The microbial world within a cat’s gut is a fascinating yet understudied frontier in veterinary science. Recent research has revealed that domestic cats possess a gut microbiome with significantly less diversity compared to humans—approximately 90% fewer microbial species. This stark difference raises important questions about feline digestion, health, and even the evolutionary adaptations that have shaped their unique internal ecosystems.

Unlike humans, whose guts teem with trillions of bacteria from thousands of species, cats host a far narrower range of microbes. This reduced diversity is thought to stem from their strict carnivorous diet, which has remained largely unchanged through domestication. The high-protein, low-fiber nutritional intake of cats provides fewer niches for microbial colonization, favoring a specialized but limited community of bacteria optimized for processing meat.

Why does this matter? The gut microbiome plays a crucial role in immune function, nutrient absorption, and overall health. In humans, low microbial diversity has been linked to conditions like obesity, inflammatory bowel disease, and allergies. While cats don’t exhibit the same range of microbiome-linked disorders, their simplified gut flora may make them more vulnerable to dietary imbalances or sudden changes in food—something pet owners should consider when switching their cat’s diet.

Another intriguing aspect is how this microbial simplicity aligns with feline evolution. Wild ancestors of domestic cats, such as the African wildcat, thrived on prey-based diets with minimal plant matter. Over millennia, their guts adapted to efficiently extract nutrients from animal tissue without relying on the complex fermentation processes seen in herbivores or omnivores. The result? A streamlined microbiome fine-tuned for carnivory.

But what about modern indoor cats? Unlike their wild counterparts, house cats often consume processed foods containing carbohydrates and additives—ingredients their microbiomes didn’t evolve to handle. Some studies suggest this shift could contribute to rising rates of feline obesity and diabetes, though the direct role of microbial diversity remains unclear. Researchers are now investigating whether probiotic supplements or tailored diets could help bridge this evolutionary gap.

One surprising discovery is that despite having fewer bacterial species, cats still maintain a stable and resilient gut ecosystem. Their microbes are highly efficient at breaking down proteins and fats, producing essential nutrients like taurine—a compound cats cannot synthesize on their own. This efficiency highlights how microbial quality, not just quantity, can be critical for survival in carnivorous species.

Comparisons between cats and dogs further emphasize the impact of diet on microbiome diversity. Dogs, being omnivorous, exhibit gut flora more similar to humans, with greater bacterial variety. This divergence underscores how dietary habits over thousands of years have sculpted the microbial landscapes of different species. For cats, a meat-centric history left little room for the fiber-digesting microbes that dominate herbivore guts.

Looking ahead, scientists are exploring whether restoring or diversifying feline microbiomes could improve health outcomes. Early experiments with prebiotics and novel protein sources show promise, but the field is still in its infancy. What’s clear is that cats march to the beat of their own microbial drum—one that’s simpler, yet perfectly suited to their predatory roots.

For pet owners, the takeaway is simple: respect the carnivore. While trends like grain-free or plant-based diets gain traction for humans (and even dogs), cats are biological obligate carnivores. Their guts, and the few microbes within them, are a testament to millions of years of meat-eating adaptation. Perhaps the real lesson isn’t about diversity at all—but rather, the beauty of specialization.