Although this carnage is largely invisible, it has a major effect on many species. Cats are responsible for 72% of all bird mortalities in the U.S. as estimated by the U.S. Fish & Wildlife Service!

Cats are cherished globally as household pets. My wife, Diane, and I have a pet cat, Izzi, that we dearly love. There are over 200 million cats kept as pets around the world. Unfortunately, there are also nearly 500 million cats that are either strays fed by humans or feral cats that live outdoors and avoid human contact.

Cats have contributed to the extinction of many bird, mammal, and reptile species. In the U.S., domestic cats kill approximately 2 billion birds, 10 billion mammals, and 500 million reptiles each year. Most of these are killed by cats that are not household pets. Feral cats are estimated to be responsible for approximately 60% of all birds killed by cats in the U.S.

Cats were domesticated approximately 10,000 years ago in the first agricultural societies in the Fertile Crescent, where the continents of Asia, Africa, and Europe come together. Agriculture changed the lifestyle of humans from nomadic groups to sedentary settlements. Grain stores and waste in these settlements attracted mice which provided a steady source of food for wildcats. The predation on rodent pests of these wildcats was beneficial so that wildcats were encouraged to live together with humans. Genetic studies have shown that domestic cats were derived from the African species of wildcats.

What can we do to reduce the harmful effects of feral cats on wildlife? Some people have advocated for live trapping, neutering, and releasing feral cats back into the wild. However, scientific studies have shown that this method is not effective in reducing the number of feral cats.

Australia is the world leader in developing programs to reduce the effects of feral cats. Australian animals have evolved in the absence of cats, and therefore they lack the ability to defend themselves against cats. For example, many Australia birds nest on the ground. An effort is underway to develop a spray that makes male cats sterile that is released from a motion sensor camera that uses artificial intelligence to recognize cats.

Australia has built 28 fenced areas covering several hundred square miles that exclude cats. One of these exclosures was built in 1995 to protect Francois Peron National Park in Western Australia. The park is on a narrow peninsula that extends nearly 100 miles into the Indian Ocean.

A predator-proof fence was constructed at the narrow base of the peninsula to prevent cats from entering the sanctuary. At the gate where cars enter, a motion detector plays a recording of a large dog barking to discourage cats from entering. Here is a video that I took 10 years ago of the fence and the dog barking. Monitoring has shown that the recorded dog barking is effective.

Reducing the harmful effects of pet cats on wildlife presents a different set of challenges. The straightforward, but not socially acceptable, solution is to not allow pet cats to roam outside. Here in Missoula, pet cats that roam outside must be neutered, and it is illegal to own cats of both sexes that are not neutered. However, these rules are difficult to enforce; no one was charged with a violation last year.

A creative method of control has been proposed by Jonathan Losos, an evolutionary biologist at Washington University in Missouri. I strongly recommend his book, “The Cat’s Meow,” which discusses the past, present, and future of domestic cats. In this book, he suggests developing pet cats that are not interested in going outside and hunting by selective breeding.