Biology subjects

Green, P. A.

Publications and source records attributed to Green, P. A..

6 recordsLinked to original sources

bioRxiv2025

Collective Self-Assessment in Banded Mongoose Intergroup Contests

Contests over resources are widespread in nature. To optimize outcomes, animals assess fighting abilities, deciding to escalate conflicts based on their own strength (self-assessment) or comparing their own strength with that of their rival (mutual assessment). While most research focuses on one-on-one (dyadic) contests, the assessment strategies employed by groups remain poorly understood. Mutual assessment is frequently assumed, as more information is thought to improve decision-making; however, this assumption has rarely been tested. Here we used a dataset spanning 23 years and 641 intergroup contests in a banded mongoose (Mungos mungo) population in Queen Elizabeth National Park, Uganda. Our results support a model of self-assessment: groups with many males tend to escalate conflicts regardless of the rival groups strength, thus contrasting the commonly held assumption that decisions during intergroup contests are made by mutual assessment. We suggest that assessing rival group strength during conflict could be disproportionately costly, compared with assessing own group strength, which can be done over longer time periods and is easier to obtain. Greater understanding of these dynamics can shed light on the drivers and escalation patterns of intergroup conflict across social species, including humans. Lay SummaryWhen two rival groups come together, what determines whether or not they fight? We found support for the hypothesis that banded mongoose groups escalate into physical fights based upon an estimation of their own groups strength, which we term collective self-assessment. We did not find evidence for a commonly held notion that groups compare their own groups strength with their rivals. Distinguishing between assessment strategies is intensively researched in contests between individuals but has rarely been applied to intergroup conflict. Here we applied the successful "assessment strategy framework" to group conflict, analyzing over 20 years of data from over 600 intergroup interactions. We suggest that collective self-assessment is employed because it is faster than mutual assessment, which offers an advantage in conflicts where time is of the essence.

animal behavior and cognition↗

bioRxiv2025

A landscape of intergroup conflict shapes den site choice in banded mongooses

BackgroundFor many social animals, intergroup conflict has major impacts on fitness and should therefore influence how groups navigate their environment. Yet most studies of group movement focus on the behaviour of single groups, usually foraging groups studied in isolation of all others. In many systems rival groups present both threats and opportunities, contributing to a landscape of intergroup conflict. This landscape could have a profound impact on group movement. MethodsHere we test how the potential for intergroup conflict influences movement decisions of wild cooperatively breeding banded mongooses, using 14 years of behavioural and GPS data. In this species, encounters between groups can present both risks (e.g. injury/mortality) and opportunities (e.g., extragroup mating). We expected that, to minimise risks and maximise rewards, the motivation to engage in conflict would depend on the groups state. Such that vulnerable groups (those that were babysitting young offspring) would select den sites closer to the core of their territory than groups without young offspring. ResultsWe found support for this pattern; non-babysitting groups were unusually risk prone choosing den locations in areas of frequent use by outgroups. During times of heightened recent conflict even choosing to den closer to the core of their rivals territory than their own. ConclusionsThese results suggest that groups of banded mongooses choose den sites that reflect not only the risks but also the potential rewards of defensive or competitive claims on space. Rival groups thus form an integral part of the social landscape shaping patterns of collective movement.

animal behavior and cognition↗

bioRxiv2024

Fitness incentives to male fighters undermine fighting performance in intergroup contests

In humans and other animal societies, groups engage in intergroup conflicts over resources. The success of groups in these conflicts depends on individual contributions to collective fighting, yet individuals may have personal fitness incentives to defect rather than fight, which could undermine group performance. Here we test the hypothesis that personal fitness incentives affect intergroup conflict success in wild banded mongooses (Mungos mungo). In this species, intergroup fights are sometimes initiated by estrous females, who gain outgroup matings while their male group-mates contribute most of the fighting effort. We found that group fighting success was highest when a groups females were in estrus, suggesting that, although females may initiate fights, their male group-mates seem motivated to chase away rival groups to defend their paternity. Surprisingly, we found that groups that won fights conceded more paternity to their rivals than groups that lost. In other words, behavioral "wins" did not always result in fitness "wins". Younger males were more successful at attaining paternity between groups compared to within their own groups, suggesting that they may forego intergroup fighting to focus on intergroup mating. Overall, our results suggest that personal fitness incentives--here, in the form of paternity--vary widely among group members and can undermine rather than promote collective fighting performance. Such conflicts of interest are likely inherent in group combat and can contribute to variation in the frequency and costliness of intergroup violence.

animal behavior and cognition↗

bioRxiv2023

Combining behavior and mechanics approaches reveals the dynamics of animal impacts in mantis shrimp (Stomatopoda)

Animals deliver and withstand physical impacts in diverse behavioral contexts, from competing rams clashing their antlers together to archerfish impacting prey with jets of water. Though the ability of animals to withstand impact has generally been studied by focusing on morphology, behaviors may also influence impact resistance. Mantis shrimp exchange high-force strikes on each others coiled, armored telsons (tailplates) during contests over territory. Prior work has shown that telson morphology has high impact resistance. I hypothesized that the behavior of coiling the telson also contributes to impact energy dissipation. By measuring impact dynamics from high-speed videos of strikes exchanged during contests between freely-moving animals, I found that over 20% more impact energy was dissipated as compared to a prior study that focused solely on morphology. This increase is likely due to behavior: because the telson is lifted off the substrate, the entire body flexes after contact, dissipating more energy than exoskeletal morphology does on its own. While variation in the degree of telson coil did not affect energy dissipation, higher velocity strikes resulted in greater energy dissipation, suggesting striking individuals may vary their behavior to affect impacts. Overall, these findings show that analysis of both behavior and morphology is crucial to understanding impact resistance, and suggest future research on the evolution of structure and function under the selective pressure of biological impacts. Summary statementFreely competing mantis shrimp dissipated over 90% of the energy of high-force strikes by raising their impact-resistant tailplates off the substrate; faster strikes led to greater energy dissipation.

biophysics↗

bioRxiv2023

The Evolution of Democratic Peace

A major goal in evolutionary biology is to elucidate common principles that drive human and other animal societies to adopt either a warlike or peaceful nature. One proposed explanation for the variation in aggression between human societies is the democratic peace hypothesis. According to this theory, autocracies are more warlike than democracies because autocratic leaders can pursue fights for private gain. However, autocratic and democratic decision-making processes are not unique to humans and are widely observed across a diverse range of non-human animal societies. We use evolutionary game theory to evaluate whether the logic of democratic peace may apply across taxa; specifically adapting the classic Hawk-Dove model to consider conflict decisions made by groups rather than individuals. We find support for the democratic peace hypothesis without mechanisms involving complex human institutions and discuss how these findings might be relevant to non-human animal societies. We suggest that the degree to which collective decisions are shared may explain variation in the intensity of intergroup conflict in nature.

evolutionary biology↗

bioRxiv2020

Threshold assessment, categorical perception, and the evolution of reliable signaling

Animals often use assessment signals to communicate information about their quality to a variety of receivers, including potential mates, competitors, and predators. But what maintains reliable signaling and prevents signalers from signaling a better quality than they actually have? Previous work has shown that reliable signaling can be maintained if signalers pay fitness costs for signaling at different intensities and these costs are greater for lower quality individuals than higher quality ones. Models supporting this idea typically assume that continuous variation in signal intensity is perceived as such by receivers. In many organisms, however, receivers have threshold responses to signals, in which they respond to a signal if it is above a threshold value and do not respond if the signal is below the threshold value. Here, we use both analytical and individual-based models to investigate how such threshold responses affect the reliability of assessment signals. We show that reliable signaling systems can break down when receivers have an invariant threshold response, but reliable signaling can be rescued if there is variation among receivers in the location of their threshold boundary. Our models provide an important step towards understanding signal evolution when receivers have threshold responses to continuous signal variation.

animal behavior and cognition↗