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The recent development of reproductive skew (RS) theory shows striking parallels with that of parent–offspring conflict (POC) theory a decade earlier. In particular, the concept of ‘battleground’ and ‘resolution’ models in POC theory is equally relevant to RS theory. The battleground of conflict in POC and RS has been defined by different constraints (which I term ‘optimization’ and ‘group stability’ constraints, respectively). This distinction is not inherent but arises simply because POC models assume that the fitness benefits of an increasing share of resource show diminishing returns, whereas skew models assume a linear relation between reproductive share and fitness. Incorporating diminishing returns into skew models reveals a simple and almost wholly neglected explanation for reproductive sharing. Models of POC have moved on from simply defining the battleground to consider how conflict within it is resolved. The development of analogous models for RS theory is at a relatively early stage. In particular, more work is needed to understand the manner and extent to which overt aggression can mediate reproductive control. Lessons learned from attempts to test POC theory can help guide tests of RS theory, and provide information on both the nature of the battleground over reproduction and the mechanism by which conflicts are resolved. [Copyright &y& Elsevier]

Studies social control of reproduction in banded mongooses. Dominant individuals' control of subordinate reproduction; Dominant males' protection of females; Reaction of dominants to subordinates' mating attempts; Gestation period of older females.

Describes a model of animal reproductive partitioning which demonstrates reproductive skew and indiscriminate infanticide. Finding that the possibility of infanticide may influence the pattern of reproduction within a group even if no offspring are actually killed at equilibrium; Association of reproductive restraints to elevated levels of offspring production.

Presents a study which looked at the evolution of skew in mating systems where dominants do not have control over subordinate reproduction and where helping is absent; Information on models; Detailed information on the methodology used to conduct the study; Discussion based on the study.

Attempts to study the effects of wing size and fluctuating asymmetry in length of wings of male Chironomus plumosus on its mating success, and examines whether a relationship exists between absolute fluctuating asymmetry and wing length. Methods; Results; Discussion.

Individual foraging specialization is a widespread occurrence and has numerous causes and consequences associated with it. However, one key area that has remained largely undiscussed, is the presence of such specialization in group-living species. This warrants special consideration as the behaviour of individuals living in groups is strongly influenced by their social environment, and so may result in distinct mechanisms favouring specialization. Here, we synthesize current theories regarding individual specialization and apply these to group-living species. In doing so we develop a set of testable predictions about the causes and consequences of individual foraging specialization in group-living species. In particular, we conclude that increased local competition between conspecifics will drive the development of individual foraging specialization in group-living species. We hypothesize that 'one-to-one' learning will promote individual foraging specialization, whereas learning from multiple role models will erode individual specialization through behavioural conformity. This increase in specialization may also make social groups more resilient to environmental change. We argue that testing predicted causes and consequences of individual specialization in group-living species is an important step in developing our understanding of the evolution of animal societies and how they are likely to be affected by a changing environment. • Individual foraging specialization in animal groups is largely unconsidered. • We develop predictions about its causes and consequences in group-living species. • Intragroup competition and social learning are likely to be important causes. • Greater within-group specialization may improve resilience to environmental change. [ABSTRACT FROM AUTHOR]

Acoustic signals degrade and attenuate as they propagate through the environment, thus transmitting information with lower efficiency. The acoustic adaptation hypothesis (AAH) states that selection should shape the vocalizations of a species to maximize transmission through their habitat. A specific prediction of the AAH is that vocalizations will transmit better when emitted in their native habitat versus non-native habitats. We tested this prediction using vocalizations of three mongoose species that dwell in structurally different habitats: banded mongooses, Mungos mungo , dwarf mongooses, Helogale parvula , and meerkats, Suricata suricatta. Representative vocalizations of the three species were broadcast and rerecorded in each habitat at six distances from the source. Rerecorded vocalizations were compared to nondegraded calls through spectrogram correlation. Using generalized linear mixed models, we then quantified the differences in transmission fidelity of each species' vocalizations. Overall, we found partial support for the AAH within the mongoose family: habitat type strongly affected sound transmission, but depending on the species, vocalizations did not always transmit best in their native habitat, suggesting various degrees of acoustic adaptation. Vegetation cover within habitat type was also found to have a significant influence on the transmission properties of vocalizations. In addition, we found evidence that by changing their behaviour, either by producing vocalizations at different amplitudes or by choosing a specific calling location, mongooses can reduce sound degradation and attenuation over distance, thereby enhancing their communication efficiency. Our work highlights how habitat features may be key determinants of vocalization structure in mongooses, and is generalizable to other species living in similar conditions. It also suggests that, given a species and habitat, other selective pressures might prevail and limit acoustic adaptation in animal communication systems. Finally, our study provides insights into how mammals can adjust their vocal behaviour to compensate for environmental constraints on the transmission of their vocalizations. • We tested the acoustic adaptation hypothesis in social mongooses' vocalizations. • Propagation experiments showed partial support for acoustic adaptations in mongooses. • Vegetation cover and habitat type significantly influenced sound propagation. • Behavioural adjustments allow mongooses to optimize efficient sound transmission. • Factors other than acoustic adaptations likely also shape mongoose vocalizations. [ABSTRACT FROM AUTHOR]

Of key importance for understanding cooperative societies is the way in which reproductive opportunities are distributed among group members. Traditionally, skew has been thought of as a product of intrasexual competition. However, cooperatively breeding species often live in mixed-sex groups, so the behaviour of one sex has the potential to influence skew in the other. We addressed the importance of inter- and intrasexual conflict in determining reproductive skew through a study of paternity sharing in the cooperatively breeding banded mongoose, Mungus mungo. Unlike banded mongoose females, where reproductive skew is low, males exhibited high skew, with 85% of paternities being assigned to the three oldest males in each group. Individual males appeared unable to monopolize reproduction because females come into oestrus in synchrony and mate multiply. Instead, older males increased their success by mate guarding the oldest, most fecund females. Our findings therefore highlight the importance of mate choice in males and reveal the behavioural differences between the sexes that generate reproductive skew. They also emphasize the considerable influence that female behaviour can have on male reproductive skew. [Copyright &y& Elsevier]

Reproductive skew theory provides a compelling explanation for the partitioning of reproduction among individuals within animal societies. One constructive criticism of the theory is that there are too many models, all of which have different assumptions and predictions, which makes it difficult to know what to test. Here we begin the process of tackling this problem, by re-examining the assumptions and predictions of basic concession and restraint models, two transactional models that are often tested as alternatives. Concession models assume that the dominant has complete control over the allocation of reproduction but may yield some of the group''s reproduction to prevent the subordinate from voluntarily departing. Restraint models assume that the subordinate has complete control over the allocation of reproduction but may not claim all of the group''s reproduction to prevent the dominant from forcibly evicting it. We show that the group dissolution tactics that individuals use (forcible eviction or voluntary departure) need not be an assumption of the model, but rather they can be predicted using Hamilton''s rule and the standard variables of skew models. We reveal that the assumption that one individual (dominant or subordinate) has complete control over the allocation of reproduction is an idea common to both models, and we resolve this semantic difference by calling this individual ‘the allocator’. We show that, regardless of the group dissolution tactics that individuals adopt, the allocator''s share of the reproduction always increases as relatedness increases, as group productivity increases, and as constraints on leaving to breed elsewhere intensify. We conclude that concession and restraint type models make qualitatively similar predictions, and should not be tested as alternatives. In summary, this study makes the transactional framework of reproductive skew more general, by eliminating restrictive assumptions, and more amenable to testing in the field, by clarifying assumptions and predictions. [Copyright &y& Elsevier]

In animal societies, conflict within groups can result in eviction, where individuals are often permanently expelled from their group. To understand the evolution of eviction and its role in the resolution of within-group conflict requires information on the demographic consequences of eviction for individuals and groups. However, such information is usually difficult to obtain because of the difficulty in tracking and monitoring individuals after they are evicted from their natal groups. Here we used a 15-year data set on life history and demography to investigate the consequences of eviction in a tractable cooperatively breeding mammal, the banded mongoose, Mungos mungo . In this species, groups of individuals are periodically evicted en masse and eviction is a primary mechanism by which new groups form in the study population. Following eviction, we found sex differences in dispersal distance: some females established new groups on the study peninsula but males always dispersed away from the study peninsula. Evicted females suffered reduced reproductive success in the year after eviction. For the evicting group, eviction was associated with increased per capita reproductive success for females, suggesting that eviction is successful in reducing reproductive competition. However, eviction was also associated with increased intergroup conflict for the evicting group. Our results suggest that within-group conflict resolution strategies affect group productivity, group interactions and the structure of the population, and hence have fitness impacts that reach beyond the individual evictors and evictees involved in eviction. [ABSTRACT FROM AUTHOR]

Conflict between groups is a notable feature of many animal societies. Recent theoretical models suggest that violent intergroup conflict can shape patterns of within-group cooperation. However, despite its prevalence in social species, the adaptive significance of violent intergroup conflict has been little explored outside of humans and chimpanzees, Pan troglodytes . A barrier to current understanding of the role of intergroup conflict in the evolution of social behaviour is a lack of information on the causes and consequences of aggression between groups. Here, we examined the causes and fitness consequences of intergroup conflict in the banded mongoose, Mungos mungo , using a 16-year data set of observed intergroup interactions, life history and behaviour. Banded mongooses are cooperative breeders that live in highly territorial groups and engage in frequent, aggressive and violent intergroup interactions. We found that intensified population-wide competition for food and mates increased the probability of intergroup interactions, and that increased intergroup conflict was associated with periods in which groups were growing in size. Intergroup conflict had fitness costs in terms of reduced litter and adult survival but no cost to pregnant females: in fact, females were less likely to abort following an intergroup interaction than when there had been no recent intergroup conflict. Our results suggest that intergroup conflict has measurable costs to both individuals and groups in the long and short term, and that levels of conflict among groups could be high enough to affect patterns of within-group cooperative behaviour. Establishing the consequences of intergroup conflict in cooperative species can shed light on patterns of conflict and cooperation within groups and, in turn, facilitate our understanding of social evolution. [ABSTRACT FROM AUTHOR]

Individual differences in contributions to cooperation can be strikingly consistent over time giving rise to alternative cooperative phenotypes within animal societies. Following the social niche specialization hypothesis, these consistent differences may be driven by social conflict over reproductive opportunities if individuals specializing as ‘breeders’ and ‘nonbreeders’ experience a beneficial reduction in social conflict and differential costs associated with cooperating. This hypothesis gives three testable predictions: (1) consistent individual differences in cooperative behaviour will be accompanied by consistent individual differences in reproductive behaviour, (2) individuals contributing heavily to reproduction will contribute relatively little to cooperative behaviours within the same breeding attempt and vice versa, and (3) individuals that consistently contribute heavily to reproduction over their lifetime will also consistently contribute less to cooperative behaviours and vice versa. We tested these predictions with a 15-year investigation into the lifetime patterns of mate guarding and two forms of cooperative offspring care (‘babysitting’ and ‘escorting’) in a wild population of banded mongooses. We found significant repeatability of individual contributions to both cooperative behaviours, as well as significant repeatability of individual levels of mate guarding. However, we found no evidence of negative covariance between contributions to cooperative and reproductive behaviours either within breeding attempts or across lifetimes. This suggests that the observed consistent individual differences in both cooperative behaviour and reproduction are not associated; there is no evidence of a trade-off between reproduction and cooperation. However, we found a significant positive covariance between babysitting and escorting when estimated both within breeding attempts and across lifetimes, which suggests that some group members are generally more cooperative than others, contributing more to both behaviours over their lifetimes. The drivers of this consistent individual variation in contributions to cooperation remain unknown. [ABSTRACT FROM AUTHOR]

In cooperatively breeding vertebrate societies, contributions to offspring care can vary greatly between group members. Kin selection theory predicts that cooperation will be favoured when directed towards relatives and when the cost to benefit ratio is low. The fitness costs of helping in turn depend on the impact of energetic investments in care on future reproductive success, which is likely to vary between helpers. For example, investments may impact more on a young helper, which needs to invest energy in growth and is an inexperienced forager. We investigated how a key predictor of cost, food availability (estimated using rainfall), influences helping behaviour in the banded mongoose, Mungos mungo. In this cooperative carnivore, a variable number of group members breed while almost all help to rear the communal litter. Nonbreeding females and juvenile males helped less when food was scarce, reflecting the potentially high costs of weight loss and reduced growth on survival and future reproductive success. In contrast, adult males maintained their investment in care as food supply decreased, probably because body condition has relatively little impact on male reproductive success in this species. Breeding females (with pups in the communal litter) also maintained their helping effort as food supply decreased. Although mothers invested highly in care, there was no evidence that they preferentially cared for their own pups, probably because synchronized birthing scrambles maternity cues. Patterns of care in the banded mongoose thus seem to reflect the benefits gained from helping and the long-term fitness costs to the helper. [Copyright &y& Elsevier]

Overmarking occurs when one individual places its scent mark directly on top of the scent mark of another individual. Although it is almost ubiquitous among terrestrial mammals, we know little about the function of overmarking and detailed field observations are rare. We investigated the chemical composition of scents and patterns of overmarking by wild banded mongooses, Mungos mungo. Chemical analyses of anal gland secretions showed that scents were sexually dimorphic. Both male and female adults were more likely to overmark the scents of same-sex individuals. An analysis of responses to two scents on the same site suggested that the sex of the top or most recent scent was more important than that of the bottom or original scent in determining overmarking response. Juveniles also overmarked scents at high rates, but did not respond to scents in a sex-specific way. Same-sex-specific patterns within groups have not been described in any other species, and may reflect a social system with intense intrasexual competition for reproduction within both sexes. Banded mongooses live in large mixed-sex groups, with intense competition between males for females, owing to the heavily male-biased adult sex ratio and highly synchronized oestrous cycles. Oestrous synchronization may also promote intrasexual competition for males within females, as females compete simultaneously for high-quality males. Female competition for males may also be enhanced by the rewards of male-biased parental care. This investigation highlights the need for detailed studies of overmarking in the natural context, to confirm and expand upon laboratory findings. [Copyright &y& Elsevier]

In contrast to numerous studies of scent marking in male mammals, studies of female scent marking are relatively rare. We have previously shown that communally breeding female banded mongooses, Mungos mungo, are more likely to overmark the scent of other females. Here we describe female overmarking patterns in more detail, and discuss these results in relation to hypotheses potentially explaining such ‘female intrasexual overmarking’. To our knowledge, this is the first study to investigate female overmarking in any wild mammal. First, although we found some evidence of individually distinctive scent marks in females, we found no evidence to suggest that female intrasexual overmarking was related to competition for food, as feeding competition was infrequent, and unrelated to overmarking scores. We also found no evidence to suggest that intrasexual overmarking in females was involved in reproductive suppression. Females with the highest and lowest overmarking scores in each group were mate-guarded by males for similar durations. Finally, we found little evidence to suggest that female intrasexual overmarking was involved in competition for males. Although the female with the highest overmarking score in each group tended to be mate-guarded by males in better condition than the female with the lowest overmarking score, a female’s overmarking score affected neither the amount of harassment she received from males nor the frequency of mating attempts received. These results are discussed in light of these and other untested hypotheses for female overmarking. [Copyright &y& Elsevier]

Sexual selection has resulted in the elaboration of secondary sexual characteristics in many animals. Although mammalian scent glands, secretions and marking behaviour are commonly sexually dimorphic, these traits have received little attention compared to avian plumage and mammalian weaponry. Overmarking, when one individual places a scent mark directly over that of another individual, is of particular interest. Owing to the costs of repeatedly monitoring and covering the scent marks of rivals, overmarking may provide an honest indication of a male’s resource-holding potential, perhaps explaining why female rodents exposed to experimental overmarks subsequently prefer to associate with males whose scent mark was on top. This study on wild banded mongooses, Mungos mungo, suggests that overmarking may primarily affect behavioural mating success through male competition not by female mate choice. First, chemical analyses of anal gland secretions demonstrated that males had individually distinctive scents, and a field experiment confirmed that mongooses were able to discriminate between scents from different individuals. Observations of overmarking patterns showed a relationship between overmarking score and behavioural mating success, but we found no evidence that females actively chose to mate with males with high overmarking scores. Instead, we found that males with higher overmarking scores first mate-guarded females at a significantly younger age than males with lower overmarking scores. Since mate-guarding males obtain the vast majority of matings, this suggests that overmarking may be an important component of intrasexual competition for mating opportunities in this species. [Copyright &y& Elsevier]