Feline Pests

By Kaleb Hill

            Invasive species are a dangerous and devastating problem for the environment and public health. Invading alien species in the United States cause major environmental damages and losses adding up to almost $120 billion per year (Update on…). When hearing the term invasive species, people often think of Burmese pythons, fire ants, and feral hogs. Although these animals are devastating to the environment, none of them compare to the damages of feral cats. Free-roaming and feral cats yearly kill hundreds of millions, perhaps as many as a billion, native North American birds, mammals, reptiles, amphibians, and fish (Coleman JS, et al. 1997). The Lindsay Museum of Walnut Creek, Calif, a full-service wildlife rehabilitation facility, received 5,669 small mammals, birds, and reptiles between January 1 and September 14, 2003. Of these, 24% (1,050) of birds, 12% (143) of mammals, and 15% (11) of reptiles were presented because of cat-related injuries or conditions (Coleman JS, et al. 1997). Many people who see cats attacking or predating wildlife think nothing of it, and many may even support this behavior. Not only do these animals damage the native wildlife by predation, but they also compete with other predators by decrease prey availability.

            Cats are predators by nature, and predation is a natural threat to all animals, but the pressure that wildlife receive from cat predation can be much greater. The term feral means in a wild state, but it is complicated with cats as this might not be the case. Many cats are free roaming pets, meaning that they are cared for by an owner who provides food and shelter but allows the cat to move around freely outside. Food and shelter are also provided for many feral cats by cat lovers. This causes cats to potentially reach a higher level of fitness than a wild animal that is always in search of resources and shelter. Feral cats and the programs that foster their free-ranging existence do not serve the welfare of individual wild animals or wildlife populations, can cause an alteration of basic biological processes, and have serious potential negative impacts on biodiversity and recovery of endangered and sensitive species in many landscapes (Dickman 1996). Having free ranging and feral cats creates a grey area when deciding how to handle this problem.

            One of the “solutions” being used to address this problem is “Trap-Neuter-Return” (TNR), a process of trapping cats and surgically sterilizing the animals to prevent them from reproducing. In the world of TNR, unless a stray cat has a collar or is microchipped, it is very difficult to distinguish from a truly feral animal (Jessup, 2004). This process is very ineffective and raises ethical concern of our actions to release invasive predators into the environment. Although the trapped cats cannot reproduce they are released to continue wreaking havoc on wildlife for the rest of their life. Despite articles claiming success, a follow-up studyh on one of the largest and most active TNR programs in California has revealed no demonstrable effects at the population level after nearly a decade of effort (Chappell, 1999). Many suggest that releasing these animals is a violation of the Endangered Species Act (ESA), due to the fact that cats can and do kill endangered wildlife.

            Other solutions have to be explored, during a time when biodiversity is severely threatened we cannot afford to waste any more time or money on a process and opinion that is not working. Changing public opinion is a very important start in this process, educating people about the hazards of feeding and sheltering feral cats is the first step to correcting this problem. Keeping pet cats on your property needs to become mandatory to protect wildlife and other pets. Through the process of TNR many free roaming cats get relocated to different areas and lost, which is an important reason to keep track of your pets. We must accept that euthanasia and poisoning could be a more effective and cost efficient solution, these pests need to be treated and viewed the same way as any other rodent, hog, snake, insect, or other wildlife that people have deemed acceptable to kill. If cats get a free pass, why shouldn’t all other invasive species get protection?

Coleman JS, Temple SA, Craven SR. Cats and wildlife: a conservation dilemma. Madison, Wis: Cooperative Extension Publications, 1997.

Dickman CR. Overview of the impacts of feral cats on Australian native fauna. Canberra, Australia: Australian Nature Conservation Agency, 1996; 92.

Jessup David A. The Welfare of Feral Cats and Wildlife. Animal Welfare Forum 2004. Vol 225,

Chappell MS. A model for humane reduction of feral cat populations. Calif Vet 1999; Sep/Oct

Pimentel David, Zuniga Rodolfo, Morrison Doug. Update on the Environmental and Economic Costs Associated with alien-invasive species in the United States. Ecological Economics, 2004; Vol 52