Philosophical Transactions of the Royal Society B: Biological Sciences

Humans and other animals live in interconnected social communities that are essential for survival and well-being. In principle, social communities can persist despite changes in constituent members. However, gradually accumulating changes to membership could push systems past critical thresholds into alternate states. We investigated social network dynamics for 443 wild female Asian elephants over 12 years by tracking community membership and structure. Following accumulated demographic turnover, networks fractured into smaller and more isolated social communities. Connections were changed not only due to turnover of members but also rewired among remaining individuals. This provides the first empirical evidence of a social network state change in a long-lived mammal.

Social relationships are foundational to animal societies, but individual social connections differ hugely in importance and strength. Key relationships, such as those between breeding partners, may be prioritised and more highly invested in by individuals, but a key question is the extent to which social flexibility allows individuals to respond to the loss of these key social relationships. Here, we use a detailed longitudinal dataset of individual breeding and social behaviour in wild great tits (Parus major) to characterise flexibility in social behaviour after the loss of their breeding partner ('widowing'). We show transient increases in two measures of sociality following the widowing event. Individuals' relationships with their replacement partner were initially weaker than those between non-widowed birds, but converged by the breeding season. Hence, we show that birds are robust to the loss of key social relationships and that great tits show a flexible ability to return to social equilibrium. Strong social resilience has implications for the response of populations to change and loss.

Social relationships are strongly linked to health and biological fitness in humans and other animals. For example, social support may buffer individuals against harsh ecological conditions. Reciprocally, better health may allow for greater investment in social relationships. We examined links between health and social behaviour in an endangered population of northern bottlenose whales (Hyperoodon ampullatus). Using photo-identifications spanning 37 years, we visually classified whether individuals had poor body condition on each day they were observed (N = 3,086 whale-days). We then used generalized linear mixed models to explore how body condition varied with sex, age, and within-individual deviations in group size or other social metrics derived from Bayesian social networks. Approximately 11% of individuals were classified as being in poor condition at any time, though the prevalence of poor condition varied across raters and years. Visually assessed condition was successfully validated with morphometric measures, though there was only weak evidence that poor condition predicted apparent survival. Contrary to expectations, whales in poor condition were found in larger groups and had more social partners than their average across the study period. These findings run counter to the expectation that health and social connectedness are positively correlated in social mammals.

Compositional syntax - the ability to combine meaningful units into structured sequences whose overall meaning depends on both the meanings of the parts and their combination - is a hallmark of human language. Recent work suggests that chimpanzees may exhibit similar capacities, raising the possibility that compositionality predates the emergence of language in humans. However, a key challenge has been to exclude simpler explanations in which call combinations are processed as independent utterances rather than integrated structures. Here, we address this issue using a source-manipulation paradigm in playback experiments with captive chimpanzees (n = 6) at the Sigean African Reserve, France. We presented sequences combining alarm and recruitment calls either from a single source (one loudspeaker) or from two spatially distinct sources (two loudspeakers). If sequences are interpreted as independent calls, responses should not differ between conditions. Instead, chimpanzees responded significantly faster when sequences originated from a single source. Bayesian survival analyses confirmed this effect. These results support a non-trivial form of compositionality, whereby the meaning of call combinations depends on their integration into a unified sequence produced by a single individual. Our findings provide experimental evidence that key features of linguistic compositionality may have evolutionary roots in the primate lineage.

Social relationships can buffer individuals against environmental challenges, reducing the physiological costs of disturbance. Assessing how social and environmental conditions jointly shape physiological stress is critical for predicting individual responses to disturbance, particularly in managed populations. We evaluated whether social and environmental stressors act additively or whether social context modifies physiological responses to environmental challenges. We combined behavioural data and faecal glucocorticoid metabolite samples from a small, intensively monitored population of African elephants (Loxodonta africana) in a fenced reserve. Using a Bayesian framework, we tested how social factors interacted with variation in the biophysical environment, including natural environmental and anthropogenic disturbances, to predict glucocorticoid concentrations. Natural environmental variables, including weather, water availability, and season, did not predict glucocorticoid concentrations. In contrast, helicopter use, a common management intervention, was associated with higher glucocorticoid concentrations. Social effects were context dependent. Following disturbance, low-ranking individuals showed higher glucocorticoid concentrations than high-ranking individuals, whereas this pattern reversed under low-disturbance conditions. Individuals with more social connections had lower glucocorticoid concentrations, but this effect was evident only under non-disturbance conditions. Measures of betweenness centrality did not predict glucocorticoid levels. These results demonstrate that social factors mediate physiological responses to anthropogenic disturbance and that management actions can impose uneven physiological costs across individuals. Quantifying interactions between social factors and the biophysical environment may improve conservation and management strategies for social species. Integrating physiological responses to interactions between social factors and the biophysical environment can guide conservation strategies and improve management interventions in social species.

Classic socio-ecological theory predicts that males and females experience different sources and mechanisms of social competition. Whether these differences translate into sex-specific structural properties of dominance hierarchies remains unclear. Here, we compiled 156 dominance interaction matrices from 80 published studies and extracted three commonly used metrics - hierarchy steepness, linearity and the directional consistency index - to investigate the structural characteristics of male and female dominance hierarchies across primates. All three metrics were strongly affected by methodological and demographic variables. Steepness increased with the number of recorded interactions and group size, linearity decreased as matrices became sparser, and directional consistency declined with increasing numbers of interactions. Steepness covaried positively with both linearity and directional consistency, indicating that groups with steeper hierarchies also exhibited more linear and more directionally consistent relationships. We found no sex differences in steepness, linearity or directional consistency. These results suggest that current metrics primarily reflect variation in the sampling effort and the rate of interaction of the recorded behaviour and appear therefore not to capture potential sex differences in the forms of competition. Our findings highlight the need for alternative measures of power asymmetries that are less confounded by sampling effort and demographic variation to better understand how competition and conflict are structured across primate societies.

Changes in fire regimes negatively impact biodiversity worldwide1,2. The immediate behavioral responses of animals to fire, however, are largely unknown. Despite presenting obvious dangers, fire can also attract animals by providing unique foraging opportunities3. Such attraction to fire (pyrophilia) has already been observed in some bird species, yet its underlying motivation remains unidentified. Here, we examined the abundance and behavior of 16 bird species before, during, and after prescribed burns in the northern Australian savanna. Eight species were on average 3 to 23 times more abundant during fires. Raptors caught on average ten times more prey per hour during burns than in the absence of fire, and their foraging success increased with fire size. Black kites, the most pyrophilic birds observed, were more numerous during larger fires and foraged more efficiently on the ground than in the air. These results underscore the importance of investigating animal behavior in response to active fire and the effects of shifting fire regimes on the foraging ecology of pyrophilic animals.

Game theory in biology started as an attempt to model animal contests by making assumptions about the fitness costs individuals pay in aggressive interactions. Among the different approaches, a notable one is to construct mechanistic models, using assumptions about behaviours and cognitive processes. Reinforcement learning is an important cognitive process, and we use it here to model pairwise and coalitional contests. We study situations where territorial neighbours become so-called dear enemies. A defending individual can get help from a neighbour through a defender-neighbour coalition against a challenger attempting territory takeover. In our model, coalition members have an advantage in contests in terms of costs of aggression, with the challenger being exposed to aggression from both members and each member only receiving part of the aggression from the challenger. We find that notable costs of border conflicts between neighbours, together with substantial advantages for coalitions, favour intervention. Neighbours intervene when they can help weaker defenders, in this way avoiding costs of border renegotiation with a new and potentially stronger territory owner. We also introduce different forms of perceived costs into the model, which we show correspond to the range from pure mutual assessment to partial self-assessment.

Global biodiversity recovery demands restoration at landscape scales, where ecological outcomes are shaped not only by habitat amount but also spatial arrangement. Alternative landscape restoration strategies can increase habitat amount, improve quality, and alter configuration in fundamentally different ways and may therefore vary in their efficiency. Here, we conceptualise five landscape restoration strategies and use a spatially explicit metapopulation framework to compare their ability to increase predicted species persistence across heterogeneous landscapes and trait space defined by dispersal ability and specialisation. We find that restoration outcomes are strongly trait-dependent, with restoration of existing degraded habitats yielding the highest benefits - particularly for specialists. Improvement of the landscape matrix to create low-quality habitat primarily benefits generalists, while strategies creating new habitat patches or enlarging patches provide more consistent but modest gains. These results reveal fundamental trade-offs among restoration strategies and highlight the utility of trait-explicit approaches to inform their implementation and evaluation.

During the lifetime of many animals, the microbiota fulfills multiple functions. After death of their hosts, these microbes contribute to cadaver decomposition, with implications for forensics, fossilization and soil nutrient and microbial community dynamics. Here, we draw attention to the possibility that host microbiota can also influence the evolution of pathogen lifestyles. We hypothesized that competition between microbiota and pathogens after host death can reduce benefits to pathogens of killing and decomposing their host. To test this hypothesis, we conducted infection experiments in which we injected the entomopathogenic bacteria Pseudomonas entomophila into Tenebrio molitor larvae. Our results show that bacterial proliferation after pathogen-induced host death occurs in larvae with strongly reduced microbiota, but not in larvae with intact gut microbiota. Strikingly, we found that gut microbiota can suppress the proliferation of an about 100 times larger pathogen population. In addition, we identified a microbiota member that might have mediated competitive suppression of pathogen proliferation after host death. Taken together, our results support our hypothesis that decomposing host microbiota can effectively compete with pathogens, thereby reducing the fitness of pathogens that kill and then exploit dead hosts. Based on a reanalysis of an existing theoretical model, we conclude that the host microbiota can facilitate the evolution of more benign pathogens that are less likely to kill their host for cadaver exploitation. Thus, our findings highlight the potentially important but so far unexplored possibility that pathogen-microbiota interactions in dead hosts can affect living hosts by influencing the evolution of pathogens lifestyles.

Primates maintain cooperative relationships largely through grooming reciprocity, yet studies disagree on the timescales over which grooming is returned. Part of this disagreement stems from statistical issues: inconsistent definitions of a reciprocation window, combined with the exclusion of unreciprocated grooming, leave the debate unresolved. We still do not know if primates exchange grooming within the short windows predicted by biological market theory or over much longer timescales. Whilst survival analysis can identify reciprocation windows objectively by retaining unreciprocated grooming as censored data, previous studies have applied it inconsistently. This inconsistency leaves the true time frames over which primates reciprocate grooming somewhat blurred. Here, we use a statistical approach that addresses these problems to examine grooming reciprocity in crested macaques (Macaca nigra), a socially tolerant macaque species. We applied survival analysis to identify each group's short-term reciprocation window without imposing arbitrary cut offs, and Bayesian survival models to test whether social bond strength and eigenvector centrality predicted reciprocation latency. Short-term reciprocation occurred rarely (29% of events in one group and 5% in the other); most reciprocation occurred over longer timescales than previous research commonly assumes. Stronger bonds predicted faster reciprocation; this finding suggests that crested macaques express social investment in valued partners through how promptly they return grooming, meaning that the timing of exchange carries information about relationship value. Eigenvector centrality showed no credible effect, though our small sample size and dense groups prevent us from interpreting this outcome more robustly. Substantial variation between dyads remained unexplained, pointing to partnerspecific properties we have yet to identify. These findings caution against assuming that reciprocity operates over short windows. They show that social predictors, such as bond strength, remain essential to understanding when primates return grooming. This work provides a baseline for testing whether grooming is exchanged for other social commodities, and for comparing reciprocation timescales across macaque species that differ in social tolerance.

Jumping is a challenging locomotive mode, requiring rapid force generation and precise coordination of multiple limbs. Many animals meet this challenge using elastic mechanisms that store and rapidly release energy. Jumping spiders (Salticidae), however, rely on a semi-hydraulic system that constrains how their legs can generate propulsion. Much about how these spiders reliably generate jumps within these mechanical constraints remains unknown. Here, we analyze 46 individuals spanning 14 genera and significant morphological diversity and show that this physically constrained system is coupled to a remarkably stereotyped coordination strategy. Whole-body kinematics and novel graph-based analyses of inter-limb coordination reveal a stereotyped two-stage takeoff sequence: a "swing" driven by extension of the fourth legs, followed by a rapid "fling" by the third legs that generates propulsion for takeoff. We further demonstrate that this pattern is preserved beyond Amazonian species, persisting in salticids from North America and Australia. Our results suggest that physical and biomechanical constraints may canalize locomotor evolution toward a common dynamical solution.

Pseudomonas aeruginosa encodes diverse defence systems against phages and mobile genetic elements, yet their variation across clinical contexts remains unclear. Here, we present a large-scale comparative analysis of the P. aeruginosa defensome across both public and clinically highly relevant datasets, including from patients with chronic lung disease and multidrug-resistant isolates. Our analysis shows that while influences on defensome composition are minor, multidrug-resistant isolates encode more defence systems and cystic fibrosis-associated isolates have fewer. Across phylogenetic clusters, defensome size correlates with cluster abundance, suggesting that defence-rich lineages persist more successfully across environments. Lastly, comparative analysis with other Pseudomonas species reveals enrichment of anti-plasmid systems in P. aeruginosa. Overall, these findings have important implications for phage therapy: multidrug-resistant infections may be more difficult to treat, while cystic-fibrosis-associated isolates may have higher phage susceptibility. This work provides a framework for understanding defensome variation and guiding the decision-making process of phage-based therapies.

From animal societies to self-organizing multi-agent systems, collectives adapt their group structure to tasks and environments. However, how they determine appropriate group sizes and the number of subgroups to form remains unclear. We formulate the Group Size and Number Regulation Problem (GSNRP), which asks how individuals regulate group sizes and numbers using only local information. In a first step, we establish a graph-theoretic model demonstrating that simple following behavior suffices to form group structures that match theoretical expectations, but is insufficient for active regulation of group size and number. In a second step, we operationalize individual group-size preferences in a decentralized fission-fusion mechanism based on perceived group size. Through multi-agent simulations, we validate that this mechanism achieves stable convergence across three signaling regimes, from position-only sensing to continuous group-size communication. Using tracking data from wild white-nosed coatis (mammals in the raccoon family), we calibrate individual group-size preferences and show that the controller recovers selected group-size, subgroup-count, and transition statistics. This in-sample case study demonstrates descriptive consistency with natural fission-fusion dynamics without establishing the underlying behavioral mechanism. These results suggest that natural and engineered collectives may share local principles of perception, preference, and response for regulating group structure.

Predicting patterns of behavioural coordination that emerge in small interacting groups is challenging because goal-directed social action is shaped by complex reciprocal and compensatory dynamics. In this study, we examined whether formal symmetry principles derived from group theory could explain coordination patterns among children performing a triadic jumping task. We investigated how geometric symmetries of the task environment and dispositional (a)symmetries associated with leader-follower tendencies jointly constrain collective behaviour. Forty-seven children were classified into symmetric or asymmetric triads based on teacher evaluations of leadership dispositions. Each triad completed multiple trials of a synchronized jumping game requiring movement between adjacent hoops arranged in triangular or square configurations. Results showed that temporal asymmetries in inter-child movement (first, second, or last to jump) were consistent with group-theoretic predictions. In triangular configurations, observed asymmetries corresponded to the highest-order subgroup defined by task and dispositional symmetries. These findings demonstrate that environmental symmetry exerts a hierarchically dominant constraint on collective coordination, within which actor dispositional (a)symmetries further modulate emerging patterns.

Biological individuals on Earth today are cellular, but the simplest cells are too complex to have arisen spontaneously. We explore the hypothesis that the emergence of biological individuality might have been driven by selection for different molecules to move through space together by forming a propagule. We predicted that propagule formation will be advantageous to an autocatalytic system primarily when 1) sites supporting autocatalysis are distantly spaced and 2) the environment undergoes periodic disturbances. We tested this hypothesis using computational reaction-diffusion models of surface-catalyzed autocatalytic systems in patchy, disturbance-prone environments. We considered two competing autocatalytic cycles, each composed of mutualistic subcycles, one of which diverts flux to the production of propagules. Our analysis shows that propagules tend to be detrimental in well-mixed environments or environments where viable surfaces are close enough together to be reliably seeded through single-species dispersal. However, propagule formation is advantageous when long stretches of empty space must be crossed to reach new resources and/or when environmental disturbances are frequent. These findings suggest spatial structure can selectively favor reliable forms of codispersal. Evolution in response to this mechanism could potentially explain the emergence of vesicles that transported many autocatalytic species and eventually became independent protocells.

1. Passive acoustic monitoring (PAM) is increasingly used for ecological research, biodiversity monitoring, assessment, and reporting. Automated species classifiers make it feasible to process large audio datasets but generate numerous detections that often need validation before use in downstream analyses or formal outputs. 2. Method development in PAM has focused on classifier building and downstream models that account for imperfect detection, yet the practical step between these - post-classification validation - remains weakly supported and is often implemented through ad hoc workflows. This increases manual handling, creates scope for transcription or consolidation errors, limits transparency and makes it difficult to document what was reviewed. 3. We introduce PAMalytics, an open-source, no-code, local browser-based application to support post-classification validation as a standardised workflow stage. PAMalytics ingests detections from any classifier, allows users to define how detections are sampled for review, and presents selected detections alongside their spectrograms with audio playback in one unified interface. Sampling strategy and review decisions are tracked alongside reviewer identity improving traceability and reproducibility across the validation workflow. 4. Case studies with Conservation International Cambodia and Imperial College London demonstrate PAMalytics in two validation settings. In Cambodia, gibbon predictions from a large, uneven dataset were sampled within sites, with likely classifier errors prioritised for validation. At Imperial, Amazon bird detections were sampled across each species classifier-confidence range before biodiversity metrics were derived. In both cases, PAMalytics reduced manual handling and validation time. By turning an ad hoc step into an accessible, structured workflow for conservation practitioners, PAMalytics fills a practical gap in the PAM bioacoustics pipeline and strengthens the link between automated detections and evidence used in biodiversity monitoring and reporting.

A central question in ecology and evolution is determining when environmental challenges translate into stress and biological harm. Human-derived pollutants are often assumed to be inherently damaging; however, their effects may depend strongly on ecological and physiological context. Microplastics exemplify this complexity, eliciting heterogeneous responses across taxa rather than uniform toxicity. Here, we synthesise evidence from 14 meta-analyses encompassing 9,101 effect sizes to identify the conditions under which microplastic exposure leads to damage, neutrality, compensation, or stimulation. These syntheses reveal clear negative effects alongside frequent neutral outcomes and occasional stimulatory responses. Microplastic effects vary with particle characteristics and exposure conditions and are strongly moderated by species-specific traits and life stage. We further argue that plasticity in the gut and in behavioural and physiological traits may buffer microplastic effects. Emerging evidence also indicates that biofilm colonisation alters the physicochemical and biological properties of microplastics, potentially modifying their ecological interactions and toxicity profiles. By reframing microplastics as context-dependent challenges rather than universally toxic agents, we provide a conceptual framework for understanding animal responses under realistic ecological conditions and identifying the biological and environmental contexts in which microplastic exposure is most likely to result in harm.

Gene drives are potentially powerful tools, able to spread throughout target populations. They could be used to modify or suppress disease vectors, invasive species, and agricultural pests. Yet, in many scenarios, confinement of the drive to only a target population is required. Several types of drives are capable of this, among the most promising of which are CRISPR toxin-antidote drives. Though showing good performance in simple models, such drives have not been thoroughly assessed in spatially structured populations. Here we evaluate three modification drive variants with varying levels of confinement. We find that Toxin-Antidote Recessive Embryo (TARE) drive and 2-locus TARE drives can usually spread in connected populations or from a single sufficiently large release. However, they can still be stopped by a migration corridor or by a sufficiently high population density gradient. 1-locus 2-drive TARE, on the other hand, will not be able to spread outside of release areas and indeed will often retreat in the face of wild-type alleles. When these drives arrive at a point source such as a port, only the standard TARE drive has a significant chance of establishing if releases occur at sufficiently high frequency and quantity. However, in models with parental care among a limited number of offspring, TARE drives become more invasive, with lower introduction thresholds. Overall, we find that spatial and other ecological factors can substantially affect the outcome of a confined CRISPR toxin-antidote drive release.

Environmental disturbances are ubiquitous in microbial ecosystems, yet their effects on community composition and interactions remain poorly understood. Here, we combine analytical derivations and large-scale generalized Lotka-Volterra simulations to examine how recurrent disturbances, varying in intensity (C), frequency (1/T), regularity, and evenness, affect microbial communities. We find that context-dependent interactions (ICD)--representing the net effect of the entire community on each species--are robust to changes in disturbance intensity and frequency. Community composition is influenced by disturbance, but this effect is primarily captured by a single composite parameter T/log(C), reducing the two-dimensional disturbance space onto a one-dimensional axis. Species abundances and ICD remain largely independent of specific values of T and C except near critical transition regions (survival thresholds and no-interaction zones). Sensitivity analyses show that disturbance-sensitive cases occur in the vicinity of these boundaries. This robustness extends to when the disturbance is irregular (even up to 50% stochastic variation in T or C), with uneven disturbances, when the disturbance is species-specific, and holds at any time point throughout the inter-disturbance growth phase. The patterns are independent of species richness, growth rates, carrying capacities, and interaction strengths. Our findings highlight that microbial community organization is largely conserved under recurrent environmental stress, with extinction acting as the dominant route by which disturbances reshape communities. These findings indicate that disturbance is not a strong driver of community structure and that minor variations in experimental or environmental conditions or sampling time are not expected to substantially impact microbiome composition.