Evidence for inbreeding depression in captive Damaraland mole-rats.

Mating between closely related individuals can result in a reduction in offspring fitness, known as inbreeding depression. Here, we investigate whether breeding with close relatives affects the reproductive output of parents and the development of their offspring in Damaraland mole-rats (), a cooperatively breeding species where females avoid mating with familiar individuals. By cross-fostering litters of pups soon after birth, we were able to form breeding pairs from full siblings that were reared apart.

Kin recognition for incest avoidance in Damaraland mole-rats, .

Across taxa, breeding among close relatives is usually avoided because it incurs fitness costs to offspring. Incest is often averted through the dispersal of either sex from the natal area to breed. In some philopatric species, association among relatives extends into adulthood, and an ability to discriminate kin may be required for individuals to reduce inbreeding risk.

Androgen-mediated maternal effects and trade-offs: postnatal hormone development, growth, and survivorship in wild meerkats.

Introduction: Mammalian reproductive and somatic development is regulated by steroid hormones, growth hormone (GH), and insulin-like growth factor-1 (IGF-1). Based largely on information from humans, model organisms, and domesticated animals, testosterone (T) and the GH/IGF-1 system activate sexually differentiated development, promoting male-biased growth, often at a cost to health and survivorship. To test if augmented prenatal androgen exposure in females produces similar developmental patterns and trade-offs, we examine maternal effects in wild meerkats (), a non-model species in which adult females naturally, albeit differentially by status, express exceptionally high androgen concentrations, particularly during pregnancy.

A female-biased gene expression signature of dominance in cooperatively breeding meerkats.

Dominance is a primary determinant of social dynamics and resource access in social animals. Recent studies show that dominance is also reflected in the gene regulatory profiles of peripheral immune cells. However, the strength and direction of this relationship differs across the species and sex combinations investigated, potentially due to variation in the predictors and energetic consequences of dominance status.

Dominance loss and tenure maintenance in Kalahari meerkats.

In many social species, both the acquisition of dominance and the duration that individuals maintain their status are important determinants of breeding tenure and lifetime reproductive success. However, few studies have yet examined the extent and causes of variation in dominance tenure and the duration of breeding lifespans. Here, we investigate the processes that terminate dominance tenures and examine how they differ between the sexes in wild Kalahari meerkats (), a cooperative breeder where a dominant breeding pair produces most of the young recruited into each group.

Climate change drives loss of bacterial gut mutualists at the expense of host survival in wild meerkats.

Climate change and climate-driven increases in infectious disease threaten wildlife populations globally. Gut microbial responses are predicted to either buffer or exacerbate the negative impacts of these twin pressures on host populations. However, examples that document how gut microbial communities respond to long-term shifts in climate and associated disease risk, and the consequences for host survival, are rare.

Damaraland mole-rats do not rely on helpers for reproduction or survival.

In eusocial invertebrates and obligate cooperative breeders, successful reproduction is dependent on assistance from non-breeding group members. Although naked () and Damaraland mole-rats () are often described as eusocial and their groups are suggested to resemble those of eusocial insects more closely than groups of any other vertebrate, the extent to which breeding individuals benefit from the assistance of non-breeding group members is unclear. Here we show that, in wild Damaraland mole-rats, prospective female breeders usually disperse and settle alone in new burrow systems where they show high survival rates and remain in good body condition-often for several years-before being joined by males.

Dispersal-induced social stress prolongs gestation in wild meerkats.

In the majority of mammals, gestation length is relatively consistent and seldom varies by more than 3%. In a few species, females can adjust gestation length by delaying the development of the embryo after implantation. Delays in embryonic development allow females to defer the rising energetic costs of gestation when conditions are unfavourable, reducing the risk of embryo loss.

Pregnancy reduces concurrent pup care behaviour in meerkats, generating differences between dominant and subordinate females.

In some mammals, and particularly in cooperative breeding ones, successive bouts of reproduction can overlap so that a female is often pregnant while still nurturing dependent young from her previous litter. Such an overlap requires females to divide their energetic budget between two reproductive activities, and pregnancy costs would consequently be expected to reduce investment in concurrent offspring care. However, explicit evidence for such reductions is scarce, and the potential effects they may have on work division in cooperative breeders have not been explored.

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.

Demographic consequences of changes in environmental periodicity.

The fate of natural populations is mediated by complex interactions among vital rates, which can vary within and among years. Although the effects of random, among-year variation in vital rates have been studied extensively, relatively little is known about how periodic, nonrandom variation in vital rates affects populations. This knowledge gap is potentially alarming as global environmental change is projected to alter common periodic variations, such as seasonality.

Gut microbiota individuality is contingent on temporal scale and age in wild meerkats.

Inter-individual differences in gut microbiota composition are hypothesized to generate variation in host fitness-a premise for the evolution of host-gut microbe symbioses. However, recent evidence suggests that gut microbial communities are highly dynamic, challenging the notion that individuals harbour unique gut microbial phenotypes. Leveraging a long-term dataset of wild meerkats, we reconcile these concepts by demonstrating that the relative importance of identity for shaping gut microbiota phenotypes depends on the temporal scale.

Two decades of tuberculosis surveillance reveal disease spread, high levels of exposure and mortality and marked variation in disease progression in wild meerkats.

Infections with tuberculosis (TB)-causing agents of the Mycobacterium tuberculosis complex threaten human, livestock and wildlife health globally due to the high capacity to cross trans-species boundaries. Tuberculosis is a cryptic disease characterized by prolonged, sometimes lifelong subclinical infections, complicating disease monitoring. Consequently, our understanding of infection risk, disease progression, and mortality across species affected by TB remains limited.

Ageing red deer alter their spatial behaviour and become less social.

Social relationships are important to many aspects of animals' lives, and an individual's connections may change over the course of their lifespan. Currently, it is unclear whether social connectedness declines within individuals as they age, and what the underlying mechanisms might be, so the role of age in structuring animal social systems remains unresolved, particularly in non-primates. Here we describe senescent declines in social connectedness using 46 years of data in a wild, individually monitored population of a long-lived mammal (European red deer, Cervus elaphus).

Genetic variance in fitness indicates rapid contemporary adaptive evolution in wild animals.

The rate of adaptive evolution, the contribution of selection to genetic changes that increase mean fitness, is determined by the additive genetic variance in individual relative fitness. To date, there are few robust estimates of this parameter for natural populations, and it is therefore unclear whether adaptive evolution can play a meaningful role in short-term population dynamics. We developed and applied quantitative genetic methods to long-term datasets from 19 wild bird and mammal populations and found that, while estimates vary between populations, additive genetic variance in relative fitness is often substantial and, on average, twice that of previous estimates.

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.

Dispersal Decreases Survival but Increases Reproductive Opportunities for Subordinates in a Cooperative Breeder.

AbstractIn most socially structured populations, the formation of new groups depends on the survival and reproduction of dispersing individuals. Quantifying vital rates in dispersers, however, is difficult because of the logistic challenges of following wide-ranging animals. Here, using data from free-ranging meerkats (), we estimate survival and reproduction of dispersing females and compare these estimates to data for established residents.

CHARACTERIZING TUBERCULOSIS PROGRESSION IN WILD MEERKATS (SURICATA SURICATTA) FROM FECAL SAMPLES AND CLINICAL SIGNS.

Tuberculosis (TB) is an increasing threat to wildlife, yet tracking its spread is challenging because infections often appear to be asymptomatic, and diagnostic tools such as blood tests can be invasive and resource intensive. Our understanding of TB biology in wildlife is therefore limited to a small number of well-studied species. Testing of fecal samples using PCR is a noninvasive method that has been used to detect Mycobacterium bovis shedding amongst badgers, yet its utility more broadly for TB monitoring in wildlife is unclear.

Combining Analytical Approaches and Multiple Sources of Information to Improve Interpretation of Diagnostic Test Results for Tuberculosis in Wild Meerkats.

Diagnostic tests are used to classify individual animals' infection statuses. However, validating test performance in wild animals without gold standard tests is extremely challenging, and the issue is further complicated in chronic conditions where measured immune parameters vary over time. Here, we demonstrate the value of combining evidence from different diagnostic approaches to aid interpretation in the absence of gold standards, large sample sizes, and controlled environments.

An intergenerational androgenic mechanism of female intrasexual competition in the cooperatively breeding meerkat.

Female intrasexual competition can be intense in cooperatively breeding species, with some dominant breeders (matriarchs) limiting reproduction in subordinates via aggression, eviction or infanticide. In males, such tendencies bidirectionally link to testosterone, but in females, there has been little systematic investigation of androgen-mediated behaviour within and across generations. In 22 clans of wild meerkats (Suricata suricatta), we show that matriarchs 1) express peak androgen concentrations during late gestation, 2) when displaying peak feeding competition, dominance behaviour, and evictions, and 3) relative to subordinates, produce offspring that are more aggressive in early development.

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

In 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, , to investigate the different causes of group failure and the factors that drive these processes.

Diurnal oscillations in gut bacterial load and composition eclipse seasonal and lifetime dynamics in wild meerkats.

Circadian rhythms in gut microbiota composition are crucial for metabolic function, yet the extent to which they govern microbial dynamics compared to seasonal and lifetime processes remains unknown. Here, we investigate gut bacterial dynamics in wild meerkats (Suricata suricatta) over a 20-year period to compare diurnal, seasonal, and lifetime processes in concert, applying ratios of absolute abundance. We found that diurnal oscillations in bacterial load and composition eclipsed seasonal and lifetime dynamics.

Contributions of genetic and nongenetic sources to variation in cooperative behavior in a cooperative mammal.

The evolution of cooperative behavior is a major area of research among evolutionary biologists and behavioral ecologists, yet there are few estimates of its heritability or its evolutionary potential, and long-term studies of identifiable individuals are required to disentangle genetic and nongenetic components of cooperative behavior. Here, we use long-term data on over 1800 individually recognizable wild meerkats (Suricata suricatta) collected over 30 years and a multigenerational genetic pedigree to partition phenotypic variation in three cooperative behaviors (babysitting, pup feeding, and sentinel behavior) into individual, additive genetic, and other sources, and to assess their repeatability and heritability. In addition to strong effects of sex, age, and dominance status, we found significant repeatability in individual contributions to all three types of cooperative behavior both within and across breeding seasons.