Domestic cats have been companions to humans for over 9,000 years. Their journey from domestication has led them across the globe, reaching hundreds of islands and inhabiting all continents except Antarctica. This makes them one of the most widespread species on Earth. 

Yet, with this widespread presence, they’ve brought significant disruptions to various ecosystems. From spreading diseases that affect a range of species, including humans, to out-competing native predators, cats have left a significant mark. This extends to threatening the genetic integrity of wild cats, preying on native species, and driving many to extinction, thereby categorizing them as one of the most challenging invasive species worldwide.

Despite the extensive body of research, a comprehensive global documentation of the range of species consumed by cats has been lacking. This study sought to address this gap by constructing the largest database of cat diets to date (over 500 publications). Researchers wanted to quantify the diet of free-ranging domestic cats (i.e. owned or unowned cats with access to the outdoors), examining aspects such as taxonomic groups, island versus continental locations, conservation status of prey, body masses of diet species, and the methodologies used in dietary analyses. This research aims to provide a deeper understanding of the global importance of domestic cats, highlighting their role in ecosystems and the challenges they pose to biodiversity conservation.

The researchers conducted a comprehensive search of literature on cat diet and predation. They used Google Scholar and Web of Science, employing keywords such as ‘cat predation,’ ‘feral cat,’ ‘cat diet,’ and ‘Felis catus.’ Each identified source was evaluated to determine if it contained relevant data on cat diet or predation. Additionally, the reference sections of these sources were reviewed to identify further unique articles or databases related to cat diet and predation. The researchers identified 544 unique publications, which included books, journal articles, theses, and agency reports, all providing data on cat diets.

The research categorizes cats as opportunistic predators and obligate carnivores, capable of thriving on a varied diet. Remarkably, cats can subsist on water found naturally in their food for extended periods, demonstrating their exceptional adaptability. This study found that cats’ diets are not limited to a specific type of prey; instead, they predate and scavenge a wide array of animals. This includes birds, reptiles, mammals, insects, and amphibians — a dietary diversity that aids in their survival in a multitude of ecosystems.

A notable finding of the study is the species-level effects of cats’ dietary habits. Out of the many species that cats consume, 347 are listed as ‘Near Threatened’ or higher on the International Union for Conservation of Nature Red List of Threatened Species, encompassing a significant portion of the world’s birds, mammals, and reptiles. The research particularly highlights a greater incidence of cats consuming threatened species on islands compared to continents, underscoring the varying effects of cats in different geographical locations.

In exploring the geographic and taxonomic patterns of cats’ diets, the study reveals that a majority of the research has been focused on Australia and North America. These regions have reported the highest diversity of species consumed by cats. Globally, birds emerge as the most commonly preyed upon species. However, the prevalence of other prey types, such as mammals and reptiles, varies depending on the geographical location, illustrating the adaptability of cats to local prey availability.

One of the key insights from the study is the range of body masses of the prey consumed by cats. Cats are observed to target prey of varying sizes, from small amphibians and birds to larger mammals and reptiles. This lack of specific size preference in their prey further attests to their versatility as predators, capable of adapting their hunting strategies to the available prey in different environmental settings.

This paper presents a detailed and comprehensive analysis of the global dietary patterns of domestic cats, emphasizing their role as a significant invasive species. The research provides crucial insights into the predatory behavior of cats and its importance on wildlife, particularly species of conservation concern. The findings are instrumental for developing informed conservation strategies and effective management policies to mitigate the environmental outcomes of free-ranging domestic cats.

For animal advocates, it’s important to note that this survey of free-ranging cats gives a good summary of their diets, but this information doesn’t necessarily imply causality of species-level effects. The issue of free-ranging cats is a fraught one. While the effects of free-ranging cats may (or may not) be significant, it’s important to ensure we have a balanced view of their management that prioritizes non-lethal approaches.