Across the globe, the introduction of domestic cats (Felis catus) to new environments has invariably resulted in harm to native wildlife. Yet when kept contained – indoors, on a leash, or in a catio – domestic cats can make wonderful pets and lead happy and healthy lives, while wildlife is protected.

In his latest book, Among the Pigeons: Why Our Cats Belong Indoors, Australian ecologist and author Dr. John Read set out to understand the latest science and management alternatives to address an exploding population of free-ranging domestic cats. In his book, Read considers the animal welfare, wildlife conservation, and human health implications of allowing cats to roam, and he presents solutions to shape a more sustainable world. Read recently answered a few questions from American Bird Conservancy about his new book.

What motivated you to write Among the Pigeons?

JR: Over the past two decades, there has been an increased focus on understanding the effects that free-ranging cats have on wildlife and various trials of potential solutions. Over the same period, our understanding of the profound chronic mental health risks to people from cat-borne diseases, as well as the animal welfare risks to outdoor cats, has deepened. Fortunately, there are solutions for all three of these risks. Explaining these, especially to caring cat owners, was my motivation for writing Among the Pigeons.

Cat kill billions of birds and other wildlife around the world each year. Photo by Piotr Velixar/Shutterstock

Can you describe the ecological impacts that cats are having in Australia and around the world?

JR: Free-ranging domestic cats are recognized by the Australian Government as the most serious threat to many species of Australian mammals and birds. Several extinctions and failed wildlife reintroduction attempts were proven to have been caused by cats — in some cases individual feral cats. Even without extinctions, significant declines in cat-vulnerable prey species are affecting ecosystem processes like pollination and seed dispersal around the globe, but particularly on islands like New Zealand, Hawaii, and Australia.

In your book, you note that human outrage over the massive numbers of birds killed by cats seems muted as compared to the losses by other human-caused events, such as oil spills or illegal hunting. What are those losses, and why do you think that is?

JR: Most people interested in wildlife or cat impacts are aware of the phenomenal tallies (billions!) of wildlife that fall victim to either cat predation or death from infection following cat attack. These tallies have been extrapolated from detailed studies in the United States, United Kingdom, Canada, Australia, and elsewhere. But unlike the media footage of birds dripping with oil or a collection of ducks or quail hanging from a hunter's belt, cat kills are typically solitary, private affairs that do not make good fodder for conventional or social media. There is also a perverse perception that it is natural and okay for introduced cats to kill native wildlife, whereas outrage is guaranteed if a fraction of those birds were demonstrated to have been killed by a wind turbine or kids with stones or guns. The end result for the birds is exactly the same, whether their death or injury was caused by us promoting outdoor cats or directly shooting them.

Indoor cats can live healthy, happy lives. Photo by Sam Roxworth/Shutterstock

Can you explain how introduced domestic cats are impacting native felines across the globe (and how native felines are different from domestic cats)?

JR: Domestic cats evolved from African wildcats relatively recently and, hence, share close relationships with many small, native felines. By moving domestic cats around the globe, we have unintentionally exposed native cats, including endangered species in Europe and Asia, to debilitating feline diseases. Because domestic cats mature quickly and can have several large litters a year, they can also breed considerably faster than native cats that have evolved limited recruitment in balance with their ecosystems. This means that along with interbreeding with rare native cats and swamping their gene pools, high densities of domestic cats also out-compete native species. They further debilitate them by spreading disease.

You prefer to call groupings of cats “clowders” rather than “colonies.” Why?

JR: It may sound pedantic, but there is a really important distinction. Social animals like wolves, lions, and ants cooperate and benefit from their interactions. They also regulate reproductive output of their colony with strong defense and protection of mates. Domestic cats are essentially solitary animals, not colonial. Feral domestic cats occupy territories with sizes determined by food availability. When food is abundant, like at seabird nest sites or cat feeding stations, these territories collapse, and many cats are happy to coexist. But they still don't cooperatively hunt or strongly defend mates or food. Most cat litters are sired by multiple toms; even queens mated by supposed ‘alpha' males are typically polygamous (have more than one male mate). Mutual tolerance in clowders is why trap, neuter, release (TNR) is ineffective, because neutered cats, like their intact brothers and sisters, don't prevent immigrants from eating their food or mating with other clowder members.

Feral cat clowder. Photo by John Mossiterino/Shutterstock.

Over the years, you've spoken with many practitioners of trap, neuter, release (TNR). What's your assessment of the practice?

JR: This is a really tough one because I've met lovely, passionate, and committed people, several of whom were profiled in Among the Pigeons, who really want to believe that TNR works and is a humane and effective tool for reducing the suffering of outdoor cats. These are often the same people who are prepared to devote their time and money to ‘assisting' stray cats and are hence best placed to help deal with this widespread and seemingly intractable issue. TNR sounds compelling – and if you believe some social media, it is effective – but unfortunately, studies convincingly demonstrate that re-abandoning sterilized cats typically exposes them to ongoing welfare threats and does not lead to substantial, sustained reductions in stray cats unless most cats are adopted and feeding of unowned cats ceases.

You state that one of your biggest influences for your thinking on cats has been your wife, Katherine. Can you explain how?

JR: Katherine developed her passion for animals through owning pet cats. Yet as a wildlife ecologist specializing in reintroducing threatened mammals, she is constantly challenged to prevent feral cats from killing ‘her' endangered study animals. Katherine still loves (indoor) cats but actively controls feral cats in the most humane and effective ways possible. I think she is a great role model for not only me but others who value both cats and wildlife.

Keeping cats on leashes helps to protect birds and other wildlife. Photo by Malyshev Oleg/Shutterstock.

What do you believe is the appropriate path forward to manage cats and protect wildlife and human health?

JR: Great question, important question. I might be parochial, but I believe New Zealand and Australia are leading the world with ethical and effective cat management in three ways.

Firstly, pet cats need to be treated and managed like loved pets. Local, state, and federal laws, promoted and endorsed by veterinarians and the animal welfare lobby, are increasingly requiring cats to be registered, sterilized, and contained within the owner's home or yard, just like dogs.

Secondly, cats shouldn't be fed outdoors, and bans on feeding unowned cats should be strongly enforced. Limiting access to food is the very best and simplest way of reducing the number, suffering, and impact of unowned cats.

Thirdly, we need to brainstorm and test better ways to control feral cats. A focus of my research is to develop novel techniques to reduce the impacts of feral cats through humane and targeted control, as outlined in the concluding chapters of Among the Pigeons.

Dr. John Read has published over 120 articles and four books.

Grant Sizemore is ABC's Director of Invasive Species Programs.