Urban mammals in Italy: the hidden role of common species in structuring communities
This study investigates medium- and large-sized mammal communities across four Italian cities using camera traps, revealing that while green cover extent and fragmentation did not significantly influence community composition, distinct inter-city assemblages were primarily driven by common species like the red fox and eastern cottontail rabbit.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
Cities are often imagined as concrete jungles where nature has been pushed out, leaving behind only the most adaptable survivors. Yet, as human settlements expand, they create a unique landscape where wildlife must navigate a world of buildings, roads, and parks. Scientists have long suspected that these urban environments act as a filter, allowing only certain species with flexible habits to thrive while others disappear. This process, known as biotic homogenization, suggests that cities around the world should eventually look more alike in terms of the animals they host, dominated by a shared group of generalists. Understanding which animals live in our cities, how they are distributed, and what factors allow them to survive is crucial for managing the delicate balance between human development and the natural world. It helps planners design green spaces that truly support biodiversity rather than just serving as decorative backdrops.
A team of researchers recently turned their attention to Italy, a country rich in mammal diversity but also facing intense urban pressure. They set out to understand the hidden dynamics of medium and large mammals living in four major Italian cities: Milan in the north, Florence and Rome in the center, and Campobasso in the south. Instead of relying on occasional sightings or citizen reports, the team deployed a systematic network of camera traps across these urban landscapes. They placed 48 cameras in a grid pattern, covering one square kilometer at a time, to capture a comprehensive picture of who was living where. The goal was to see if the amount of green space and how fragmented those green areas were would determine which animals showed up. They also wanted to know if the cities, despite being in different parts of the country, hosted similar communities of animals or if each city had its own unique character.
Over the course of the study, the cameras recorded nearly 18,000 independent sightings of wild animals across more than 8,700 days of monitoring. The researchers identified 12 different wild species, ranging from the common red fox and wild boar to more elusive animals like the wolf and the European hedgehog. The results revealed a surprising reality about urban wildlife. Contrary to the expectation that the size of green parks or how broken up they were would be the main factors deciding which animals lived there, the data showed no significant link between these landscape features and the mix of species found in each city. The amount of green cover or its fragmentation did not explain why one city had a different set of animals than another.
Instead, the most striking finding was that the cities themselves were the primary drivers of difference. Each city hosted a distinct community of mammals, shaped more by local conditions than by the general rules of green space availability. Milan stood out as the most unique, hosting a community that differed significantly from the other three cities. In Milan, an invasive species, the eastern cottontail rabbit, dominated the landscape, accounting for nearly half of all animal sightings. This rabbit, introduced from North America decades ago, had become the most common large mammal in the city, overshadowing native species. In contrast, Rome and Campobasso were dominated by the wild boar and the red fox, while Florence showed a more even distribution of species, with wild boars and European hares being the most frequent.
The researchers used advanced statistical methods to identify which specific animals were responsible for these differences between cities. They found that the most common species, rather than the rare ones, were the ones driving the variation. The red fox and the eastern cottontail were the most influential in distinguishing the cities from one another. In Rome, the red fox was particularly abundant, while in Milan, its presence was much lower. The study also highlighted the unexpected arrival of species in new areas. For instance, wild boars and wolves were detected in Milan for the first time in the context of this urban survey, suggesting these animals are expanding their ranges into cities even at the edges of their known territories.
The findings challenge the idea that all cities are becoming biologically identical. While some species, like the red fox, are indeed successful urban adapters found in many places, the specific mix and abundance of animals vary greatly from city to city. This suggests that urban environments are not uniform filters but complex mosaics where local factors create unique ecological niches. The study also underscored the importance of monitoring invasive species, as the eastern cottontail's dominance in Milan showed how quickly non-native animals can reshape a local ecosystem. Furthermore, the presence of large predators and herbivores in dense urban areas indicates that cities can support a surprising level of biodiversity, provided the right conditions exist.
The research also brought to light the practical challenges of studying wildlife in cities. The team faced significant difficulties, including the theft and damage of camera equipment, particularly in Rome and Florence. Despite these obstacles, the study provided a robust baseline for understanding urban mammal communities in Italy. It suggests that managing urban wildlife requires looking beyond simple measures like the total area of green space. Instead, planners and conservationists need to consider the specific characteristics of each city and the behaviors of the most common species living there. By understanding which animals are driving community patterns and how they interact with the urban environment, cities can better manage the coexistence of humans and wildlife, ensuring that these shared spaces remain vibrant and diverse for both people and the animals that call them home.
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