Understanding Cats and Predation

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Many studies have shown that cats do not have a detrimental impact on wildlife on continents. However, many people still feel that cats are to blame for the depletion of songbirds and other animals. Two studies most often quoted to support placing blame on feral cats are the Stanley Temple study and the Churcher/Lawton study. Some individuals and groups use these studies in misguided efforts to discredit Alley Cat Allies’ and others work to humanely control feral cats. However, over sixty studies on feral cats have been written from different continents throughout the world—all showing three very important points:

1. Cats are opportunistic feeders, eating what is most easily available. Feral cats are scavengers, and many rely on garbage and handouts from people;
2. Cats are rodent specialists. Birds make up a small percentage of their diet when they rely solely on hunting for food
3. And, cats may prey on a population without destroying it. If this were not so, we would no longer have any mice around.

Even though some cats can become efficient hunters and do kill birds, many international biologists agree that only on small islands do cats pose a severe threat to the wildlife populations. They agree with biologist C.J. Mead that “any bird populations on the continents that could not withstand these levels of predation from cats and other predators would have disappeared long ago.”

And finally, while many concentrate their efforts on blaming cats, the real culprit, homo sapiens, goes free; continuing the destruction of habitat, hunting, killing, and using pesticides that endanger entire populations of wildlife, including millions of birds. The following is a collection of opinions from experts who have studied feral cat predation and who do not blame cats for detrimentally impacting wildlife.

OPINIONS FROM THE EXPERTS

The following is an excerpt from Roger Tabor’s Understanding Cats, (The Reader’s Digest Association, Inc.: New York/Montreal, 1995).

“From the mid-nineteenth century mankind’s own numbers and destruction of huge areas of virgin planet surface have exploded exponentially. As man thrived, so did the domestic cat due to the massive increase in food supply for both house and feral animals.” (pp. 8-9)

“Cats hunt, catch prey, and eat it—they are carnivores. To expect them not to hunt is unreasonable both because of their biology and the natural order of things. Almost incredibly, in the USA there is a growing idea that carnivores are somehow immoral. Although that view may be extreme, that cats catch birds causes cat-owning bird lovers much concern…

“While the size of the range of rural feral cats reflects their prey requirements, prey is not necessary for the survival of domestic house cats, their range sizes are independent of its abundance. While this could make them more of a danger to wildlife, this does not occur for a number of reasons….Not all house cats are competent hunters and most only catch prey occasionally….Although cats are superb hunters, it is their scavenging ability that allows them to survive as feral-living animals and live with us eating food off a saucer.

“Contrary to common belief, cats do not catch many birds, but mainly small mammals. Proportionately, town cats will catch more birds than their country cousins. What is often overlooked is that although cats are far more common in towns than in the country, so are birds! As well as feeding cats, we also feed birds. We provide artificial nest sites in the form of nestboxes and buildings. Our gardens provide good habitat in the form of rich scrubland, with excellent insect support due to an increased flowering time in the year, and lawns with abundant earthworms. Our actions can be seen as providing optimum conditions to maximize bird numbers! Consequently, when Chris Mead of the British Trust for Ornithology assessed the numbers of ringed garden birds caught by cats, he found that they were not having a harmful effect on bird populations.”( pp. 101-102)

Are concerns of cat predation and effects on birds/wildlife valid?

Jeff Elliott wrote an extensive article for The Sonoma County Independent, “The Accused,” (March 3-16, 1994), which investigated frequently used studies that implicate cats in the decrease of wildlife populations. Following is an excerpt from the article listing the studies and his findings of their accuracy.

“But what do those studies actually say? And how good is the science in them? Here’s some background on the two most frequently mentioned studies, cited in Cats and Wildlife: A Factsheet from the National Audubon Society. “Britain’s 5 million cats kill about 20 million birds per year’

“Studying the hunting trophies brought home by 78 cats in a single English village, Peter Churcher and John Lawton found birds were 35 percent of the kill —by far the highest estimate in any such study. In a 1989 condensation for Natural History magazine, they multiplied their results by the estimated number of cats in the entire nation. Rarely are projections made with such limited data, except in junior high science projects—which may be an appropriate comparison, considering Churcher teaches at a boys’ school.

“Researchers in Wisconsin cite cats for killing 19 million songbirds.

“Doctor Stanley Temple, co-author of this frequently quoted work, seemed exasperated when asked again to rehash his findings. ‘The media has had a field day with this since we started,’ he sighed. Those figures were from our proposal. They aren’t actual data; that was just our projection to show how bad it might be.’ No one interviewed has seen Temple’s unpublished research.

“But the [Sonoma County] supervisors appeared to give special attention to a letter written by Drs. Peter Connors and Victor Chow, UC/Davis researchers working at the Bodega Marine Laboratory. By projecting the numbers cited from Wisconsin and Great Britain, they estimated 500,000 Sonoma County birds are killed by cats annually. In a telephone interview, Connors said he has read only the condensation of the British study and has seen only “extracted forms” of Temple’s work, which of course were guesstimates for the proposal. He was surprised to learn this study was unpublished. ‘Look, we’re not cat researchers,’ said Connors. ‘I’ve never worked with cats at all; I’m an ornithologist.’ Then what expertise does he have about cats? ‘Vic (Chow) has been participating in a mentor program with Piner High School students on a project tracking feral cats,’ he explained. ‘We had (radio transmitter) collars on three animals. We didn’t do a full study; it’s just a program with high school students.’”

The following is an excerpt from Peter Neville’s Claws and Purrs: Understanding the Two Sides of Your Cat (Sidgwick and Jackson: London, 1992), p. 164. Mr. Neville is the Director of the Center of Applied Pet Ethology in the United Kingdom.

“In England, at least, there is no evidence to suggest that the occasional high mortality of birds due to pet cats has had any damaging effect on even one species of bird, however distressing to birds, bird lovers and cat owners that predation may be….

“In any case, as we have seen, the strategy used by cats for catching birds is not hugely successful at the best of times and only increases in efficiency when the birds stalked are more vulnerable or less able to escape.”

B.M. Fitzgerald, Ecology Division, Department of Scientific and Industrial Research, New Zealand Mead has studied various aspects of feral cats (home range, effect on birdlife, food) and the effects of various predators on local wildlife, since 1970, in New Zealand.

“As Mead (1982) emphasized, the birds in suburban and rural parts of Britain have coexisted with cats for hundreds of generations. And they may now be under less pressure from cats than they were in the past from a variety of assorted natural predators. Any bird populations on the continents that could not withstand these levels of predation from cats and other predators would have disappeared long ago.”

The following is an excerpt from Gary J. Patronek’s, VMD, Ph.D. Tufts University, “Letter to Editor,” Journal of the American Veterinary Medical Association, Vol. 209, No. 10, November 15, 1996.

“If the real objection to managed colonies is that it is unethical to put cats in a situation where they could potentially kill any wild creature, then the ethical issue should be debated on its own merits without burdening the discussion with highly speculative numerical estimates for either wildlife mortality or cat predation. Whittling down guesses or extrapolations from limited observations by a factor of 10 or even 100 does not make these estimates any more credible, and the fact that they are the best available data is not sufficient to justify their use when the consequences may be extermination for cats.

“If asking for reasonable data to support the general assertion that wildlife mortality across the United States attributable to cat predation is unacceptably high can be construed as ‘attempting to minimize the impact,’ then I am guilty as charged. What I find inconsistent in an otherwise scientific debate about biodiversity is how indictment of cats has been pursued almost in spite of the evidence.”

The following is an excerpt from a speech by John Terborgh (Director of the Center for Tropical Conservation, Duke University) at The Manomet Symposium in 1989, Smithsonian Institution, Washington, DC.

“The global environmental crisis has caught up with migratory birds. There are simply too many people making ever increasing demands on a fixed supply of resources. It is inconceivable that we can continue on the same reckless path for very long.

“The conversion of forests to cropland, pasture and urban sprawl, the downgrading of virgin stands to second growth, and the conversion of mixed forests to pine monocultures… The inescapable implication of this for conservation is that there is only a limited amount of time left in which to slow human population growth and to institute other fundamental changes in the countries of this hemisphere or many of our migratory birds will be little more than memories.

“One country after another will pass the 100 per square kilometer population threshold in the coming two or three decades. After this has happened, there is really not much that can be done to salvage winter habitat for migratory birds.”

What then is responsible for the decreasing number of birds?

The following is an excerpt from a speech by biologist Dr. Robert Berg.

“Habitat destruction: As man’s development of the planet continues, available habitat for animals and plants is being carved up into smaller pieces. The fragmentation of ecosystems separates populations genetically from each other, and if a particular habitat is not large enough, remnant populations contained within them are doomed due to genetic inbreeding. If there are not enough large areas, chance occurrences such as an extremely harsh winter, floods, localized disease, etc., can drive remaining populations to the brink of extinction.

“Some species are dependent on environmental policy in more than one place. One endangered species of bird, Bachman’s warbler, is disappearing not because there is a scarcity of riverine swampland in the (Southeast) United States in which it breeds, but because it used to winter in the forests of western Cuba virtually all of which have been cleared for sugar cane.

“In some cases other birds have been responsible for the demise of some bird species. Kirtland’s warbler, already compressed into a small remaining jack-pine country in Michigan, was subjected to nest parasitism by the brown-headed cowbird laying its eggs in their nests. The baby cowbirds push the Kirtland’s own young from the nest and are then raised by these hapless birds. The European starling has spread across the United States since its introduction in the early 1900’s, depriving many of our resident and less aggressive birds of habitat. In the words of Pogo, ‘We have met the enemy and he is us.’”

© 2006 Alley Cat Allies