Predation of wildlife by domestic cats (Felis catus) presents a threat to biodiversity conservation in some ecological contexts. The proportions of wild prey captured and eaten by domestic cats and thus the contributions of wild prey to cat diets are hard to quantify. In a new study published in the journal Ecosphere, a team of researchers at the University of Exeter analyzed the diets of domestic cats through stable isotope analysis of cats’ whiskers and of samples of wild and provisioned foods; they found that the cats that regularly catch wild animals still get most of their nutrition from the provisioned foods.
The diet of domestic cats consist primarily of provisioned foods, though the contribution of wild animals to their diets, all of which regularly caught wild animals, is low (cat food 96%, wild animals 3-4%). Image credit: Birgit.
“Predation of wild animals by domestic cats, in combination with their global distribution and abundance, constitutes a hazard for the conservation of biodiversity in a range of ecological contexts,” said Dr. Martina Cecchetti from the Environment and Sustainability Institute at the University of Exeter and her colleagues.
“In particular, cats living on islands are often considered to be invasive, non-native species that are responsible for the decline, extirpation, and, in some cases, extinction, of endemic species.”
“Our aim was to improve understanding of the factors that might drive domestic cats that are kept as companion animals and are fed regularly, to hunt wild prey.”
“We sought to understand the importance of wild foods to the diets of cats that regularly captured wild prey and to ask whether this prey likely contributed to the cats’ macro- or micro-nutritional needs.”
The researchers used forensic evidence from cats’ whiskers to see what regular hunters of wildlife had been eating.
They trimmed a whisker from each cat in the study, once at the start and once at the end. Stable isotope ratios in the whiskers were then analyzed, allowing the sources of protein from different wild and provisioned foods to be identified.
The results showed that about 96% of their diet came from food provided by their owners, while just 3-4% came from eating wild animals.
This suggests that predatory instinct — rather than hunger — is probably the main reason why some domestic cats regularly hunt wild prey.
“When food from owners is available, our study shows that cats rely almost entirely on this for nutrition,” Dr. Cecchetti said.
“Some owners may worry about restricting hunting because cats need nutrition from wild prey, but in fact it seems even prolific hunters don’t actually eat much of the prey they catch.”
“As predators, some cats may hunt instinctively even if they are not hungry — so-called ‘surplus killing’ — to capture and store prey to eat later.”
The authors also tested the effects of different measures designed to prevent cats killing wild prey.
These measures included bells, Birdsbesafe collar covers, meat-rich diets, providing food using a puzzle feeder and regular play.
Based on analysis of their whiskers, cats with a Birdsbesafe collar cover consumed less wild prey — probably because they caught fewer birds.
“This study reassures owners of cats who hunt that the motive to hunt is instinctive, not driven by nutritional needs,” said Dr. Susan Morgan, chief executive of Songbird Survival, which sponsored the study.
“Furthermore, pet owners can help us reverse the shocking decline in songbirds via three simple, ‘win-win’ steps: fit collars with a Birdsbesafe cover; feed cats a premium meaty diet; play with cats for five to ten minutes a day to ‘scratch that itch’ to hunt.”
“In the UK, we’ve lost half our songbirds in 50 years, but we can all help to stem this tide.”
Martina Cecchetti et al. Contributions of wild and provisioned foods to the diets of domestic cats that depredate wild animals. Ecosphere, published online September 26, 2021; doi: 10.1002/ecs2.3737