Cooperative Breeding Research Articles

Small-scale land-use change effects on breeding success in a desert-living social bird

Abstract Human villages in deserts can provide resources in an otherwise stark environment, potentially buffering against extreme environmental conditions. It is thus expected that breeding within these villages would result in higher fitness. However, choosing to raise offspring in these resource-rich environments may have unintended negative consequences. Here, we studied the breeding success of a cooperative breeding bird nesting in habitats with different levels of human disturbance—the Arabian babbler (Argya squamiceps), in the Negev desert of Israel. We recorded 42 breeding attempts from 15 groups between March and July 2022. We examined overall breeding success, brood size, and causes of nest failure. When nestlings were 6 days old, we also calculated daily change in body mass and adult provisioning rate. We found that despite higher resource abundance in villages, proximity to villages did not affect provisioning rate, and nestlings gained less mass at higher temperatures for all nests. Currently, there is no evidence that human villages are providing oases of resources for nesting babblers. Further, various conservation interventions (e.g., encouraging residents to keep cats indoors) could improve babblers’ overall fitness. Ultimately, we highlight how, for some desert specialists, additional resources provided by humans may not do enough to counter potential negative effects.

Limited evidence of biased offspring sex allocation in a cavity-nesting conspecific brood parasite.

Sex allocation theory predicts that mothers should bias investment in offspring toward the sex that yields higher fitness returns; one such bias may be a skewed offspring sex ratio. Sex allocation is well-studied in birds with cooperative breeding systems, with theory on local resource enhancement and production of helpers at the nest, but little theoretical or empirical work has focused on birds with brood parasitic breeding systems. Wood ducks (Aix sponsa) are a conspecific brood parasite, and rates of parasitism appear to increase with density. Because female wood ducks show high natal philopatry and nest sites are often limiting, local resource competition (LRC) theory predicts that females should overproduce male offspring-the dispersing sex-when competition (density) is high. However, the unique features of conspecific brood parasitism generate alternative predictions from other sex allocation theory, which we develop and test here. We experimentally manipulated nesting density of female wood ducks in 4 populations from 2013 to 2016, and analyzed the resulting sex allocation of >2000 ducklings. In contrast to predictions we did not find overproduction of male offspring by females in high-density populations, females in better condition, or parasitic females; modest support for LRC was found in overproduction of only female parasitic offspring with higher nest box availability. The lack of evidence for sex ratio biases, as expected for LRC and some aspects of brood parasitism, could reflect conflicting selection pressures from nest competition and brood parasitism, or that mechanisms of adaptive sex ratio bias are not possible.

Social support during pregnancy and the risk of postpartum depression in Polish women: A prospective study

Social support has been proposed as an important determinant of women's physical and emotional well-being during pregnancy and after childbirth. Our study aimed to examine the association between the risk of postpartum depression (PPD) and perceived social support during pregnancy. A web-based prospective study survey was conducted among Polish women. The level of social support was measured with the Berlin Social Support Scales during pregnancy. Four weeks after the birth the risk of PPD was assessed using the Edinburgh Postpartum Depression Scale. Data from 932 mothers aged 19–43 (mean 30.95; SD 3.83) were analyzed using multinomial logistic regression. Higher perceived available support (emotional and instrumental), currently received support (emotional, instrumental and informational), satisfaction with the support, and sum of score were all associated with lower risk of PPD, after controlling for selected covariates (woman's age, socioeconomic status, parity status, place of residency, education, child's Apgar score, type of delivery, complications during birth, kin assisting the labor, breastfeeding). Our results suggest that the more social support the pregnant woman receives, the lower is her risk of PPD. Since humans evolved as cooperative breeders, they are inherently reliant on social support to raise children and such allomaternal help could improve maternal well-being.

Investment by maternal grandmother buffers children against the impacts of adverse early life experiences

Exogenous shocks during sensitive periods of development can have long-lasting effects on adult phenotypes including behavior, survival and reproduction. Cooperative breeding, such as grandparental care in humans and some other mammal species, is believed to have evolved partly in order to cope with challenging environments. Nevertheless, studies addressing whether grandparental investment can buffer the development of grandchildren from multiple adversities early in life are few and have provided mixed results, perhaps owing to difficulties drawing causal inferences from non-experimental data. Using population-based data of English and Welsh adolescents (sample size ranging from 817 to 1197), we examined whether grandparental investment reduces emotional and behavioral problems in children resulting from facing multiple adverse early life experiences (AELEs), by employing instrumental variable regression in a Bayesian structural equation modeling framework to better justify causal interpretations of the results. When children had faced multiple AELEs, the investment of maternal grandmothers reduced, but could not fully erase, their emotional and behavioral problems. No such result was observed in the case of the investment of other grandparent types. These findings indicate that in adverse environmental conditions the investment of maternal grandmothers can improve child wellbeing.

First detailed report of cooperative breeding in red-billed blue magpie (Urocissa erythrorhyncha) in central China

Abstract The cooperative breeding system of birds is an ideal model for studying and exploring social evolution in animals. However, a basic question, i.e., how many cooperative-breeding bird species exist in the world, remains controversial due to the lack of accumulated knowledge of the natural history of many birds, which prevents a generalized understanding of the evolution of cooperative breeding in birds and challenges the accuracy of results in many comparative studies. In this paper, we provide the first evidence of cooperative breeding in red-billed blue magpies (Urocissa erythrorhyncha). Moreover, we document and discuss potential relationships between cooperative breeding and nest predation, brood parasitism and breeding performance in U. erythrorhyncha. These findings about cooperative breeding in red-billed blue magpie will lay a foundation for further research on this species’ sociality and provide useful insights into the evolution of cooperative breeding and other social systems in birds.

Ambrosia beetles adjust dispersal preferences to their degree of exhaustion

Abstract Delayed dispersal of sexually mature offspring is a fundamental component of cooperative breeding in fungus farming ambrosia beetles. These beetles dwell in logs of recently deceased trees, where female offspring postpone reproduction and invest in alloparental care before dispersing to found a new nest. The wood quality affects investment of adult offspring in alloparental care and hence the breeder's reproductive success. This raises the question of whether dispersing breeders choose habitats strategically to optimise breeding prospects and modulate their offspring's helping propensity. To answer this question, here we tested experimentally whether during dispersal, Xyleborinus saxesenii Ratzeburg (Coleoptera: Scolytinae) uses olfactory cues emitted by mutualistic or pathogenic fungi as an information source on prospective habitat quality. As the mutualistic relationship between the fungi and beetles is obligate, fungus scent should provide a reliable source of information on habitat quality, indicating prior successful colonisation by conspecifics. We found no evidence for direct pathogen avoidance. However, the beetles clearly responded to scent of their mutualistic fungi, dependent on dispersal state. At the onset of dispersal, females avoided the scent of fungus mutualists, whereas they were attracted to them after being exhausted by an experimentally prolonged dispersal time. The observed change of preference during dispersal suggests that beetles freshly emerging from their home gallery may choose pristine habitat by avoiding mutualist scent. This might help to avoid competition with conspecifics and potential pathogen and parasite cross contamination. Exhausted beetles, however, may accept these risks and choose successfully colonised habitat to avoid starvation. State‐dependent adjustment of habitat preferences may be exhibited also in other economically impactful bark and ambrosia beetles, which prompts further study of the olfactory cues used by these beetles during dispersal.

Interplay of cooperative breeding and predation risk on egg allocation and reproductive output.

Predation risk can influence behavior, reproductive investment, and, ultimately, individuals' fitness. In high-risk environments, females often reduce allocation to reproduction, which can affect offspring phenotype and breeding success. In cooperative breeders, helpers contribute to feed the offspring, and groups often live and forage together. Helpers can, therefore, improve reproductive success, but also influence breeders' condition, stress levels and predation risk. Yet, whether helper presence can buffer the effects of predation risk on maternal reproductive allocation remains unstudied. Here, we used the cooperatively breeding sociable weaver Philetairus socius to test the interactive effects of predation risk and breeding group size on maternal allocation to clutch size, egg mass, yolk mass, and yolk corticosterone. We increased perceived predation risk before egg laying using playbacks of the adults' main predator, gabar goshawk (Micronisus gabar). We also tested the interactive effects of group size and prenatal predator playbacks on offspring hatching and fledging probability. Predator-exposed females laid eggs with 4% lighter yolks, but predator-calls' exposure did not clearly affect clutch size, egg mass, or egg corticosterone levels. Playback-treatment effects on yolk mass were independent of group size, suggesting that helpers' presence did not mitigate predation risk effects on maternal allocation. Although predator-induced reductions in yolk mass may decrease nutrient availability to offspring, potentially affecting their survival, playback-treatment effects on hatching and fledging success were not evident. The interplay between helper presence and predator effects on maternal reproductive investment is still an overlooked area of life history and physiological evolutionary trade-offs that requires further studies.

Evolution of delayed dispersal with group size effect and population dynamics

Individuals delay natal dispersal for many reasons. There may be no place to disperse to; immediate dispersal or reproduction may be too costly; immediate dispersal may mean that the individual and their relatives miss the benefits of group living. Understanding the factors that lead to the evolution of delayed dispersal is important because delayed dispersal sets the stage for complex social groups and social behavior. Here, we study the evolution of delayed dispersal when the quality of the local environment is improved by greater numbers of individuals (e.g., safety in numbers). We assume that individuals who delay natal dispersal also expect to delay personal reproduction. In addition, we assume that improved environmental quality benefits manifest as changes to fecundity and survival. We are interested in how do the changes in these life-history features affect delayed dispersal. We use a model that ties evolution to population dynamics. We also aim to understand the relationship between levels of delayed dispersal and the probability of establishing as an independent breeder (a population-level feature) in response to changes in life-history details. Our model emphasizes kin selection and considers a sexual organism, which allows us to study parent–offspring conflict over delayed dispersal. At evolutionary equilibrium, fecundity and survival benefits of group size or quality promote higher levels of delayed dispersal over a larger set of life histories with one exception. The exception is for benefits of increased group size or quality reaped by the individuals who delay dispersal. There, the increased benefit does not change the life histories supporting delay dispersal. Next, in contrast to previous predictions, we find that a low probability of establishing in a new location is not always associated with a higher incidence of delayed dispersal. Finally, we find that increased personal benefits of delayed dispersal exacerbate the conflict between parents and their offspring. We discuss our findings in relation to previous theoretical and empirical work, especially work related to cooperative breeding.

Chemical Profiles Differ between Communal Breeding Groups in a Highly Social Bird.

AbstractGregarious species must distinguish group members from nongroup members. Olfaction is important for group recognition in social insects and mammals but rarely studied in birds, despite birds using olfaction in social contexts from species discrimination to kin recognition. Olfactory group recognition requires that groups have a signature odor, so we tested for preen oil and feather chemical similarity in group-living smooth-billed anis (Crotophaga ani). Physiology affects body chemistry, so we also tested for an effect of egg-laying competition, as a proxy for reproductive status, on female chemical similarity. Finally, the fermentation hypothesis for chemical recognition posits that host-associated microbes affect host odor, so we tested for covariation between chemicals and microbiota. Group members were more chemically similar across both body regions. We found no chemical differences between sexes, but females in groups with less egg-laying competition had more similar preen oil, suggesting that preen oil contains information about reproductive status. There was no overall covariation between chemicals and microbes; instead, subsets of microbes could mediate olfactory cues in birds. Preen oil and feather chemicals showed little overlap and may contain different information. This is the first demonstration of group chemical signatures in birds, a finding of particular interest given that smooth-billed anis live in nonkin breeding groups. Behavioral experiments are needed to test whether anis can distinguish group members from nongroup members using odor cues.

Costs and benefits of solitary living in mammals

AbstractWhile for decades behavioural ecologists have studied the costs and benefits of group living, solitary living has received little attention. Instead, it was assumed to be the default stage from which sociality evolved. Mammals underwent around 200 million years of social evolution, with a few species evolving communal or cooperative breeding in harsh environments. Other mammal species are successful with solitary living in exactly the same and many other environments, indicating that solitary living is beneficial under many environmental conditions. Comparative studies on mammals indicate that solitary living might not be the ancestral but a derived state. Solitary living in mammals is less common than previously believed, occurring in 22% of the studied species. Here, we review costs and benefits of solitary living in mammals. We found very few studies that considered solitary living and show important future avenues of research based on the factors that are important for the evolution of group living. We also emphasize that a solitary form of social organization does not imply an unsocial lifestyle: solitary mammals typically have non‐random but individualized social interactions with their neighbours, indicating important social structure.

Hunter-Gatherer children's close-proximity networks: Similarities and differences with cooperative and communal breeding systems.

Among vertebrates, allomothering (non-maternal care) is classified as cooperative breeding (help from sexually mature non-breeders, usually close relatives) or communal breeding (shared care between multiple breeders who are not necessarily related). Humans have been described with both labels, most frequently as cooperative breeders. However, few studies have quantified the relative contributions of allomothers according to whether they are (a) sexually mature and reproductively active and (b) related or unrelated. We constructed close-proximity networks of Agta and BaYaka hunter-gatherers. We used portable remote-sensing devices to quantify the proportion of time children under the age of 4 spent in close proximity to different categories of potential allomother. Both related and unrelated, and reproductively active and inactive, campmates had substantial involvement in children's close-proximity networks. Unrelated campmates, siblings and subadults were the most involved in both populations, whereas the involvement of fathers and grandmothers was the most variable between the two populations. Finally, the involvement of sexually mature, reproductively inactive adults was low. Where possible, we compared our findings with studies of other hunter-gatherer societies, and observed numerous consistent trends. Based on our results we discuss why hunter-gatherer allomothering cannot be fully characterised as cooperative or communal breeding.

Twenty-four-year investigation of the reproductive biology of Glis glis in England (Rodentia: Gliridae)

Nest boxes were used to monitor a population of edible dormice (Glis glis) for 24 years. Details were recorded of reproductive condition, age and co-habitation by ca. 10,000 tagged individuals. Age at first breeding, periodic failure to breed, ‘absenteeism’ among adults, changing litter size with growth of young, survival rates and lifetime reproductive output were documented. The proportion of communal breeders and their kinship was examined as well as the occurrence of breeding by subadults. Life strategy and potential benefits of seasonal and annual behaviour are discussed.

Cooperative breeding alters physiological and behavioral responses to habitat fragmentation

Animals respond to habitat alteration with changes in their behavior and physiology. These changes determine individual performance and thus precede changes in population size. They are therefore hypothesized to provide important insights into how animals cope with environmental change. Here, we investigated physiological and behavioral responses of a cooperatively breeding bird, the placid greenbul (Phyllastrephus placidus), in a severely fragmented tropical biodiversity hotspot and combined these data with remotely sensed (LiDAR) environmental data. We found that individuals had increased glucocorticoid hormone levels when breeding in territories with low native canopy cover or located within small fragments. However, when breeding with the help of subordinates, breeders in low quality territories had similar glucocorticoid levels as those in higher quality territories. Our study shows that sociality may impact how well animals cope with environmental change and contributes to our understanding of the role of glucocorticoid physiology and behavior in response to anthropogenic change.

Natal dispersal, philopatry and cooperative breeding in Eastern Yellow Robin Eopsaltria australis

ABSTRACT Delayed natal dispersal is thought to have evolved in response to survival benefits of philopatry and group formation under environmental and/or demographic constraints, with kin selection subsequently promoting the emergence of cooperative breeding behaviours. We studied sociality and natal and breeding dispersal of a colour-banded population of Eastern Yellow Robin Eopsaltria australis over 10 years to better understand the evolution of facultative cooperative breeding in this long-lived, territorial songbird. Breeding group size averaged 3.08 (range 2–6) adults and 82% of helpers were males. All male young delayed dispersal to help one or both parents (82.1%), another first order relative (12.5%) or other relatives (5.4%) for between one and four years before establishing as a dominant breeder. The social relationships of female helpers was confirmed in only two instances, with the helper being the daughter of the breeding pair. Helpers significantly increased annual productivity, which averaged 1.44 (95% confidence intervals: 1.07–1.81) with no helpers and 2.04 (95% confidence intervals: 1.74–2.34) with helpers present. Male young were highly philopatric; most either inherited the natal territory or budded off a portion of the natal territory, and none dispersed more than one territory away. Most females appeared to disperse further after reaching independence to become floaters. Breeding dispersal was limited to females, who dispersed after either divorce or to avoid incest once a son inherited the territory. These results confirm that Eastern Yellow Robin helpers likely gain indirect fitness benefits from helping.

Best of both worlds? Helpers in a cooperative fairy-wren assist most to breeding pairs that comprise a potential mate and a relative.

In cooperative breeders, individuals forego independent reproduction and help others raise offspring. Helping is proposed to be driven by indirect benefits from raising relatives, and/or direct benefits from raising additional recruits or helping itself. We propose that consideration of social context is also important, in particular the characteristics of the breeding pair: helping may also serve to lighten the workload of-or maintain social bonds with-breeders (e.g. kin, potential mates) who in turn can offer benefits to helpers (e.g. prolonged nepotism, future mating, future production of relatives). Here, we test this hypothesis, while controlling for potential direct and indirect benefits from raising offspring, in purple-crowned fairy-wrens (Malurus coronatus) exhibiting variation in social group composition, and thus, breeder value. We show that helper provisioning rates to the nest were explained by characteristics of breeders that helpers assisted, rather than benefits from raising offspring. The presence of at least one related breeder was a prerequisite to help, but helpers provisioned most if assisting a relative and potential mate. Neglecting to take group composition into account would have led to misinterpretation of our results. A comprehensive understanding of the evolution of cooperative breeding hence requires nuanced consideration of social context.

Are sentinels rewarded by their groupmates? A study in a cooperative breeder

Are sentinels rewarded by their groupmates? A study in a cooperative breeder

Time allocation to balance group living trade-offs in Ethiopian wolves

Living in groups requires individuals to make trade-offs to maintain group cohesion and enhance individual and inclusive fitness. One way animals can do this is by adjusting the way they allocate time to different behaviours. Ethiopian wolves (Canis simensis) are highly social, cooperative breeders (only the dominant pair breeds and all members help to raise the litter), but solitary foragers. To investigate how Ethiopian wolves allocate their time to balance the costs and benefits of group living, we analysed the time budgets of 47 wolves across six behaviours. We hypothesized that group size and territory density would affect wolves’ time allocation between solitary (foraging) and communal activities (patrolling and socialising) differently in relation to their age, dominance status or sex, and whether the pack was breeding or not. Our results showed that the time spent foraging alone increased at higher territorial densities, as expected from interference competition, particularly among subadults, subordinates and individuals in breeding packs. On the other hand, as pack size increased, adult wolves spent a lower proportion of time patrolling, while the time spent socialising did not change. Living in groups reduces the costs of communal activities, but crowded territories come at the cost of interference competition for solitary foragers, particularly the animals further down the hierarchy ranks, subadults, and individuals investing in breeding. Such trade-offs could impose an upper limit to group size and population growth within a limited space. Furthermore, anthropogenic disturbance could alter the balance of social and solitary activities of Ethiopian wolves.

Planetary Rifting and the Paleogeography of Care

With their specter of intergenerational betrayal, global environmental crises increasingly entangle politics with matters of care, attachment, and love—especially the unconditional bonds we are so often assumed to share with our offspring. As a contribution to the nascent field of paleoenvironmental humanities, this article’s approach to questions of care and responsibility turns from future horizon-scanning to the realm of human origins. It focuses on two broad sets of paleo stories that share a concern with rifts or stress points that complicate originary events and scenes. The first of these is a family of hypotheses which propose that pivotal evolutionary developments took place in the climatically variable and tectonically active terrain of the East African Rift. The second is the cooperative breeding hypothesis, which contends that communally distributed childcare arrangements are a definitive characteristic of the genus Homo, while also highlighting the conditionality and precariousness of human intergenerational care. Taken together, these approaches point to deep-seated fault lines running through both our home planet and our own psychosocial being. Confronting these rifts might help loosen the hold of notions of ontological reconciliation between humans and nature that risk exacerbating the very problems they seek to resolve, while also helping us to seek attachments that are more conducive to living with and through earthly volatility.

For a paleogeography of childcare: Infant-carrying technics on a dynamic planet

What happens to the mundane practice of carrying infants if we situate it in the context of intensifying climate change and a deep past of geoclimatic instability? This article takes the resurgence of baby slings in the United Kingdom as an entry point into the deep, evolutionary history of child carrying and, in this way, as a prompt for an experiment in repurposing the field of paleogeography. This involves viewing the technics of the baby sling both as an aid to mobility and as a materialization of care relations. We extend this approach with the help of the cooperative breeding hypothesis which contends that communally shared childcare has been pivotal to human evolution and survival. We also draw upon theories that attend to the geologically dynamic landscapes of East Africa where humans evolved and the impact of long-term instabilities of global climate. Fusing these approaches while also accounting for critiques of evolutionary thought, we make a case that infant-carrying slings help facilitate a confident, outward-facing orientation both to worlds of complex social interactivity and to an Earth which is rifted, variegated and dynamic.

Territory inheritance and the evolution of cooperative breeding in the acorn woodpecker

Territory inheritance and the evolution of cooperative breeding in the acorn woodpecker