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ABSTRACT Environment structure often shapes social interactions. Spatial attractors that draw multiple individuals may play a particularly important role in dispersed groups, where individuals must first encounter one another to interact. We use GPS data recorded simultaneously from five spotted hyenas (Crocuta crocuta) within a single clan to investigate how communal dens and daily ranging patterns shape fission-fusion dynamics (subgroup splits and merges). We introduce a species-general framework for identifying and characterizing dyadic fission-fusion events and describe a taxonomy of ten possible configurations of these events. Applying this framework to the hyena data illuminates the spatiotemporal structure of social interactions within hyenas’ daily routines. The most common types of fission-fusion events involve close approaches between individuals, do not involve co-travel together, and occur at the communal den. Comparison to permutation-based reference models suggests that den usage structures broad-scale patterns of social encounters, but that other factors influence how those encounters unfold. We discuss the dual role of communal dens in hyenas as physical and social resources, and suggest that dens are an example of a general “social piggybacking” process whereby environmental attractors take on social importance as reliable places to encounter conspecifics, causing social and spatial processes to become fundamentally intertwined. 

Abstract 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. 

Abstract 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. 

Abstract As fecal steroid methods increasingly are used by researchers to monitor the physiology of captive and wild populations, we need to expand our validation protocols to test the effects of procedural variation and to identify contamination by exogenous sources of steroid hormones. Mammalian carnivore feces often contain large amounts of hair from the prey they consume, which itself may contain high concentrations of hormones. In this study, we report first a validation of two steroid hormone antibodies, corticosterone and progesterone, to determine fecal concentrations of these hormones in wild spotted hyenas (Crocuta crocuta). Next, we expand on these standard validation protocols to test two additional metrics: (i) whether hair from consumed prey or (ii) the specific drying method (oven incubation vs. lyophilization) affect steroid hormone concentrations in feces. In the first biological validation for the progesterone antibody in this species, progesterone concentrations met our expectations: (i) concentrations of plasma and fecal progesterone were lowest in immature females, higher in lactating females, and highest in pregnant females; (ii) across pregnant females, fecal progesterone concentrations were highest during late pregnancy; and (iii) among lactating females, fecal progesterone concentrations were highest after parturition. Our additional validation experiments indicated that contamination with prey hair and drying method are hormone-specific. Although prey hair did not release hormones into samples during storage or extraction for either hormone, its presence appeared to “dilute” progesterone (but not corticosterone) measures indirectly by increasing the dry weight of samples. In addition, fecal progesterone, but not corticosterone, values were lower for lyophilized than for incubated samples. Therefore, in addition to the standard analytical and biological validation steps, additional methodological variables need to be tested whenever we measure fecal hormone concentrations, particularly from predatory mammals. 

Abstract Toxoplasma gondiiis hypothesized to manipulate the behavior of warm-blooded hosts to promote trophic transmission into the parasite’s definitive feline hosts. A key prediction of this hypothesis is thatT. gondiiinfections of non-feline hosts are associated with costly behavior towardT. gondii’s definitive hosts; however, this effect has not been documented in any of the parasite’s diverse wild hosts during naturally occurring interactions with felines. Here, three decades of field observations reveal thatT. gondii-infected hyena cubs approach lions more closely than uninfected peers and have higher rates of lion mortality. We discuss these results in light of 1) the possibility that hyena boldness represents an extended phenotype of the parasite, and 2) alternative scenarios in whichT. gondiihas not undergone selection to manipulate behavior in host hyenas. Both cases remain plausible and have important ramifications forT. gondii’s impacts on host behavior and fitness in the wild. 

Abstract The gut microbiota is critical for host function. Among mammals, host phylogenetic relatedness and diet are strong drivers of gut microbiota structure, but one factor may be more influential than the other. Here, we used 16S rRNA gene sequencing to determine the relative contributions of host phylogeny and host diet in structuring the gut microbiotas of 11 herbivore species from 5 families living sympatrically in southwest Kenya. Herbivore species were classified as grazers, browsers, or mixed-feeders and dietary data (% C4 grasses in diet) were compiled from previously published sources. We found that herbivore gut microbiotas were highly species-specific, and that host taxonomy accounted for more variation in the gut microbiota (30%) than did host dietary guild (10%) or sample month (8%). Overall, similarity in the gut microbiota increased with host phylogenetic relatedness (r = 0.74) across the 11 species of herbivores, but among 7 closely related Bovid species, dietary %C4 grass values more strongly predicted gut microbiota structure (r = 0.64). Additionally, within bovids, host dietary guild explained more of the variation in the gut microbiota (17%) than did host species (12%). Lastly, while we found that the gut microbiotas of herbivores residing in southwest Kenya converge with those of distinct populations of conspecifics from central Kenya, fine-scale differences in the abundances of bacterial amplicon sequence variants (ASVs) between individuals from the two regions were also observed. Overall, our findings suggest that host phylogeny and taxonomy strongly structure the gut microbiota across broad host taxonomic scales, but these gut microbiotas can be further modified by host ecology (i.e., diet, geography), especially among closely related host species. 

Abstract How social development in early‐life affects fitness remains poorly understood.Though there is growing evidence that early‐life relationships can affect fitness, little research has investigated how social positions develop or whether there are particularly important periods for social position development in an animal's life history. In long‐lived species in particular, understanding the lasting consequences of early‐life social environments requires detailed, long‐term datasets.Here we used a 25‐year dataset to test whether social positions held during early development predicted adult fitness. Specifically, we quantified social position using three social network metrics: degree, strength and betweenness. We determined the social position of each individual in three types of networks during each of three stages of ontogeny to test whether they predict annual reproductive success (ARS) or longevity among adult female spotted hyenasCrocuta crocuta.The social positions occupied by juvenile hyenas did predict their fitness, but the effects of social position on fitness measures differed between stages of early development. Network metrics when individuals were young adults better predicted ARS, but network metrics for younger animals, particularly when youngsters were confined to the communal den, better predicted longevity than did metrics assessed during other stages of development.Our study shows how multiple types of social bonds formed during multiple stages of social development predict lifetime fitness outcomes. We suggest that social bonds formed during specific phases of development may be more important than others when considering fitness outcomes. 

Abstract Populations of large carnivores are declining in many parts of the world due to anthropogenic activity. Some species of large carnivores, however, are able to coexist with people by altering their behavior. Altered behaviors may be challenging to identify in large carnivores because these animals are typically cryptic, nocturnal, live at low densities, and because changes in their behavior may be subtle or emerge slowly over many years. We studied the effects of livestock presence on the movements of one large carnivore, the spotted hyena (Crocuta crocuta). We fit 22 adult female spotted hyenas with GPS collars to quantify their movements in areas with and without livestock or herders present, in and around a protected area in southwestern Kenya. We investigated anthropogenic, social, and ecological effects on the speed of movement, distances traveled, long-distance movements, and extraterritorial excursions by spotted hyenas. Hyenas living primarily within the protected area, but in the presence of livestock and herders, moved faster, traveled over longer distances, and were more likely to be within their territories than did conspecifics living in areas without livestock and herders. Hyenas of low social rank were more likely than hyenas of high social rank to engage in long-distance travel events, and these were more likely to occur when prey were scarce. The movement patterns of this large African carnivore indicate a flexibility that may allow them to persist in landscapes that are becoming increasingly defined by people. 

Abstract Anthropogenic disturbance can have important influences on the fitness and behaviors of wild animals, including their boldness when exposed to risky conditions. We presented spotted hyenas (Crocuta crocuta) from two populations, each exposed to a different level of human activity, with a life‐size model hyena representing an intruder from another clan. The high‐disturbance population lived adjacent to human settlements, and the low‐disturbance population inhabited a relatively undisturbed part of the same national park in Kenya. The mock intruder was presented to individual hyenas to assess their reactions to an alien hyena, and to determine whether their reactions varied with their exposure to anthropogenic activity. We found that human disturbance was indeed associated with hyena risk‐taking behavior in response to the model intruder. Hyenas tested in the low‐disturbance area exhibited more risk‐taking behaviors by approaching the mock intruder more closely, and spending more time near it, than did their counterparts living in high‐disturbance areas. Hyenas that spent less time in close proximity to the model had greater survivorship than those that spent more time in close proximity to it, regardless of disturbance level. Furthermore, the individual differences in risk‐taking measured here were consistent with those obtained previously from the same animals using a different set of experimental manipulations. However, the experimentally induced behaviors were not consistent with naturally occurring risk‐taking behaviors in proximity to lions; this suggests that risk‐taking behaviors are consistent within individuals across experimental contexts, but that exposure to lions elicits different responses. Although our results are consistent with those from earlier tests of anthropogenic disturbance and boldness in spotted hyenas and other predators, they differ from results obtained from birds and small mammals, which are generally found to be bolder in areas characterized by human disturbance. 

Abstract Environmental factors early in life can have lasting influence on the development and phenotypes of animals, but the underlying molecular modifications remain poorly understood. We examined cross‐sectional associations among early life socioecological factors and global DNA methylation in 293 wild spotted hyenas (Crocuta crocuta) in the Masai Mara National Reserve, Kenya, grouped according to three age classes (cub, subadult and adult). Explanatory variables of interest included annual maternal rank based on outcomes of dyadic agonistic interactions, litter size, wild ungulate prey density and anthropogenic disturbance in the year each hyena was born based on counts of illegal livestock in the Reserve. The dependent variable of interest was global DNA methylation, assessed via the LUminometric Methylation Assay, which provides a percentage methylation value calculated at CCGG sites across the genome. Among cubs, we observed approximately 2.75% higher CCGG methylation in offspring born to high‐ than low‐ranking mothers. Among cubs and subadults, higher anthropogenic disturbance corresponded with greater %CCGG methylation. In both cubs and adults, we found an inverse association between prey density measured before a hyena was 3 months old and %CCGG methylation. Our results suggest that maternal rank, anthropogenic disturbance and prey availability early in life are associated with later life global DNA methylation. Future studies are required to understand the extent to which these DNA methylation patterns relate to adult phenotypes and fitness outcomes.