Costs of mating competition limit male lifetime breeding success in polygynous mammals.

This is the accepted version of the paper. The final published version is available from the Royal Society at http://rspb.royalsocietypublishing.org/content/281/1786/20140418.abstract.Although differences in breeding lifespan are an important source of variation in male fitness, the factors affecting the breeding tenure of males have seldom been explored. Here, we use cross-species comparisons to investigate the correlates of breeding lifespan in male mammals. Our results show that male breeding lifespan depends on the extent of polygyny, which reflects the relative intensity of competition for access to females. Males have relatively short breeding tenure in species where individuals have the potential to monopolize mating with multiple females, and longer ones where individuals defend one female at a time. Male breeding tenure is also shorter in species in which females breed frequently than in those where females breed less frequently, suggesting that the costs of guarding females may contribute to limiting tenure length. As a consequence of these relationships, estimates of skew in male breeding success within seasons overestimate skew calculated across the lifetime and, in several polygynous species, variance in lifetime breeding success is not substantially higher in males than in females.The Leverhulme Trust, the Isaac Newton Trust, and the European Research Council provided the funding for this study

Male immigration triggers increased growth in subordinate female meerkats.

There is increasing evidence that some vertebrates can adjust their growth rate in relation to changes in the social context that affect their probability of breeding. Here, we show that, in meerkats (Suricata suricatta), which are singular cooperative breeders, subordinate females increase in body mass after their father is replaced as the dominant male in their natal group by an immigrant male, giving them regular access to an unfamiliar and unrelated mating partner, while their brothers showed no similar increase nor did subordinate females living in other stable groups (where male immigration did not occur did) in this time period. Moreover, subordinate females showed a greater increase in growth rate when their father was succeeded by an unfamiliar immigrant male than when he was replaced by a familiar male who was already resident. These results suggest that female meerkats can adjust their rate of growth to changes in the kinship composition of their groups that provide them with increased access to unrelated breeding partners, which may occur in other mammals as well when breeding opportunities change.Natural Environment Research Council European Research Counci

Turnover in male dominance offsets the positive effect of polygyny on within-group relatedness

Evidence of an association between cooperative breeding systems and average coefficients of relatedness between group members in vertebrates have led to increased interest in the social and ecological factors affecting average kinship within groups. Previous studies have suggested that polygynous mating systems and high degrees of male reproductive skew increase average relatedness because they increase the proportion of offspring born in each group that are paternal siblings. Although this may be the case in semelparous organisms, in many multiparous polygynous animals, intense competition between males shortens the breeding tenure of males and leads to their frequent replacement by competitors which reduces paternal relatedness and average kinship between members of multigenerational groups. Here, we explore the interaction between male reproductive skew and the frequency of turnover in breeding males and its effects on within-group relatedness. Our theoretical model shows that increases in rates of dominance turnover in polygynous systems can offset the positive effect of male skew on relatedness between group members within seasons, showing that polygynous mating systems will not necessarily lead to significant increases in average relatedness, especially in species where there is extensive overlap between generations among group members

Validating methods for estimating endocranial volume in individual red deer (Cervus elaphus).

Comparing brain sizes is a key method in comparative cognition and evolution. Brain sizes are commonly validated by interspecific comparisons involving animals of varying size, which does not provide a realistic index of their accuracy for intraspecific comparisons. Intraspecific validation of methods for measuring brain size should include animals of the same age and sex to ensure that individual differences can be detected in animals of similar size. In this study we compare three methods of measuring the endocranial volume of 33 red deer skulls to investigate the accuracy of each method. Methods for estimating endocranial volume included scanning each skull using computerised tomography (CT) and quantifying the volume with OsiriX software, filling the cranium with glass beads and measuring the bead volume, and linear measurements (length, width, and height) of the cranium using callipers. CT scan volumes were highly correlated with results from the bead method, but only moderately correlated with the linear method. This study illustrates the importance of validating intraspecies measurement methods, which allows for the accurate interpretation of results.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.beproc.2012.10.01

Ontogenetic changes in alarm-call production and usage in meerkats ( Suricata suricatta ): adaptations or constraints?

In many species, individuals suffer major mortality in their first year because of predation. Behaviours that facilitate successful escape are therefore under strong selection, but anti-predator skills often emerge gradually during an individual's early development. Using long-term data and acoustic recordings of alarm calls collected during natural predator encounters, we aimed to elucidate two largely unsolved issues in anti-predator ontogeny: (1) whether incorrect predator assignment is adaptively age-appropriate, given that vulnerability often changes during development, or whether age-related differences reflect true mistakes made by immature individuals; and (2) the extent to which the development of adult-like competence in alarm-call production and usage is simply a function of maturational processes or dependent upon experience. We found that young meerkats (Suricata suricatta) were less likely to give alarm calls than adults, but alarmed more in response to non-threatening species compared to adults. However, stimuli that pose a greater threat to young than adults did not elicit more calling from young; this argues against age-related changes in vulnerability as the sole explanation for developmental changes in calling. Young in small groups, who were more likely to watch out for predators, alarmed more than less vigilant young in larger groups. Moreover, despite similarities in acoustic structure between alarm call types, calls appeared in the repertoire at different rates, and those that were associated with frequently encountered predators were produced relatively early on. These results indicate that experience is a more plausible explanation for such developmental trajectories than maturatio

Decline and fall: The causes of group failure in cooperatively breeding meerkats.

Funder: MAVA FoundationFunder: Universität ZürichIn many social vertebrates, variation in group persistence exerts an important effect on individual fitness and population demography. However, few studies have been able to investigate the failure of groups or the causes of the variation in their longevity. We use data from a long-term study of cooperatively breeding meerkats, Suricata suricatta, to investigate the different causes of group failure and the factors that drive these processes. Many newly formed groups failed within a year of formation, and smaller groups were more likely to fail. Groups that bred successfully and increased their size could persist for several years, even decades. Long-lived groups principally failed in association with the development of clinical tuberculosis, Mycobacterium suricattae, a disease that can spread throughout the group and be fatal for group members. Clinical tuberculosis was more likely to occur in groups that had smaller group sizes and that had experienced immigration

Strategic growth in social vertebrates

Individual differences in growth and size of vertebrates often represent adaptive, plastic responses to contrasts in ecological conditions. Recent studies show that vertebrates can also modify their growth and size in an adaptive fashion in response to fine-grain changes in social conditions (which we refer to as strategic growth). Here, we review experimental evidence for strategic growth in social vertebrates. We describe a set of conditions under which strategic growth commonly occurs, and highlight potential examples of convergent evolution of strategic growth across the tree of life. This synthesis has implications for the way we think about organismal growth and size, because it underscores that the size of individuals can often be fine-tuned to their social environment.Accepted manuscrip

Evolution of social monogamy in primates is not consistently associated with male infanticide.

This is the accepted manuscript version of the article. The final published version is available from PNAS Online at http://www.pnas.org/content/111/17/E1674.extract