Surprisingly simple measures can prevent domestic cats from killing a lot of wildlife.
Estimates vary, but billions of birds and mammals are likely to succumb to our outdoor feline friends each year (SN: 29/1/13). Calls to keep cats indoors are often disputed among cat owners, and sometimes cats may reject colorful collars or loud bells designed to make them more noticeable.
But a meat-rich diet or a few minutes of play like hunting can significantly reduce the amount of wildlife they bring home, researchers report Feb. 11 in Current Biology.
Interventions that reduce cat predation and that cat owners welcome “are so important because we’re only decimating bird populations,” says Susan Willson, an ecologist at St. Louis University. Lawrence in Canton, NY, who did not participate in the study. Although preliminary, he says this study shows that "simply feeding your cat a meat-rich diet can work."
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Most attempts to curb the impact of cats on wildlife have focused on restricting cats ’behavior and their ability to hunt. But Robbie McDonald, an ecologist at the University of Exeter in Cornwall, England, and his colleagues investigated the root of the problem: the desire to go hunting first. “We wanted to find out why well-fed cats could still kill wildlife,” he says.
The team reasoned that this desire could stem from natural hunting instincts or the need for cats to supplement their diet. Cats are carnivores and some cat food may not meet all of a cat’s needs, McDonald says. If any of these influence hunting behavior, then perhaps enhancing the amount of meat in a cat’s diet or mimicking hunting behavior through play could meet those needs without the collateral damage to wildlife.
McDonald and colleagues tested these new interventions on 355 domestic cats in 219 homes in the south-west of England. Only known hunters were recorded and owners first calculated all the birds, mammals or other critters their cats brought home for seven weeks, to establish a baseline for each cat.
The owners then implemented one of the few interventions for six weeks: switching to a commercially available food without grades and with high meat; play five to 10 minutes each day; put your cat’s normal food in a puzzle feeder; and existing methods such as Birdsbesafe bells or necklaces. Some owners have not changed anything, but have continued to track their cats.
Cats fed a meat-rich diet brought home 36 percent fewer prey, on average, than before the diet change, the team calculated. For example, a cat that normally brings home a daily catch would return about 20 critters a month. “That may not seem like much,” McDonald says of the fall. But "a very large population of cats means that if this average were applied in general, there would be many millions fewer deaths."
Cats treated until playtime, which consisted of owners getting their cats to stalk, chase and jump on a feather toy and then give the cats a mouse toy to bite, returned 25 percent less prey. , although that drop came mainly from mammals, not birds. Cats that started using jigsaw puzzles brought home more wildlife. The bells had no noticeable effect, while cats equipped with Birdsbesafe collars brought home 42 percent fewer birds, but about the same number of mammals, which matches previous research.
“We were surprised that the diet change had such a strong effect,” McDonald says, in part because cat pretreatment diets were variable. “Nutrition seems to influence a cat’s tendency to kill things and some cats that hunt may need something extra” which provides a more meaty diet, he says. McDonald’s is already working to pinpoint what that extra something might be.
“It’s a robust study that I hope will continue with more research,” says Willson, the San Lorenzo ecologist. Because the study focused on prey brought home, wild animals that were dead and eaten or left out could be missing.
McDonald says the safest way to prevent cats from killing wildlife is to keep them indoors. Although many cat owners care about wildlife, they also resist such unnatural restrictions for their cat. But McDonald's found these new interventions to be less controversial. After the trial, 33 percent of participants reported that they planned to continue feeding their cats meat-rich diets and 76 percent reported that they would play more with their cats.
“We expect hunting cat owners to consider testing these changes,” McDonald says. "It's good for conservation and good for cats."