Environmental and phylogenetic correlates of Eulemur behavior and ecology (Primates: Lemuridae)

The extent of diversity within closely related taxa may be a function of their shared evolutionary history or of selective forces causing adaptive changes. Examining variation among taxa within a single genus may help to identify flexibility in trait variation because recently diverged populations are more likely living in the environment of adaptation. This study examines correlates of diversity in Eulemur, a genus that has a wide distribution in a variety of habitat types throughout Madagascar. Previously published data were gathered from 11 long-term studies of Eulemur populations. Variables were categorized into multiple datasets: (1) environmental characteristics, (2) social organization, and (3) ecology, which included subsets for ranging behavior, diet, and activity budget. Molecular phylogenies from the literature were used to create the fourth and final dataset, a dissimilarity matrix of evolutionary distance among the 12 species and subspecies. Principal components and cluster analyses were implemented to examine the overall ecological similarity among Eulemur populations and to determine which variables contribute most to the variation among taxa. Partial Mantel tests were conducted to test for correlations among the dataset matrices. The results suggest ecological flexibility for the genus, in particular, populations in similar environments displayed similar activity patterns. In contrast, social organization showed no relationship with environment but was correlated with phylogenetic distance among populations. While Eulemur seems to demonstrate some flexibility for ecological adaptations, characteristics related to group size and sex ratio more closely track phylogeny and thus may be less flexible.Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible to authorized users.     

Female territoriality and the function of scent-marking in a monogamous antelope (Oreotragus oreotragus)

In monogamous species, females often choose between males according to the quality of the territories they defend, but the extent to which females themselves contribute to territory defence is frequently underestimated. Here we test for differences in male and female roles during paired scent-marking bouts, a key component of territorial defence, in a monogamous antelope. In two populations (Kenya, Zimbabwe) of klipspringer, Oreotragus oreotragus, both males and females usually scent-marked at the same site, but there were significant differences between sexes in terms of investment within bouts. Females initiated most bouts, thus dictating the marking strategy of the pair. Males initiated relatively few bouts, but deposited more scent marks per bout than females and were usually the last to scent-mark before leaving the site; they marked on the same branches as the female and thus overmarked her scent. Both sexes deposited more marks during paired than solo visits. Immediately preceding and following scent-marking bouts, males approached females and females left males more often than expected. Female scent-marking rates were higher when they were receptive than at other times, and this increase was matched by elevated marking rates of males. Females may increase marking rates when they are receptive in order to test the quality of their mate or to incite male competition. However, these ideas are unlikely to explain female scent-marking behaviour outside the mating season, which appears to be related primarily to territorial defence. We suggest that these differences in investment in scent-marking bouts are consistent with predictions that females may be autonomously territorial and that overmarking of female scent by males is a form of mate-guarding. Received: 17 November 1999 / Received in revised form: 24 February 2000 / Accepted: 13 March 2000     

Molecular genetic and behavioral analysis of social organization in the Asian elephant (Elephas maximus)

We report on the genetic evaluation and behavioral study of social organization in the Asian elephant (Elephas maximus). Although Asian elephants and African elephants (Loxodonta africana) were previously thought to have similar social organizations, our results demonstrate a substantial difference in the complexity and structure of Asian elephant social groupings from that described for African savanna elephants. Photographic cataloging of individuals, radio telemetry, and behavioral observations in Ruhuna National Park, Sri Lanka, enabled us to assign associated females and young to four groups with overlapping ranges. Genetic sampling of individuals from the four groups in Ruhuna National Park and three other groups in surrounding areas, conducted through PCR amplification and sequencing of mitochondrial DNA from dung, supported the matriarchal nature of female groups and the lack of inter-group transfer of females. Behaviorally and genetically, the identified social groups were best described as ”family groups”. We did not find any evidence for the existence of social groups of higher complexity than family groups. Received: 25 March 2000 / Received in revised form: 28 March 2000 / Accepted: 1 April 2000     

Extent and variation of sound enhancement inside burrows of the frog Eupsophus emiliopugini (Leptodactylidae)

Variation of the amplification effect of burrows of the leptodactylid frog Eupsophus emiliopugini on conspecific calls generated externally was investigated. Advertisement calls broadcast through a loudspeaker placed in the vicinity of a burrow were monitored with small microphones positioned inside and outside the cavity. For 150 presentations of calls of 15 individuals in 12 burrows, 134 were amplified and 16 were attenuated (range –6–13 dB). The fundamental resonant frequency of burrows, measured with broadcast noise and pure tones, averaged 814 Hz (range 302–1361 Hz) and covaried with burrow length. The dominant frequency of the calls of burrow occupants (average 1062 Hz, range 636–1459 Hz) was not correlated with the fundamental resonant frequency of these cavities. In burrows with low resonant frequencies, externally broadcast calls with high dominant frequencies were attenuated, or amplified to a lower extent than calls with lower dominant frequencies. The dominant frequencies of the calls experienced shifts towards the burrows’ fundamental resonant frequencies. The amplification of calls inside burrows of E. emiliopugini exhibits manifest variability, with considerable potential for facilitating acoustic interactions in this species. Received: 18 July 1999 / Received in revised form: 19 July 1999 / Accepted: 25 July 1999     

Testosterone and the allocation of reproductive effort in male house finches (Carpodacus mexicanus)

Testosterone has been proposed to serve as the mediator that controls the relative effort that an individual male bird will devote to mating effort versus parental effort. Here, we demonstrate a testosterone-influenced trade-off between parental and mating efforts in male house finches. Male house finches with experimentally elevated testosterone fed nestlings at a significantly lower rate, but sang at a higher rate than males without manipulated testosterone levels. Females mated to testosterone-implanted males fed nestlings at a significantly higher rate than females mated to males without testosterone implants, resulting in similar feeding rates for both treated and untreated pairs. The effects of testosterone on male house finches, however, were not as dramatic as the effects of testosterone observed in some other socially monogamous species of birds. Because extra-pair copulations are uncommon in house finches and males provide substantial amounts of parental care, these more modest effects may be due to differences in how the allocation of reproductive effort affects the costs and benefits of different reproductive behaviors. Received: 6 June 2000 / Accepted: 17 July 2000     

Physiological correlates of genetic variation for rate of behavioral development in the honeybee, Apis mellifera

Two factors that influence age at onset of foraging in honeybees are juvenile hormone (JH) and colony age demography (older bees inhibit behavioral development of younger bees). We tested the hypothesis that genetic variation among bees for these factors influences genetic variation in behavioral development. Pairs of colonies showing genetic differences in rates of behavioral development were identified in a screening experiment and bees from these colonies were used for physiological and behavioral assays. Six pairs were assayed, three with European bees only and three with both European and Africanized bees. There was genetic variation for the following four components: (1) production of JH in four pairs (experiment 1); (2) sensitivity to JH in three pairs (experiment 2); (3) sensitivity to social inhibition in three pairs (experiment 3), and (4) potency of social inhibition in four pairs (experiment 4). Cross-fostering assays (experiment 5), which allowed all four components to be evaluated simultaneously, revealed genetic variation for production of JH, sensitivity to JH, or sensitivity to social inhibition in five of six pairs, and potency of social inhibition in five of six pairs. There was often evidence for genotypic differences in more than one component, and no consistent pattern of association among any of the components. Africanized bees had faster rates of behavioral development than European bees, but there were no racial differences in patterns of variation among the four components. These results indicate that there are at least several, apparently distinct, physiological processes associated with JH and colony age demography upon which natural selection can act to alter the rate of behavioral development in honeybees. Received: 8 December 1998 / Received in revised form: 29 July 1999 / Accepted: 8 August 1999     

The effects of testosterone on antibody production and plumage coloration in male house sparrows (Passer domesticus)

Many bird species have patches of colour in their plumage, contrasting with their basic coloration, which are used to display and signal status to conspecifics. These are called ’badges of status’, because they are believed to be low-cost signals of social status. For a signalling system to be evolutionarily stable, cheating must be controlled. The conventional view is that there is frequent testing, which uncovers cheats. Recently, the immunocompetence handicap hypothesis (ICHH) suggested that signals may be dependent on testosterone for their development, with a cost being imposed through immune suppression. We report experiments on house sparrows (Passer domesticus) which show that testosterone significantly influences the size of the bib (a ’badge of status’). The ultimate effect of the testosterone manipulation was to impair antibody production, as predicted by the ICHH. However, testosterone manipulations also changed the levels of the ’stress hormone’ corticosterone. The level of corticosterone was also related to the degree of immunosuppression. After controlling for the effect of corticosterone, testosterone enhanced the birds’ ability to produce antibodies, counter to the ICHH. The hypothesis therefore must be modified. We suggest that testosterone has a dual effect: it leads to immunosuppression through a mechanism involving corticosterone but, conversely, leads to increased immunocompetence probably via dominance influencing access to resources. Received: 5 March 1999 / Received in revised form: 1 October 1999 / Accepted: 16 October 1999     

Estimating paternity with spatial behaviour and DNA fingerprinting in the striped plateau lizard, Sceloporus virgatus (Phrynosomatidae)

The association between spatial proximity and paternity was studied in a population of the striped plateau lizard, Sceloporus virgatus. The relationship between estimated mating success and male phenotypic traits was examined for a sample of 55 males. DNA samples were obtained from 13 female-offspring families. The males with the closest spatial proximity to each female were tested as possible sires within each family. Fingerprinting with two multilocus hypervariable minisatellite probes revealed a strong correspondence between male-female spatial proximity and actual paternity. Paternity could be assigned for 72 of the 100 hatchlings. Most hatchlings with identifiable sires were attributed to a male with the highest category of spatial proximity to the mother. However, there was a low to moderate level of multiple paternity within clutches, and for some clutches probable sires could not be identified even though the most likely behavioural candidates were tested. Thus, nonterritorial males or other males lacking strong social and spatial relationships with females may achieve some degree of reproductive success. Analysis of mating success revealed that male success increased with body size, up to a point beyond which larger size conferred no advantage. Received: 7 January 1997 / Accepted after revision: 16 June 1997     

How resources and encounters affect the distribution of foraging activity in a seed-harvesting ant

We examined how the foraging ecology of the seed-harvesting ant Messor andrei depends upon the distribution of resources and the presence of conspecifics. Bait experiments showed that colonies can recruit to high-density patches of seeds. However, at the seasonal scale, natural resource distribution did not affect the distribution of foraging activity. We conducted the study in years of high rainfall and thus seed availability may not have been a limiting factor. Colonies always preferred to forage in areas closer to their nest, which may reduce travel time between the nest and foraging sites. On a day-to-day scale, encounters between neighboring colonies at a site increased the probability that colonies would return to forage at that site; this was true both for natural and experimental encounters. In the summer, this resulted in colonies foraging at the sites of intraspecific encounters on more days than in areas where no encounter had occurred. Encounters between colonies included fighting, and there was little overlap between the foraging areas of neighboring colonies: both results suggest that one function of encounters is to defend foraging space. The high probability of return to the site of an encounter between colonies suggests that encounters may have a second function: to indicate the presence of resources. Received: 28 June 1999 / Received in revised form: 12 October 1999 / Accepted: 16 October 1999     

Trade-off between fitness components in males of the polygynous butterfly Callophrys xami (Lycaenidae): the effect of multiple mating on longevity

The differential costs of mating paid by males and females influence the nature and strength of sexual selection. In butterflies, males invest a relatively large amount of time and resources in each mating, but male survival costs of mating have not been demonstrated. I present the results of experiments designed to measure the effect of different aspects of mating on male longevity in the polygynous butterfly Callophrys xami. In experiment 1, I compared the longevity of pairs of males that produced similar amounts of spermatophore, but that mated at different rates, a different numbers of times, and that produced spermatophores at different rates, and found that the longevity of ”low-mating-rate” males was not different from that of ”high-mating-rate” males. In experiment 2, the longevity of virgin males was not significantly different from that of multiply mated males. In experiment 3, I used resource-limited males resulting from experimental food limitation of last-instar larvae; resource-limited virgin males lived significantly more days than resource-limited multiply mated males. Since ecological costs of mating (e.g., disease transmission, predation risk) were excluded in the experiment, diminished male longevity was a product of physiological costs of sexual interactions. These results suggest that the cost of ejaculate production is an important cause of longevity reduction when there are resource limitations; however, the role of other possible physiological costs of mating in longevity reduction is still unknown. Received: 21 March 2000 / Accepted: 26 August 2000     

The influence of potential reproductive rate and variation in mate quality on male and female choosiness in the sand goby, Pomatoschistus minutus

Recent models of choosiness in mate choice have identified two particularly important factors: the potential reproductive rate (PRR) of the choosing sex relative to that of the chosen sex, and the variation in quality of potential mates. This experimental study tested how these factors affected choosiness in male and female sand gobies, Pomatoschistus minutus. We manipulated relative PRR by means of water temperature, and mate quality by means of body length. The choosing male or female was offered a choice between two mates with either a small or a large difference in body length representing a small or a large variation in mate quality. Choosiness was measured as (1) preference for the larger mate, and (2) as whether or not spawning occurred with the smaller mate, while the larger mate was visible but screened off. We found that females preferred large males, and that their level of choosiness was affected by variation in male quality, but not by their own relative PRR. Males, on the other hand, seemed unselective in all treatments and were in general more likely than females to spawn with their provided partner. This suggests that in the sand goby, variation in male mate quality has a greater influence than relative PRR on facultative changes in female choosiness. However, a general difference in PRR between males and females may be one important factor explaining the observed sex difference in choosiness. Received: 17 April 2000 / Revised: 24 June 2000 / Accepted: 17 July 2000     

Predatory behavior of crowned hawk-eagles (Stephanoaetus coronatus) in Kibale National Park, Uganda

Evaluating the nature and significance of predation on populations of wild primates has been difficult given a paucity of data regarding the phenomenon. Here we addressed this problem in a 37-month study of the predatory behavior of crowned hawk-eagles living at the Ngogo study site in Kibale National Park, Uganda. We collected prey remains underneath the nests of two pairs of eagles and census data on potential prey species to investigate prey selection and the ecological impact of predation on the Ngogo primate population. Results indicate that primates form the vast majority of all prey items. Eagles prey selectively on monkeys according to sex and species. Male primates were taken more often than females, while two species, redtail monkeys and mangabeys, were captured significantly more and less, respectively, than chance expectation. In addition, there was no bias in the age of prey: adult and non-adults were killed in numbers roughly equal to their proportional representations in the forest. Further analyses indicate that a non-trivial fraction of the entire primate population at Ngogo succumbs to crowned hawk-eagle predation each year. These results reveal both parallels and contrasts with those reported previously. Some of the parallels are due to similarities in prey availability, while contrasts are likely related to methodological differences between studies, inter- individual variations in predator hunting styles, and differences in prey abundance, demography, and behavior. Received: 29 March 2000 / Revised: 6 June 2000 / Accepted: 15 October 2000     

Sperm characteristics associated with different male reproductive tactics in bluegills (Lepomis macrochirus)

We examined the availability and motility of sperm from parental and sneaker male bluegills (Lepomis macrochirus), a colonially nesting sunfish (Family Centrarchidae) with male parental care and a high incidence of cuckoldry by both sneaker and satellite males. We found no differences between sneakers and parentals in length and swimming speed of sperm, or percent and duration of sperm activity. In sneaker milt, however, sperm was almost 50% more concentrated than in parental milt (16.5×10⁶ vs 11.5×10⁶ sperm/μl of milt, respectively). Despite this difference in sperm concentration, stripped ejaculates from sneakers contained almost 400 million fewer sperm (only 32% as many sperm) than those from parentals due to their much smaller stripped ejaculate volumes (only about 19% that of parentals). Thus unless sneakers can compensate by releasing more sperm or gaining closer proximity to eggs at the time of spawning, they may be at a disadvantage with respect to sperm competition. We discuss these results in relation to models for the evolution of alternative reproductive behaviours in this species and suggest that the cuckolders may be making the best of a bad situation. Received: 18 February 2000 / Revised: 23 March 2000 / Accepted: 14 September 2000     

Testosterone is involved in acquisition and maintenance of sexually selected male plumage in superb fairy-wrens, Malurus cyaneus

Testosterone has been proposed as a physiological link between the level of sexual signalling and male condition. Bright plumage is one of the most noticeable sexual signals and is often used by females as a basis for mate choice. Yet bright male plumage is not necessarily testosterone dependent. We investigated the role of testosterone in the moult into seasonal nuptial plumage in male superb fairy-wrens. Early pre-nuptial moult is under intense intersexual selection and males can acquire the bright plumage any time between autumn and the next spring. Testosterone was always undetectable or very low in males in dull eclipse plumage. During the pre-nuptial moult, both the number of males with detectable testosterone and average testosterone levels increased sharply. High testosterone was more correlated with nuptial plumage than with presence of the cloacal protuberance (indicative of sperm storage). Subcutaneous testosterone implants always induced the pre-nuptial moult within 2–3 weeks after implantation, even well outside the natural time range of moulting. Moreover, removal of the implants before the nuptial plumage was completed, arrested the moult process. The evidence suggests that development of the nuptial plumage is testosterone dependent, although we cannot exclude that testosterone exerts its action after conversion to a metabolite such as oestrogen. Once the nuptial plumage was completed, all males maintained substantially elevated testosterone, sometimes months before the onset of breeding. These high levels could be necessary to maintain the plumage, and/or are involved in courtship displays. The results are discussed with respect to potential costs involved in acquiring and maintaining the nuptial plumage. Received: 17 January 2000 / Received in revised form: 24 February 2000 / Accepted: 25 February 2000     

Begging calls and parental feeding decisions in tree swallows (Tachycineta bicolor)

We conducted playback experiments to examine how parent tree swallows (Tachycineta bicolor) use nestling begging calls to distribute feedings to individuals within broods. In a first study, we used a paired-choice test to determine if parents discriminated between the taped begging calls of nestlings deprived of food and those of nestlings that had been recently fed. Our results showed that parents directed their first feeding attempt towards model nestlings near speakers playing deprived calls significantly more often than to models near speakers playing fed calls. They also made more feeding attempts overall to models with deprived calls. In the second study, we varied call rate and amplitude to examine which call features parents might use to discriminate begging calls. Parents directed significantly more first feeding attempts and more feeding attempts overall towards non-begging nestlings near speakers playing high call rates than to nestlings near speakers playing low call rates. They did not, however, discriminate between calls differing in amplitude. Previous studies have shown that parent birds use begging calls to regulate overall feeding rates to the brood. Our results suggest that parent tree swallows also use begging calls when feeding individual nestlings and, in particular, prefer calls associated with increased levels of nestling hunger. Received: 14 February 2000 / Revised: 6 October 2000 / Accepted: 16 October 2000     

Duetting and mate-guarding in Australian magpie-larks (Grallina cyanoleuca)

A recently favored hypothesis is that duetting in birds has a mate-guarding function: a male responds vocally to his partner’s song, thereby forming a duet that repels males who are attracted to her song. Previous studies have not provided unambiguous tests of the mate-guarding hypothesis because: (1) the probability of a male answering his partner’s song has not been shown to increase specifically when the female is fertile, and (2) the probability of a male answering his partner’s song has not been assessed separately from simply a higher song initiation rate. We investigated extra-pair paternity, mate-guarding, and duetting in the socially monogamous Australian magpie-lark (Grallina cyanoleuca). DNA fingerprinting revealed that 3% of young were the result of extra-pair paternity, and we found that males guarded fertile females by staying close to them. However, males did not initiate songs at a higher rate when females were fertile and actually reduced their probability of replying to female song during this period. We conclude that although male magpie-larks did guard fertile females in an attempt to prevent extra-pair copulations, they did not use duetting for this purpose. Received: 10 May 1999 / Received in revised form: 27 September 1999 / Accepted: 2 October 1999     

Lack of detectable nepotism in multiple-queen colonies of the fire ant Solenopsis invicta (Hymenoptera: Formicidae)

Multiple-queen (polygyne) colonies of the introduced fire ant Solenopsis invicta present a paradox for kin selection theory. Egg-laying queens within these societies are, on average, unrelated to one another, and the numbers of queens per colony are high, so that workers appear to raise new sexuals that are no more closely related to them than are random individuals in the population. This paradox could be resolved if workers discriminate between related and unrelated nestmate sexuals in important fitness-related contexts. This study examines the possibility of such nepotism using methods that combine the following features: (1) multiple relevant behavioral assays, (2) colonies with an unmanipulated family structure, (3) multiple genetic markers with no known phenotypic effects, and (4) a statistical technique for distinguishing between nepotism and potentially confounding phenomena. We estimated relatedness between interactants in polygyne S. invicta colonies in two situations, workers tending egg-laying queens and workers feeding maturing winged queens. In neither case did we detect a significant positive value of relatedness that would implicate nepotism. We argue that the non-nepotistic strategies displayed by these ants reflect historical selection pressures experienced by native populations, in which nestmate queens are highly related to one another. The markedly different genetic structure in native populations may favor the operation of stronger higher-level selection that effectively opposes weaker individual-level selection for nepotistic interactions within nests. Received: 28 June 1996 / Accepted after revision: 6 October 1996     

Experimental tests of the information-center hypothesis with black vultures (Coragypsatratus) and turkey vultures (Cathartesaura)

In field tests of the information-center hypothesis (ICH) in south Texas with black vultures (Coragyps atratus) and turkey vultures (Cathartes aura), large carcasses were provided and kept under continuous observation. The use vultures made of these bait sites and their patterns of arrival were recorded to evaluate predictions derived from the ICH. Turkey vultures discovered most bait sites (30 of 31) first, but frequently were displaced from the food by later-arriving black vultures. This competitive exclusion by black vultures limited subsequent feeding opportunities for turkey vultures sufficiently that few (27%) returned on subsequent days to bait sites they had previously visited. I found no evidence that those turkey vultures that did return to bait sites acted as leaders for groups of naive birds and led them to bait sites – knowledgeable and naive turkey vultures did not arrive at bait sites together, and groups arriving at bait sites were not larger on subsequent days than on the first days carcasses were available. In contrast, a significantly larger percentage (47%) of knowledgeable black vultures returned to bait sites they had visited on previous days, and the first groups of black vultures arriving at bait sites on subsequent days were significantly larger than the equivalent groups on first days. Nine flocks of black vultures that arrived on subsequent days at bait sites before sunrise (which suggests the birds had commuted directly from a roost) contained knowledgeable birds, and two of these flocks contained both knowledgeable and naive individuals. Overall, 10 of 54 naive tagged black vultures (18.5%) arrived at bait sites under circumstances that suggested they had followed conspecifics to the food from a roost. However, most black vultures apparently found carcasses through independent search or by using local enhancement. Therefore, I conclude that while following from roosts to food sites is a strategy used by black vultures, at this study site it is one they use relatively infrequently. Received: 20 February 1997 / Accepted after revision: 28 June 1997     

Reproductive suppression and inbreeding avoidance in wild populations of co-operatively breeding meerkats (Suricata suricatta)

Meerkats live in co-operatively breeding familial groups in which reproduction is monopolised by a dominant pair of breeders. Offspring of the breeders are behaviourally subordinate, and typically remain in their natal group as sexually mature, non-breeding helpers. In this study, we investigated the proximate factors limiting subordinate reproduction. Evidence for reproductive suppression by dominants was investigated by comparing life history, behaviour and hormonal profiles of dominants and subordinates. Baseline levels of plasma luteinising hormone (LH) were significantly higher in dominant than in subordinate females. However, following an exogenous injection of gonadotrophin-releasing hormone (GnRH), both categories had comparable concentrations of circulating LH. There were no significant differences in pre- or post-GnRH challenge LH levels in dominant or subordinate males. Reproduction in both dominant and subordinate females rarely occurred in the absence of unrelated males. Given that groups typically comprise parents and offspring, lack of suitable mates emerged as the primary constraint on subordinate reproduction. When this constraint was removed, subordinates typically bred but at a lower rate than dominants. This difference in reproduction may be attributed to intrasexual competition manifested through direct interference by dominant females through subordinate evictions, infanticide and the abandoning of subordinate litters. We argue that differences in reproductive regulation within mammalian co-operative breeding systems may be explained by differences in the mating strategy (inbreeding versus outbreeding) and the probability that subordinates in obligate outbreeding species will encounter unrelated opposite-sex partners. Received: 19 April 2000 / Accepted: 17 July 2000     

Reproductive success increases with degree of kinship in cooperative coalitions of female red howler monkeys (Alouatta seniculus)

Evaluation of evolutionary mechanisms proposed to promote cooperative behavior depends on the relative influence of the behavior on the reproductive success of individuals, the reproductive success of the group in which they interact behaviorally, and the degree of gene correlation among cooperators. The genetic relationship within cooperative coalitions of female red howler monkeys was examined for three populations with different densities and growth rates. Patterns of gene correlation change within coalitions is documented using data from the mitochondrial and nuclear genomes, and long-term census monitoring. Differences in fecundity and infant survivorship within and between groups of unrelated (rˉ=0) and related (rˉ≥ 0.25) females are compared. Females that emigrate from their natal groups form coalitions with other migrant females. These coalitions attempt to establish a territory and, once successful in producing offspring, exclude other females from feeding resources. Females in these coalitions had different mtDNA haplotypes and a genetically estimated mean r of 0, supporting demographic data on emigration patterns indicating that these females rarely have the opportunity to form coalitions with kin. Patterns of recruitment and rate of matriline development within social groups supported behavioral data indicating that females actively attempt to promote their own matriline as breeders over that of other females, and that some matrilines are more successful at this than others. Mean r among females was significantly higher in coalitions established as social groups for several generations (rˉ=0.44). In these groups, females all shared the same mtDNA haplotype, and mtDNA haplotype divergence was significantly higher between than within groups. Females in coalitions with kin had significantly higher reproductive success than females in unrelated coalitions in all populations. This difference was not a function of coalition size, number of males, socionomic sex ratio, or primiparity, although anecdotal evidence suggests that allomothering may compensate for inept new mothers in related coalitions more often than in unrelated ones. Differences in territory quality could not be ruled out as a potential causal factor in the saturated populations, but were unlikely in the low-density, growing population. There were substantial differences among long-established coalitions in overall reproductive output in all three populations, and this was significantly correlated with the number of breeding females. Increase in coalition size was a function of both group age and the behavioral tolerance among females. Regardless of the underlying reasons for the patterns observed, reproductive success clearly increases with degree of gene correlation among females within cooperative coalitions, and coalitions that recruit more daughters produce more offspring. The nature of the cooperative relationship among group females directly influences both of these outcomes. This is associated with substantial genetic differentiation among social groups within populations, creating conditions in which genetic tendencies towards cooperative behavior can become tightly associated with group reproductive success. Received: 15 September 1999 / Revised: 27 April 2000 / Accepted: 27 May 2000