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By Sofia Moutinho
Minnie, three, is a serial killer. Like many domestic cats, the female tabby cat usually flees at night to hunt and bring its prey back. “We had birds in the room, rats in the trash, rabbits in the pantry and several worms that died of fear,” says its owner, Lisa George, from Cornwall, UK
Things changed when George enrolled his kitten in an unusual scientific test. For nearly 3 months, Minnie and dozens of cats were fed a much richer meat diet; a different group had extra play time. At the end of the test, both groups brought home a third less animals than before.
The findings “make sense,” says behavioral veterinarian Sharon Crowell-Davis of the University of Georgia in Athens, who was not part of the study. She says that hunting is embedded in the brain of cats, and that playing seems to satisfy that desire. In the meantime, she says, fleshy food can satisfy your craving for “the diet your ancestors have been eating for thousands of generations”.
Studies have found that free-ranging domestic cats kill up to 22 billion mammals and 4 billion birds a year in the United States and that they have contributed to the extinction of 63 species worldwide. Many cat advocacy organizations question these numbers, however, and many owners still leave their cats outside, arguing that they should be free to express their natural behaviors.
“There has been a lot of dislike between people who defend wildlife and those who defend cats,” says ecologist Robbie McDonald of the University of Exeter. Despite loving dogs, he decided to find a solution that could please both sides.
McDonald and his colleagues recruited 219 cat owners from southwest England, whose pets used to hunt outside. They divided the animals into six groups, including a control that did not change their habits. Some used bells to make it easier for the prey to hear them coming, while others wore colorful Birdsbesafe collars that birds can easily see.
In other groups, owners fed their cats “puzzle feeders”, food dispensing toys designed to challenge the feline. Still others have traded their cats’ food for a store-bought, grain-free brand made entirely of animal protein. (It comes in both wet and dry forms.) Owners of a final group of cats spent 5 to 10 minutes a day playing with their pets; people were instructed to use a feather toy on a string to simulate hunting and then replace it with a wrinkled mouse-like toy.
For 12 weeks, the owners took pictures of all the animals that their cats brought home.
Almost all approaches have restricted the killing instinct of cats, scientists today report in Current Biology. The Birdsbesafe collar was the most effective way to reduce the number of birds that the kittens brought home, reducing the total by 42% on average. But the meat-rich diet and playful approaches have had the most far-reaching impacts, reducing all types of animals on their doorstep by 36% and 25%, respectively.
The bells had no effect. The puzzle feeder increased predation by 33%. The researchers speculate that the cats were frustrated with the devices, became hungry and decided to go hunting.
The study did not analyze what makes each strategy work. But McDonald believes that meat-rich food may have filled a nutrient gap in the cats’ diet and that the joke has satiated some of his hunting instinct. “Most cats still killed wild animals because old habits are hard to die,” he says. “But in general the numbers have been greatly reduced.”
Minnie herself, who was in the high meat group, brought back only two animals during the trial, compared with 22 in the previous 7 weeks. “I couldn’t believe the difference when I found out that my cat barely hunted,” says George. Still, Minnie’s owner says the approach was too expensive to sustain. Minnie is now back to her old hunting habits.
Not everyone is buying the results. Grant Sizemore, a wildlife biologist at the American Bird Conservancy, argues that cats may have killed the same number of animals – just bringing less home. He also notes that previous studies have shown that cats hunt even when well fed.
Sizemore says the best solution is still to keep cats indoors. Cats that live indoors are also less likely to get hurt or contract diseases that can harm themselves and people, he notes. “Keeping cats indoors is certainly better for wildlife, cats and the human community as well.”
Crowell-Davis says a better solution would be a compromise – perhaps letting the cats exercise in a fenced-in yard. And she argues that cats sometimes replace native predators – making it a zero-sum game for prey – and that feline hunters can do both good and evil, for example, by reducing the number of disease-bearing rodents. “It’s important to realize,” she says, “that a cat’s impact on wildlife is not a simple problem with a simple answer.”