Social species show considerable variation in the extent to which dominant females suppress subordinate reproduction. Much of this variation may be influenced by the cost of active suppression to dominants, who may be selected to balance the need to maximize the resources available for their own offspring against the costs of interfering with subordinate reproduction. To date, the cost of reproductive suppression has received little attention, despite its potential to influence the outcome of conflict over the distribution of reproduction in social species. Here, we investigate possible costs of reproductive suppression in banded mongooses, where dominant females evict subordinates from their groups, thereby inducing subordinate abortion. We show that evicting subordinate females is associated with substantial costs to dominant females: pups born to females who evicted subordinates while pregnant were lighter than those born after undisturbed gestations; pups whose dependent period was disrupted by an eviction attained a lower weight at independence; and the proportion of a litter that survived to independence was reduced if there was an eviction during the dependent period. To our knowledge, this is the first empirical study indicating a possible cost to dominants in attempting to suppress subordinate breeding, and we argue that much of the variation in reproductive skew both within and between social species may be influenced by adaptive variation in the effort invested in suppression by dominants.

Reproductive events in animal societies often show a high degree of temporal clustering, but the evolutionary causes of this synchronization are poorly understood. Here, we suggest that selection to avoid the negative effects of competition with other females has given rise to a remarkable degree of birth synchrony in the communal-breeding banded mongoose (Mungos mungo). Within banded mongoose groups, births are highly synchronous, with 64 per cent of females giving birth on exactly the same night. Our results indicate that this extreme synchrony arises because offspring suffer an increased risk of infanticide if their mother gives birth before other females, but suffer in competition with older littermates if their mother gives birth after them. These findings highlight the important influence that reproductive competition can have for the evolution of reproductive synchrony.

Despite the widespread occurrence of communal breeding in animal societies, the fitness consequences for mothers are poorly understood. One factor that may have an important influence on the net benefits mothers gain from breeding communally is the competitive ability of their offspring, as mothers are likely to gain substantial advantages from producing young who can outcompete the offspring of other females for access to resources. Here, we investigate the factors that influence offspring competition in the communally breeding banded mongoose (Mungos mungo). We show that heavy offspring are more likely to win competitive interactions with their littermates. Heavy offspring also receive more care and are more likely to survive to independence in large communal litters where competition is most intense. Our results also indicate that offspring weight at emergence is positively correlated with the weight of the mother at conception. As a consequence, the offspring of heavy mothers are likely to enjoy marked competitive advantages during early life. Together, our findings strongly suggest that the competitive ability of offspring will influence the costs and benefits that females experience while breeding communally and highlights the need for closer examination of the factors that influence offspring competitive ability and the influence this may have on the evolution of communal breeding.

1. In cooperative societies with high reproductive skew, selection on females is likely to operate principally through variation in the probability of acquiring dominant status and variation in reproductive success while dominant. Despite this, few studies of cooperative societies have investigated the factors that influence which females become dominant, and/or their reproductive output while in the dominant position. 2. Here we use long-term data from a wild meerkats population to describe variation in the breeding success of dominant female meerkats Suricata suricatta and investigate its causes. 3. Female meerkats compete intensely for breeding positions, and the probability of acquiring the breeding role depends upon a female's age in relation to competitors and her weight, both at the time of dominance acquisition and early in life. 4. Once dominant, individual differences in breeding success depend principally on the duration of dominance tenure. Females remain for longer in the dominant position if they are heavier than their competitors at the start of dominance, and if the number of adult female competitors at the start is low. 5. Female breeding success is also affected by variation in fecundity and pup survival, both of which increase with group size. After controlling for these effects, female body weight has a positive influence on breeding rate and litter size, while the number of adult female competitors reduces litter survival. 6. These findings suggest that selection for body weight and competitive ability will be high in female meerkats, which may moderate their investment in cooperative activities. We suggest that similar consequences of competition may occur among females in other cooperative societies where the benefits of attaining dominance status are high.

Kin selection theory predicts that animals should direct costly care where inclusive fitness gains are highest. Individuals may achieve this by directing care at closer relatives, yet evidence for such discrimination in vertebrates is equivocal. We investigated patterns of cooperative care in banded mongooses, where communal litters are raised by adult ‘escorts’ who form exclusive caring relationships with individual pups. We found no evidence that escorts and pups assort by parentage or relatedness. However, the time males spent escorting increased with increasing relatedness to the other group members, and to the pup they had paired with. Thus, we found no effect of relatedness in partner choice, but (in males) increasing helping effort with relatedness once partner choices had been made. Unexpectedly, the results showed clear assortment by sex, with female carers being more likely to tend to female pups, and male carers to male pups. This sex-specific assortment in helping behaviour has potential lifelong impacts on individual development and may impact the future size and composition of natal groups and dispersing cohorts. Where relatedness between helpers and recipients is already high, individuals may be better off choosing partners using other predictors of the costs and benefits of cooperation, without the need for possibly costly within-group kin discrimination.

Female intrasexual competition is intense in cooperatively breeding species where offspring compete locally for resources and helpers. In mammals, females have been proposed to adjust prenatal investment according to the intensity of competition in the postnatal environment (a form of ‘predictive adaptive response’; PAR). We carried out a test of this hypothesis using ultrasound scanning of wild female banded mongooses in Uganda. In this species multiple females give birth together to a communal litter, and all females breed regularly from one year old. Total prenatal investment (size times the number of fetuses) increased with the number of potential female breeders in the group. This relationship was driven by fetus size rather than number. The response to competition was particularly strong in low weight females and when ecological conditions were poor. Increased prenatal investment did not trade off against maternal survival. In fact we found the opposite relationship: females with greater levels of prenatal investment had elevated postnatal maternal survival. Our results support the hypothesis that mammalian prenatal development is responsive to the intensity of postnatal competition. Understanding whether these responses are adaptive requires information on the long-term consequences of prenatal investment for offspring fitness.

Social animal species show considerable variation in the way in which reproduction is distributed among group members. Recent attempts to explain this variation have proposed that differences in reproductive skew are attributable to differences in the net benefits group members receive from suppressing each other's breeding attempts. Despite receiving relatively little theoretical and empirical attention, the availability of resources required for successful breeding may have an important influence in determining the costs and benefits of suppressing reproduction and thus influence reproductive skew within social groups. Here, we test this possibility using a long-term study of female reproductive success in the banded mongoose Mungos mungo. We find that females experience greater costs of co-breeding when resources are in short supply and that older, more dominant females respond to this cost by suppressing subordinate breeding. This results in differing patterns of reproductive success for females of different competitive abilities, with the oldest, most dominant females breeding regardless of resource availability and younger, subordinate females breeding only when resources are abundant. Our findings highlight the role of resource limitation in determining the distribution of reproductive opportunities within social groups. © 2012 the Author.

Social species show considerable variation in the extent to which dominant females suppress subordinate reproduction. Much of this variation may be influenced by the cost of active suppression to dominants, who may be selected to balance the need to maximize the resources available for their own offspring against the costs of interfering with subordinate reproduction. To date, the cost of reproductive suppression has received little attention, despite its potential to influence the outcome of conflict over the distribution of reproduction in social species. Here, we investigate possible costs of reproductive suppression in banded mongooses, where dominant females evict subordinates from their groups, thereby inducing subordinate abortion. We show that evicting subordinate females is associated with substantial costs to dominant females: pups born to females who evicted subordinates while pregnant were lighter than those born after undisturbed gestations; pups whose dependent period was disrupted by an eviction attained a lower weight at independence; and the proportion of a litter that survived to independence was reduced if there was an eviction during the dependent period. To our knowledge, this is the first empirical study indicating a possible cost to dominants in attempting to suppress subordinate breeding, and we argue that much of the variation in reproductive skew both within and between social species may be influenced by adaptive variation in the effort invested in suppression by dominants.

Reproductive events in animal societies often show a high degree of temporal clustering, but the evolutionary causes of this synchronization are poorly understood. Here, we suggest that selection to avoid the negative effects of competition with other females has given rise to a remarkable degree of birth synchrony in the communal-breeding banded mongoose (Mungos mungo). Within banded mongoose groups, births are highly synchronous, with 64 per cent of females giving birth on exactly the same night. Our results indicate that this extreme synchrony arises because offspring suffer an increased risk of infanticide if their mother gives birth before other females, but suffer in competition with older littermates if their mother gives birth after them. These findings highlight the important influence that reproductive competition can have for the evolution of reproductive synchrony.

Considerable research has focused on understanding variation in reproductive skew in cooperative animal societies, but the pace of theoretical development has far outstripped empirical testing of the models. One major class of model suggests that dominant individuals can use the threat of eviction to deter subordinate reproduction (the 'restraint' model), but this idea remains untested. Here, we use long-term behavioural and genetic data to test the assumptions of the restraint model in banded mongooses (Mungos mungo), a species in which subordinates breed regularly and evictions are common. We found that dominant females suffer reproductive costs when subordinates breed, and respond to these costs by evicting breeding subordinates from the group en masse, in agreement with the assumptions of the model. We found no evidence, however, that subordinate females exercise reproductive restraint to avoid being evicted in the first place. This means that the pattern of reproduction is not the result of a reproductive 'transaction' to avert the threat of eviction. We present a simple game theoretical analysis that suggests that eviction threats may often be ineffective to induce pre-emptive restraint among multiple subordinates and predicts that threats of eviction (or departure) will be much more effective in dyadic relationships and linear hierarchies. Transactional models may be more applicable to these systems. Greater focus on testing the assumptions rather than predictions of skew models can lead to a better understanding of how animals control each other's reproduction, and the extent to which behaviour is shaped by overt acts versus hidden threats.

Both the rate and severity of sibling aggression are predicted to be higher when food availability is low. Although there is now good evidence that food availability influences sibling aggression in facultatively siblicidal species, where aggression commonly results in the death of a competitor, little is known about the proximate causes of aggression in nonsiblicidal species, where aggression rarely results in serious injury. Here, we investigated patterns of aggression between juvenile meerkats (Suricata suricatta), a species where littermate aggression is common, but never lethal. We show that the frequency of aggression between littermates increased when rainfall and helper number, both predictors of the amount of food available to pups, were low. Short-term feeding experiments demonstrated that reducing pup hunger by provisioning them before a foraging session significantly reduced their frequency of aggression in comparison to unfed controls. There was no evidence that offspring sex or weight influenced either the rate at which pups were aggressive, or which littermates they were aggressive to. These results suggest that food availability is an important factor affecting the severity of aggressive competition between offspring, even in the absence of lethal aggressive attacks.

Despite the widespread occurrence of communal breeding in animal societies, the fitness consequences for mothers are poorly understood. One factor that may have an important influence on the net benefits mothers gain from breeding communally is the competitive ability of their offspring, as mothers are likely to gain substantial advantages from producing young who can outcompete the offspring of other females for access to resources. Here, we investigate the factors that influence offspring competition in the communally breeding banded mongoose (Mungos mungo). We show that heavy offspring are more likely to win competitive interactions with their littermates. Heavy offspring also receive more care and are more likely to survive to independence in large communal litters where competition is most intense. Our results also indicate that offspring weight at emergence is positively correlated with the weight of the mother at conception. As a consequence, the offspring of heavy mothers are likely to enjoy marked competitive advantages during early life. Together, our findings strongly suggest that the competitive ability of offspring will influence the costs and benefits that females experience while breeding communally and highlights the need for closer examination of the factors that influence offspring competitive ability and the influence this may have on the evolution of communal breeding.

Animals of many species tend to target their foraging attempts toward particular microhabitats within their habitat. Although these preferences are critical determinants of the foraging niche and have important ecological and evolutionary implications, we know little about how they develop. Here, we use detailed longitudinal data from meerkats (Suricata suricatta) to examine how individual learning and the use of social information affect the development of foraging microhabitat preferences. Despite living in an open, arid environment, adult meerkats frequently foraged at the base of vegetation. Young pups seldom did so, but their foraging microhabitat choices became increasingly adult-like as they grew older. Learning about profitable microhabitats may have been promoted in part by positive reinforcement from prey capture. Foraging may also have become increasingly targeted toward suitable locations as pups grew older because they spent more time searching before embarking on foraging bouts. The development of microhabitat preferences might also have been influenced by social cues. Foraging in close proximity to adults may increase the probability that pups would dig in similar microhabitats. Also, pups often dug in holes created by older individuals, whereas adults never dug in existing holes. Foraging in existing holes was no more profitable to pups than creating their own foraging hole but could provide pups with important informational benefits. The integration of personal and social information is likely to be a common feature in the development of the foraging niche in generalist species. © the Author 2008. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved.

1. In cooperative societies with high reproductive skew, selection on females is likely to operate principally through variation in the probability of acquiring dominant status and variation in reproductive success while dominant. Despite this, few studies of cooperative societies have investigated the factors that influence which females become dominant, and/or their reproductive output while in the dominant position. 2. Here we use long-term data from a wild meerkats population to describe variation in the breeding success of dominant female meerkats Suricata suricatta and investigate its causes. 3. Female meerkats compete intensely for breeding positions, and the probability of acquiring the breeding role depends upon a female's age in relation to competitors and her weight, both at the time of dominance acquisition and early in life. 4. Once dominant, individual differences in breeding success depend principally on the duration of dominance tenure. Females remain for longer in the dominant position if they are heavier than their competitors at the start of dominance, and if the number of adult female competitors at the start is low. 5. Female breeding success is also affected by variation in fecundity and pup survival, both of which increase with group size. After controlling for these effects, female body weight has a positive influence on breeding rate and litter size, while the number of adult female competitors reduces litter survival. 6. These findings suggest that selection for body weight and competitive ability will be high in female meerkats, which may moderate their investment in cooperative activities. We suggest that similar consequences of competition may occur among females in other cooperative societies where the benefits of attaining dominance status are high.

Identifying traits that affect the reproductive success of individuals is fundamental for our understanding of evolutionary processes. In cooperative breeders, a dominant male typically restricts mating access to the dominant female for extended periods, resulting in pronounced variation in reproductive success among males. This may result in strong selection for traits that increase the likelihood of dominance acquisition, dominance retention and reproductive rates while dominant. However, despite considerable research on reproductive skew, few studies have explored the factors that influence these three processes among males in cooperative species. Here we use genetic, behavioural and demographic data to investigate the factors affecting reproductive success in dominant male meerkats (Suricata suricatta). Our data show that dominant males sire the majority of all offspring surviving to 1 year. A male's likelihood of becoming dominant is strongly influenced by age, but not by weight. Tenure length and reproductive rate, both important components of dominant male reproductive success, are largely affected by group size and composition, rather than individual traits. Dominant males in large groups have longer tenures, but after this effect is controlled, male tenure length also correlates negatively to the number of adult females in the group. Male reproductive rate also declines as the number of intra- and extra-group competitors increases. As the time spent in the dominant position and reproductive rate while dominant explain > 80% of the total variance in reproductive success, group composition thus has major implications for male reproductive success.

In animal societies, contrasts in reproductive skew among females are caused by variation in the frequency of reproduction by subordinates. However, despite widespread interest in the extent and causes of reproductive skew, few empirical studies have investigated the factors affecting the frequency of successful reproduction by subordinates. We tested the prediction that the extent to which dominants restrict the reproductive success of subordinates should increase as group size rises and the marginal benefits of additional helpers falls. In a long-term study of wild meerkats, Suricata suricatta, we found that dominants were more likely to evict subordinates in large groups than small ones, and that the frequency of breeding by subordinate females declined with group size, largely as a result of increases in abortion rate. The breeding frequency of subordinate females was also influenced by their age and weight, which probably reflects the capability of subordinates to breed and their ability to resist the attempts of dominants to suppress them. These findings highlight the importance of investigating variation in the benefits to dominants of controlling subordinate reproduction as well as variation in the benefits of breeding to subordinate females when attempting to understand variation in subordinate breeding success. © 2008 the Association for the Study of Animal Behaviour.

In cooperatively breeding vertebrate societies, male and female helpers commonly vary in how much they invest in cooperative activities. Most explanations for this phenomenon centre on sex differences in the fitness benefits that helpers accrue through providing care, and few studies have explored how sex differences in the costs of helping are likely to influence how much care males and females provide. I investigated helper contributions in the banded mongoose, Mungos mungo, and asked whether differences in the way that helping trades off against male and female reproductive success can explain sex biases in helping effort. Contributions to the two main pup care activities were strongly male biased, and helping resulted in both sexes losing weight in the short term. This weight loss is unlikely to reduce the breeding success of males, as, although heavy males are more likely to gain access to oestrous females, any weight lost through helping can be regained before the next oestrous event. Furthermore, males less than 2 years old rarely gain access to oestrous females regardless of their body weight. Short-term reductions in body weight are likely to be more costly for females as the helping period coincides with conception and gestation of the next litter, and weight loss at this time is likely to reduce their probability of breeding successfully. These results suggest that male-biased care in this species has arisen because males and females differ in the way that helping trades off against their reproductive success. © 2007 the Association for the Study of Animal Behaviour.

In cooperatively breeding vertebrates, helpers commonly vary in how much care they provide. We investigated whether meerkat, Suricata suricatta, pups responded to variation in helper feeding rates by associating with the most productive helpers preferentially throughout the period of pup care. Helpers varied widely in how much food they provided, and pup food intake increased with the time spent in exclusive association with productive helpers. Pups spent more time following productive helpers than poor helpers, and we confirmed the causality of this finding by conducting long-term feeding experiments which increased helper productivity and showed that pups spent significantly more time with helpers whose feeding rate had been experimentally raised. Pups aggressively defended helpers from approaches by littermates, but there was no evidence that pups defended productive helpers more strongly, or that larger pups were more likely to gain exclusive access to the most productive helpers. Our results provide evidence that, by associating with particular helpers, meerkat pups can influence how much care they receive during development. These findings highlight the importance of considering the behaviour of offspring, when investigating the way care is distributed in cooperative societies. © 2007 the Association for the Study of Animal Behaviour.

In most animals, the sex that invests least in its offspring competes more intensely for access to the opposite sex and shows greater development of secondary sexual characters than the sex that invests most. However, in some mammals where females are the primary care-givers, females compete more frequently or intensely with each other than males. A possible explanation is that, in these species, the resources necessary for successful female reproduction are heavily concentrated and intrasexual competition for breeding opportunities is more intense among females than among males. Intrasexual competition between females is likely to be particularly intense in cooperative breeders where a single female monopolizes reproduction in each group. Here, we use data from a twelve-year study of wild meerkats (Suricata suricatta), where females show high levels of reproductive skew, to show that females gain greater benefits from acquiring dominant status than males and traits that increase competitive ability exert a stronger influence on their breeding success. Females that acquire dominant status also develop a suite of morphological, physiological and behavioural characteristics that help them to control other group members. Our results show that sex differences in parental investment are not the only mechanism capable of generating sex differences in reproductive competition and emphasize the extent to which competition for breeding opportunities between females can affect the evolution of sex differences and the operation of sexual selection.

Helpers in cooperative and communal breeding species are thought to accrue fitness benefits through improving the condition and survival of the offspring that they care for, yet few studies have shown conclusively that helpers benefit the offspring they rear. Using a novel approach to control for potentially confounding group-specific variables, I compare banded mongoose (Mungos mungo) offspring within the same litter that differ in the amount of time they spend with a helper, and hence the amount of care they receive. I show that pups that spend more time in close proximity to a helper are fed more, grow faster and have a higher probability of survival to independence than their littermates. Moreover, high growth rates during development reduce the age at which females breed for the first time, suggesting that helpers can improve the future fecundity of the offspring for which they care. These results provide strong evidence that it is the amount of investment per se that benefits offspring, rather than some correlate such as territory quality, and validate the assumption that helpers improve the reproductive success of breeders, and hence may gain fitness benefits from their actions. Furthermore, the finding that helpers may benefit offspring in the long-term suggests that current studies underestimate the fitness benefits that helpers gain from rearing the offspring of others.