Wildlife’s Worst Enemy


Feral cats are defined as domestic (home) cats gone wild.  Domesticated cats have been and remain one of the favorite choices for pet lovers. Thus, broaching the “downside” of cats may easily raise the ire of those who treasure their favorite animal as not capable of doing anything wrong. Even reading or writing about them negatively often elicits emotional outbursts from cat lovers.

Wild or “feral” cats cast a negative downside to their domesticated house cat “siblings.”   They cause significant predation of small mammals, reptiles, and amphibians. Besides being a general nuisance, they can transmit such disease organisms as rabies and toxoplasmosis. Along with house pets that are allowed outside, “human-linked” feral cats are said to be the leading cause of death for birds and mammals. Their most likely prey animals are squirrels, shrews, mice, voles, rabbits, small birds, and any other likely and available “meal.”

Biology of feral cats.* Feral cats weigh up to eight pounds, are up to 36 inches long and live in the wild up to five years. Domestic or home cats may live as long as 15 years. Feral cats may live in barns of other outbuildings, alleys, sewer systems, overgrown areas, under bridges, along creeks, or other places offering shelter. They roam in an area of 1.5 square miles, their home range. For food, they feed upon human refuse, birds, small mammals, reptiles, amphibians, and human-provided food. Feral cats can potentially produce up to five litters/year, beginning generally in the spring when the increasing length of daylight triggers female estrus. Two to 10 young are born in each litter after a 65 day gestation period. The Humane Society has estimated that one pair of cats potentially can produce progeny numbering 400,000 under ideal conditions with no deaths. It is estimated that there are 60 to 88 million domesticated cats in the U.S, with an additional 60 million more belonging to the feral ranks.

A systematic review and estimate of cat caused mortality in the United States by S.R. Loss, T. Will, and P.P.Marra** suggested that cats kill 1.4 to 3.7 billions of birds and 6.9 to 20.7 billions of mammals each year. Most of the damage is caused by un-owned cats, which are most likely the greatest single source of human-related mortality of U.S. mammals and birds.

Based on these figures, the enormity of this impact on natural populations of wildlife has long been underestimated. However, cat lovers insist that cats are wrongly being blamed for bird habitat loss, and animal loss actually due to chemicals used in fertilizers, and insecticides. Human impact is to blame for the real threat to birds, they say.

George Fenwick, president of ABC, is quoted*** as saying, “To maintain the integrity of our ecosystem, we have to conserve the animals that play integral roles in those ecosystems. Every time we lose another bird species or suppress their population numbers, we’re altering the very ecosystems that we depend on as humans. This issue clearly needs immediate conservation attention.”

Past policies dealing with stray cats has been to capture them, neuter them, then return them to their hunting grounds—where they continue to prey upon the same wildlife which also serves as prey for owls, eagles, and hawks.

As a biologist, the writer has frequently encountered stray or feral cats in the field. In fact, I inadverdently caught one while attempting to trap red foxes a number of years ago during a bitter winter night underneath a highway overpass in South Dakota, though I don’t remember what I did with it.   I have, presently, a neighbor who maintains a set and baited live trap for free roaming cats. He takes his “captures” several miles away and releases them—which really only moves the problem to someone else’s “backyard.” without resolving the problem. Another well intentioned neighbor keeps a supply of cat food available for free ranging, wild neighborhood cats near her carport. She even maintains an electric warming pad available for them in the wintertime. Do these latter two examples illustrate why we continue to have the feral cat problem?

My own opinion on the feral cat subject is to seek to maintain traditional natural balance in the ecosystems. Inasmuch as humans are blamed for domesticating the European and African wild cat, seven thousand years ago, we should do our best to manage them today for the purpose intended—solely that of being house pet companions. It is irresponsible to allow cats to become wild or feral. Small mammals and birds have ample predator pressure to survive under natural conditions without the added hazard of becoming prey to prowling domesticated cats gone wild.

*Hildreth, A.M., S. M. Vantassel, and S. E. Hygnstrom. 2010. Feral cats and their management. Nebraska Extension, EC1781.

**Loss, S.R., T. Will and P.P. Marra. 2013. Nature Communications, 4, No. 1396, 29 January.

***Collins, L. M., 2013. Outdoor cats kill billions of birds, mammals. Deseret News, Salt Lake City, Utah.