Mucosal immune responses and intestinal microbiome associations in wild spotted hyenas (Crocuta crocuta).

Little is known about host-gut microbiome interactions within natural populations at the intestinal mucosa, the primary interface. We investigate associations between the intestinal microbiome and mucosal immune measures while controlling for host, social and ecological factors in 199 samples of 158 wild spotted hyenas (Crocuta crocuta) in the Serengeti National Park, Tanzania. We profile the microbiome composition using a multi-amplicon approach and measure faecal immunoglobulin A and mucin. Probabilistic models indicate that both immune measures predicted microbiome similarity among individuals in an age-dependent manner. These associations are the strongest within bacteria, intermediate within parasites, and weakest within fungi communities. Machine learning models accurately predicted both immune measures and identify the taxa driving these associations: symbiotic bacteria reported in humans and laboratory mice, unclassified bacteria, parasitic hookworms and fungi. These findings improve our understanding of the gut microbiome, its drivers, and interactions in wild populations under natural selection.