Mounting evidence suggests that the cyclic interaction between host cells and the gut microbiota orchestrates metabolic and immunological homeostasis throughout the day. Yet, examples of gut microbial rhythms in natural populations are scarce, limiting our understanding of their downstream consequences for host health, particularly in mammals that demonstrate strong co-evolutionary links with their microbiota. Furthermore, disregarding diurnal microbial variation restricts our ability to account and control for them in future studies. Here, we re-analyzed gut microbiota data from a 23-year longitudinal field study of 12 wild adult female spotted hyenas (Crocuta crocuta) in the Masai Mara National Reserve in Kenya to examine whether time of day was correlated with variation in gut microbial composition in this crepuscular–nocturnal carnivore. Overall, we found that gut microbial composition and structure, but not alpha diversity, slightly changed over the course of the day. Differences in microbiota composition between morning and afternoon became particularly apparent when restricting the analysis to the core microbiota (i.e., bacterial genera present in more than 85% of samples). Among the core microbiota, 11 genera—composed largely of the bacterial class Clostridia—varied in abundance with time of day, making this the second study to document gut microbial rhythms in a longitudinally sampled wildlife population. In contrast with the diurnal gut microbial oscillations of wild meerkats, those of hyenas are subtle, yet both species exhibit shifts specifically in the bacterial class Clostridia. This pattern implies that diurnal fluctuations are likely a characteristic of specific, common host-associated bacteria and their amplitude may be a product of host ecology. While our study detected diurnal trends, we encourage studies to employ a temporally denser sampling scheme. In this way, one can overlay short-term oscillations of the microbiome with information on host ecology and clarify consequences for the circadian phenotype of the host.
- Award ID(s):
- 1853934
- PAR ID:
- 10132920
- Date Published:
- Journal Name:
- FEMS Microbiology Ecology
- Volume:
- 96
- Issue:
- 2
- ISSN:
- 0168-6496
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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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.more » « less
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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 hyenas
Crocuta 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.
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1093/femsec/fiaa007
