Fluid dynamics of moving fish in a two-dimensional multiparticle collision dynamics model in 2D

The fluid dynamics of animal locomotion, such as that of an undulating fish, are of great interest to both biologists and engineers. However, experimentally studying these fluid dynamics is difficult and time consuming. Model studies can be of great help because of their simpler and more detailed analysis. Their insights may guide empirical work. Particularly the recently introduced multiparticle collision dynamics method may be suitable for the study of moving organisms because it is computationally fast, simple to implement, and has a continuous representation of space. As regards the study of hydrodynamics of moving organisms, the method has only been applied at low Reynolds numbers (below 120) for soft, permeable bodies, and static fishlike shapes. In the present paper we use it to study the hydrodynamics of an undulating fish at Reynolds numbers 1100–1500, after confirming its performance for a moving insect wing at Reynolds number 75. We measure (1) drag, thrust, and lift forces, (2) swimming efficiency and spatial structure of the wake, and (3) distribution of forces along the fish body. We confirm the resemblance between the simulated undulating fish and empirical data. In contrast to theoretical predictions, our model shows that for steadily undulating fish, thrust is produced by the rear 2/3 of the body and that the slip ratio U/V (with U the forward swimming speed and V the rearward speed of the body wave) correlates negatively (instead of positively) with the actual Froude efficiency of swimming. Besides, we show that the common practice of modeling individuals while constraining their sideways acceleration causes them to resemble unconstrained fish with a higher tailbeat frequenc

Reconciliation and relationship quality in Assamese macaques (Macaca assamensis)

A consistent conclusion in reconciliation research is that animals that reconcile are likely to have strong social bonds. This has led to the hypothesis that reconciliation occurs most often between valuable social partners. We tested this hypothesis in a group of Assamese macaques (Macaca assamensis) living near a temple in Assam, India. Using focal sample and ad libitum data collection, we recorded the occurrence of reconciliation, grooming, and agonistic aiding, and the outcomes of approach. We used matrix association methods (Tau(Kr) correlation) to correlate reconciliation with grooming, aiding, and approach outcome. Females reconciled more often with females with which they had stronger grooming and aiding relationships. The correlation between reconciliation and aiding was significant for support to the aggressor and the victim. In contrast, no such correlations with reconciliation were found for males. This study provides evidence that females reconcile most often with valuable and compatible social partners. The results do not support the relationship-quality hypothesis for males, and we suggest that future studies give more consideration to the possibility that males reconcile for reasons other than to repair relationships with valuable partners. (c) 2005 Wiley-Liss, Inc

Editorial: Sex and gender effects on power, status, dominance, and leadership – an interdisciplinary look at human and other mammalian societies

In human societies, men tend to have more power, status, dominance, and occupy leadership positions more often than women; similarly, in animal societies, power and dominance are often unequally distributed between males and females. Despite these similarities across societies of humans and animals, the scientific study of power, status, dominance, and leadership have (for the most part) progressed in isolation, with little cross-disciplinary exchange or fertilization between the natural and social sciences. In the social sciences, an extensive body of work has investigated the relation between gender (or sometimes sex) and power, status, dominance, and leadership outcomes (e.g., Eagly & Karau, 2002; Goldin, 2014; Eagly and Heilman, 2016; Meeussen et al., 2016; Hentschel et al., 2018; Von Rueden et al., 2018; Smith et al., 2020; Eckel et al., 2021; Shen et al., in press; Heilman et al., 2024). This effort notwithstanding, many questions remain. For example, we lack a comprehensive understanding of the contexts and circumstances that favor (or undermine) women’s advancement to powerful positions, and about why and when female and male leaders are evaluated differently (Williams and Tiedens, 2016; Cardador et al., 2022). In the natural sciences, empirical investigations in mammalian societies have primarily focused on the evolutionary origins and dynamics of male-female power asymmetries. Specifically, such investigations often focus on a few taxa with female dominance, such as bonobos, lemurs, and spotted hyenas (Kappeler, 1993; Lewis, 2018; Davidian et al., 2022; Smith et al. in this Research Topic). Notably, intersexual dominance–the distribution of power and status between the sexes—is often treated as a binary (i.e., a species is described as either male-dominant or female-dominant) and as a fixed (rather than flexible) trait of a given species (Lewis, 2018; Davidian, 2022). Contrary to this view, recent studies suggest the relative power of the sexes in some animal societies may be less biased in favor of one sex and more flexible than previously assumed (Kappeler et al.). With this Research Topic, we aim to facilitate academic exchange, to learn from perspectives that typically lie outside of each of our disciplinary boundaries, to draw comparisons and insights across these perspectives, and to promote an integrative understanding of gender and sex1 inequalities in power, status, dominance, and leadership. To do so, this Research Topic combines contributions from ecology, biology, psychology, and management. It houses a collection of 21 articles, including 10 articles from the social sciences and 11 articles from the natural sciences. We hope this trans-disciplinary Research Topic will not only deepen our understanding of the roots and origins of gender and sex inequalities in humans and non-humans, but also generate new insights into possible solutions for reducing sex and gender disparities

Sexual attraction and inter-sexual dominance among virtual agents

In many group-living primates, males are dominant over females, but despite this dominance, they allow females access to resources during the period when females are sexually attractive - but only then and not otherwise. Conventionally, such male 'courtesy' is explained as a special strategy to gain mating access to females. In the present paper I propose a simpler hypothesis that is based on an agent-centered model, namely that male 'courtesy' to females is in fact a kind of 'timidity' that arises because sexual attraction automatically increases female dominance. The model consists in a homogeneous, virtual world with agents that group and perform dominance interactions. VirtualMales have a higher intensity of aggression and start with a greater capacity to win conflicts than VirtualFemales. I shall explain how the addition of attraction of VirtualMales by VirtualFemales leads to female dominance, and other phenomena that are relevant to the study of animal behaviour ER