mated with foreign males introduced in five experimental groups. None of the subordinate workers mated. The probability of mating is thus regulated by dominance interactions among workers and immobilizations initiated by infertile workers in this polygynous queenless ant.     

Effects of age, dominance, and seasonal changes on proximity relationships in female Japanese macaques (Macaca fuscata) in a free-ranging group at Katsuyama

The present study compares the behavior of old female Japanese macaques (Macaca fuscata) with that of their full adult daughters in a free-ranging group, with respect to dominance and seasonal changes. Old mothers (21 to 25 years old) spent more time resting and alone than did their middle-aged adult daughters (10 to 17 yr old). However, the number of skin-related animals in proximity to the subject females, did not differ between mothers and their adult daughters. Mothers maintained proximity to more non-kin-related immature animals in the mating season than did their adult daughters, perhaps to avoid sexual aggression from males and to reduce the loss of body temperature in the cold. Dominance rank clearly influenced the social interactions of old mothers: high-ranking mothers interacted with more non-related adult females and immature animals than did low-ranking mothers, indicating that old age does not decrease the attractiveness of high-ranking animals.     

Reproductives and eggs trigger worker vibration in a subterranean termite

In insect societies, the presence of reproductives or eggs has been shown to shape several biological traits in the colony members. Social interactions are one of these traits that involve modification of the communication system of the entire colony. Many studies described the role of chemical compounds and dominance behaviors in the presence of reproductive but vibratory behaviors received very few investigations. Yet, vibratory behaviors are ideal candidates, particularly for subterranean species like termites, as they could be quickly transmitted through the substrate and could be very diversified (origin, modulation). Here, we investigated whether the presence of reproductives/eggs affects the vibratory behavior (body‐shaking) of workers in the subterranean termite Reticulitermes flavipes. Our results reveal that the presence of reproductives or eggs triggers an increase of workers' body‐shaking, independent of their colony of origin after 24 hr. We hypothesize that vibratory communication could be used to transfer information about the presence of reproductives and eggs to the entire colony, suggesting that vibratory behaviors could serve as an important yet neglected mediator of social regulation.     

<Emphasis Type="Italic">Polistes japonicus</Emphasis> (Hymenoptera,Vespidae) queens monopolize ovipositing but are not the most active aggressor in dominant-subordinate interactions

In order to elucidate the dominant–subordinate relationship between the foundress and workers, five colonies of the paper wasp Polistes japonicus were observed in a netted and covered cage located outdoors. The number of workers in each colony ranged from four to eight. Workers were divided into first and second broods. Abdominal wagging and ovipositing were performed almost exclusively by the foundress throughout colony development. However, an analysis of aggressive encounters indicated that although the foundress hardly received dominance behaviors (aggression) from workers, it lacked either partially or completely the following characteristics of the queen that are usually seen in paper-wasp colonies with independent-founding queens (except in one colony that produced no second brood): the queen being socially dominant over any worker (the queen had more wins than losses in one-on-one dominance contests with any worker), exhibiting the highest frequency of dominance behaviors, and directing dominance behaviors primarily toward the socially most-dominant worker. In particular, during the mixed-brood period (when all first- and second-brood workers were present on the nest) the foundress hardly exhibited dominance behaviors toward socially dominant workers (mainly second brood) but frequently directed dominance behaviors toward socially subordinate workers (mainly first brood). The foundress disappeared in two colonies before the reproductives emerged; in these colonies the socially most-dominant worker inherited the colony and laid many eggs. The frequency of abdominal wagging by these two foundresses decreased during colony development, while it did not in the other colonies. This suggests that abdominal wagging provides information about the vigor of the performer. The superseder was socially dominant over all other workers, but spent little time wagging its abdomen and allowed some workers to lay eggs.     

Self-restraint and sterility in workers of Acromyrmex and Atta leafcutter ants

Summary. Queens of leafcutter ants (Acromyrmex and Atta) are highly multiply mated, resulting in a potential queenworker and worker-worker conflict over who should produce the males in the colony. We studied whether this conflict is expressed, by determining the amount of reproductive egg-laying by workers in queenright colonies of Acromyrmex echinatior, Acromyrmex octospinosus, Atta cephalotes, and Atta sexdens through ovary dissections. Worker sons are absent or rare in queenright Acromyrmex colonies, but can be produced in orphaned colonies. In Atta, most workers have rudimentary ovaries that never produce eggs, but a few (mostly small and medium workers that form a retinue around the queen) lay many trophic eggs for consumption by the queen. These eggs are large, flaccid, and lacking in yolk compared to queen-laid eggs, and appear to be always inviable. In Acromyrmex, many workers (especially young large workers) lay eggs that are similar in size to queen-laid eggs, but mostly with a reduced amount of yolk. Trophic eggs appear to be an important source of food for larvae in Acromyrmex (especially in Ac. echinatior), but not in Atta. Five (0.8) of 616 dissected Ac. echinatior workers but no Ac. octospinosus workers (n = 552), had ready-to-lay reproductive eggs. Old workers in all four species are incapable of laying eggs due to ovary resorption. We conclude that Atta workers are sterile, while Acromyrmex workers display reproductive self-restraint, possibly representing an earlier stage in the evolution towards worker sterility. Worker selfrestraint in Acromyrmex may be maintained by a queen or worker policing mechanism, but individual cost-benefit explanations may also apply.Received 1 March 2004; revised 28 June 2004; accepted 1 July 2004.     

Factors influencing dominance behaviour in queenless bumblebee workers (Bombus terrestris)

ABSTRACT. The establishment of a dominance order within seventy eight groups of four callow workers was investigated. The dominant worker establishes its position by means of overt aggression. Aggression starts 20—40 h after confinement. Dominance order becomes established within 2 days of removal from the colony. Once established, the dominance order is maintained by dominant-subordinate interactions.
The dominant worker starts ovipositing at an age of about 6 days. Subordinates rarely lay eggs. In 25% of the groups the dominant worker is superseded by another worker before any oviposition occurs. Once the dominance order is established, the dominant worker inhibits endocrine activity in subordinates.
Differences in body size and in endocrine activity are thought to be responsible for the ranking of workers in the dominance hierarchy. Ranking seems to depend more on the activity of the corpora allata (CA) than on the activity of the ovaries. Ovariectomized workers do not differ from control workers in the performance of dominance behaviour. Dominant ovariectomized workers do not construct egg cells, but they do defend these if they are present.     

Worker reproduction and related behavior in orphan colonies of a Japanese paper wasp,Polistes jadwigae (Hymenoptera,Vespidae)

Worker reproduction and related behavior in 2 orphan colonies ofPolistes jadwigae, one of which had been maintained by a queen and 5 artificially introduced alien workers, were observed. After the queen loss, a dominance hierarchy was established among workers, and several workers laid eggs without physical interference from other workers. Only males emerged from worker-laid eggs, however, a few new queens were produced from queen-laid eggs. Investment sex ratio of queenright (=normal) colonies (0.27) fell between the 2 theoretical values, corresponding to worker control (0.20 or 0.18) and queen control (0.48 or 0.46) of the sex ratio, both being calculated by considering the excess of males produced in the orphan colonies.