# Gut Microbiome Variations in Herring Gulls (Larus argentatus) from Different Environments in the United Kingdom

## TL;DR

This study explores how the gut microbiome of herring gulls varies across different UK environments, finding differences linked to urbanization and captivity.

## Contribution

The study provides new insights into how environmental factors influence gut microbiome diversity in wild and captive herring gull populations.

## Key findings

- Captive gulls and those in Bristol had higher gut microbiome diversity compared to urban and suburban gulls.
- Urban gulls showed higher abundance of Ligilactobacillus and lower abundance of Streptococcus compared to suburban gulls.
- The Liverpool population had a high proportion of Mycoplasma, potentially indicating avian mycoplasmosis.

## Abstract

In recent years, scientists have been actively seeking non-invasive approaches to monitoring the health and welfare of wildlife. The Herring Gull is a highly adaptable species, which offers an excellent opportunity to study various potential environmental influences, including captivity, level of urbanisation, habitat types and geographical location. Here, we utilised faecal samples from different herring gull populations to analyse variation in their gut microbiome—the bacterial community residing in the guts. Populations sampled for this study include Bristol, Gloucester, Weston Super-Mare, Portishead, Hinkley Point, Steepholm Island, Hereford Wildlife Rescue Centre, Liverpool, Swansea and West Kirby. Significant differences were found between individual populations. Higher gut microbiome diversity (number of bacterial species) was identified in the captive population and in gulls from the city of Bristol. Moreover, several bacterial taxa were found to have significant differences in abundance when compared between areas and levels of urbanisation. Differences may be driven by factors such as higher pollution in urban areas, varied foraging ranges, and disease outbreaks, such as the possibility of Avian mycoplasmosis, an infectious respiratory disease, in the Liverpool population. These results suggest a need for further investigation into the effects of urbanisation on the health and welfare of wild animals. They demonstrate the applicability of gut microbial analysis to wildlife health monitoring at the population level and zoonotic disease control for the safety of both humans and animals.

Over the last century, anthropogenic activities have contributed to habitat degradation and fragmentation but have also affected the individual health of animals. In this study, we investigated the effect of environmental differences on the gut microbiome of Herring Gulls (Larus argentatus) by collecting fresh faecal samples from ten geographically different populations in the UK, including captive and wild birds, and comparing the resulting gut microbiome diversity and composition. A significantly higher alpha diversity was identified in captive gulls than in urban and suburban gulls for the 46 sequenced samples. When comparing gut microbiome composition, urban inhabitants exhibited a higher abundance of Ligilactobacillus and a lower abundance of Streptococcus than suburban gulls. Such differences could suggest a highly polluted environment for urban-dwelling gulls, while suburban populations could have a wider foraging range and a more diverse diet. In addition, samples from Bristol, West Kirby, Gloucester and Liverpool were all characterised by a significantly higher abundance of one or more of the other bacterial taxa. The high proportion of Mycoplasma could indicate avian mycoplasmosis in the Liverpool population. This study sheds light on the understudied subject of the wild avian gut microbiome and its possible application to wildlife health and disease management.