Whisker analysis shows urban foxes getting third of their food from people
Researchers warn there could be health impacts for foxes from eating too much processed foods.
Urban foxes are sourcing more than a third of their diet from humans – raising concerns they could face health risks from processed foods.
Scientists at Nottingham Trent University analysed the whiskers of nearly 100 foxes to reveal that food sourced directly or indirectly from people made up 35% of city fox diets, compared with only 6% for their country cousins.
Foxes are omnivores that eat a range of foods from small mammals, birds, beetles, grubs and worms to fruit and carrion.
In cities in particular, they exploit food sources from people, including discarded meals and food waste, as well as things left out for wildlife including pet food, leftovers and bird food.
But the researchers warned it is possible that processed foods, with their high levels of saturated fat and refined sugars and grains and low amounts of fibre and micronutrients, could lead to poor health in foxes.
The study used chemical analysis of the whiskers of 93 dead foxes across Britain to reveal what they had been eating over a period of weeks to months as the hairs grew, rather than a snapshot of dietary information gained from looking at stomach contents or faeces.
It found that human food made up 16% of the urban fox diet, while pet food accounted for 19%, compared with just 2.5% human food and 3.5% pet food for rural foxes.
Overall both city and country foxes were getting the biggest share of their food from birds, which accounted for nearly a third (32%) of the diet for rural foxes.
Foxes in the countryside also sourced 32% of their food from mammal prey, 26% from fruit and 4% from invertebrates.
But while birds accounted for just over a fifth (22%) of the diet for the urban foxes, their 19% pet food intake was a close second.
Fruit accounted for 17% of the urban fox diet, mammals accounted for the same share as human food, at 16% of the overall diet, and invertebrates made up 10%.
The analysis also revealed that female foxes may eat more food from people than males, possibly because they are making use of abundant human sources of food while raising their cubs.
Nottingham Trent University’s Professor Dawn Scott, senior author on the study, said: “Although urban fox diet does include a range of natural food items, we found less natural food along with a higher anthropogenic diet which could include ultra-processed foods, left overs or commercial foods not intended for wildlife.
“This is not to say that all anthropogenic food will be nutritionally inadequate, but since processed foods can be high in saturated fats and refined sugar, it would not be unreasonable to suggest that a degree of this food source is likely to be nutritionally poor for wildlife.”
Dr Jonathan Fletcher, from Nottingham Trent University, added: “Human-derived or ‘anthropogenic’ foods have been implicated in poor health outcomes for species that consume them, so it is important we examine the extent of such foods in the diet of British foxes.
“A diet high in anthropogenic food may set them up for failure if such foods do not allow them to achieve their nutritional requirements, therefore impacting their body condition and perhaps making them more susceptible to disease.”
He said more work was needed to understand the potential health impacts of their diet, but warned it would affect urban and female foxes more.
The study, which also involved the Animal and Plant Health Agency, the University of Brighton and the University of Glasgow, is published in the Journal Ecology and Evolution.
