Recently, an animal rights organization known as the Network for Animals issued an alarm concerning New Zealand’s attempt to eradicate feral cats. Feral cats are a serious threat to New Zealand’s endemic, ground-dwelling birds such as the kiwis. To address the problem, the New Zealand government has promoted the trapping and killing of feral cats. Network for Animals wants to stop that program and replace it with what they call “trap, neuter and release,” essentially a practice in which cats are trapped, surgically neutered and released back to the wild. All of us should be paying attention to what is going on in New Zealand as we have a serious house cat problem in the U.S. In what follows, I outline the dimensions of that problem, analyze the effectiveness of trap, neuter and release, and suggest alternatives for minimizing the damage done to wildlife by house cats.
Simply put, there are too many house cats roaming around the countryside in the U.S. To better understand the conservation implications of our house cats, I recommend a book entitled Cat Wars by Peter Marra and Chris Santella. The book explains that scientists have documented a huge cat impact on wildlife. Our best estimates indicate that cats kill between 1.3 and 4 billion birds across the U.S. each year. They kill even more mammals and are responsible for the deaths of hundreds of millions of amphibians and reptiles. These should be shocking figures to anyone concerned about conserving what is left of the world’s biodiversity.
Destruction of wildlife is only part of the house cat problem. In rare cases, cats can spread such lethal diseases as the black plague and rabies. Much more common is the spread of toxoplasmosis, a disease caused by a protozoan parasite (Toxoplasma gondii) for which cats serve as the primary host. Oocysts, an early developmental stage of the parasite, are spread in cat feces. Humans can become infected when handling cat litter boxes, soil where cats have defecated, and through drinking water contaminated by runoff from areas frequented by cats. It is estimated that up to 22% of U.S. citizens are infected with T. gondii. Pregnant women can pass the parasite to their unborn babies and have been warned for decades to avoid contact with cat litter boxes. In most healthy people, the immune system relegates the parasites to what was thought to be a latent stage. However, recent research indicates that the parasites are not so latent and can induce severe depression, bipolar disorder, and schizophrenia.
So what should we do about cats? First, people who own cats must keep them indoors. Keeping cats indoors protects wildlife, reduces the spread of parasites, and protects cats from being hit by cars or contracting diseases such as feline leukemia. Second, we must reduce the number of feral house cats in the U.S. Unfortunately, some people leave food out for these cats. Instead of helping the cats, feeding them only keeps their numbers high and ensures the spread of disease and the loss of wildlife. We need to prohibit the feeding of feral cats and fine individuals who persist in doing so. As for actually reducing feral cat numbers, animal rights advocates have favored trap-neuter-release (TNR). The thinking is that the neutered cats will exclude other cats from their territories, resulting in a slow decline in cat numbers due to a lack of reproduction. However, scientific studies of TNR indicate that it does not work. The reason is that cats are not particularly territorial and move around a lot. Fertile cats will move into an area populated by sterile cats and soon begin reproducing. Furthermore, sterile cats still hunt wildlife, so TNR does little to reduce the impact on birds and other wild animals. The only effective means of reducing the number of feral cats is to trap and remove them to shelters where some might be adopted. Those that are not adopted may have to be euthanized due to limitations on shelter space and resources.
Sierra Club could play a positive role in dealing with the feral house cat problem. We could mount a campaign in conjunction with other conservation groups, e.g. Audubon and the American Bird Conservancy, to educate people about the dangers posed by free-ranging house cats. We could also lobby our political representatives, particularly at the local level, for more effective legislation to provide incentives for proper house cat management. We should also lobby officials to enforce ordinances already in existence that restrict where pet cats can roam. None of this will be easy as people become very emotional when it comes to house cats. Nevertheless, the facts are clear: house cats are a major threat to wildlife and public health. We have to confront and manage that threat if we are serious about protecting biodiversity here and around the world.