Anthrax, caused by Bacillus anthracis, is a globally distributed zoonosis with major ecological, economic, and health consequences, particularly in agropastoral systems. For environmentally persistent pathogens, transmission is shaped by carcass persistence, environmental amplification, and host exposure. Carnivore scavenging and predation may influence these pathways, but are often omitted from multi-host disease models. We developed a deterministic One Health model framework linking humans, livestock, wild herbivores, environmental spores, and hyena scavenging and predation. We simulated nine 180-day scenarios varying hyena population size (N = 0, 20, or 150) and prey preference, parameterized for East African savannas and calibrated to attack rates from Ugandan outbreaks. Monte Carlo sensitivity analyses evaluated uncertainty in transmission, dose–response, scavenging, and environmental parameters. Cumulative human infections were strongly correlated with livestock infections (Pearson’s r = 1.00) and final environmental spore load (Pearson’s r = 0.96). Small and large hyena population sizes reduced mean cumulative human infections by 69% and 71%, compared to the no-hyena baseline. The largest reductions occurred when infected livestock were removed before carcass-mediated sporulation, lowering mean cumulative human infections by 85–86%. These results suggest that scavenging and predation may reduce outbreak severity in environmentally maintained anthrax systems.

Abstract Here, we present HyenaSET, a large (~1640 hours) bioacoustic dataset derived from collar-mounted audio recorders deployed on 19 spotted hyenas in the Maasai Mara National Reserve, Kenya. Within this dataset, 243 hours have been strongly labeled by identifying the onset and offset of all vocalizations as well as their types, and the labels have been validated by experts on hyena vocalizations and behavior. Within the strongly labeled data, the total amount of time hyenas were vocalizing was 9.5 hours (3.9%). Furthermore, each vocalization has been manually identified as “focal” (emitted by the hyena wearing the collar) or “non-focal” (emitted by a nearby conspecific), making use of information from collar-mounted accelerometers that picked up vibrations of the animal’s throat when it produced vocalizations. In addition to the labeled data, we also provide a large corpus of unlabeled data from the same recordings, which can be used for un- or self-supervised machine learning tasks. To ensure reproducibility of this dataset as a benchmark in machine learning studies, we present it alongside five stratified cross-validation train/test splits to enable accurate comparisons, and we also provide a train/test split in which specific individuals are left out of the training set to assess generalizability across individuals. Finally, as a performance benchmark, we present baseline results for this dataset using animal2vec , a recently developed transformer-based model optimized for bioacoustic data.

Spotted hyaenas, Crocuta crocuta, have well-defined membership in social groups called 'clans'. In most parts of the species'range, each spotted hyaena clan controls its own space, with its members actively advertising and defending the group's communal territory. Clanmates compete daily for food, but they also often join forces to defend both territory boundaries from neighbouring clans and kills from neighbours and lions, Panthera leo. Although most clans contain multiple matrilines, these matrilineal family units are secondary in importance to clans as the enduring social units that defend key resources, especially the group's shared space, but also individual ungulate carcasses. Females are philopatric but most males disperse, and clan membership is permeable to males but not females. These hyaenas can clearly distinguish conspecifics that belong to their clan from those that do not, using various sensory modalities. Clan membership changes as new members are born or immigrate into the clan, and as others emigrate or die, yet clans typically persist for multiple generations, although they are not permanent. (c) 2025 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Animal behavior can be decomposed into a sequence of discrete activity bouts over time. Analyzing the statistical structure of such behavioral sequences can provide insights into the drivers of behavioral decisions. Laboratory studies, predominantly in invertebrates, have suggested that behavioral sequences exhibit multiple timescales and long-range memory, but whether these results can be generalized to other taxa and to animals in natural settings remains unclear. By analyzing accelerometer-inferred predictions of behavioral states in three species of social mammals (meerkats, white-nosed coatis, and spotted hyenas) in the wild, we found surprisingly consistent structuring of behavioral sequences across all behavioral states, all individuals, and all study species. Behavioral bouts were characterized by decreasing hazard functions, wherein the longer a behavioral bout had progressed, the less likely it was to end within the next instant. The predictability of an animal's future behavioral state as a function of its present state always decreased as a truncated power-law for predictions made farther into the future, with very similar estimates for the power law exponent across all species. Finally, the distributions of bout durations were also heavy-tailed. Why such shared structural principles emerge remains unknown, and we explore multiple plausible explanations, including environmental nonstationarity, behavioral self-reinforcement, and the hierarchical nature of behavior. The existence of highly consistent patterns in behavioral sequences across our study species suggests that these phenomena could be widespread in nature, and points to the existence of fundamental properties of behavioral dynamics that could drive such convergent patterns.

Much historic work has focused on establishing geographical and ecological rules that broadly explain patterns in size variation. We examined geographic variation in Spotted Hyena skull size using geometric morphometrics and spatial statistics. We quantified size variation and sexual size dimorphism of the skull, and evaluated the influence of temperature, precipitation, land cover type, and population density on skull size. We found that female spotted hyenas are slightly larger on average than males. Our analysis of regional differences did not indicate geographic variation in sexual size dimorphism. Skull size of Spotted Hyenas varies with geography but does not adhere to Bergmann's Rule. The smallest individuals of both sexes occur between -5.00° and 10.00° latitude and east of 28.50° longitude, with larger individuals being found elsewhere. Although Spotted Hyena skull size co-varies in some views with such variables as habitat type and climate indicators, skull size in this species most strongly co-varies with population density. The highest population densities are associated with the smallest skull size, possibly reflecting a relationship between high population density and access to resources. These results suggest that geographic variation in Spotted Hyena skull size is better explained by the energetic equivalence rule than Bergmann's Rule.

Fission–fusion dynamics describe the tendency for members of some animal societies to associate in subgroups that change size and structure fluidly over time. These dynamics shape social complexity and social structure, but are difficult to study because they unfold simultaneously over large spatial scales. Here we use simultaneous, fine-scale GPS data from spotted hyenas to examine fission–fusion dynamics through a dyadic analysis of merge-split events between pairs of individuals. We introduce a species-agnostic framework for identifying merge-split events and discretizing them into three phases (merging, together, and splitting), enabling analysis of each phase as well as the connections among phases. Applying this framework to the hyena data, we examine the temporal and spatial properties of merges and splits between dyads and test the extent to which social encounters are driven by key locations. Specifically, we focus on communal dens—shelters for juvenile hyenas where classical observational studies often report large aggregations of adults. We find that overall, 62

Integrated community models-an emerging framework in which multiple data sources for multiple species are analyzed simultaneously-offer opportunities to expand inferences beyond the single-species and single-data-source approaches common in ecology. We developed a novel integrated community model that combines distance sampling and single-visit count data; within the model, information is shared among data sources (via a joint likelihood) and species (via a random-effects structure) to estimate abundance patterns across a community. Parameters relating to abundance are shared between data sources, and the model can specify either shared or separate observation processes for each data source. Simulations demonstrated that the model provided unbiased estimates of abundance and detection parameters even when detection probabilities varied between the data types. The integrated community model also provided more accurate and more precise parameter estimates than alternative single-species and single-data-source models in many instances. We applied the model to a community of 11 herbivore species in the Masai Mara National Reserve, Kenya, and found considerable interspecific variation in response to local wildlife management practices: Five species showed higher abundances in a region with passive conservation enforcement (median across species: 4.5× higher), three species showed higher abundances in a region with active conservation enforcement (median: 3.9× higher), and the remaining three species showed no abundance differences between the two regions. Furthermore, the community average of abundance was slightly higher in the region with active conservation enforcement but not definitively so (posterior mean: higher by 0.20 animals; 95% credible interval: 1.43 fewer animals, 1.86 more animals). Our integrated community modeling framework has the potential to expand the scope of inference over space, time, and levels of biological organization, but practitioners should carefully evaluate whether model assumptions are met in their systems and whether data integration is valuable for their applications.

Collective action problems arise when cooperating individuals suffer costs of cooperation, while the benefits of cooperation are received by both cooperators and defectors. We address this problem using data from spotted hyenas fighting with lions. Lions are much larger and kill many hyenas, so these fights require cooperative mobbing by hyenas for them to succeed. We identify factors that predict when hyena groups engage in cooperative fights with lions, which individuals choose to participate and how the benefits of victory are distributed among cooperators and non-cooperators. We find that cooperative mobbing is better predicted by lower costs (no male lions, more hyenas) than higher benefits (need for food). Individual participation is facilitated by social factors, both over the long term (close kin, social bond strength) and the short term (greeting interactions prior to cooperation). Finally, we find some direct benefits of participation: after cooperation, participants were more likely to feed at contested carcasses than non-participants. Overall, these results are consistent with the hypothesis that, when animals face dangerous cooperative dilemmas, selection favours flexible strategies that are sensitive to dynamic factors emerging over multiple time scales.

Animal activity patterns are highly variable and influenced by internal and external factors, including social processes. Quantifying activity patterns in natural settings can be challenging, as it is difficult to monitor animals over long time periods. Here, we developed and validated a machine-learning-based classifier to identify behavioural states from accelerometer data of wild spotted hyenas (Crocuta crocuta), social carnivores that live in large fission–fusion societies. By combining this classifier with continuous collar-based accelerometer data from five hyenas, we generated a complete record of activity patterns over more than one month. We used these continuous behavioural sequences to investigate how past activity, individual idiosyncrasies, and social synchronization influence hyena activity patterns. We found that hyenas exhibit characteristic crepuscular-nocturnal daily activity patterns. Time spent active was independent of activity level on previous days, suggesting that hyenas do not show activity compensation. We also found limited evidence for an effect of individual identity on activity, and showed that pairs of hyenas who synchronized their activity patterns must have spent more time together. This study sheds light on the patterns and drivers of activity in spotted hyena societies, and also provides a useful tool for quantifying behavioural sequences from accelerometer data.

Once considered mere scavengers, it is now widely recognized that hunting is more important than scavenging in the feeding ecology of spotted hyenas (Crocuta crocuta). In this chapter, we outline the extraordinary morphological and behavioral adaptations possessed by these bone-cracking hyenas for efficient hunting and foraging within the context of their complex social organization. These social carnivores live in female-dominated societies structured by fission-fusion dynamics in which individuals hunt alone or in small groups to avoid feeding competition but join forces in large-scale cooperation with kin and non-kin group-mates to defend food from African lions (Panthera leo) and members of neighboring groups of hyenas. We discuss how social rank and age influence every aspect of their hunting behavior and consider the inevitable trade-offs faced regarding cooperative hunting of ephemeral prey. Finally, we evaluate what is known about the cognitive demands and conservation implications associated with the behavioral flexibility possessed by these efficient hunters.

There is a gap in knowledge regarding the genomic diversity and variation of the gut microbiome across a host’s life span and across multiple generations of hosts in wild mammals. Using two types of sequencing approaches, we found that although gut microbiomes were individualized and temporally variable among hyenas, they correlated similarly to large-scale changes in the ecological conditions experienced by their hosts.

Wide-ranging carnivores experience tradeoffs between dynamic resource availabilities and heterogeneous risks from humans, with consequences for their ecological function and conservation outcomes. Yet, research investigating these tradeoffs across large carnivore distributions is rare. We assessed how resource availability and anthropogenic risks influence the strength of lion ( Panthera leo ) responses to disturbance using data from 31 sites across lions’ contemporary range. Lions avoided human disturbance at over two-thirds of sites, though their responses varied depending on site-level characteristics. Lions were more likely to exploit human-dominated landscapes where resources were limited, indicating that resource limitation can outweigh anthropogenic risks and might exacerbate human-carnivore conflict. Lions also avoided human impacts by increasing their nocturnal activity more often at sites with higher production of cattle. The combined effects of expanding human impacts and environmental change threaten to simultaneously downgrade the ecological function of carnivores and intensify human-carnivore conflicts, escalating extinction risks for many species.

From population estimates to social evolution, much of our understanding of the family Hyaenidae is drawn from studies of known individuals. The extant species in this family (spotted hyenas, Crocuta crocuta, brown hyenas, Parahyaena brunnea, striped hyenas, Hyaena hyaena, and aardwolves, Proteles cristata) are behaviorally diverse, presenting an equally diverse set of logistical constraints on capturing and marking individuals. All these species are individually identifiable by their coat patterns, providing a useful alternative to man-made markings. Many studies have demonstrated the utility of this method in answering a wide range of research questions across all four species, with some employing a creative fusion of techniques. Despite its pervasiveness in basic research on hyenas and aardwolves, individual identification has rarely been applied to the conservation and management of these species. We argue that individual identification using naturally occurring markings in applied research could prove immensely helpful, as this could further improve accuracy of density estimates, reveal characteristics of suitable habitat, identify threats to population persistence, and help to identify individual problem animals.

In ecology and evolutionary biology (EEB), the study of developmental plasticity seeks to understand ontogenetic processes underlying the phenotypes upon which natural selection acts. A central challenge to this inquiry is ascertaining a causal effect of the exposure on the manifestation of later-life phenotype due to the time elapsed between the two events. The exposure is a potential cause of the outcome—i.e. an environmental stimulus or experience. The later phenotype might be a behaviour, physiological condition, morphology or life-history trait. The latency period between the exposure and outcome complicates causal inference due to the inevitable occurrence of additional events that may affect the relationship of interest. Here, we describe six distinct but non-mutually exclusive conceptual models from the field of lifecourse epidemiology and discuss their applications to EEB research. The models include Critical Period with No Later Modifiers, Critical Period with Later Modifiers, Accumulation of Risk with Independent Risk Exposures, Accumulation of Risk with Risk Clustering, Accumulation of Risk with Chains of Risk and Accumulation of Risk with Trigger Effect. These models, which have been widely used to test causal hypotheses regarding the early origins of adult-onset disease in humans, are directly relevant to research on developmental plasticity in EEB.

In traditional definitions of endurance rivalry, individuals compete to remain reproductively active longer than their rivals, but these time periods are typically brief, such as a single breeding season. Here, we explored endurance rivalry among adult males in a long-lived species that breeds year-round, the spotted hyena (Crocuta crocuta). We found that most dispersing males navigated the adaptive challenges of remaining in their new clans ("enduring") for over 2 years before siring their first cub. Additionally, sires remained in their new clans at least 4 years, whereas males that never sired any cubs typically disappeared by their fourth year of tenure. This suggests that males might incorporate their initial reproductive success in the clan into their decisions regarding whether to "endure" by remaining in the current clan or to disperse again to another clan. Finally, we used Bayesian mixed modeling to explore variation in annual male reproductive success, which we found to have a positive linear relationship with tenure and a quadratic relationship with age. A male's rate of social associations with adult females, but not aggressive interactions with those females, was predictive of his annual reproductive success. We also found substantial individual variation in annual reproductive success across males. Our results support the notion that male spotted hyenas compete via an extended endurance rivalry; tenure unequivocally improves male reproductive success, but advanced age does not, and questions remain regarding other traits that might be salient to the rivalry or to female mate choice in this species. Significance statement Some animals compete indirectly for mates by trying to outlast their competitors during a finite breeding season; individuals that can endure the longest in this "marathon" reap the reproductive rewards. Male spotted hyenas face a different challenge because females breed year-round, so the competition to remain viable as mates is seemingly endless. Here, we show that male spotted hyenas seem to make decisions about whether to stay in a clan based on their initial reproductive success in that clan. For males with early success, the longer they stay and the more time they spend with females, the more cubs they sire each year. Our findings suggest that male spotted hyenas compete for mating opportunities via an "ultramarathon" in which they must remain in a single social group at the bottom of the hierarchy for many years to demonstrate to females their ability to endure.

The apparent virilization of the female spotted hyena raises questions about sex differences in behavior and morphology. We review these sex differences to find a mosaic of dimorphic traits, some of which conform to mammalian norms. These include space-use, dispersal behavior, sexual behavior, and parental behavior. By contrast, sex differences are reversed from mammalian norms in the hyena's aggressive behavior, social dominance, and territory defense. Androgen exposure early in development appears to enhance aggressiveness in female hyenas. Weapons, hunting behavior, and neonatal body mass do not differ between males and females, but females are slightly larger than males as adults. Sex differences in the hyena's nervous system are relatively subtle. Overall, it appears that the "masculinized" behavioral traits in female spotted hyenas are those, such as aggression, that are essential to ensuring consistent access to food; food critically limits female reproductive success in this species because female spotted hyenas have the highest energetic investment per litter of any mammalian carnivore. Evidently, natural selection has acted to modify traits related to food access, but has left intact those traits that are unrelated to acquiring food, such that they conform to patterns of sexual dimorphism in other mammals.

Physical problem-solving paradigms are popular for testing a variety of cognitive abilities linked with intelligence including behavioral flexibility, innovation, and learning. Members of the mammalian order Carnivora are excellent candidates for studying problem-solving because they occupy a diverse array of socio-ecological niches, allowing researchers to test competing hypotheses on the evolution of intelligence. Recent developments in the design of problem-solving apparatuses have enhanced our ability to detect inter-specific and intra-specific variation in problem-solving success in captive and wild carnivores. These studies suggest there may be some links between variation in problem-solving success and variation in urbanization, diet, and sociality.

Introduction Dominance relationships in which females dominate males are rare among mammals. Mechanistic hypotheses explaining the occurrence of female dominance suggest that females dominate males because (1) they are intrinsically more aggressive or less submissive than males, and/or (2) they have access to more social support than males. Methods Here, we examine the determinants of female dominance across ontogenetic development in spotted hyenas (Crocuta crocuta) using 30 years of detailed behavioral observations from the Mara Hyena Project to evaluate these two hypotheses. Results Among adult hyenas, we find that females spontaneously aggress at higher rates than males, whereas males spontaneously submit at higher rates than females. Once an aggressive interaction has been initiated, adult females are more likely than immigrant males to elicit submission from members of the opposite sex, and both adult natal and immigrant males are more likely than adult females to offer submission in response to an aggressive act. We also find that adult male aggressors are more likely to receive social support than are adult female aggressors, and that both adult natal and immigrant males are 2–3 times more likely to receive support when attacking a female than when attacking another male. Across all age classes, females are more likely than males to be targets of aggressive acts that occur with support. Further, receiving social support does slightly help immigrant males elicit submission from adult females compared to immigrant males acting alone, and it also helps females elicit submission from other females. However, adult females can dominate immigrant males with or without support far more often than immigrant males can dominate females, even when the immigrants are supported against females. Discussion Overall, we find evidence for both mechanisms hypothesized to mediate female dominance in this species: (1) male and female hyenas clearly differ in their aggressive and submissive tendencies, and (2) realized social support plays an important role in shaping dominance relationships within a clan. Nevertheless, our results suggest that social support alone cannot explain sex-biased dominance in spotted hyenas. Although realized social support can certainly influence fight outcomes among females, adult females can easily dominate immigrant males without any support at all.