Study shows changes in social living conditions affect the gut microbiome of primates

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A recent study published in Animal Microbiome investigated how alterations in the social environment and diet of primates could lead to changes in their gut microbiota, and found that the diversity of these animals’ gut microbiome was influenced by both factors. However, different types of bacteria were affected by changes in the primates’ diet compared to changes in their living conditions. According to the authors, these findings highlight how social dynamics can affect microbiota composition and potentially impact the health and sociality of primates.

“While diet profoundly shapes gut microbial community composition, our findings demonstrate that an individual’s social environment also plays a unique role,” wrote the authors in the study.¹

The study was a 15-month longitudinal investigation on 13 captive male cynomolgus macaques. Participants were placed in single housing for the first 3 months of the study and were fed a variable diet for baseline data collection. Thereafter, these macaques were put on a controlled diet consisting of fruit, foraging mix, and additional food rewards that were provided equally to all animals daily for the rest of the study. Once the diet change was implemented, the primates were housed in pairs for 6 months to promote increased social interaction. On month 9, these animals were returned to “single living” housing.

To assess the impact of social changes on gut microbiota, researchers used a combination of observational methods and microbiome sequencing techniques. They collected fecal samples from the primates before and after changes in their social environment. These samples were then analyzed using sequencing technology to identify and characterize the microbial communities present in their gut.

Results

Diet

The study revealed that dietary changes significantly influenced the alpha and beta diversity of the gut microbiome. “These findings were to be expected, as diet is a well-established modulator of [gut microbiota] composition,” wrote the authors in the study.¹

However, changes in the amounts of certain bacteria as a result of the diet change were also seen in bacteria that previous literature has linked to sociality, such as Helicobacteraceae and Prevotellaceae. “This finding emphasizes the need to disentangle dietary and social effects on the [gut microbiota]. Where prior studies have claimed certain bacteria to be influenced by sociality, our findings suggest that in fact such changes may be diet related,” the authors wrote.¹

Social living conditions

Unlike the effects from diet change, the study’s findings revealed that changes in social living arrangements, such as living alone vs pairwise living, only affected beta diversity. The study’s authors noted that certain bacterial families previously associated with social behavior, like Helicobacteraceae and Prevotellaceae—which were influenced by diet—did not show significant changes when the social living conditions of the primates were changed. Lactobacillaceae and Clostridiaceae were the bacterial families “involved in driving this social living effect,” with Lactobacillaceae increasing when the primates were moved into pairwise housing and remaining constant thereafter, but decreasing when the diet was controlled. Clostridiaceae on the other hand, showed low abundance during the period of uncontrolled diet, increasing when the diet was altered, and then decreasing again thereafter.

“These findings uncover the separate impacts of diet and social factors on [gut microbiota] composition, highlighting a complex interaction between social environments and gut health,” concluded the authors of the study.

Reference

1. Pearce CS, Bukovsky D, Douchant K, et al. Changes in social environment impact primate Gut Microbiota composition. Animal Microbiome. 2024;6(1). https://doi.org/10.1186/s42523-024-00355-y