Posted on April 27th, 2012
When I was a fourth grader, we had a cat. Dad made Tiger a little hanging door in a basement window, like a dog door, and she could come and go as she pleased. Tiger would go out in the morning, and she would play in our backyard.
One day, my parents told me that our neighbors were mad at us because Tiger was killing their chickens. This was obviously not true – Tiger wouldn’t do that, and besides, the chickens were bigger than her. And my parents didn’t like those neighbors anyway. Innocent Tiger continued to roam.
One night, I heard Tiger screaming in the basement. I was too young for bravery, and got into bed with my mom, who assured me that Dad would take care of things when he got home. Mom seemed too scared to go downstairs too. I must have finally fallen asleep, and didn’t see Dad until the morning. When I came downstairs, he was washing the shovel in the laundry tub. He had buried Tiger.
Tiger had been bleeding from the mouth, there was blood all over the basement floor, and I believed she had accidentally swallowed broken glass. Not until much later in life did I learn that rat poisons are tasteless and odorless in lethal concentrations, and that rodenticide causes bloody, painful deaths like the one Tiger had.
I now know that Tiger had been killing our neighbor’s chickens. I now know how angry they must have been when my parents did nothing, particularly with repeated killings. I now know that the rat poison might not have been an accident, but rather an eye for an eye kind of justice. I feel bad for Tiger, bad for the chickens, and bad for our neighbors.
Tiger is gone, but conflicts continue over outdoor cats. The conflicts are usually emotional – between those who love their cats and others who see the harm that an outdoor cat can cause. Such harm is not always so easy to see: cats don’t deposit all of their quarries at the doorstep. But even if they did, love is blind, and the love that many cat owners have for their cats helps blind them to some unpleasant facts.
Cats are hunters. They hunt, catch, and usually kill birds, small mammals, reptiles, amphibians, and insects – anything that moves.
Cats are successful hunters.
- Woods, McDonald, and Harris (2003)i did a questionnaire survey of species brought home by domestic cats. Surveyed cat owners reported that their 986 cats brought home 14,370 “prey items” in a 152 day period, which works out to 35 “prey items” per year per cat.
- Crooks and Soule (1999)ii had California cat owners collect the prey their cats brought home. On average, the domestic cats averaged 56 “prey items” brought home per year.
- Cats do not bring home all of their prizes. George (1974) found that three farm cats brought home about 50% of the prey they capturediii.
- Cats do not succeed in every attempt. Many attempts to catch prey result in the prey bitten, but escaping.
Wounded prey usually dies. When a cat bites into fur or feathers, it creates a deep, non-obvious puncture wound that inoculates bacteria and viruses from the cat’s saliva into deep tissues. Studies have shown that these bacteria may include Actinomyces, Bacteroides tectum, Clostridium, Erysipelothrix rhusiopathiae, Fusobacterium, Moraxella, Neisseria, Pasteurella multocida multocida, Pasteurella multocida septica, Peptostreptococcus, Porphyromonas, Prevotella heparinolytica, Porphyromonas, Propionibacterium, Reimerella anatipestifer, Staphylococci, Streptococci, Wolinella, etc. Pasteurella multocida, the most common bacteria in a cat’s saliva, kills quickly. About 30-50% of cat bites of humans become infectediv v. When small mammals and birds are bitten by a cat, the bites are generally undetectable, but usually severe in their effect, and in a majority of cases result in death. Even with expert care from qualified wildlife rehabilitators, animals attacked by cats have a very poor survival ratevi – perhaps about 20%.
Doing the math.
- If we average the findings of the Woods et al study and the Crooks and Soule study, we would have 45 prey brought home by the average house cat each year.
- Using the George (1974) findings, we estimate that only about 50% of all prey are brought home, so the average house cat may directly kill about 90 prey each year.
- If we assume that the average cat bites as many victims as it captures and kills, and assume that the survival rate for these victims is 20%, then an additional 72 animals die each year from bites for each cat.
- In the U.S., about 50 million cats go outside for part of the day. 50 million cats killing 90 prey each and causing 72 additional deaths from infection and injury… means that in the U.S. each year, cats kill 8,100,000,000 (8.1 Billion!) birds, small mammals, and reptiles. Suddenly, we don’t like math. Our wildlife cannot sustain these losses.
Feeding does not reduce predation. Adamec (2004)vii let cats eat their favorite food, and while they were eating, presented a live rat. In all cases, the cats stopped eating, traveled 4 ft, and leaped off a shelf to attack and kill the rat. They then brought the rat back to the food dish and and resumed their original meal. Quantitative measures of attack latency, biting, and latency to kill revealed a uniform attack pattern which did not differ from attacks seen when the cats were presented with a rat only. Cats are opportunistic predators, and hunt at any opportunity, regardless of how well-fed they areviii. As cat owners know, though, cats don’t eat at any opportunity, but only when they are hungry.
Changing the Balance
Cat lovers argue that cats just do what is natural, that hunting is natural, and that predation occurs in nature. But a hunting cat is not “natural”. Originally, the house cat was a wild cat – Felis silvestris libyca – living in the Fertile Crescent of the Middle East.ix Reptiles, birds, and mammals in North America, Europe and the rest of the world outside the Middle East did not evolve with them. As a result, most animals have not developed the defenses needed to detect and avoid cats. And worse, the density of outdoor house cats is far greater than nature could support, thanks to human feeding: in urban areas, cat ranges are as little as 0.2 acresx. A house cat could quickly eliminate all birds, small mammals, and reptiles in such an area, because it is being fed. Natural predators would need a much larger range so that prey availability was sustainable.
Changing composition. A two-year study comparing two parks in California found that the park without cats had nearly twice as many birds as the other park, where a group of cats was fed daily. Cats not only affected the amount of wildlife, but they also changed its composition. In areas with cats, there were fewer native mice but more non-native house mice. The researchers concluded “Cats at artificially high densities, sustained by supplemental feeding, reduce abundance of native rodent and bird populations, change the rodent species composition, and may facilitate the expansion of the house mouse into new areas.”xi More cats may mean more mice.
Wildlife Extinctions. On Marion Island in the Sub-Antarctic Indian Ocean, cats were estimated to kill 450,000 seabirds annually prior to cat eradication effortsxii. When an animal that loves to hunt is introduced to large colonies of birds that have never had a terrestrial predator, very bad things happen. Feral cats, along with feral cows, feral pigs, and introduced rats, are blamed for the extinction of 70 species of birds in Hawaii.
Despite our wishes, some “solutions” don’t work.
Belling. Adding a bell to your cat’s collar appears to have no effect on its success in killing songbirds, but in one study, cut small mammal mortality in half. That is, add a bell and your cat will kill fewer mice, but just as many birds.xiii More research is needed, but from what we know, belling either doesn’t work, or only works sometimes or improves a cat’s hunting! And it puts the cat at risk of becoming entangled and perhaps strangled.
Declawing. Declawing is a very bad idea. As one source writes “Declawing is more than simply removing the cat’s claws. The last bone on the cat’s claw is amputated. This is an excruciatingly painful procedure & one which not all cats will fully recover from. Many declawed cats are surrendered to shelters because of behavioral problems they developed after being declawed including biting & refusal to use their litter tray. Cats by nature walk on their toes, so after they’ve been declawed, walking often becomes extremely painful to them.”xiv
Feeding, neutering, spaying, vaccinating feral cat colonies. As we’ve learned, feeding a feral cat does not reduce predation. But it may increase longevity. A feral cat, over a 10 year lifespan, killing just 3 prey each week, would take 1,560 lives in its own life. While we should value the life of a feral cat, we shouldn’t value it over the lives of 1,560 other wild animals.
The Good News
Cats do not need to go outdoors at all. Cats who have been allowed to spend their days outdoors will quickly adjust to a life indoors, ending their threat to wildlife.
Join the Cats Indoors movementxv. Your cat will benefit. Your indoor cat won’t be hit by a car, chased by a dog, cause problems with the neighbors, get an abscess from a fight, get lost or stolen. It won’t eat the neighbor’s chickens, and won’t eat the neighbor’s rat poison. Remember Tiger.
iMichael Woods, Robbie A. McDonald, and Stephen Harris. “Predation of Wildlife by Domestic Cats in Great Britain.” The Mammal Society March 1, 2003 http://www.abdn.ac.uk/~nhi775/cat_predation.htm
ivJulia Barrett. Animal bite infections. Encyclopedia of Medicine, April 6, 2001. http://findarticles.com/p/articles/mi_g2601/is_0000/ai_2601000079/
vTalan DA, Citron DM, Abrahamian FM, Moran GJ, Goldstein EJC. Bacteriologic analysis of infected dog and cat bites. N Engl J Med 1999;340:85-92 http://www.ncbi.nlm.nih.gov/pubmed/9887159
viErin Luther, Toronto Wildlife Center. “Keeping cats indoors is for the birds… and the cats” http://www.cwf-fcf.org/en/what-we-do/habitat/gardening-for-wildlife/animals/problem-wildlife/keeping-cats-indoors-is-for.html
viiRobert E. Adamec The interaction of hunger and preying in the domestic cat (Felis catus): An adaptive hierarchy? Behavioral Biology Volume 18, Issue 2, October 1976, Pages 263–272 http://www.sciencedirect.com/science/article/pii/S0091677376921660
ixBrian Handwerk, “House Cat Origin Traced to Middle Eastern Wildcat Ancestor”. National Geographic News June 28, 2007. http://news.nationalgeographic.com/news/2007/06/070628-cat-ancestor.html
xiiiBarrette D.G. (1998). Predation by house cats, Felis catus (L.), in Canberra, Australia, II. Factors affecting the amount of prey caught and estimates of the impact on wildlife. Wildlife Research. 25: 475-487; Woods M., McDonald R.A. and Harris S. (in press). Predation of wildlife by domestic cats Felis catus in Great Britain. The Mammal Society, 15 the Cloisters, 8 Battersea park road, London SW8 4BG, UK; and school of biological science, university of Bristol, Woodland road, Bristol BS8 1UG, UK.