It has been known that diet and environmental conditions are the main factors affecting GM (Rinninella et al. 2019). In many studies, the efficacy of differences in the GM of species Canidae – that adapted to different ecological niches and habitats – was evaluated, and the relationship between GM composition and environmental conditions was examined (Peng et al. 2018; DeCandia et al. 2021; Wang et al. 2022, Nardi et al. 2022). In this work, we investigated the relationship between diet and the compositional and functional diversity of the GM in red fox, chosen as a model organism that can inhabit many different habitats, including human settlements (Hoffmann and Sillero-Zubiri 2021). To address this question, fecal samples of red foxes were collected from four different habitat types (natural, rural, suburban, and urban) in Adana province, Turkiye, and applied 16S rRNA amplicon-based next-generation sequencing.
Our results showed that a diverse microbial community with Firmicutes, Proteobacteria, Actinobacteria, Fusobacteridota, and Bacteroidota were the most abundant phyla across all samples. This observation was consistent with previous studies about red foxes (Peng et al. 2018; Wang et al. 2022), and also the core microbiota determined in this study has been found similar to the dominant members in the GM of other canids such as wolves (Zhang & Chen 2010; Zhang et al. 2012; Wu et al. 2017; Lyu et al. 2018), coyotes (Sugden et al. 2021), raccoon dogs (An et al. 2017), and domestic dogs (Pinna and Biagi 2014). Notably, Firmicutes and Bacteroidetes were significantly more abundant in urban and suburban habitats, comprising over 70% of the microbial community, whereas the rural habitat exhibited a more balanced distribution among major phyla. It is known that urban areas significantly affect animal foraging behavior and diet due to increased access to human-associated food impacting animal GM by altering factors such as microbial diversity and composition (Anders et al. 2022). The higher prevalence of Firmicutes and Bacteroidetes in urban habitats reflected potential dietary adaptations rich in anthropogenic food sources, contrasting with the broader dietary diversity observed in less urbanized habitats. These results were consistent with previous fecal microbiota studies in animals with different diets (O'Donnell et al. 2017; Youngblut et al. 2019). On the contrary, natural and rural habitats showed higher proportions of Fusobacteridota, potentially indicative of a diet based on wild or agricultural food sources. Since this phylum plays a role in the digestion of amino acids (Vázquez-Baeza et al. 2016; Pilla and Suchodolski 2020), it is known to be increased in protein-based diets (Bermingham et al. 2017; Sugden et al. 2021).
Collinsella, Fusobacterium, Faecalibacterium, Escherichia-Shigella, and Blautia were the most abundant genera in the GM of red foxes in this study, and significant differences were observed at the genus level in different habitat types. Faecalibacterium was more prevalent in urban samples, which may indicate the adaptations to urban diets rich in lipids and processed foods (Louis et al. 2010; Peng et al. 2018). Conversely, Fusobacterium showed higher abundance in natural and rural habitats, which may reflect a diet influenced by habitat-specific food availability. It suggests that the relatively higher abundance of Fusobacterium in natural and rural habitats might be due to the higher protein intake from prey. On the other hand, the significant decrease in the relative abundance of Fusobacterium in the GM of urban red foxes may be related to a diet based on anthropogenic food sources rich in carbohydrates and fats (Vital et al. 2015; Pilla and Suchodolski 2020).
Red foxes have an opportunistic feeding behavior that allows them to survive in various environments, including highly modified urban areas, where they consume anthropogenic foods (Bateman and Fleming 2012). Available food sources can turn their protein-based diets, mainly consist of rodents, birds, lizards, and invertebrates in natural areas, into carbohydrate and fat-based diets, including garbage in urban areas (Castañeda et al. 2022). Our results showed that the diet of urban foxes was based on less protein and - high fat, and consistently found a higher abundance of Catenibacterium and Peptoclostridium in the samples from suburban and urban habitats (Phungviwatnikul et al. 2021; Xu et al. 2021).
Functional predictions based on PICRUSt revealed no significant differences in the functional diversity of microbial communities in different habitats, which may suggest the functional capabilities of the microbial communities are often conserved (Louca et al. 2016). Similarly, alpha and beta diversity indices did not significantly vary among habitat types in our work, which may indicate a relatively consistent microbial community structure regardless of environmental variabilities, possibly due to shared functional roles within the GM.
In conclusion, this study is the first report that determined the compositional changes of the GM of a wild animal in the Anatolian peninsula. In addition, four distinct habitat types sampled in this work may improve our understanding of how urbanization and human activities influence the GM of red foxes. Our results showed that the GM of red foxes varies significantly across different habitats, which suggests that it may play a crucial role in red foxes’ adaptation to diverse environments. Future research could incorporate longitudinal sampling to assess temporal dynamics and explore additional environmental factors impacting GM, such as dietary preferences, habitat fragmentation, and pollution levels. Revealing the microbiome of generalist carnivores can provide deeper insights into the ecological strategies of these species and improve conservation and wildlife management practices.