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Context: Abiotic filtering, including environmental and dispersal filtering, is frequently observed resulting in reduced diversity and more similar species assemblages following habitat fragmentation. Nonetheless, the significance of competitive exclusion is often underestimated. Objectives: We investigated the dominant assembly process among termite communities on land-bridge islands, focusing on species known for their high territoriality. We hypothesized that competitively superior species tend to dominate more favorable habitats, such as larger and less isolated islands. Consequently, we anticipated lower diversity and greater similarity in species assemblages than would be expected. Methods: Termite communities were surveyed using standardized transects on 24 islands. We quantified the standardized effects of island area and isolation on taxonomic, phylogenetic and functional diversity by comparing observed patterns with randomly generated communities (i.e., stochastic process). A phylogenetic generalized linear mixed model (PGLMM) was conducted to examine species-specific responses to environmental factors and competition intensity (i.e., heterospecific abundance). Results: We found that taxonomic, phylogenetic and functional diversity were lower than expected on larger and less isolated islands, suggesting that competitive exclusion was the dominant mechanism shaping termite communities in TIL. PGLMM showed that two fungus-growing species with larger body sizes increased with competition intensity, while other species exhibited negative responses. Notably, the abundance of fungus-growing species showed sharper increase with island area and decrease with isolation compared to other feeding groups. These findings demonstrate that competitively superior species prefer high-quality habitats and are more sensitive to habitat fragmentation. Conclusions: Our study highlights the significance of competitive exclusion in shaping termite communities and emphasizes the need to consider both competitive and niche difference among species or functional groups when predict changes in community structure and biodiversity loss resulting from habitat fragmentation. [ABSTRACT FROM AUTHOR]

A fundamental question of ecology is why species coexist in the same habitat. Coexistence can be enabled through niche differentiation, mediated by trait differentiation. Here, behaviour constitutes an often-overlooked set of traits. However, behaviours such as aggression and exploration drive intra- and interspecific competition, especially so in ants, where community structure is usually shaped by aggressive interactions. We studied behavioural variation in three ant species, which often co-occur in close proximity and occupy similar dominance ranks. We analysed how intra- and allospecific aggression, exploration and foraging activity vary under field conditions, namely with temperature and over time. Behaviours were assessed for 12 colonies per species, and four times each during several months. All behavioural traits consistently differed among colonies, but also varied over time and with temperature. These temperature-dependent and seasonal responses were highly species-specific. For example, foraging activity decreased at high temperatures in Formica rufibarbis, but not in Lasius niger; over time, it declined strongly in L. niger but much less in F. rufibarbis. Our results suggest that, owing to these species-specific responses, no species is always competitively superior. Thus, environmental and temporal variation effects a dynamic dominance hierarchy among the species, facilitating coexistence via the storage effect. [ABSTRACT FROM AUTHOR]

Animals have evolved complex foraging strategies to obtain a nutritionally balanced diet and associated fitness benefits. Recent research combining state-space models of nutritional geometry with agent-based models (ABMs), show how nutrient targeted foraging behavior can also influence animal social interactions, ultimately affecting collective dynamics and group structures. Here we demonstrate how social network analyses can be integrated into such a modeling framework and provide a practical analytical tool to compare experimental results with theory. We illustrate our approach by examining the case of nutritionally mediated dominance hierarchies. First we show how nutritionally explicit ABMs that simulate the emergence of dominance hierarchies can be used to generate social networks. Importantly the structural properties of our simulated networks bear similarities to dominance networks of real animals (where conflicts are not always directly related to nutrition). Finally, we demonstrate how metrics from social network analyses can be used to predict the fitness of agents in these simulated competitive environments. Our results highlight the potential importance of nutritional mechanisms in shaping dominance interactions in a wide range of social and ecological contexts. Nutrition likely influences social interactions in many species, and yet a theoretical framework for exploring these effects is currently lacking. Combining social network analyses with computational models from nutritional ecology may bridge this divide, representing a pragmatic approach for generating theoretical predictions for nutritional experiments. [ABSTRACT FROM AUTHOR]

In group-living animals, males are assumed to be dominant over females when they are larger than females. Despite this, females have sometimes been proven to be dominant over some males via the winner-loser effect, which becomes stronger when the intensity of aggression in the group is higher. To test whether the winner-loser effect leads to (partial) female dominance in a species with a pronounced sexual dimorphism, we studied the hierarchy in 12 rat colonies (Rattus norvegicus) in which the rats could freely interact with their group members within a spacious area. To investigate the underlying mechanisms, we compared the empirical data to hypotheses generated by the agent-based model 'DomWorld'. We show that females dominated on average 55% of the males, and occupied the alpha position in four colonies, in three of them they shared it with one or several males. Moreover, in line with the predictions of the computational model, females dominated a higher percentage of males when the intensity of aggression of the colony was higher. This shows that although females are only half as heavy as males, they dominate part of the males probably through the winner-loser effect. We suggest that this effect may be widespread in many other species and can be tested experimentally. Significance statement: It is often assumed that males automatically dominate females because males are bigger and stronger than females in many species. However, the present study shows that females can dominate males due to the winner-loser effect. We used an agent-based computational model to generate specific hypotheses that we empirically tested in a large sample of rat colonies. Despite this species having a pronounced male-biased sex dimorphism, some females dominated males – with one female even occupying an unshared alpha position. Such partial female dominance was stronger in colonies with higher intensity of aggression. Here, defeated males may suffer a drastic decrease in their fighting capability and consequently give females more opportunities to surpass them in the hierarchy. [ABSTRACT FROM AUTHOR]

Social interactions are fundamental properties of gregarious species, helping to establish dominance hierarchies and maintain social bonds within groups. Cattle, Bos taurus , are social ungulates which engage in affiliative and agonistic relationships with other individuals. Although there are approximately 1.5 billion cattle on the planet, the opportunity to research cattle behaviour in free-ranging groups is rare, as there are few feral populations worldwide. Cattle engage in positive social behaviours such as allogrooming, where one individual licks the body of another. The relationship between affiliative behaviours and other individual characteristics (such as sex and dominance status) are frequently studied in other gregarious species, but are largely undetermined in cattle. To investigate the relationships between sex, dominance status and allogrooming, we observed a mixed-sex feral cattle herd in Hong Kong, recording dominance interactions and allogrooming events. The hierarchy was linear and stable, consisting of 22 adult males and 33 adult females. We found that dominant females received more allogrooming than subordinate females, but subordinate females did not perform it more. Males performed allogrooming more towards females than other males, but females groomed both sexes equally. Sex affected dominance position, with males obtaining higher status than females, but not all females were subordinate to males. These preferential allogrooming patterns improve our knowledge of sex-specific interactions and help us to understand the dynamics of agonistic and affiliative behaviours in multimale, multifemale ungulate groups. Studying a free-ranging feral population provides us with a unique insight into ungulate behavioural patterns and the evolution of cattle social behaviours. • Cattle are social ungulates that engage in affiliative and agonistic behaviours. • Feral cattle present a novel opportunity to study free-ranging cattle behaviour. • Sex affected dominance status, and both affected allogrooming performance. • High-ranking animals received more allogrooming and exchanged preferential grooming. • Results aid our understanding of cattle sociality, dominance and positive welfare. [ABSTRACT FROM AUTHOR]

Rodents establish dominance hierarchy as a social ranking system in which one subject acts as dominant over all the other subordinate individuals. Dominance hierarchy regulates food access and mating opportunities, but little is known about its significance in other social behaviors, for instance during collective navigation for foraging or migration. Here, we implemented a simplified goal-directed spatial task in mice, in which animals navigated individually or collectively with their littermates foraging for food. We compared between conditions and found that the social condition exerts significant influence on individual displacement patterns, even when efficient navigation rules leading to reward had been previously learned. Thus, movement patterns and consequent task performance were strongly dependent on contingent social interactions arising during collective displacement, yet their influence on individual behavior was determined by dominance hierarchy. Dominant animals did not behave as leaders during collective displacement; conversely, they were most sensitive to the social environment adjusting their performance accordingly. Social ranking in turn was associated with specific spontaneous neural activity patterns in the prefrontal cortex and hippocampus, with dominant mice showing higher firing rates, larger ripple oscillations, and stronger neuronal entrainment by ripples than subordinate animals. Moreover, dominant animals selectively increased their cortical spiking activity during collective movement, while subordinate mice did not modify their firing rates, consistent with dominant animals being more sensitive to the social context. These results suggest that dominance hierarchy influences behavioral performance during contingent social interactions, likely supported by the coordinated activity in the hippocampal-prefrontal circuit. [ABSTRACT FROM AUTHOR]

Snakes are traditionally considered to be the least social among non-avian reptiles. Therefore, social behaviours that are not related to mating have rarely been studied in wild snakes. Nonetheless, in two species of snakes, Lycodon semicarinatus and Oligodon formosanus , intraspecific interactions unrelated to mating have been reported among individuals that forage on sea turtles and cluster around sea turtle nests. In this study, we conducted a field survey on L. semicarinatus on a sandy beach on Okinawa Island for four years by route census and fixed videography to quantify interactions between individuals that occurred at sea turtle nests. Snakes repelled conspecifics from the nest by using a ritual combat dance. Whether the snakes attacked the conspecific depended on the opponent at the nest. Some snakes waited for the conspecific to leave the nest. This decision-making may be based on individual recognition by chemical cues, because the snakes exhibited frequent tongue-flicking toward the occupant before contacting. Their tongue-flicking duration was significantly longer when the subsequent response was attacking than when it was fleeing. These intraspecific interactions imply the occurrence of territoriality and suggest the possible occurrence of a dominance hierarchy in L. semicarinatus. A comparison of L. semicarinatus with a previous study on O. formosanus revealed that they express different social interactions, although the two species use a similar feeding environment. Oligodon formosanus removes conspecifics from the nest by simply biting, but L. semicarinatus competed for the priority to access the nest by combat dance, and its decision-making whether to challenge the combat dance changed flexibly depending on the opponent. In addition, several L. semicarinatus that did not challenge the combat dance waited for hours near the opponent that were foraging on the nest. Lycodon semicarinatus exhibited behaviours to avoid encounter and fights with conspecific individuals. Although there are differences in the social level between the two snake species, the exploitation of a food resource that contains large numbers of prey in one place, such as sea turtle nests, may be an ecological factor that favours the evolutionary development of social behaviours in solitary snakes. [ABSTRACT FROM AUTHOR]

Animals can form dominance relationships that vary from highly unequal, or despotic, to egalitarian, and this variation likely impacts the fitness of individuals. How and why these differences in relationships and fitness exist among groups, populations, and species has been the subject of much debate. Here, we investigated the influence of two major factors: (1) spatial resource distribution and (2) the presence or absence of winner-loser effects. To determine the effects of these factors, we built an agent-based model that represented 10 agents directly competing over food resources on a simple landscape. By varying the food distribution and using either asymmetry of strength or experience, we contrasted four scenarios from which we recorded attack decisions, fight outcomes, and individual energy intake to calculate dominance hierarchy steepness and energetic skew. Surprisingly, resource distribution and winner-loser effects did not have the predicted effects on hierarchy steepness. However, skew in energy intake arose when resources were distributed heterogeneously, despite hierarchy steepness frequently being higher in the homogeneous resource scenarios. Thus, this study confirms some decades-old predictions about feeding competition but also casts doubt on the ability to infer energetic consequences from observations of agonistic interactions. [ABSTRACT FROM AUTHOR]

Objective: Three trials were conducted to determine the effects of broodfish management on reproductive efficiency of pond‐spawned Channel Catfish Ictalurus punctatus. Methods: Trial 1 compared male to female broodfish sex ratios of 1:1 versus 1:4, trial 2 compared low (1065 kg/ha) versus high (2050 kg/ha) broodfish stocking densities, and trial 3 compared low (1525 kg/ha) and high (5780 kg/ha) postspawn broodfish holding‐pond densities on measures of reproductive efficiency. Result: Males had lower survival than females in all trials. Age, weight, and survival of broodfish were similar for each treatment within trials. A higher percentage of females spawned at the 1:1 male to female ratio than at the 1:4 ratio (40.8% versus 12.5%), resulting in more eggs per hectare, eggs per kilogram of broodfish, fry per hectare, and fry per kilogram of broodfish for the 1:1 ratio compared to the 1:4 ratio. Male spawning success (~31%) was similar for 1:1 and 1:4 sex ratios. Spawning fish weighed more than nonspawning fish for both sexes, and surviving males weighed less than nonsurviving males in trial 1. In trial 2, the percentage of egg masses collected per female stocked was higher for the high broodfish density than the low density (34.0% versus 16.4%), resulting in more eggs per hectare and fry per hectare for the high stocking density resulting in whole‐farm economic benefits ranging from US$323/ha to $828/ha primarily from the reduction in the area required for broodstock. Conclusion: Results indicate that the 1:1 male to female broodfish ratio (trial 1) and high broodfish stocking density (trial 2) resulted in better reproduction than the 1:4 sex ratio and low broodfish stocking density. The effects of low versus high broodfish holding‐pond densities did not affect reproductive output. Impact statementTrials were conducted to determine the effects of proportions of males and females, biomass of broodfish in ponds during spawning season, and biomass of broodfish during winter on spawning success of Channel Catfish. A ratio of one male to one female provided better spawning than one male to four females. A higher biomass of broodfish during the spring spawning season resulted in better spawning efficiency than a lower biomass. Biomass of broodfish during the winter had no effect on spawning. This information will help reduce costs associated with producing catfish and benefit both producers and consumers of catfish. [ABSTRACT FROM AUTHOR]

Co-occurring species sharing a limited resource are thought to adopt alternative strategies to coexist. Here, we investigate four species of co-occurring albatrosses in southern New Zealand that share food resources but differ in dominance status to test for variation in strategies to acquire supplemental food provided by ecotourism boats. We found evidence for distinct foraging strategies consistent with each species' dominance rank. Buller's albatross (Thalassarche bulleri) was the most subordinate species and frequently pursued scraps of fish on the periphery of the feeding flocks and avoided interacting with other species. Salvin's albatross (Thalassarche salvini) and White-capped albatross (Thalassarche cauta) were intermediate in dominance status; both had fast responses to fish and typically pursued the largest fish scraps, though T. cauta successfully stole fish while T. salvini did not. In contrast, Southern Royal albatross (Diomedea epomophora) was the dominant species and did not avoid interactions with other species and pursued the largest fish scraps but was slower to respond compared with some subordinates. Natural food sources approximate the scenarios seen behind ecotourism boats, suggesting that differences in foraging strategies are likely present without human intervention. Overall, our results suggest that foraging strategies associated with dominance hierarchies could help structure seabird communities. [ABSTRACT FROM AUTHOR]

Power is an all-pervasive, and fundamental force in human relationships and plays a valuable role in social, political, and economic interactions. Power differences are important in social groups in enhancing group functioning. Most people want to have power and there are many benefits to having power. However, power is a corrupting force and this has been a topic of interest for centuries to scholars from Plato to Lord Acton. Even with increased knowledge of power's corrupting effect and safeguards put in place to counteract such tendencies, power abuse remains rampant in society suggesting that the full extent of this effect is not well understood. In this paper, an effort is made to improve understanding of power's corrupting effects on human behavior through an integrated and comprehensive synthesis of the neurological, sociological, physiological, and psychological literature on power. The structural limits of justice systems' capability to hold powerful people accountable are also discussed. [ABSTRACT FROM AUTHOR]

Individual differences in aggressiveness, if consistent across time and contexts, may contribute to the long-term maintenance of social hierarchies in complex animal societies. Although agonistic interactions have previously been used to calculate individuals’ positions within a dominance hierarchy, to date the repeatability of agonistic behaviour has not been tested when calculating social rank. Here, we examined the consistency and social relevance of aggressiveness as a personality trait in a free-flying population of greylag geese (Anser anser). For each individual, we quantified (i) aggressiveness using a standardized mirror stimulation test and (ii) dominance ranking based on the number of agonistic interactions won and lost in a feeding context. We found that individual differences in aggressiveness were significantly repeatable and that individuals’ aggressiveness predicted their dominance rank position. The flock showed a robust and intermediately steep dominance hierarchy. Social rank was higher in paired birds, males and older birds, and most agonistic interactions occurred between individuals with moderate rank differences. We suggest that selection favours aggressiveness as a personality trait associated with resource acquisition and social rank, whereby a dominance hierarchy may increase the benefits of group living and reduce costs over conflict within dyads.

Rodents establish dominance hierarchy as a social ranking system in which one subject acts as dominant over all the other subordinate individuals. Dominance hierarchy regulates food access and mating opportunities, but little is known about its significance in other social behaviors, for instance during collective navigation for foraging or migration. Here, we implemented a simplified goal-directed spatial task in mice, in which animals navigated individually or collectively with their littermates foraging for food. We compared between conditions and found that the social condition exerts significant influence on individual displacement patterns, even when efficient navigation rules leading to reward had been previously learned. Thus, movement patterns and consequent task performance were strongly dependent on contingent social interactions arising during collective displacement, yet their influence on individual behavior was determined by dominance hierarchy. Dominant animals did not behave as leaders during collective displacement; conversely, they were most sensitive to the social environment adjusting their performance accordingly. Social ranking in turn was associated with specific spontaneous neural activity patterns in the prefrontal cortex and hippocampus, with dominant mice showing higher firing rates, larger ripple oscillations, and stronger neuronal entrainment by ripples than subordinate animals. Moreover, dominant animals selectively increased their cortical spiking activity during collective movement, while subordinate mice did not modify their firing rates, consistent with dominant animals being more sensitive to the social context. These results suggest that dominance hierarchy influences behavioral performance during contingent social interactions, likely supported by the coordinated activity in the hippocampal-prefrontal circuit.

Abstract Background Mixing pigs at weaning can compromise pig welfare and growth. Therefore, grouping littermates together may allow a diet nutrient and energy density reduction during the nursery period to reduce feed cost without affecting slaughter weight. This study investigated the combined effect of mixing and reducing dietary energy and nutrient density on growth performance, body lesions (BL), and behaviour in pigs from weaning to slaughter. Results Forty-eight litters [554 pigs, 11–12 pigs/litter; Danish Duroc × (Large White × Landrace)] were included in the trial. At 28 days of age, pigs were weaned and housed in nursery rooms in litter groups (INTACT, n = 24) or mixed with other litters and grouped by weight to reduce within-pen pig weight variation (MIXED, n = 24). A dietary regimen meeting pigs’ nutritional requirements (CON) and a low-density dietary regimen (LOW; -10% energy and protein) completed a 2 × 2 factorial arrangement (Mixing x Diet, n = 12). On day 74 of age, pigs moved to the grower-finisher accommodation without further mixing and all pigs received the CON dietary regimen. Mixing increased FCR by 4.0% during the nursery period (p = 0.003). Nursery pigs fed LOW experienced a growth retardation which was maintained until slaughter (-2.6 kg slaughter weight; p = 0.025). Initial differences in the coefficient of variation (CV) between MIXED (10.4%) and INTACT (17.6%; p

Background: Mixing pigs at weaning can compromise pig welfare and growth. Therefore, grouping littermates together may allow a diet nutrient and energy density reduction during the nursery period to reduce feed cost without affecting slaughter weight. This study investigated the combined effect of mixing and reducing dietary energy and nutrient density on growth performance, body lesions (BL), and behaviour in pigs from weaning to slaughter. Results: Forty-eight litters [554 pigs, 11–12 pigs/litter; Danish Duroc × (Large White × Landrace)] were included in the trial. At 28 days of age, pigs were weaned and housed in nursery rooms in litter groups (INTACT, n = 24) or mixed with other litters and grouped by weight to reduce within-pen pig weight variation (MIXED, n = 24). A dietary regimen meeting pigs' nutritional requirements (CON) and a low-density dietary regimen (LOW; -10% energy and protein) completed a 2 × 2 factorial arrangement (Mixing x Diet, n = 12). On day 74 of age, pigs moved to the grower-finisher accommodation without further mixing and all pigs received the CON dietary regimen. Mixing increased FCR by 4.0% during the nursery period (p = 0.003). Nursery pigs fed LOW experienced a growth retardation which was maintained until slaughter (-2.6 kg slaughter weight; p = 0.025). Initial differences in the coefficient of variation (CV) between MIXED (10.4%) and INTACT (17.6%; p < 0.001) pigs were reduced in CON pens but not in LOW pens (interaction p = 0.025) at the end of the nursery period. MIXED pigs had more fights and BL (p < 0.001) at weaning and showed more aggression (p = 0.003) after being moved to the grower-finisher rooms. At the end of the nursery period, MIXED pigs fed LOW showed the highest number of aggressive behaviours around the feeder (interaction; p = 0.003) and pigs fed LOW showed more damaging behaviour (p < 0.001). Conclusions: Mixing animals at weaning had limited impact on growth performance but impaired welfare which was aggravated by energy and nutrient reduction in the nursery diet. Decreasing dietary nutrient density in the nursery stage retarded growth, which could not be compensated for during the growing-finishing period. [ABSTRACT FROM AUTHOR]

Abstract The steepness of dominance hierarchies provides information about the degree of competition within animal social groups and is thus an important concept in socioecology. The currently most widely used metrics to quantify steepness are based on David's scores (DS) derived from dominance interaction networks. One serious drawback of these DS‐based metrics is that they are biased, that is, network density systematically decreases steepness values. We provide a novel approach to estimate steepness based on Elo‐ratings, implemented in a Bayesian framework (STEER: Steepness estimation with Elo‐rating). We evaluate and validate its performance by means of experimentation on empirical and artificial datasets and compare its performance to that of several other steepness estimators. STEER has two key advantages. First, it is unbiased, precise and more robust to data density than DS‐based steepness. Second, it provides explicit probability distributions of the estimated steepness coefficient, which allows uncertainty assessment. In addition, it relies on the same underlying concept and is on the same scale as the original measure, and thus allows comparison to existing published results. STEER provides a considerable improvement over existing methods to estimate dominance hierarchy steepness. We demonstrate its application with an example comparing within‐ and between species variation in steepness in a comparative analysis and present guidelines on how to use it. The R package EloSteepness allows convenient numeric and graphical assessment of the new steepness measure.

Social cognition guides social behavior. Subjects with proper social cognition should be able to: (1) have reasonable social motivation, (2) recognize other people and infer their intentions, and (3) weigh social hierarchies and other values. The choice of appropriate behavioral paradigms enables the use of rodents to study social behavior disorders in humans, thus enabling research to go deeper into neural mechanisms. This paper reviews commonly used rodent behavioral paradigms in studies of social behavior disorders. We focused specifically on sorting out ways to transfer the study of human social behavior to rodents through behavioral paradigms. [ABSTRACT FROM AUTHOR]

Dominance hierarchies help to reduce unnecessary fights and associated costs during the mating season. Fallow deer, Dama dama , typically have high levels of male–male competition and strong reproductive skew. Nevertheless, how male dominance and daily fight rates affect mating success is still uncertain. We used a 2-year data set from a large population of tagged fallow deer (620–689 individuals), to calculate male dominance ranks based on their agonistic interactions prior to the mating season ('prerut'), to then examine how rank is related to fight rates and mating success during the mating season ('rut'). Overall, higher-ranked males fought at least twice a day on a higher proportion of days during the start and peak of the rut and secured more matings than lower-ranked males. Males engaging in more than 10 fights per day were less likely to secure a mating that same day, and those males exceeding 15 fights per day secured no matings at all. Nevertheless, males with the highest numbers of fights (i.e. 15 – 21 fights per day) and higher proportion of won fights on a given day had higher mating success on the next day compared to those males fighting fewer than 15 fights per day. Although higher-ranked males secured most matings during the rut, their fight rates decreased towards the end. We propose that engaging in more fights negatively affects daily individual mating success but may benefit mating success on the following day and potentially increase long-term fitness benefits. Additionally, engaging in more fights as the rut progresses probably allows lower-ranked males to secure some matings before the availability of oestrous females ends for almost a year. • Male fallow deer establish social hierarchies that help reduce unnecessary fights. • Higher-ranked males fight and mate more than lower-ranked males. • Males that fight and win most have increased probability of mating the next day. • Dominant males have fewer fights towards the end of the mating season. • Fighting may provide delayed fitness benefits among socially mature males. [ABSTRACT FROM AUTHOR]

Dominance hierarchies can provide many benefits to individuals, such as access to resources or mates, depending on their ranks. In some species, rank can emerge as a product of a group's history of social interactions. However, it can be difficult to determine whether social history is critical to rank in observation-based studies. Here, we investigated rank dynamics in three captive groups of monk parakeets (Myiopsitta monachus). We used experimental social perturbations to test whether social history shapes rank emergence in these groups. Using targeted removals and reintroductions, we tested whether differently ranked individuals could re-take their ranks in hierarchies after reintroduction following their removal period from the group. We performed perturbations that consisted of an 8-day removal and an 8-day reintroduction period of 15 differently ranked focal birds. We found that no focal birds could regain their previous rank immediately following reintroduction and that the top-ranked birds showed greater relative rank loss than middle/low-ranked birds. We also found that morphology, specifically bodyweight, was unassociated with rank. Combined with previous results, this experiment supports the hypothesis that rank in monk parakeet dominance hierarchies is more likely to be an emergent outcome of past interactions and memory rather than based on individual characteristics. Gaining a better understanding of how individuals achieve and maintain rank can give insight into the role of cognition on rank acquisition, as rank position can have significant biological effects on individuals in hierarchically structured groups. [ABSTRACT FROM AUTHOR]

Keywords: agonistic behaviors; dominance hierarchy; ethological observations; flower visitor insects; flowers; Paris; urban parks EN agonistic behaviors dominance hierarchy ethological observations flower visitor insects flowers Paris urban parks 1 5 5 03/06/23 20230301 NES 230301 A few minutes of observation of flowers are sufficient to notice that some flower-visiting insects threaten, harass, or attack individuals from other species. We observed that large hoverflies and gray bees tended to attack most of the other individuals, whereas honeybees and yellow-striped bumblebees were much calmer and more peaceful. Thus, large hoverflies, gray bees, "other wild bees" and the "Other" categories are more aggressive than honeybees, yellow-striped bumblebees, and "other bumblebees" (Appendix S1: Figure S3). Honeybees, yellow-striped bumblebees, and the "other bumblebees" and "other wild bees" categories mainly attacked within their own morphospecies. [Extracted from the article]

Though lion‐tailed macaques are managed ex situ as an assurance population, little information is available on the relationship between behavior and reproductive physiology to ensure successful management and evaluate welfare. To facilitate social and reproductive management in a group of one male and three female lion‐tailed macaques at Disney's Animal Kingdom®, we observed behaviors associated with dominance and reproduction, rated genital swellings, recorded menses, tracked ovarian cycles as determined by measurement of fecal immunoreactive progesterone (P4) and estradiol (E2), and monitored fecal cortisol (CORT). We analyzed the dominance hierarchy of females, compared hormone patterns of ovarian cycles with genital swellings and copulations relative to menses, and tested for correlations between hormones and behavior. The strength of the dominance hierarchy indicated moderate linearity, but relaxed after the dominant female received anxiolytic medications to reduce intraspecific aggression. Fecal P4 and E2 patterns revealed ovarian cycle lengths averaging 29.7 ± 0.8 days. The timing of single‐day E2 peaks varied between and within females' cycles. However, on average, E2 peaks occurred 6–10 days after the first day of menses, with maximum genital swellings and copulations occurring slightly thereafter in uncontracepted females. Female‐to‐female aggression and sexual behaviors with the male were related to ovarian cycle phase, but correlations between behaviors and hormones varied between females. Initiated aggression was positively correlated with E2 in the dominant and mid‐ranked females, while aggression received was positively correlated with P4 or negatively correlated with E2 in the mid‐ranked and subordinate females. In one uncontracepted female, sexual behaviors with the male were negatively correlated to P4. CORT was positively correlated to aggression in the dominant and mid‐ranked females and negatively correlated to grooming in the subordinate female. Results indicate observations of visual and behavioral cues can be used to track ovarian cycles and evaluate social dynamics and welfare in zoo‐housed lion‐tailed macaques. Research highlights: The strength of the dominance hierarchy in a group of three zoo‐housed female lion‐tailed macaques reduced from moderate linearity to more egalitarian after the dominant female received anxiolytic medication to reduce intraspecific aggression.In uncontracepted ovarian cycles, estrogen peaked 6–10 days post menses; this preceded maximum genital swellings and copulations by the male, which are visual cues that can be used together to estimate the fertile period in lion‐tailed macaques.Social behavior correlated to estradiol, progesterone, and cortisol, but correlations varied between females; male sexual behavior correlated to low progesterone in the uncontracepted mid‐ranked female and may be used to estimate fertile periods. [ABSTRACT FROM AUTHOR]

Arboreal birds in the Sahel are highly selective in their tree choice. Most migrant, but also resident, birds are found in a few tree species and within those species often only in trees with abundant leaves and flowers. For this reason alone, preferred trees were expected to teem with birds. This was not the case. Most bird species were present in trees as singletons, even half of the Senegal Eremomela Eremomela pusilla – the most social species of all – were recorded as solitary birds. The probability that two different bird species were in the same tree was also very small, 2.8% on average. Mixed-group foraging flocks of arboreal birds, as so often reported for tropical forests, did not occur in the Sahel. Perhaps birds forage singly because they have no need to fear the raptors that are common in the forests further south. Some species, such as European Pied Flycatcher Ficedula hypoleuca and Common Redstart Phoenicurus phoenicurus, defend winter territories, but for other species individual home ranges show overlap. In the humid forests further south, and among resident species in the Sahel, few agonistic interactions were seen, but migratory birds were often agonistic with congeners and even more frequently with birds of other species. Larger bird species usually won agonistic interactions, but Western Olivaceous Warblers Iduna opaca chased off birds twice their own body size. Subalpine Warbler Curruca iberiae + subalpina + cantillans and other Curruca species, with the exception of Lesser Whitethroat Curruca curruca, were also intolerant. Western Bonelli's Warblers Phylloscopus bonelli, and during migration also Willow Warblers Phylloscopus trochilus, were most often on the receiving end of agonistic interactions. Far fewer agonistic interactions were recorded in the more humid regions to the south of the Sahel. This disparity may hinge on the higher intra- and interspecific encounter rate in the Sahel, where a greater fraction of trees are occupied by birds, than in the humid forests. [ABSTRACT FROM AUTHOR]

The steepness of dominance hierarchies provides information about the degree of competition within animal social groups and is thus an important concept in socioecology. The currently most widely used metrics to quantify steepness are based on David's scores (DS) derived from dominance interaction networks. One serious drawback of these DS‐based metrics is that they are biased, that is, network density systematically decreases steepness values.We provide a novel approach to estimate steepness based on Elo‐ratings, implemented in a Bayesian framework (STEER: Steepness estimation with Elo‐rating). We evaluate and validate its performance by means of experimentation on empirical and artificial datasets and compare its performance to that of several other steepness estimators.STEER has two key advantages. First, it is unbiased, precise and more robust to data density than DS‐based steepness. Second, it provides explicit probability distributions of the estimated steepness coefficient, which allows uncertainty assessment. In addition, it relies on the same underlying concept and is on the same scale as the original measure, and thus allows comparison to existing published results.STEER provides a considerable improvement over existing methods to estimate dominance hierarchy steepness. We demonstrate its application with an example comparing within‐ and between species variation in steepness in a comparative analysis and present guidelines on how to use it. The R package EloSteepness allows convenient numeric and graphical assessment of the new steepness measure. [ABSTRACT FROM AUTHOR]

Interspecific dominance hierarchies have been widely reported across animal systems. High-ranking species are expected to monopolize more resources than low-ranking species via resource monopolization. In some ant species, dominance hierarchies have been used to explain species coexistence and community structure. However, it remains unclear whether or in what contexts dominance hierarchies occur in tropical ant communities. This study seeks to examine whether arboreal twig-nesting ants competing for nesting resources in a Mexican coffee agricultural ecosystem are arranged in a linear dominance hierarchy. We described the dominance relationships among 10 species of ants and measured the uncertainty and steepness of the inferred dominance hierarchy. We also assessed the orderliness of the hierarchy by considering species interactions at the network level. Based on the randomized Elo-rating method, we found that the twig-nesting ant species Myrmelachista mexicana ranked highest in the ranking, while Pseudomyrmex ejectus was ranked as the lowest in the hierarchy. Our results show that the hierarchy was intermediate in its steepness, suggesting that the probability of higher ranked species winning contests against lower ranked species was fairly high. Motif analysis and significant excess of triads further revealed that the species networks were largely transitive. This study highlights that some tropical arboreal ant communities organize into dominance hierarchies.

Dominance hierarchy (DH) is never bi-(inter-)sexual. Rare ostensible female dominance (over males) is not even amenable to modelling, and actually is male non-engagement in dominance terms (deference, not submission). Any female hierarchy is not DH, as it is not contest-based, but from either mutually signalled differential fecundity or maternal rank inheritance. Otherwise, apparent female hierarchy is either non-dominance-based first-among-equals -- winner-takes-all -- sociality of a female sole reproducer, or a loose artefact of ad hoc resource competition. DH entails neuro-hormonally processing winner/loser effects, for which there is evidence only in males, and requires the Y chromosome's SRY gene. Male-specificity is anticipated from the male root function of genetic filtration/mutational cleansing, necessitating male ranking in terms of genomic integrity. [ABSTRACT FROM AUTHOR]

In some social groups, non-breeding subordinates regulate their growth, relative to the size of their immediate dominants in ways that reduce conflict over dominance rank. We predicted that such strategic growth adjustment should also occur in breeding pairs, if this is beneficial for the more subordinate individual within a pair. Using the cichlid fish, Julidochromis transcriptus , held in a laboratory, we examined whether strategic growth regulation occurs in monogamous pairs. In female-largest pairs, smaller males grew slower than their partner when the initial size ratio of pairs (large/small) was small, but faster when the ratio was large, and the number of pairs with an intermediate size ratio increased over time. However, in male-largest pairs, smaller females had a low growth rate and the size ratio of these pairs increased over time. The most important factors for predicting the growth rate of fish were the initial size ratio of pairs for smaller males in female-largest pairs and the initial body size for larger individuals in both pair types, but no such predictors were found for smaller females in male-largest pairs. Neither feeding rate nor attacking rate of the two individuals in a pair predicted the growth rate of smaller fish in a pair. These results suggest that smaller males strategically adjust their own growth, relative to the size of their partner in female-largest pairs, wherein the growth of larger females unrestrained by social relationship with their partner can increase female fecundity, being beneficial for both sexes. The adaptive significance of a low growth rate of smaller females in male-largest pairs is also discussed. [ABSTRACT FROM AUTHOR]

Apex predators have critical roles in maintaining the structure of ecosystem functioning by controlling intraguild subordinate populations. Such dominant–subordinate interactions involve agonistic interactions including direct or indirect impacts on the subordinates. As these indirect effects are often mediated through physiological processes, it is important to quantify such responses to better understand population parameters. We used a large carnivore intraguild system involving tiger (Panthera tigris) and leopard (Panthera pardus) to understand the dietary and physiological responses under a spatio-temporal gradient of tiger competition pressures in Rajaji Tiger Reserve (RTR) between 2015 and 2020. We conducted systematic faecal sampling in the winters of 2015 and 2020 from the park to assess diet and physiological measures. Analyses of leopard-confirmed faeces suggest a dietary-niche separation as a consequence of tiger competition. In 2020, we found an increased occurrence of large-bodied prey species without tiger competition in western-RTR. Physiological measures followed the dietary responses where leopards with large-sized prey in the diet showed higher fT3M and lower fGCM measures in western-RTR. In contrast, eastern-RTR leopards showed lower levels of fT3M and fGCM in 2020, possibly due to intense competition from tigers. Overall, these patterns strongly indicate a physiological cost of sympatry where competition with dominant tigers resulted in elevated nutritional stress. We recommend expansion of leopard monitoring and population estimation efforts to buffers, developing appropriate plans for human–leopard conflict mitigation and intensive efforts to understand leopard population dynamics patterns to ensure their persistence during the ongoing Anthropocene. [ABSTRACT FROM AUTHOR]

We studied social relationships in a captive group of female Himalayan tahr (Hemitragus jemlahicus). Female tahr showed frequent aggression and a strictly linear age‐graded dominance hierarchy. Coalitions, in contrast, were rare. Female tahr formed differentiated social relationships, as they interacted with different individuals at widely different rates. A principal component analysis revealed that social relationships were best described along three independent dimensions that we labelled as Affiliation, Agonism and Ambivalence. Both Affiliation and Agonism were directed preferentially down the hierarchy. Affiliation was also directed preferentially to kin, while Agonism showed the reverse pattern. Ambivalence was unrelated to both dominance and kinship. Overall, these results show that an ungulate species can form differentiated social relationships that vary in relation to dominance rank and kinship. [ABSTRACT FROM AUTHOR]

In mutualistic interactions, all parties are usually considered to benefit; yet there may be asymmetries in mutualisms where some partners/individuals benefit more than others. Such is thought to be the case in mixed-species flocks of birds, where following species are thought to benefit more than leading species, and leading species may not be able to escape the association if they are subordinate to other species. We measured dominance and affiliation patterns of a mixed-species flock system of southern China in an aviary where these variables could be measured in a standardized way. In eight wild-caught flocks, the leading species, David's Fulvetta (Alcippe davidi), was usually among the more subordinate flock members (ranking 9 of 13 species, with the the most dominant species ranked number one, and dominance measured by normalized David's scores). Dominance was strongly influenced by body mass, and not by bill length or the number of individuals. Female fulvettas in particular tended to be among the most subordinate individuals in the flock. There was evidence of a negative relationship between a species pair's affiliation, measured as the percentage of all observations in which these two species were found perching together, and their difference in ranking in the dominance hierarchy, particularly when some ground species, which are not likely to remain in flocks long term, were removed from the analysis. Species pairs that had more pronounced differences in their dominance rankings were less likely to be affiliated, which is consistent with the idea that subordinate species may avoid dominants. David's Fulvetta is a strong information provider, so other species are likely benefitted in this relationship. Our data suggest one reason that fulvettas stay in flocks is that they may be subordinate and therefore have little control over who associates with them.

Cooperative breeding, a social system in which offspring receive care from other group members as well as their parents, occurs in insects, fish, birds and mammals. In this study, we report a new example of cooperative breeding in the cichlid fish (Neolamprologus bifasciatus). This species, endemic to Lake Tanganyika, Africa, inhabits rocky areas at depths below 30 m. Observations of eight nests using underwater video cameras showed that one to six subordinates were present in the nests of breeding pairs. The subordinates shared shelters with juveniles and breeders and engaged in brood/territorial defence and nest maintenance (removing sand from the nest), albeit at a lower frequency than female breeders. The frequency of sand digging by subordinates and female breeders decreased as the number of subordinates in the group increased, suggesting that subordinates reduce the costs of nest maintenance for breeders. The male breeders seldom showed territorial defence and nest maintenance. Subordinates exhibited submissive behaviours towards dominant breeders and larger subordinates within their breeding group, indicating a dominance hierarchy among group members. Gonad examination revealed that the subordinates of both sexes were sexually immature, suggesting that they may not participate in reproduction. An aquarium experiment showed that juveniles become subordinates in their natal nest and participate in territory defence. We conclude that N. bifasciatus is a cooperative breeder, with social systems and subordinate roles similar to those observed in other cooperatively breeding cichlids. [ABSTRACT FROM AUTHOR]

The task of ranking individuals or teams, based on a set of comparisons between pairs, arises in various contexts, including sporting competitions and the analysis of dominance hierarchies among animals and humans. Given data on which competitors beat which others, the challenge is to rank the competitors from best to worst. Here we study the problem of computing rankings when there are multiple, potentially conflicting types of comparison, such as multiple types of dominance behaviours among animals. We assume that we do not know a priori what information each behaviour conveys about the ranking, or even whether they convey any information at all. Nonetheless, we show that it is possible to compute a ranking in this situation and present a fast method for doing so, based on a combination of an expectation–maximization algorithm and a modified Bradley–Terry model. We give a selection of example applications to both animal and human competition. [ABSTRACT FROM AUTHOR]

Interruption is a simple, recognisable, and affectively charged phenomenon. Interruption also has complex, patterned implications. In the aftermath of ethnographic investigations into music's uses for violence, this essay seeks general principles according to which interruption does help and harm. An account of sonic normativity results, based on the principle that sound is difficult to escape. While epistemically useful, susceptibility to sound is also a vulnerability that social frames variously exploit – or protect by cultivating resilience. "Sonic interruptivity" – the propensity of sound to interrupt – gives dramatic import to styles of performing, recording, and audiencing, and provides a point of interdisciplinary convergence around which schools of thought from theatre performance praxis, culture critique, music theory, and soundscape ecology possess shared insight. Anticipating crises of interruption with rituals of interruption, performing extremes of immunity to interruption, or dominating discourses, invading niches, and projecting styles through frequent interruption, creative practitioners engage interruption as a widely understood communicative device whose very insensitivity constitutes part of its meaning. If this essay takes a normative stance, it is that students of sound should not neglect sonic interruptivity – from subtle elision to aggressive blare, the very uncouthness of interruption signals the attention it deserves. [ABSTRACT FROM AUTHOR]

We propose a novel model to explain the mechanisms underlying dominance hierarchical structures. Guided by a predetermined social convention, agents with limited cognitive abilities optimize their strategies in a Hawk-Dove game. We find that several commonly observed hierarchical structures in nature such as linear hierarchy and despotism, emerge as the total fitness-maximizing social structures given different levels of cognitive abilities. [ABSTRACT FROM AUTHOR]

Social relationships are critical components of health and fitness for humans and other animals. For female-philopatric species, affiliative relationships among females (kin and nonkin alike) can influence components of fitness that include individual survival, interbirth interval and offspring survival. Affiliative relationships with males have attracted somewhat less attention, with most studies focusing on female–male relationships as adaptations for infanticide avoidance. Here, we use 8 years of behavioural data on Kinda baboons, Papio kindae , to assess whether maternal social relationships—both among females and between females and males—affect infant survival, interbirth interval and the pace of infant development. Kinda baboons are an ideal system for these analyses because males and females form strong relationships outside of the periovulatory period and in the absence of obvious infanticide threat. We calculated social metrics that reflected dominance status, total social integration and social bond strength and paired these metrics with data on offspring survival, interbirth interval (IBI) duration and infant behavioural maturation. Neither dominance rank nor sociality had a significant effect on interbirth interval or survival, but higher rank and the stronger affiliative relationships between a female and her top female and top male social partners predicted more rapid infant behavioural maturation. These results suggest that maternal dominance and sociality may confer advantages related to infant development and independence that ultimately may permit females to more quickly invest in subsequent offspring and point to advantages of relationships with males outside of lowering infanticide threat. • Kinda baboon female–male bonds persist outside of fertility or infanticide threat. • Social bonds did not affect interbirth interval or infant survival and growth. • Dominance and affiliative bonds predicted more rapid infant development. • Top-partner bonds were the strongest predictors of infant development. • Strong maternal bonds with females and males enhanced infant development. [ABSTRACT FROM AUTHOR]

• Dominant mice exhibit higher proportion of adaptive immune cells in blood. • Subordinate mice exhibit higher proportions of innate immune cells in blood. • Dominants show increased hepatic expression of genes involved in organic acid, carboxylic and lipid catabolic processes. • Genes related to wound healing and DNA repair genes are upregulated in subordinates. • Genes related to maintaining and signaling social status are upregulated in dominants. Social status is a critical factor determining health outcomes in human and nonhuman social species. In social hierarchies with reproductive skew, individuals compete to monopolize resources and increase mating opportunities. This can come at a significant energetic cost leading to trade-offs between different physiological systems. In particular, changes in energetic investment in the immune system can have significant short and long-term effects on fitness and health. We have previously found that dominant alpha male mice living in social hierarchies have increased metabolic demands related to territorial defense. In this study, we tested the hypothesis that high-ranking male mice favor adaptive immunity, while subordinate mice show higher investment in innate immunity. We housed 12 groups of 10 outbred CD-1 male mice in a social housing system. All formed linear social hierarchies and subordinate mice had higher concentrations of plasma corticosterone (CORT) than alpha males. This difference was heightened in highly despotic hierarchies. Using flow cytometry, we found that dominant status was associated with a significant shift in immunophenotypes towards favoring adaptive versus innate immunity. Using Tag-Seq to profile hepatic and splenic transcriptomes of alpha and subordinate males, we identified genes that regulate metabolic and immune defense pathways that are associated with status and/or CORT concentration. In the liver, dominant animals showed a relatively higher expression of specific genes involved in major urinary production and catabolic processes, whereas subordinate animals showed relatively higher expression of genes promoting biosynthetic processes, wound healing, and proinflammatory responses. In spleen, subordinate mice showed relatively higher expression of genes facilitating oxidative phosphorylation and DNA repair and CORT was negatively associated with genes involved in lymphocyte proliferation and activation. Together, our findings suggest that dominant and subordinate animals adaptively shift immune profiles and peripheral gene expression to match their contextual needs. [ABSTRACT FROM AUTHOR]

Group-living species are often organized into social dominance hierarchies, where high-ranking individuals have priority of access to resources, including estrous females. Traits associated with male dominance status should thus be correlated with reproductive success, but, with the exception of research on some primates, studies with both behavioral data to determine dominance hierarchies and a pedigree to identify male siring success are rare. For a wild population of sexually dimorphic eastern grey kangaroos Macropus giganteus, we characterized the social hierarchy over 6 non-consecutive years to investigate the relationship between male dominance and yearly reproductive success. Dominance hierarchies were steep, linear, and stable over time. Asymmetries in body mass and size between contestants were strong predictors of contest outcomes, and these morphological traits were positively correlated with dominance status. Males did not spatially avoid each other but tended to fight with individuals of similar size, suggesting that when asymmetries were large, contests were unlikely. Dominance status was under strong sexual selection, despite moderate monopolization of paternities by highly dominant males. Overall, these results suggest that body size and weapons are important determinants of dominance status and male reproductive success but that other traits play a considerable role. A clear-cut dominance hierarchy and strong selection on dominance status do not necessarily lead to monopolization of reproduction by the most dominant males in this strongly sexually dimorphic species. Significance statement: It is generally assumed that high social rank in males is a very strong determinant of access to mates in polygamous species. Like other sexually dimorphic species, male kangaroos are thought to establish dominance hierarchies based on size. A few high-ranking males are then believed to monopolize matings. Our study confirms a strong correlation between body size and dominance status, and that males mostly engage in contests with males of similar size. However, we also found weak monopolization of reproduction, despite strong, positive sexual selection on dominance status. This result suggests that strong selection for high rank does not imply that subordinate males cannot sire offspring. A few highly dominant males had high reproductive success but did not monopolize matings. [ABSTRACT FROM AUTHOR]

In many social species physical attributes correlate with dominance rankings and influence the outcomes of dyadic interactions. We investigated the processes that affect white rhinoceros' social behaviour in response to a reduction in horn size asymmetries within a group of subadult individuals. We monitored agonistic social interactions and the orderliness of social rankings between six free ranging rhinoceroses before and after they underwent a second dehorning procedure. We used a modified version of Landau's h' to measure linearity, a score of steepness to measure power asymmetry, and a measure of triangle transitivity to assess relationships in the presence of null dyads. Agonistic social interactions were significantly greater after the monitored dehorning procedure. Hierarchies possessed significant steepness and transitivity prior to the procedure, but not after. Linearity was non-significant and rank order did not correspond with changes in horn size or age. Our results provide the first evidence of a dominance hierarchy among free-ranging white rhinoceroses outside of reproductive competition, but indicate that physical attributes alone do not explain social rankings. Rhinoceroses transitioned to a more egalitarian dominance structure than a despotic one after the procedure, but dominance ranks were only weakly differentiated within the group. Although a reduction in horn asymmetries may increase agonistic behaviours via psychosocial or behavioural changes, drier climatic conditions cannot be ruled out as the causative factor and because the subadult group stayed together, rather than dispersing, any increased fitness costs are likely to be minimal and outweighed by the benefits of group membership. [ABSTRACT FROM AUTHOR]

Seed dispersal directly affects plant establishment, gene flow and fitness. Understanding patterns in seed dispersal is, therefore, fundamental to understanding plant ecology and evolution, as well as addressing challenges of extinction and global change. Our ability to understand dispersal is limited because seeds may be dispersed by multiple agents, and the effectiveness of these agents can be highly variable both among and within species. We provide a novel framework that links seed dispersal to animal social status, a key component of behaviour. Because social status affects individual resource access and movement, it provides a critical link to two factors that determine seed dispersal: the quantity of seeds dispersed and the spatial patterns of dispersal. Social status may have unappreciated effects on post‐dispersal seed survival and recruitment when social status affects individual habitat use. Hence, environmental changes, such as selective harvesting and urbanisation, that affect animal social structure may have unappreciated consequences for seed dispersal. This framework highlights these exciting new hypotheses linking environmental change, social structure and seed dispersal. By outlining experimental approaches to test these hypotheses, we hope to facilitate studies across a wide diversity of plant‐animal networks, which may uncover emerging hotspots or significant declines in seed dispersal. [ABSTRACT FROM AUTHOR]

A dominance hierarchy is the set of ranks occupied by species within an assemblage. Species with a high position within the dominance hierarchy tend to dominate subordinate species in contests for access to resources. In hummingbirds, greater weight and wing disc loading have been associated with highest ranks within the dominance hierarchy. Nevertheless, the limit to which the difference between the weight of contending species represents a competitive advantage has not yet been determined. Here, we determined the dominance hierarchy of a hummingbird assemblage exploiting the most abundant floral resource (Palicourea padifolia, Rubiaceae) in a cloud forest of central Veracruz, Mexico. Specifically, we tested whether species weight and wing disc loading influence the dominance hierarchy. Additionally, we tested whether the flowers visited per foraging bout increases with species weight and dominance. We further tested whether weight, wing disc loading, and the genetic relatedness between contenders influenced the dominance relationships in species-pair interactions. Our results indicate that the hierarchy is positively influenced by weight. Hummingbirds visited similar number of flowers regardless their weight or their dominance. Nevertheless, the probability that the heaviest contender won contests was positively associated with the differences of weight and genetic relatedness between contenders. Contrarily, the probability that the contender with greatest wing disc loading won contests was positively associated with differences of weight and negatively associated with the relatedness between contenders. However, these models only explained between 22% and 34% of the variation, respectively. Our results demonstrate that the weight was the major contributor to high dominance values. However, future studies should include (1) the temporal variability of the weight and (2) experimental predictor variables such the burst power of the hummingbirds to evaluate its effects on the dynamics of dominance hierarchies in hummingbird assemblages. All the hummingbird species present in the studied assemblage have developed wide behavioral mechanisms that compensate their morphological differences, which allow them to coexist, even when they compete for the access to the same resource. [ABSTRACT FROM AUTHOR]

Dominance behaviours have been collected for many groups of animals since 1922 and serve as a foundation for research on social behaviour and social structure. Despite a wealth of data from the last century of research on dominance hierarchies, these data are only rarely used for comparative insight. Here, we aim to facilitate comparative studies of the structure and function of dominance hierarchies by compiling published dominance interaction datasets from the last 100 years of work. This compiled archive includes 436 datasets from 190 studies of 367 unique groups (mean group size 13.8, s.d. = 13.4) of 135 different species, totalling over 243 000 interactions. These data are presented in an R package alongside relevant metadata and a tool for subsetting the archive based on biological or methodological criteria. In this paper, we explain how to use the archive, discuss potential limitations of the data, and reflect on best practices in publishing dominance data based on our experience in assembling this dataset. This archive will serve as an important resource for future comparative studies and will promote the development of general unifying theories of dominance in behavioural ecology that can be grounded in testing with empirical data. This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’. [ABSTRACT FROM AUTHOR]

Reproductive division of labour is a hallmark of eusocial insects. However, its stability can often be hampered by the potential for reproduction by otherwise sterile nest-mates. Dominance hierarchy has a crucial role in some species in regulating which individuals reproduce. Compared with those in vertebrates, the dominance hierarchies in eusocial insects tend to involve many more individuals, and should require additional selective forces unique to them. Here, we provide an overview of a series of studies on dominance hierarchies in eusocial insects. Although reported from diverse eusocial taxa, dominance hierarchies have been extensively studied in paper wasps and ponerine ants. Starting from molecular physiological attributes of individuals, we describe how the emergence of dominance hierarchies can be understood as a kind of self-organizing process through individual memory and local behavioural interactions. The resulting global structures can be captured by using network analyses. Lastly, we argue the adaptive significance of dominance hierarchies from the standpoint of sterile subordinates. Kin selection, underpinned by relatedness between nest-mates, is key to the subordinates’ acceptance of their positions in the hierarchies. This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’. [ABSTRACT FROM AUTHOR]

Dominance is important for access to resources. As dominance interactions are costly, individuals should be strategic in whom they interact with. One hypothesis is that individuals should direct costly interactions towards those closest in rank, as they have most to gain—in terms of attaining or maintaining dominance—from winning such interactions. Here, we show that male vulturine guineafowl (Acryllium vulturinum), a gregarious species with steep dominance hierarchies, strategically express higher-cost aggressive interactions towards males occupying ranks immediately below themselves in their group’s hierarchy. By contrast, lower-cost aggressive interactions are expressed towards group members further down the hierarchy. By directly evaluating differences in the strategic use of higher- and lower-cost aggressive interactions towards competitors, we show that individuals disproportionately use highest-cost interactions—such as chases—towards males found one to three ranks below themselves. Our results support the hypothesis that the costs associated with different interaction types can determine their expression in social groups with steep dominance hierarchies. This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’. [ABSTRACT FROM AUTHOR]

In group-living vertebrates, dominance status often covaries with physiological measurements (e.g. glucocorticoid levels), but it is unclear how dominance is linked to dynamic changes in physiological state over a shorter, behavioural timescale. In this observational study, we recorded spontaneous aggression among captive juvenile pheasants (Phasianus colchicus) alongside infrared thermographic measurements of their external temperature, a non-invasive technique previously used to examine stress responses in non-social contexts, where peripheral blood is redirected towards the body core. We found low but highly significant repeatability in maximum head temperature, suggesting individually consistent thermal profiles, and some indication of lower head temperatures in more active behavioural states (e.g. walking compared to resting). These individual differences were partly associated with sex, females being cooler on average than males, but unrelated to body size. During pairwise aggressive encounters, we observed a non-monotonic temperature change, with head temperature dropping rapidly immediately prior to an attack and increasing rapidly afterwards, before returning to baseline levels. This nonlinear pattern was similar for birds in aggressor and recipient roles, but aggressors were slightly hotter on average. Our findings show that aggressive interactions induce rapid temperature changes in dominants and subordinates alike, and highlight infrared thermography as a promising tool for investigating the physiological basis of pecking orders in galliforms. This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’. [ABSTRACT FROM AUTHOR]

Dominance hierarchies have been studied for almost 100 years. The science of science approach used here provides high-level insight into how the dynamics of dominance hierarchy research have shifted over this long timescale. To summarize these patterns, I extracted publication metadata using a Google Scholar search for the phrase ‘dominance hierarchy’, resulting in over 26 000 publications. I used text mining approaches to assess patterns in three areas: (1) general patterns in publication frequency and rate, (2) dynamics of term usage and (3) term co-occurrence in publications across the history of the field. While the overall number of publications per decade continues to rise, the percent growth rate has fallen in recent years, demonstrating that although there is sustained interest in dominance hierarchies, the field is no longer experiencing the explosive growth it showed in earlier decades. Results from title term co-occurrence networks and community structure show that the different subfields of dominance hierarchy research were most strongly separated early in the field’s history while modern research shows more evidence for cohesion and a lack of distinct term community boundaries. These methods provide a general view of the history of research on dominance hierarchies and can be applied to other fields or search terms to gain broad synthetic insight into patterns of interest, especially in fields with large bodies of literature. This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’. [ABSTRACT FROM AUTHOR]

A dominance hierarchy is the set of ranks occupied by species within an assemblage. Species with a high position within the dominance hierarchy tend to dominate subordinate species in contests for access to resources. In hummingbirds, greater weight and wing disc loading have been associated with highest ranks within the dominance hierarchy. Nevertheless, the limit to which the difference between the weight of contending species represents a competitive advantage has not yet been determined. Here, we determined the dominance hierarchy of a hummingbird assemblage exploiting the most abundant floral resource (Palicourea padifolia, Rubiaceae) in a cloud forest of central Veracruz, Mexico. Specifically, we tested whether species weight and wing disc loading influence the dominance hierarchy. Additionally, we tested whether the flowers visited per foraging bout increases with species weight and dominance. We further tested whether weight, wing disc loading, and the genetic relatedness between contenders influenced the dominance relationships in species-pair interactions. Our results indicate that the hierarchy is positively influenced by weight. Hummingbirds visited similar number of flowers regardless their weight or their dominance. Nevertheless, the probability that the heaviest contender won contests was positively associated with the differences of weight and genetic relatedness between contenders. Contrarily, the probability that the contender with greatest wing disc loading won contests was positively associated with differences of weight and negatively associated with the relatedness between contenders. However, these models only explained between 22% and 34% of the variation, respectively. Our results demonstrate that the weight was the major contributor to high dominance values. However, future studies should include (1) the temporal variability of the weight and (2) experimental predictor variables such the burst power of the hummingbirds to evaluate its effects on the dynamics of dominance hierarchies in hummingbird assemblages. All the hummingbird species present in the studied assemblage have developed wide behavioral mechanisms that compensate their morphological differences, which allow them to coexist, even when they compete for the access to the same resource.

Across a wide range of animal taxa, winners of previous fights are more likely to keep winning future contests, just as losers are more likely to keep losing. At present, such winner and loser effects are considered to be fairly transient. However, repeated experiences with winning and/or losing might increase the persistence of these effects, generating long-lasting consequences for social structure. To test this, we exposed genetically identical individuals of a clonal fish, the Amazon molly (Poecilia formosa), to repeated winning and/or losing dominance interactions during the first two months of their life. We subsequently investigated whether these experiences affected the fish's ability to achieve dominance in a hierarchy five months later after sexual maturity, a major life-history transition. Individuals that had only winning interactions early in life consistently ranked at the top of the hierarchy. Interestingly, individuals with only losing experience tended to achieve the middle dominance rank, whereas individuals with both winning and losing experiences generally ended up at the bottom of the hierarchy. In addition to demonstrating that early social interactions can have dramatic and long-lasting consequences for adult social behaviour and social structure, our work also shows that higher cumulative winning experience early in life can counterintuitively give rise to lower social rank later in life.