1,721,247 research outputs found
Constraints and flexibility in mammalian social behaviour: introduction and synthesis
No full textThis paper introduces a Theme Issue presenting the latest developments in research on the interplay between flexibility and constraint in social behaviour, using comparative datasets, long-term field studies and experimental data from both field and laboratory studies of mammals. We first explain our focus on mammals and outline the main components of their social systems, focusing on variation within- and among-species in numerous aspects of social organization, mating system and social structure. We then review the current state of primarily ultimate explanations of this diversity in social behaviour. We approach the question of how and why the balance between behavioural flexibility and continuity is achieved by discussing the genetic, developmental, ecological and social constraints on hypothetically unlimited behavioural flexibility. We introduce the other contributions to this Theme Issue against this background and conclude that constraints are often crucial to the evolution and expression of behavioural flexibility. In exploring these issues, the enduring relevance of Tinbergen's seminal paper ‘On aims and methods in ethology’, with its advocacy of an integrative, four-pronged approach to studying behaviour becomes apparent: an exceptionally fitting tribute on the 50th anniversary of its publication
Social complexity: Patterns, processes, and evolution
No full textAnimal and human societies exhibit extreme diversity in the size, composition and cohesion of their social units, in the patterning of sex-specific reproductive skew, in the nature of parental care, in the form and frequency of cooperation and in their competitive regime, creating a diversity of socially complex societies. However, there is an ongoing debate about whether social complexity is a real, emergent property of a society or whether it only provides a conceptual framework for studying the diversity and evolution of societies. In this introduction to our topical collection, we identify three areas of current research addressing relevant challenges in the study of social complexity. First, previous studies have suffered from a lack of a common conceptual framework, including shared definitions, and existing measures of social complexity do not acknowledge its multiple components and dimensions. Second, most previous studies have ignored intraspecific variation, and the proximate and ultimate determinants of variation in social complexity, as well as their interactions, remain poorly known. Third, comparative studies of social complexity offer opportunities to explore its biological causes and correlates and but it is frequently difficult to identify the causal relationships involved and the development of general insights has been hampered by conceptual and methodological difficulties. In this paper, we briefly characterize these three challenges and offer guidance to the other contributions to this topical collection on social complexity by placing their key results in the context of these three topics
Cost of dispersal in a social mammal: body mass loss and increased stress
No full textDispersal is a key process influencing the dynamics of socially and spatially structured populations. Dispersal success is determined by the state of individuals at emigration and the costs incurred after emigration. However, quantification of such costs is often difficult, due to logistical constraints of following wide-ranging individuals. We investigated the effects of dispersal on individual body mass and stress hormone levels in a cooperative breeder, the meerkat (
Suricata suricatta
). We measured body mass and faecal glucocorticoid metabolite (fGCM) concentrations from 95 dispersing females in 65 coalitions through the entire dispersal process. Females that successfully settled lost body mass, while females that did not settle but returned to their natal group after a short period of time did not. Furthermore, dispersing females had higher fGCM levels than resident females, and this was especially pronounced during the later stages of dispersal. By adding information on the transient stage of dispersal and by comparing dispersers that successfully settled to dispersers that returned to their natal group, we expand on previous studies focusing on the earlier stages of dispersal. We propose that body mass and stress hormone levels are good indicators to investigate dispersal costs, as these traits often play an important role in mediating the effects of the environment on other life-history events and individual fitness.Swiss National Science Foundation http://dx.doi.org/10.13039/501100001711ERC Advance
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Population dynamics in meerkats, Suricata suricatta
Full text linkResearch on cooperatively breeding species has shown that their population dynamics can differ from those of conventional breeders. Populations of obligate cooperators are structured into social groups, the link between individual behaviour and population dynamics is mediated by group-level demography, and population dynamics can be strongly affected both by features of sociality per se and by resultant population structure. Notably, groups may be subject to inverse density dependence (Allee effects) that result from a dependence on conspecific helpers, but evidence for population-wide Allee effects is rare. To develop a mechanistic understanding of population dynamics in highly social species, we need to investigate how processes within groups, processes linking groups, and external drivers act and interact in space and time to produce observed patterns.
Here, I consider these issues as they relate to meerkats, Suricata suricatta, obligate cooperative breeders that inhabit southern Africa. I use mathematical and statistical models, in conjunction with long-term data from a wild meerkat population, to explore population dynamics, group dynamics, group demography, Allee effects, and territory dynamics in this species. I start out by examining broad-scale patterns, and then examine some of the constituent processes.
In Chapter Two, I assess the ability of phenomenological models, lacking explicit group structure, to describe population dynamics in meerkats, and I assess potential population-level Allee effects. I detect no Allee effect and conclude that explicit consideration of population structure will be key to understanding the mechanisms behind population dynamics in cooperatively breeding species.
In Chapter Three, I focus on annual group-level dynamics. Using phenomenological population models, modified to incorporate environmental conditions and potential Allee effects, I first investigate overall patterns of group dynamics and find support for only conventional density dependence that increases after years of low rainfall. To explain the patterns, I examine demographic rates and assess their contributions to overall group dynamics. While per-capita meerkat mortality is subject to an Allee effect, it contributes relatively little to observed variation, and other (conventionally density dependent) demographic rates – especially emigration – govern group dynamics.
In Chapter Four, I investigate group dynamics in more detail. I model demographic rates in different sex, age, and dominance classes on short timescales. Using these to build predictive and individual-based simulation models of group dynamics, I examine the demographic mechanisms responsible for declines in group size after dry years. Results reveal the delayed effect of environmental conditions, partially mediated by group structure.
In Chapter Five, I explore meerkat territorial patterns. Using mechanistic home-range models, I examine group interactions, habitat selection, territory formation, and territory movement. I use meerkat data to test proposed improvements to these models, and I use the model results to start building a picture of spatial processes in meerkat population dynamics, laying the groundwork for future research. This thesis highlights the role of environment and social structure in characterizing population dynamics. I discuss the implications of my findings for the population dynamics of cooperative breeders and for population dynamics generally, noting the importance of sub-populations in drawing conclusions about socially complex systems
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Extraterritorial prospecting and territory defence in cooperatively breeding meerkats
Full text linkIn group living animals where natal dispersal is delayed, prospecting allows individuals to asses their future dispersal and breeding opportunities and, in males of some species, may minimize the costs of delaying dispersal by enabling extra-group breeding while still resident in the natal group. While evidence of prospecting is widespread, comparatively little is known about the development of this behaviour and few studies have investigated the factors that may affect investment in prospecting, as it is typically difficult to monitor such mobile individuals. Prospectors typically encounter neighbouring groups during extraterritorial forays and resident individuals in these groups respond aggressively to approaches by extra- group males, given the potential loss in direct and indirect fitness that prospectors may inflict. As with prospecting behaviour, few studies have investigated the causes of individual differences in investment in repelling prospectors and measured the costs of such territory defence. In this dissertation, I exploit our ability to closely monitor prospecting males in meerkats, to investigate the causes of individual variation in extraterritorial prospecting effort and aggressive responses to prospector intrusions. In Chapter 3, I show that, as adults, heavier males invest more in prospecting than lighter ones, and that males time their forays in order to maximize their chances of dispersal, while minimizing the associated costs by prospecting when neighbouring groups are in close proximity to their own. In Chapter 4, I demonstrate that males that are heavier in early life start prospecting at a younger age and contribute less to helping later in life, than lighter males. In Chapter 5, I show that the threats posed by prospectors towards residents are associated with high investment by resident males in repelling intruders, which has measurable costs in terms of weight gain and cooperative contributions to offspring care. Finally, in Chapter 6, the experimental presentation of scent cues reveals that meerkats discriminate between resident and extra-group male scent cues, and that resident dominant males exhibit stronger responses to indirect evidence of prospectors than other group members
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Individual variation in cooperative behaviour in meerkats
Full text linkIndividual variation in cooperation is a striking yet poorly understood feature of many animal societies, particularly in cooperative breeders where individuals assist in the care of young that are not their own. While previous research on these systems has emphasised the plasticity of helping and how it varies with current environmental and social conditions, in this dissertation I examine how individual variation is constrained and influenced by trade-offs with other behaviours and experiences in early life. I demonstrate that variation in cooperative pup care (babysitting and provisioning) is consistent within individuals over time (Chapter 3). Provisioning is more consistent than babysitting, although the two behaviours are highly correlated within individuals. I then focus on the variation in helping that remains once current factors, such as condition, group size and food availability, are taken into account. In Chapter 4, I explore the possibility that variation in helping can be explained by personality, or consistency in behavioural traits such as exploration or risk-taking. I find little evidence for consistent individual differences in field measures of personality traits, however, with such behaviours instead being group-specific. Early social experiences are known to have important and lasting effects on later fitness and behaviour: in Chapter 5, I demonstrate that, in female meerkats only, growing up in a group with more helpers is correlated with reduced cooperation later in life. This result suggests the importance of future fitness in influencing current cooperative behaviour, as females raised in larger groups are more likely to attain dominance. Finally, I examine the extent to which vocal communication between carers and young is influenced by variation in contributions to cooperation. Females are more sensitive to increased begging rate (Chapter 6), which reflects general sex differences in cooperative behaviour. Carers modify their vocalizations but not their foraging behaviour in the presence of pups, and the way in which they vocalize during provisioning events suggests these calls serve to increase efficiency of prey transfer (Chapter 7)
The influence of stress hormones and aggression on cooperative behaviour in subordinate meerkats
Full text linkIn cooperative breeders, aggression from dominant breeders directed at subordinates may raise subordinate stress hormone (glucocorticoid) concentrations. This may benefit dominants by suppressing subordinate reproduction but it is uncertain whether aggression from dominants can elevate subordinate cooperative behaviour, or how resulting changes in subordinate glucocorticoid concentrations affect their cooperative behaviour. We show here that the effects of manipulating glucocorticoid concentrations in wild meerkats (Suricata suricatta) varied between cooperative activities as well as between the sexes. Subordinates of both sexes that were treated with a glucocorticoid receptor antagonist (mifepristone) exhibited significantly more pup protection behaviour (‘babysitting’) compared to those treated with glucocorticoids (cortisol) or controls. Females treated with mifepristone had a higher probability of exhibiting pup food provisioning (‘pupfeeding’) compared to those treated with cortisol. In males, there were no treatment effects on the probability of pupfeeding, but those treated with cortisol fed a higher proportion of the food they found to pups than those treated with mifepristone. We also used 19 years of behavioural data to show that dominant females did not increase the frequency with which they directed aggression at subordinates at times when their need for assistance was highest. Our results suggest that it is unlikely that dominant females manipulate the cooperative behavior of subordinates through the effects of aggression on their glucocorticoid levels and that the function of aggression directed at subordinates is probably to reduce the probability they will breed
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