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BIOME9’s Industry Journal Club - What Feral Cats Can Teach Us About Gut Health

At our most recent BIOME9 Journal Club, we explored a fascinating new study examining the gut microbiomes of feral versus domestic cats across six countries. The paper takes a global look at how lifestyle, diet, and behaviour shape the feline gut and what this means for animal health more broadly

December 16, 2025 • 4 min read

Bushra Schuitemaker

Lead Microbiologist

Why Study Feralisation in Cats?

Feralisation describes what happens when a species transitions from domesticated living back to a free-living or wild state. Unlike many animals, cats currently coexist in both forms: house cats living with humans, feral cats living independently, and many fluidly shifting between the two.

This makes cats an ideal model for exploring two key questions:

Do feral and domestic cats have different microbiomes?
Do gut bacteria track behavioural traits, such as tameness or aggression?

To answer these, researchers collected faecal samples from 96 cats in Aruba, Brazil, Cape Verde, Denmark, Malaysia, and Spain, combining deep metagenomic sequencing with behavioural scoring and advanced ecological modelling.

A Global Look at the Feline Microbiome

Across all cats, the researchers assembled 229 high-quality meta-assembled genomes (MAGs) representing 10 bacterial phyla. Despite huge geographical distances, the cats shared a recognisable “core microbiome”, much like what we see in dogs and humans.

But one thing stood out sharply: Geography was the strongest driver of microbiome variation.

Where the cat lived, the country, region, land, and local environment explained more of the differences than whether it was feral or domestic. This mirrors BIOME9’s own findings in dogs: lifestyle and environment often outweigh breed or genetics in shaping the gut.

Domestic vs Feral Cats: Not What You Might Expect

Surprisingly, feral and domestic cats did not differ significantly in microbial diversity. In other words, feral cats weren’t wilder or more diverse. But they differed in which bacteria they carried and, even more importantly, in what those bacteria were doing.

Domestic cats harboured higher abundances of Bacteroidota, Pseudomonadota, and Bifidobacterium. Feral cats carried more Bacillota (including lactobacilli and clostridia) and Fusobacteria, both taxa linked to protein and fat digestion.

This fits their assumed lifestyle and diets: domestic cats eat more plant-inclusive commercial foods, while feral cats rely on prey, scraps, and higher-fat, higher-protein sources.

Lifestyle-Specific Functions

Functional differences were even more striking. Domestic cats showed more pathways for breaking down complex plant carbohydrates. Feral cats showed enriched pathways in, lipid metabolism, amino acid breakdown, short-chain fatty acid (SCFA) production, and vitamin synthesis. In fact, feral cats had 30 enriched functional pathways, while domestic cats had only four. This suggests diet and lifestyle shape functions far more strongly than they shape raw diversity.

Behaviour and the Microbiome: A Two-Way Conversation?

The study also explored whether the microbiome tracks behaviour. Cats were scored on a tame-to-aggressive scale. Amazingly, the gut microbiome did show a behavioural signature.

Certain genomes were strongly linked to tame cats
Others to aggressive cats
Some functions overlapped; feral + aggressive cats shared several metabolic pathways
Some bacteria appear almost exclusively in tame/domestic cats, such as: Trueperella and Lawsonella → these are only found in domestic + tame individuals.
Others associate with aggressive/feral cats, such as: Enterococcus → enriched only in feral and aggressive behaviour groups.
Lactobacillus species are more common in feral cats in this study.
– This is different to dogs, where BIOME9 data shows lower Lactobacillus in anxious or reactive dogs.
– It may also reflect ecology: Lactobacilli often deter pathogens and support immune function, which fits a more variable, wild diet.

This doesn’t mean bacteria cause aggression or tameness. Behaviour is complex, involving hormones, environment, experience, and genetics. But it suggests gut microbes and behaviour may evolve together an emerging theme across many species, including dogs.

How Does This Compare to Dogs? (BIOME9 Data Insights)

During the Journal Club, we compared this to our own datasets at BIOME9. Dogs have far higher species richness, with an average of 400 species equivalents, compared to ~60 MAGs in cats. Dogs also have more fermenter diversity, reflecting their ability to process fibre far more efficiently than obligate carnivores like cats.

Interestingly, BIOME9 data show that dogs living with cats have some of the healthiest, most resilient microbiomes. They may be exposed to unique cat-associated bacteria in shared homes, an unexpected but charming example of cross-species microbiome enrichment.

What This Means for BIOME9’s Feline Launch in 2026

This paper came at the perfect time for us. As we prepare for BIOME9’s first feline microbiome test, the findings highlight crucial considerations:

Cats require completely different reference ranges from dogs
Functional pathways (especially SCFAs, amino acids, vitamins) may be more critical diagnostic markers
Differences between indoor, outdoor, multi-cat and single-cat homes will be huge
Cat samples may have a higher contamination risk due to burial behaviours
Interpretation frameworks must account for the cat’s unique ecology; they are not just “small dogs”

This study confirms that a feline test cannot simply be adapted from canine models. Cats need and deserve their own dedicated scientific framework.

Final Thoughts

The gut microbiome is a dynamic reflection of diet, lifestyle, environment, and behaviour. In cats, these factors interact in complex, surprising ways, revealing a system that is both simpler (fewer species) and more variable (more environmental influence) than in dogs.

For BIOME9, this work is a reminder of why microbiome science matters: it helps us understand animals as individuals, shaped by the worlds they move through. As we move toward our 2026 feline launch, studies like this will guide how we design better tests, create clearer insights, and ultimately support healthier lives for pets everywhere.

Frequently asked questions

The microbiome is the name given to the collection of microbes, mostly bacteria, but also fungi and protozoa, that exist within your dog’s gut. It is a diverse and complex microbial community which can directly affect health and wellbeing. We know that 90% of a human’s body cells are microbes, with only 10% being human cells – it’s just that human cells are markedly larger than the microbes. It’s similar for our four-legged friends. Testing the microbiome gives us an idea of exactly which bacteria are present in your dog’s gut and this can help indicate existing or future health problems.
A healthy diversity within the microbiome has been found to be an accurate indicator of overall health and wellbeing. If your dog appears healthy, but has an imbalance in their microbiome, then this could be an indicator of a potential future health issue. If your dog has any existing health complaints, then improving the health of their microbiome can help to improve immune system health and overall wellbeing, as well as improving disease symptoms.
Testing and treatment have the potential to help with a whole range of different health complaints. The immune system is very closely associated with the gut, so any imbalance in the microbiome can influence immune system health, overall vitality and wellbeing. Our supplement recommendations are also tailored to your individual dog, with specific ranges designed to help with gastrointestinal inflammation, joint problems, allergies and skin complaints, to name a few.
All you need to do is order a kit online and fill in our questionnaire about your dog and their general health. We will then send the kit out to you by post. You then just need to collect a sample and return it to us, again by post. Once the test is performed, we will email the results directly to you.
You do not need to get your vet’s permission to test, or talk to them about performing the test beforehand. We do recommend that you pass on a copy of your test results to your regular vets, as it may help them in understanding your pet’s current health, and any future complaints they may have.