Complex social organization reflects genetic structure and relatedness in the cooperatively breeding bell miner, Manorina melanophrys

The cooperatively breeding bell miner, Manorina melanophrys, differs from most other cooperative breeding species in the complexity of its social system, where discrete social organization occurs on at least three levels. Microsatellite markers were used to investigate the degree of genetic structure underlying the social organization of M. melanophrys by comparing colonies, coteries and nest contingents. The genetic data confirmed behavioural observations of M. melanophrys living in male kin-based groups between which females disperse short distances to breed. Estimates of FST revealed restricted gene flow between eight colonies located within 30 km that was significantly associated with geographical distance when the two most distant colonies were included. Within a high density colony significant differences were found between coteries; analysis of the degree of relatedness between coterie members showed that this is due to related individuals associating preferentially with each other. Similarly, the contingent of individuals attending a nest were generally close relatives of the young they were aiding, supporting models invoking kin selection as the selective agency mediating helping.     

Dominance and aggression in social groups of male and female rats

Two experiments were performed to examine aggression and dominance in domestic male and female $\text{Rattus norvegicus}$ living in small mixed-sex (3 males and 3 females) groups. Experiment 1 examined the development of aggression in females. A single female (alpha) within each of the six colonies tested showed the preponderance of attacks on male intruders placed into the home-cage when male colony residents were absent. Over 12 weeks of intruder-aggression training female alphas showed only a mild nonsignificant elevation of aggressive behavior. A comparison of aggression of male and female colony alphas tested with opponents of each sex revealed that aggression was mainly directed at like-sex opponents, and that female attack was more defensive in character than male attack regardless of opponent sex. The highest intensity of aggression occurred when male alphas confronted male intruders. Although intruders never showed offense toward male residents, 61% of intruding males showed offense in response to attack by females.Experiment 2 investigated the relationship between aggressive dominance and competitive measures of dominance within each of 10 mixed-sex colonies. Alpha stat s of male and female colony residents did not reliably predict priority of access to food or water in tests of direct resource competition with like-sex colony members. When colony males were simultaneously tested for copulation, the copulatory behavior of alpha males was significantly greater than that of other colony males. Results are discussed in relation to the role of aggression in the reproductive strategy of male and female $\text{Rattus norvegicus}$.     

Gender effects on aggression, dominance rank, and affiliative behaviors in a flock of captive adult cockatiels (Nymphicus hollandicus)

Agonistic and affiliative behaviors and spatial positioning were studied in a small psittacine species, Nymphicus hollandicus. Subjects studied were flock-housed breeders including five hens and seven cocks. Fifteen-minute focal animal samples were collected for the entire flock in a randomly distributed order during mate selection and the onset of the breeding season. All agonistic behaviors were recorded, including the winner and loser of each interaction, along with allopreening and copulation behavior. Point samples were recorded every 60s to determine social spacing. Rates of aggression were significantly higher for male cockatiels than female cockatiels. Results based on dyadic agonistic interactions showed males to rank significantly higher in the social hierarchy than females. Associations within the flock were not random. Individual birds associated more with specific birds than would be predicted by chance. Analysis of spatial data revealed that there were both same-sex and opposite-sex preferred associations within the flock. Male cockatiels engaged in allopreening behavior with females significantly more than with other males. Observations of breeding and nesting behaviors revealed pairs, a triad, and extra-pair mating.     

Dominance and queen succession in captive colonies of the eusocial naked mole-rat,Heterocephalus glaber.

Naked mole-rat colonies exhibit a high reproductive skew, breeding being typically restricted to one female (the ''queen'') and one to three males. Other colony members are reproductively suppressed, although this suppression can be reversed following the removal or death of the queen. We examined dominance and queen succession within captive colonies to investigate the relationship between urinary testosterone and cortisol, dominance rank and reproductive status; and to determine if behavioural and/or physiological parameters can be used as predictors of queen succession. Social structure was characterized by a linear dominance hierarchy before and after queen removal. Prior to queen removal, dominance rank was negatively correlated with body weight and urinary testosterone and cortisol titres in males and females. Queen removal results in social instability and aggression between high ranking individuals. Dominance rank appears to be a good predictor of reproductive status: queens are the highest ranking colony females and are succeeded by the next highest ranking females. The intense dominance-related aggression that accompanies reproductive succession in naked mole-rats provides empirical support for optimal skew theory.     

Playback of colony sound alters the breeding schedule and clutch size in zebra finch (Taeniopygia guttata) colonies

The hypothesis that social stimulation, derived from the presence and activities of conspecifics, can hasten and synchronize breeding in colonies of birds was tested. A modified playback/recorder system was used to continuously exaggerate the amount of colony sound available to zebra finches throughout their courtship period. Males that heard 'sound supplements' generated from their own colony sang more than males in control colonies that did not receive playback; males that heard samples from a different colony, sang at an intermediate level. Females that were exposed to the vocalizations of their mate and playback from a colony other than their own, laid eggs earlier and more synchronously than females in control colonies. Females that heard the vocalizations of their mate along with playback samples generated from their own colony, laid eggs more synchronously but not earlier than control females. Both acoustic treatments caused females to lay larger clutches. Social stimulation influences the breeding schedule and clutch size in zebra finch colonies. If there are advantages associated with these effects, social stimulation may contribute to the maintenance of colonial breeding systems.     

Modification of aggression through socialization and the special case of adult and adolescent male rhesus monkeys (Macaca mulatta)

Significant differences exist in the frequencies with which age-sex classes of rhesus macaques engage in agonistic interactions with other age-sex classes. In the study reported here, individuals engaged in significantly more agonistic interactions within their own age-sex classes, but, adult females also showed significantly more aggression toward infants and young females whereas adult males directed significantly more aggression toward adolescent males. Infants directed aggression toward infants of both sexes, but adults showed significantly less aggression toward adults of the opposite sex. These findings are hypothesized to reflect (1) competitive conflict among those individuals in the group most similar to each other (members of the same age-sex class); (2) the protection and socialization of offspring by adult females; and (3) the modification of adolescent male aggressive expression by the selective interference of adult males. As a consequence of adult response to the agonistic behavior of adolescent males, maturing males (1) selectively target other older males, avoid aggression against females and immatures; (2) form alliances with other males; and (3) become progressively isolated from their matrilines.     

Colony structure and parentage in wild colonies of co-operatively breeding Damaraland mole-rats suggest incest avoidance alone may not maintain reproductive skew

Colonies of co-operatively breeding African mole-rats have traditionally been thought to be composed of a single breeding female, one or two breeding males, and their offspring. In the naked mole-rat (Heterocephalus glaber), the occurrence of facultative inbreeding means incest avoidance cannot prevent reproduction in subordinate group members, and physiological suppression of reproductive function by the breeding female occurs in both sexes. In contrast, previous studies of captive colonies of the Damaraland mole-rat (Cryptomys damarensis) suggest that breeding within a colony is restricted to a single breeding pair, simply because all other colony members are highly related (first- or second-order relatives) and this species is an obligate outbreeder. Using microsatellite markers, we investigated parentage and colony composition in 18 wild Damaraland mole-rat colonies to determine whether inbreeding avoidance alone can explain the high levels of reproductive skew in this species. Multiple and unidentified paternity was widespread within colonies and immigrants of both sexes were regularly identified. Unrelated, opposite-sex nonbreeders were found coexisting in two colonies. These results suggest that, in the wild, conditions exist where nonreproductive females can come into contact with unrelated males, even when they do not disperse from their natal colony. Inbreeding avoidance alone is therefore insufficient to maintain the high levels of reproductive skew identified in this species suggesting that the breeding female somehow suppresses the reproductive function in nonbreeding females.     

Intra-sexual female agonistic behaviour of the South American sea lion (Otaria flavescens) in two colonies with different breeding substrates

Female agonistic behaviour during pregnancy and lactation is common in several pinnipeds and has been associated to pup or territory defence. Previous studies on female agonistic behaviour in pinniped breeding groups have not usually considered the number of females per breeding group, which could influence the degree of aggressiveness. We compared female agonistic behaviour (open-mouth displays and bites) within two colonies with different breeding substrates (homogeneous, Punta Norte; heterogeneous, Pirámide) of South American sea lions using two methods: weighted means and general linear models. We found that both aggressive interaction rates were significantly affected by female density, which accounted for a greater proportion on the variability in bite rates than in open-mouth rates. Controlling for the number of females, we found with both methods that open-mouth rates were higher than bite rates within the Pirámide colony; however, no differences were found within the Punta Norte colony. In Pirámide, open-mouth rates could be used more often as threats to minimise the chances of more severe aggressions. The conclusion is that females vary their use of agonistic interactions in relation to their density in the colony with heterogeneous substrate, which may be related to the presence of limited numbers of tide pools that heightens competition for thermoregulatory resources.     

Movements of Eiders Somateria mollissima on the east coast of Britain

Movement patterns, sex differences in natal dispersal and breeding dispersal, and interchange of birds between colonies were studied in the population of Eiders Somateria mollissima breeding on the east coast of Britain. First-winter Eiders reared at the Sands of Forvie, Grampian, remain at or close to the colony, while most adults move about 100 km south to winter on the Firths of Forth and Tay. A proportion of the Forvie population is sedentary. Eiders which breed in Northumberland either move north to winter on the Tay and Forth estuaries or remain close to their breeding areas. Eiders breeding in Fife are sedentary. Recoveries of British-ringed Eiders in Scandinavia indicate that some British-born males join the Baltic breeding population, probably by pairing with Scandinavian females wintering in Britain. There is extensive natal dispersal of males from Forvie, with more than twice as many Forvie-bred females as males returning to the colony to breed. The breeding dispersal of males is also twice that of females. Dispersal of males from the relatively sedentary Forvie wintering population is less than that from the breeding population. Previous work suggested that at Forvie sedentary birds nesting close to the estuary were genetically isolated from migratory ones nesting along the coast. This situation is less clear cut than had been supposed previously, with many migrants nesting close to the estuary. It is unlikely that the genetic differences between females nesting in different parts of the Forvie colony will remain stable in the long term, due to the natal and breeding dispersal of males.     

Combined Olfactory Contact with the Parent Colony and Direct Contact with Nonbreeding Animals Does Not Maintain Suppression of Ovulation in Female Naked Mole-Rats (Heterocephalus glaber)

The study investigated the role of odor cues from two naked mole-rat colonies, in conjunction with behavioral cues from nonbreeding colony members, in maintaining suppression of ovulation in subordinate female naked mole-rats isolated from the two parent colonies. Four high ranking nonbreeding female naked mole-rats were removed from their respective parent colonies and singly housed in separate burrow systems. For a 64-day period, the removed females were maintained in daily odor contact with their parent colony by daily rotating soiled bedding material between the parent colony and the burrow systems of removed females. In addition, subsets of nonbreeding animals from the respective parent colony were regularly moved into the burrow systems of removed females for 2-day periods during this 64-day period. Removed females were therefore in continual social contact with subsets of parent colony animals except for the breeding pair. All four removed females exhibited raised levels of urinary progesterone (< 2 ng/mg Cr) indicative of the onset of ovarian function within 3 days of being separated from the parent colony. Removed females exhibited a normal ovulatory cycle with levels of progesterone remaining elevated for 25–35 days (mean concentration of progesterone ± SEM; 16.2 ± 2 ng/mg Cr). Initiation of aggression and sexual behavior by removed females increased significantly when they were isolated from the parent colony. The results demonstrated that odor cues from the complete colony in conjunction with behavioral / tactile / vocal cues from the nonbreeding colony members were not the major cues maintaining reproductive suppression in nonbreeding female naked mole-rats. Instead, our results suggest that female reproductive suppression in naked mole-rats is caused by a dominance-related behavioral mechanism requiring direct contact with the breeding female.     

Agonistic Behaviour and Sexual Conflict in Atypical Reproductive Groups: The Case of Bearded Vulture Gypaetus barbatus Polyandrous Trios

Social behaviour in species forced to form atypical breeding coalitions is poorly documented. The saturation of optimum territories in the Bearded vulture Gypaetus barbatus population in the Pyrenees has led floating males to settle in already occupied territories, thereby forming polyandrous trios. We examined the patterns of intrasexual aggression in five trios (nine reproductive events in total) during courtship. Alpha males initiated 82% of agonistic encounters that were mainly aimed at preventing or disrupting copulations. During the fertile period in recently formed groups, intrasexual aggression had a negative influence on the frequency of heterosexual copulations, which may be a contributing factor to the lower productivity of polyandrous trios. Females rejected a higher proportion of beta male- than alpha male-initiated copulations, and rejected copulations with both alpha and beta males more often when the other male was present close by. These results indicate that alpha males cannot effectively prevent all copulation attempts by beta males and that females avoid harassment by minimizing sexual activity when both males are present. Aggression between males decreased with time, occurring less often in established than in recent trios, despite the fact that the frequency of heterosexual copulations – the cause of conflicts – was similar. The frequency of homosexual interactions tended to increase in established trios, suggesting that this behaviour may help to regulate aggression within these groups, although no significant relationship between homosexual interactions and aggression was found. In summary, reproductive conflicts in trios seem to be unavoidable, although they tend to decrease if the group is maintained. This suggests that, for birds in these groups, the maintenance of a quality territory is more important than solving sexual conflicts.     

Patterns of dominance and affiliation in wild pig-tailed macaques (Macaca nemestrina nemestrina) in West Sumatra

Patterns of agonistic and nonagonistic behaviors were studied in a troop of wild pig-tailed macaques in West Sumatra, Indonesia. The animals were provisioned and the identities of all adult and adolescent individuals were known. The females could be divided into high-, mid-, and low-ranking subsets of individuals. Most grooming occurred within, instead of between members of these subsets. The members of each subset also tended to feed together at the baiting sites, and they probably represented groups of close kin. Among females, grooming appeared to be a conciliatory behavior and was generally performed by the subordinate partner, while mounting was performed by the dominant partner and appeared to be a reassertion of dominance. High-ranking males tended to form agonistic alliances with females and to exchange grooming with estrous females. Low-ranking males did not have such associations with females and were frequently the targets of agonistic alliances of females and juveniles. Mounting between males appeared to be a conciliatory behavior. It seemed effective since severe aggression between males was not observed. The subordinate partner mounted more frequently than the dominant one, but the direction of mounting was apparently controlled by the latter. This suggests that, among pig-tailed macaques, the dominant male plays an important role in the coexistence of males in the troop.     

SYNCHRONY AND SOCIAL STIlMULATION IN COLONIES OF THE BLACK-HEADED WEAVER PLOCEUS CUCULLATUS AND VIEILLOT'S BLACK WEAVER MELANOPTERYX NIGERRIMUS

The paper is concerned with the relative importance of environmental changes and social stimulation in bringing about synchronized social breeding in Ploceus cucullatus and Melanopteryx (Ploceus) nigerrimus . Field work was carried out in central Uganda.
Observations on a single colony of each species extending over a complete breeding period showed that breeding started abruptly with the arrival of a large number of males and the construction of new nests. The majority of females arrived later within a relatively short space of time. Subsequently the number of birds and the amount of activity declined gradually. Nests were repeatedly destroyed and reconstructed in the same positions. In P. cucullatus an entrance funnel was generally added only after occupation of the nest by a female.
Studies extending over a large number of colonies showed that main breeding seasons correspond approximately with the two rainy seasons each year. Isolated colonies may be active between seasons, however.
Nest-building and breeding are highly synchronized within colonies. Uniform responses to rain may partly account for this synchrony, but fluctuations of activity in neighbouring colonies are relatively unsynchronized, suggesting that social stimulation is also an important factor. This is supported by direct observations of social interactions and by the fact that small colonies are relatively less successful than larger ones, apparently because the pair-formation process may fail in the absence of sufficient social stimulation.     

Aspects of the Social Organisation of the European Wild Rabbit (Oryctolagus cuniculus)

The social organisation of a free-living population of wild rabbits was examined. Discrete breeding groups were recognised which consisted of individuals who shared access to underground refuges. Males attempted to maximise their access to females by a) occupying large home ranges; b) defending female access indirectly through territorial defence; c) defending female access directly within groups. Females defended nest site access within groups. Intergroup interactions between females were rare because of limited home range overlap. Interruption of female-female aggression by males was observed suggesting that conflicts of interest arose between the sexes. Adult-juvenile aggression was primarily intra-sexual; females initiated more interactions than males who adopted a protective role in some cases.     

Hormonal and behavioural correlates of male dominance and reproductive status in captive colonies of the naked mole-rat,Heterocephalus glaber.

Naked mole-rat colonies are societies with a high reproductive skew, breeding being restricted to one dominant female (the ''queen'') and 1-3 males. Other colony members of both sexes are reproductively suppressed. Experimental removal of breeding males allowed us to investigate the relationship between urinary testosterone and cortisol, dominance rank, and male reproductive status. Dominance rank was strongly correlated with body weight, age, and urinary testosterone titres in males. No relationship between urinary cortisol levels and male reproductive status or dominance was found. Breeding males were among the highest-ranking, heaviest and oldest males in their respective colonies, and were succeeded by other high-ranking, large, old colony males. In contrast to females, no evidence of competition over breeding status was observed among males. Male-male agonism was low both before and after removal of breeders and mate guarding was not observed. The lower reproductive skew for males compared with female skew or queen control over male reproduction may explain why males compete less strongly than females over breeding status after removal of same-sexed breeders.     

The social structure and reproductive biology of the common mole-rat, Cryptomys h. hottentotus and remarks on the trends in reproduction and sociality in the family Bathyergidae

Cryptomys h. hottentotus occurs in mesic and semi-arid regions of South Africa. It lives in colonies ofup to 14 individuals, in which reproduction is limited to one ofthe largest males and the largest female in the colony.
Reproduction and details of colony size and the number of breeding animals in a colony are described for one complete and two incomplete field-captured colonies. One incomplete colony was kept in captivity for more than 3 years, whereas the complete colony was autopsied.
The social hierarchy of the common mole-rat is almost linear and has a value of 0.7 1 calculated from Landau's linearity index. Subordinate mole-rats weighed less than dominant mole-rats. The reproductive mole-rats are the dominant animals within the colony. The non-reproductive females rank lowest in the hierarchy.
Mating was not confined to a particular season, but occurred more frequently during the summer months. The alpha male initiated pre-copulatory behaviour. The gestation length is 55 to 66 days (n = 2). Two litters each of three pups were born to the colony during captivity. The pups were relatively altricial. They wandered out of the nest 5 days after birth, began to eat solids when 10 days old, and were fully weaned at 4 weeks. When 2 weeks old the pups began to spar with each other and with some of the adult colony members, but levels of aggression were never high. The pups did not disperse but were incorporated into the colony, this suggesting that C. h. hottentotus colonies are largely composed of related individuals.     

The relative influence of age and weight on the reproductive behaviour of male grey seals Halichoerus grypus

The breeding behaviour of male grey seals Halichoerus grypus of known age and weight was studied on Sable Island, Nova Scotia. Branded males ranged in age from 8 to 16 years and although there was a positive relationship between age and weight, there was a large overlap between age classes. In general, there was an increase in length of tenure and rates of copulation with increasing male age but this was less marked among males between the ages of 13 and 16 years. Compared to older ones, males of 8 and 12 years were observed at more sites, travelled more extensively around the breeding colony, were transient more frequently and were unable to lie as close to females. There was no correlation between male body weight and either length of tenure or rates of copulation when males of age 8 (the smallest males) were excluded from the analysis. Most agonistic behaviour was made by larger, older males towards smaller, younger ones and appeared to be responsible for the short length of tenure and low reproductive rates of young bulls.     

Individuality in northern lapwing migration and its link to timing of breeding

We tracked eight adult northern lapwings Vanellus vanellus (six females and two males) from a Dutch breeding colony by light‐level geolocation year‐round, three of them for multiple years. We show that birds breeding virtually next to each other may choose widely separated wintering grounds, stretching from nearby the colony west towards the UK and Ireland, and southwest through France into Iberia and Morocco. However, individual lapwings appeared relatively faithful to a chosen wintering area, and timing of outward and homeward migration can be highly consistent between years. Movements of migratory individuals were usually direct and fast, with some birds covering distances of approximately 2000 km within 2 to 4 days of travel. The two males wintered closest and returned earliest to the breeding colony. The female lapwings returned well before the onset of breeding, spending a pre‐laying period of 19 to 54 days in the wider breeding area. Despite the potential for high migration speeds, the duration that birds were absent from the breeding area increased with distance to wintering areas, a pattern which was mainly driven by an earlier outward migration of birds heading for more distant wintering grounds. Moreover, females that overwintered closer to colony bred earlier. A large variation in migration strategies found even within a single breeding colony has likely supported the species’ responsiveness to recent climate change as evidenced by a shortened migration distance and an advanced timing of reproduction in Dutch lapwings since the middle of the 20th century.     

Colony sound facilitates sexual and agonistic activities in royal penguins

A unique playback system was used to exaggerate continuously the number of calls heard in royal penguin, Eudyptes schlegeli, colonies to determine whether social facilitation increases a female's exposure to both sexual and agonistic activities, a process that could influence the timing of reproduction in colonies. We also determined whether the source of colony sound or the phase of the breeding cycle influenced the facilitation of sexual or agonistic activities. The system recorded and then played a new 12-min colony sound sample every 24 min throughout the first four phases of the breeding cycle. Because each broadcast was unique, this playback system avoids the possibility of habituation and can modify the acoustic environment in social groups for extended periods of time. The activities of penguins in control colonies (with no playback) were compared with those in colonies that heard samples derived from either their own or a different colony. Colony sound facilitated both sexual and agonistic activities from male and female royal penguins during all four phases of the cycle that we examined. Playbacks from the perceiver's own colony facilitated a greater response than sound originating from a different colony. Studies comparing egg-laying dates in colonies exposed continuously to the sounds of agonistic activities with those in control colonies, or colonies exposed continuously to the sounds of sexual activities are now needed to determine whether the facilitation of agonistic activities opposes the effects of social stimulation on the hormonal changes leading to ovulation in colony-dwelling birds. Copyright 2000 The Association for the Study of Animal Behaviour.     

Philopatry and colony fidelity of Shags Phalacrocorax aristotelis on the east coast of Britain

Shag Phalacrocorax aristotelis colonies from the Firth of Forth south to the Fame Islands (SE Scotland and NE England) were surveyed in 1982 and 1983 for nesting Shags ringed as chicks or adults in the previous 20 years. On average, 5% of 863 Shags ringed as chicks were breeding away from their natal colony, and only 1% of 401 marked adults had left their breeding colony. The proportion p of chicks that settled at or beyond distance D from the natal colony followed the relationship p = 0.263D-^0.771, implying that more Shags moved 10 km or beyond to breed than expected from diffusion models or a constant-rate dispersal model; adjusted for birds that settled outside the study area, the relationship was p = 0.314D^-0771. There was no effect of colony size on emigration rate, but females showed a greater tendency to settle away from the natal colony than did males. At the natal colony, more males (69%) than females (47%) nested within 300 m of their birthplace. Two mechanisms appear to determine where a Shag settles to breed: a navigational one governing the return to the natal colony, plus the competitive process of nest-site establishment.