Conflict In Animal Societies Research Articles

Group size and the resolution of insider–outsider conflict in animal societies

Group size and the resolution of insider–outsider conflict in animal societies

Reproductive conflict resolution in cooperative breeders

Abstract Female infanticide is common in animal societies where groups comprise multiple co-breeding females. To reduce the risk that their offspring are killed, mothers can synchronize breeding and pool offspring, making it hard for females to avoid killing their own young. However, female reproductive conflict does not invariably result in reproductive synchrony, and we lack a general hypothesis explaining the variation in conflict resolution strategies seen across species. Here, we investigate the fitness consequences of birth timing relative to other females and the prevalence of birth synchrony in cooperatively breeding Kalahari meerkats (Suricata suricatta). We show that, although there would be substantial benefits to females in synchronizing births and reducing their risk of infanticide, birth synchrony is rare. Since precise breeding synchrony has evolved in a related species with similar infanticidal female reproductive conflict, its absence in meerkats requires an evolutionary explanation. We therefore explore the costs and benefits of synchronizing breeding in two theoretical models, each of which contrasts synchrony with an alternative reproductive strategy: (i) breeding opportunistically and accepting fitness losses to infanticide or (ii) suppressing the reproduction of others to prevent infanticide. Our models show that the costs of synchrony constrain its development if subordinates breed infrequently, and that selection instead favors the suppression of subordinate reproduction by the dominant and opportunistic reproduction by subordinates. Together, our results suggest that the resolution of reproductive conflict in animal societies is shaped by differential breeding propensities among female group members, leading to divergent conflict resolution strategies even in closely related species.

Queen Longevity and Fecundity Affect Conflict with Workers over Resource Inheritance in a Social Insect.

Resource inheritance is a major source of conflict in animal societies. However, the assumptions and predictions of models of conflict over resource inheritance have not been systematically tested within a single system. We developed an inclusive fitness model for annual eusocial Hymenoptera that predicts a zone of conflict in which future reproductive workers are selected to enforce nest inheritance before the queen is selected to cede the nest. We experimentally tested key elements of this model in the bumblebee Bombus terrestris. In colonies from which queens were sequentially removed, queen tenure was significantly negatively associated with worker male production, confirming that workers gain direct fitness by usurping the queen. In unmanipulated colonies, queen fecundity decreased significantly over the latter part of the colony cycle, confirming that workers' indirect fitness from maintaining queens declines over time. Finally, in an experiment simulating loss of queen fecundity by removal of queens' eggs, worker-to-queen aggression increased significantly and aggressive workers were significantly more likely to become egg layers, consistent with workers monitoring queen fecundity to assess the net benefit of future reproduction. Overall, by upholding key assumptions and predictions of the model, our results provide novel empirical support for kin-selected conflict over resource inheritance.

The four elements of within-group conflict in animal societies: an experimental test using the clown anemonefish, Amphiprion percula

Conflicts of interest are part and parcel of living in a social group, yet actual conflict can be rare in established groups. Within limits, individuals can maximize the benefits of group living by resolving conflict with other group members. Thus, understanding what causes conflict, what determines its outcome, and how it is resolved holds the key to understanding the evolution and maintenance of sociality. Here, we investigate these questions using the clown anemonefish Amphiprion percula. Clownfish live in groups composed of a breeding pair and zero to four non-breeders that queue for breeding positions. Within groups, there is potential conflict over rank yet actual conflict is very rare. We staged contests in aquaria between pairs of non-breeding individuals over access to a key resource (an anemone), analogous to contests that would occur at the onset of group formation in the wild. The initial size ratio between individuals tended to predict the intensity, and predicted the outcome and resolution of conflict: conflict intensity was greater when individuals were more similar in size; the probability of the smaller individual winning was greater when individuals were more similar in size; and the loser of the contest grew less than the winner when individuals were more similar in size. These results provide a critical test of foundational assumptions upon which our understanding of clownfish and other fish societies has been built. More generally, the results show that one of the simplest and most effective ways for animals to resolve conflict is to modify the phenotype that triggers conflict. The study provides a critical test of the foundational assumptions on which our understanding of conflict and its resolution in animal societies has been built. Importantly, this study highlights that four elements of conflict must be investigated for a complete understanding of societal maintenance, and broadens the taxonomic basis of empirical research of conflict (focused on terrestrial organisms) by examining these four elements in a fish society. Specifically, the study demonstrates the key importance of relative body size (competitive ability) in determining conflict intensity, contest outcome, and subsequent conflict resolution via the regulation of subordinate growth rates. The occurrence of strategic subordinate growth regulation is intriguing because it shows that the simplest and most effective way for animals to resolve conflict is to modify the phenotypes that trigger conflict in the first place.

Group Size and Social Conflict in Complex Societies

Conflicts of interest over resources or reproduction among individuals in a social group have long been considered to result in automatic and universal costs to group living. However, exploring how social conflict varies with group size has produced mixed empirical results. Here we develop a model that generates alternative predictions for how social conflict should vary with group size depending on the type of benefits gained from being in a social group. We show that a positive relationship between social conflict and group size is favored when groups form primarily for the benefits of sociality but not when groups form mainly for accessing group-defended resources. Thus, increased social conflict in animal societies should not be viewed as an automatic cost of larger social groups. Instead, studying the relationship between social conflict and the types of grouping benefits will be crucial for understanding the evolution of complex societies.

Longevity suppresses conflict in animal societies

Models of social conflict in animal societies generally assume that within-group conflict reduces the value of a communal resource. For many animals, however, the primary cost of conflict is increased mortality. We develop a simple inclusive fitness model of social conflict that takes this cost into account. We show that longevity substantially reduces the level of within-group conflict, which can lead to the evolution of peaceful animal societies if relatedness among group members is high. By contrast, peaceful outcomes are never possible in models where the primary cost of social conflict is resource depletion. Incorporating mortality costs into models of social conflict can explain why many animal societies are so remarkably peaceful despite great potential for conflict.

Absence of nepotism toward imprisoned young queens during swarming in the honey bee

Nepotism is an important potential conflict in animal societies. However, clear evidence of nepotism in the rearing of queens in social insects is limited and controversial. In the honey bee, Apis mellifera, multiple mating by queens leads to the presence of many patrilines within each colony. When the colonies reproduce through swarming, workers rear a number of new queens, only a few of which will ultimately head a colony. Workers can potentially increase their inclusive fitness by nepotistically favoring full-sister over half-sister queens during the queen rearing and elimination process. Most studies have focused on interactions between workers and immature queens (eggs and larvae) or adult queens who have exited their queen cells. However, adult queens often remain in their queen cells for up to 1 week after emerging from their pupa. In this situation, workers prevent the queens from emerging, feed them, and protect them from other emerged queens. This stage in queen rearing is therefore one in which nepotism could occur. The current study is the first to investigate the kinship between workers and adult queens who have not emerged from their queen cells. We observed the full suite of behaviors expected during this phase of colony reproduction. Although there was no evidence for nepotism in the worker?queen interactions, there was a nonrandom distribution across patrilines of the workers interacting with the queen cells. In addition, in one colony we found differential treatment of fostered (nonkin)-queen cells.

Reproductive conflict in animal societies: hierarchy length increases with colony size in queenless ponerine ants

Dominance interactions determine reproductive status in many animal societies, including many cooperatively breeding vertebrates and eusocial Hymenoptera without queen-worker dimorphism. Typically, the dominant individual monopolises reproduction, and subordinates behave like helpers. In Dinoponera queenless ants, workers are totipotent females and can potentially reproduce, yet only the top-ranking worker actually reproduces. Individual workers ranked immediately below the dominant breeder worker (gamergate) are hopeful reproductives. Whether or not a worker benefits from joining the hierarchy of high-ranking workers depends on the trade-off between the probability of becoming dominant and reproducing directly, and the colony-level cost of an additional lazy high ranker. Inclusive fitness models predict that the length of the dominance hierarchy depends on relatedness, colony size, and the linearity of the hierarchy. Here, we test the effect of colony size by comparing hierarchy length among three species that differ in colony size (Dinoponera australis: median=14 workers, quartiles=10 and 19 workers; D. gigantea: median=41, quartiles=33 and 74; D. quadriceps: median=78, quartiles=55 and 90). Although difficulties in defining where the hierarchy ends hamper comparisons, the results are in broad agreement with the predictions. Hierarchies are close to the predicted lengths and are longer in species with larger colonies (one, three and three workers in the three species in order from smallest to largest colony vs two, three and four predicted). These conclusions are further supported by determining Kokko and Lindstrom's λ index of skew, which is smaller (i.e. characteristic of a longer hierarchy) in species with larger colonies.

Survival Strategies: Cooperation and Conflict in Animal Societies

R. Gadagkar 1997. Survival Strategies: Cooperation and Conflict in Animal Societies. Harvard University Press, Cambridge, Massachusetts, x + 196 pp. ISBN 0-674-17055-5, price (hardcover), $22.00. This book describes a number of instances in which social behavior can be explained as a by-product of genetic relatedness. The intended readership is avowed by the author to be “ordinary people from all walks of life” (p. ix), and the book's organization, tone, and style reflect this intent. The examples, too, are drawn more for illustrative purposes than for a synthesis or a comprehensive treatment. Perhaps as a result of this intended readership, the book is thin for someone working on problems of evolutionary ecology. Unfortunately, inconsistencies in tone and levels of explanation may make it less than satisfying for the interested nonecologist as well. More seriously, some of the language describing natural selection is reifying, which does a disservice to Darwin and to people who do not fully understand the mechanisms causing natural selection. Outwardly, the organization is straightforward enough. Gadagkar begins with 4 chapters of definitions: social animals, the basics of natural selection and genetic relationships, and an outline of cooperation, altruism, selfishness, and spite. Through the next 5 chapters, Gadagkar uses a series of examples, often returning repeatedly to the same systems, to deal with topics such as inclusive fitness, Hamilton's Rule, nepotism, kin recognition, the Prisoner's dilemma, tit-for-tat, animal consciousness, and situations in which individuals are in reproductive conflict. The final brief chapter summarizes a few conclusions and paints a simplistic view of future research areas. In a short book, this coverage of topics is impressive. Gadagkar has chosen examples from a variety of taxa (mostly social insects, but also sticklebacks, bee-eaters, moths, chimpanzees, crickets, vampire bats, house mice, and others). This diversity of taxa is a strength of the book because these animals do display interesting social behavior. Given the intent of the book, most …

Reproductive skew and the threat of eviction: a new perspective

Most recent models of the partitioning of reproduction attempt to explain patterns of skew on the assumption that dominant individuals have complete control over breeding opportunities within the group, but may nevertheless concede a share of direct reproduction to subordinates as an incentive to remain peacefully in the association. Although these models may be applicable to some animal societies, we argue that they fail to provide a comprehensive theory of skew. Instead, we suggest that subordinates may often be able to claim unsanctioned reproduction for themselves, but will be forced to exercise a degree of reproductive restraint lest they incite ejection by the dominant. Reproductive skew, in other words, may reflect the threat of ejection (inducing subordinate restraint) rather than the threat of subordinate departure (inducing reproductive concessions by dominants). We present a simple ESS model of reproductive skew under these circumstances, which demonstrates that a shift in emphasis from reproductive concessions by dominants to reproductive restraint on the part of subordinates, radically alters the predictions of skew models. High group productivity, high relatedness and (when group members are related) strong ecological constraints are all expected to lead to reduced skew (the opposite conclusions to those of previous, concession-based analyses). The reason is that these factors reduce the benefits (or increase the costs) of ejection to the dominant, who therefore does best to tolerate more subordinate reproduction.

Survival Strategies: Cooperation and Conflict in Animal Societies.Raghavendra Gadagkar

Previous articleNext article No AccessNew Biological BooksSurvival Strategies: Cooperation and Conflict in Animal Societies. Raghavendra Gadagkar Patricia Adair GowatyPatricia Adair Gowaty Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 73, Number 4Dec., 1998 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/420515 Views: 3Total views on this site Copyright 1998 The University of ChicagoPDF download Crossref reports no articles citing this article.

Survival strategies: cooperation and conflict in animal societies

Tasmanian hens have two husbands, cellular slime molds commit suicide, vampire bats will share food with hungry fellow bats and hanuman langurs commit infanticide. Why creatures great and small behave in such ways is explained in this account of the evolutionary foundations of animal social behaviour. Only in recent years have biologists and ethologists begun to apply evolutionary thinking to the study of animal societies. This book presents the some of these findings, with insights into the myriad strategies that animals have developed to perpetuate their kind. Raghavendra Gadagkar explores the strategies of cooperation and conflict adopted by animals from the lordly lion to the primitive wasp worker as they choose mates, raise their young, communicate with others, and establish the division of labour necessary to feed and protect the group and safeguard their territory. Whether focusing on the birds or the bees, this book offers both descriptions and explanations of many different behaviours encountered in the animal world: why a ground squirrel will sound an alarm - even risk its own safety - to warn fellow squirrels of impending danger; why weaver ant larvae donate silk for nest building; why house mice raise their offspring in a communal nursery; and how animals can recognize the relatives they want to favour or avoid. Illustrated with both photographs and explanatory diagrams, this tour of the social world of animals will inform readers curious about the motivations behind the range of activity in the animal kingdom.