Scientists have found a surprising way to make domestic cats hunt less and reduce their impact on wildlife. In a trial that involved hundreds of cats across the United Kingdom, the researchers discovered that changing cats’ diets in animal-sourced protein and playing more with them can make a big difference to stop them from hunting wildlife.

Adorable killing machines

Domestic cats (Felis catus) are one of the most numerous carnivores on the planet, numbering over 600 million. The number of domestic cats is so great that it outnumbers the collective number of all other felines in the world — and while they are beloved by billions of people, they can also be a plague on local species when they are allowed to roam free outside.

Unless cats are kept for pest control, owners rarely consider killing wild animals to be desirable — and yet it happens so much it can devastate whole environments. To reduce killing, owners might completely or partly restrict outdoor access, or attempt to inhibit or impede hunting with collar-mounted devices such as bells on collars, but it’s not clear just how well these work. While these have varied success, they don’t actually repress the cat’s desire to hunt.

“Previous measures like bells tried to stymie the cat at the last minute. What we did was try to head them off at the pass by addressing some of their needs or wants before they think about going out hunting. With entirely non-invasive methods, owners can change what the cats themselves want to do,” Robbie McDonald, co-author of the study, told The Guardian.

Permanent confinement of cats would solve the problem of wildlife depredation, the researchers argued, but this is unpopular among cat owners in many areas. Outdoor access is seen by many as critical to cat welfare (although that often puts cats at risk, in addition to the environmental damage). Instead, the researchers suggested prioritizing behaviors that are likely to be widely adopted by cat owners, which would lead to more effective advocacy.

With this in mind, McDonald and her team tested whether something as simple as dietary and behavioral interventions can ostensibly benefit cats and reduce killing, not by directly impeding hunting but by reducing the cats’ tendency to hunt. They recruited cat owners whose cats regularly hunted and captured wild animals and brought them back to the house.

With a before-after-control-impact design, the researchers evaluated two existing inhibitory measures:

• the first group of cats had their collars equipped with a bell or with a Birdsbesafe collar cover that hampered hunting;
• the second group was treated to three novel measures: provision of food in a “puzzle” feeder, provision of a commercial, grain-free food in which meat was the principal source of protein, and 5- to 10-min daily object play. There was also a control group.

The study involved 355 cats from 219 households in southwestern England and lasted for 12 weeks. Feeding a cat with commercial food in which proteins came from meat reduced by 36% the number of prey animals brought home, while 5 to 10 minutes of daily play resulted in a 25% reduction. Colorful bird-friendly collar covers also reduced 42% the number of birds captured.

“Our work shows that non-invasive methods, like food and play, can change cats’ inclination to hunt and be positive for cats and their owners,” McDonald said. “Some cat foods contain protein from plant sources such as soy, and it is possible that despite forming a complete diet, these foods leave some cats deficient in one or more micronutrients, prompting some of them to hunt.”

The findings are consistent with the theory that some cats may hunt more because they are stimulated to address some deficiency in their provisioned food, while others do it just to keep themselves entertained. Nevertheless, the researchers couldn’t distinguish specific drivers of the beneficial effect of dietary change. They suggested this could be due to a specific micronutrient or amino acid, but more research is needed to demonstrate this.

Reproduction of natural behaviors in the home environment was also found to be beneficial for pet cats. During hunting and play, similar behaviors are observed, and hunger increases both predation rate and play motivation in cats. The study showed most cast readily engaged with the toys, with three-quarters of households planning to continue with regular play.

The researchers hope the findings will help address the predation of wildlife by cats, which they described as an ecological and social problem. In the US alone, domestic cats have been found to kill at least 1.3 billion birds and 6.3 billion small mammals each year. In New Zealand and Australia, there’s also some evidence that cats have contributed to the decline and extinction of native species.

The study was published in the journal Current Biology.