About 10,000 in London Source - that's 1 for every 800 humans.
I hate the foxes in my area. They shit, dig, etc. But are just living their lives.
Could our cities be designed to live with foxes in harmony?
They control the population of rodents Source They also mostly eat 'natural' food - our trash is only supplementary to their diet. Source
We don't know much about foxes - there is little research into their social lives - vision - etc.
Foxes... self regulate [their population] and it is clear that diseases such as mange have some influence on numbers. This also means that culling foxes has little long-term impact on populations. Source
What is the city like through the eyes of a fox?
HEARING - They can hear a mouse squeak 100 ft away. Sensitive to low-frequency noises like rustling. Source
VISION - Similar to dogs. More blue-y green - reds become green and purples become blue. Can see well in the dark. Vision is based mainly on movement. Source They also have a slightly wider field of view, and are near-sighted (can't see as far as us) Source.
DISTANCE - They use the earth's magnetic field to tell distance from prey. Source