Rats and shrews living close together trade gut bacteria

Humans have reshaped the planet’s green corners into highways, buildings, and sprawling neighborhoods. These developments are now reaching farther into ancient tropical habitats, prompting questions about how wildlife like rats and shrews cope with the shifting environment.

A recent project reveals that small mammals in parts of Borneo’s rainforest are not just adjusting to human-altered landscapes; they may also be exchanging gut bacteria.

Alessandra Giacomini of Swansea University helped direct this work, shining a spotlight on how native and invasive species can end up sharing microscopic companions in ways that might surprise people who think of rats and shrews as entirely separate creatures.

Rats and shrews are adaptable

Urban boundaries in northern Borneo sit next to aging forests. This zone contains four small mammal species, including three rats and one shrew called Suncus murinus, which is known to dine on insects and scurry through residential corners.

Rattus rattus and Rattus norvegicus are the best-known invasive rodents worldwide, with the former often seen in varied settings across Asia. The native Sundamys muelleri appears more comfortable in lush habitats but has somehow found a way to persist near people.

The researchers looked at the microbiomes of these animals across different sections of the urban-rural boundary. Each species has its own natural feeding style and distinct digestion processes, yet certain rodents shared bacterial groups when they occupied similar terrain.

Rats and shrews share gut bacteria

“Our findings suggest that shared environmental use can drive microbiome similarity as much or even more than the genetic relatedness of host species,” said Giacomini. This reveals a pattern where animals living in similar conditions may acquire overlapping sets of gut bacteria.

The scientists noticed that Rattus rattus and the native Sundamys muelleri had particularly close microbiome profiles when found in the same suburban zones.

Habitat appears to be a factor that might nudge bacteria to flow between species, especially when they rummage for food in overlapping patches of vegetation or navigate the same drainage areas.

Differences in a changing habitat

“This raises important questions about the role of gut microbiomes in helping animals adapt to new and changing environments,” stated Dr. Konstans Wells, an expert in Swansea University’s animal health research group.

Environment-driven changes appeared strongest in Norway rats, which showed contrasting microbial patterns between city and suburban locations.

Shrews, on the other hand, have diets heavier in insects and do not share digestive traits with rats. Shrew samples had the lowest variety of bacteria in their guts. They still showed some bacterial strains that popped up in the rodents, but in much smaller numbers.

Potential health implications

Rats are known carriers of certain pathogens linked to human illnesses, such as leptospirosis.

When invasive rats and local species like shrews trade bacteria, there might be pathways for zoonotic microbes to shift from wildlife to people. This highlights the delicate balance between animals adapting to city life and the unseen microbes that tag along.

Researchers plan to see whether future shifts in land use could place more species in prolonged contact. Gathering evidence about bacterial transfers could inform decisions on limiting potential disease risks.

There is growing interest in whether animals like rats and shrews, with flexible appetites or broad tolerance for disturbed spaces, are better at adapting microbiomes to new diets.

Tracking more microbial exchanges

Dr. Tamsyn Uren Webster and Dr. Wells are expanding these efforts. They want to examine whether other communities of creatures exhibit a similar overlap of microscopic life.

Borneo’s rainforests remain a frontier for biodiversity, yet people continue to occupy these spaces with shops, farms, and new homes.

It is possible that native wildlife, including certain rodents, will keep settling near people as the push for housing spreads. Researchers wonder if these animals will pick up even more bacteria from one another, creating scenarios where local and foreign species unknowingly blend their gut microbes.

Predicting which rodents will thrive

Seeing rats and shrews in a city might seem normal, but their exchanges of gut bacteria could have wide-ranging consequences.

These hidden microbes can shape how creatures digest food and defend themselves against infections. They can also carry disease-causing agents that might slip into human populations if left unchecked.

Scientists believe that understanding each animal’s unique gut flora helps predict which species are poised to thrive. Over time, these data might become a key ingredient for policymakers who aim to manage invasive rodents in newly built neighborhoods.

The hope is to balance development with safeguards against the unforeseen effects of living alongside opportunistic animals.

The study is published in Molecular Ecology.

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