Walk any residential street after dark and you will pass half a dozen fox beds without knowing it. A compost heap behind a garage, the gap beneath a neighbour's decking, a bramble tangle beside the railway line — urban foxes are experts at using what we build and then leaving no obvious trace. A true den, though, is different. It is a place a fox returns to again and again, often for weeks, and it is frequently far closer to your back door than you would guess.

Do urban foxes really use dens?

For most of the year, a fox simply finds somewhere comfortable and curls up. Long grass, a shrubby border, the sheltered side of a wheelie bin store — any of these will do for a night or two. Dens matter for two reasons: raising cubs, and sitting out the worst of the weather.

A vixen looking for a nursery wants four things: dry ground, a secure entrance, quiet, and a space nothing bigger than a cat can reach. In the countryside that usually means an earth dug into a bank. In a town, it more often means something already built — a void, a gap, a hollow someone else created.

Where foxes den in British towns and cities

Urban dens tend to fall into a few recognisable categories. Once you know the pattern, you start spotting the potential in your own street.

• Under garden sheds, garages and outbuildings, particularly where the base has shifted and left a gap.
• Beneath decking, raised patios and porches, where a dry void sits above bare soil.
• Against house foundations, where a gap between wall and path has been widened over time.
• Railway embankments, cuttings and disused sidings, which offer sloping, free-draining ground and long ribbons of undisturbed cover.
• Allotments, cemeteries, churchyards and golf courses — quiet, dug-over ground with plenty of escape routes.
• Bramble patches, dense ivy and the base of mature hedges, where a scrape can be hollowed out with very little digging.
• Brownfield land, empty buildings and the quiet edges of industrial estates.
• Compost heaps, log piles and stacked pallets, which are warm and quick to claim.

Sheds, decking and the space under buildings

These are the dens most likely to affect you directly, because they are in your garden. A gap barely wider than a house brick along the base of a shed is enough for an adult fox to slip through. If the soil underneath is soft, the animal will often enlarge the space into a proper chamber, pushing excavated earth out onto the lawn or patio.

Decking is the classic. A raised deck with a gap at one edge gives a fox everything it needs: cover overhead, dry ground below, and a route in that a person would have to crawl to follow. The first sign is usually a small pile of soil appearing at the edge of the boards, or a patch of bare earth where a plant used to be.

Railway embankments and green corridors

Foxes travel along linear features: railway lines, canal towpaths, the backs of long gardens, the edges of playing fields. Embankments and cuttings are ideal because they are sloped, well drained, rarely walked and thick with scrub. A fox can dig into a bank without much effort and be twenty metres from a footpath with no chance of being seen.

This is why foxes appear in streets with no obvious countryside nearby. They are not living in the middle of a housing estate so much as living along the corridor that runs past it, and using gardens as an extension of that corridor.

How to tell whether a den is nearby

You do not need to see a fox to know one is established. Look for a combination of these signs, ideally more than one:

• An entrance hole roughly the size of a dinner plate — about 20 cm across — often with a fan of loose soil scattered in front of it.
• Worn paths through long grass or beneath a fence, where vegetation has been flattened by regular traffic.
• A musky, slightly sweet smell around the entrance, strongest in warm, still weather. Foxes scent-mark heavily near a den.
• Scats left in prominent places — on a path, a wall top, a garden step. Fox scats are usually twisted with a tapered end and often contain fur or berry pips.
• Cached food: buried scraps, feathers, or the remains of a pigeon tucked under a shrub.
• Hair caught on brambles or on the rough edge of a concrete slab.
• Cubs calling in spring — a rapid, high chattering that sounds oddly bird-like until you realise it is coming from underground.
• Footprints in soft soil: four toes with claws showing, arranged in a neat diamond, with a pad print behind.

When a den is likely to be in use

Timing matters more than anything else when you are deciding what to do. Foxes mate between late December and February, with most activity in January. Cubs arrive about seven to eight weeks later, so late February through April, with March the busiest month.

The cubs stay underground for their first few weeks, then start appearing at the entrance in late April and May. The family group tends to use the den through spring and early summer, and a vixen who feels disturbed may move her cubs to a second site without warning. By late summer the youngsters are roaming widely, and by autumn they are dispersing to find their own territories.

Outside that window, an earth may sit empty for months at a time. That matters, because it is the safest period to make changes if you want a den closed off.

Rule of thumb: treat any den as occupied between February and August unless you have clear evidence otherwise.

If a fox dens in your garden

Most people can live with it, and many end up enjoying the cubs. The straightforward approach is to leave the den alone, watch from a distance at dawn and dusk, keep dogs away from the entrance, and never feed the foxes. Feeding creates dependence, draws in other foxes, and encourages the family to stay put.

If you would rather they moved on, make the site less appealing. Open up the area to light, remove cover, block the gap with mesh — but do it in autumn or early winter, after the family has dispersed. Check carefully that nothing is inside before you seal anything.

Never use smoke, chemicals or deterrents poured into a den. Causing unnecessary suffering to a wild mammal is an offence under the Wild Mammals (Protection) Act 1996, and blocking an entrance with cubs inside is both cruel and likely to leave you with a far worse problem. If you are unsure about your legal position, or a den is causing you concern about the structure of a building, take advice from your local wildlife trust, a wildlife rescue, or a qualified builder before acting.

A sensible plan when you find a den

1. Watch quietly for a few days, at dawn and dusk, before you do anything at all.
2. Note the date. Between roughly February and August, assume cubs could be present and leave it alone.
3. Keep children and dogs back from the entrance, and do not block it.
4. Take a few photographs from a distance so you can compare the site in a month's time.
5. If you want the foxes gone, plan the work for autumn, once the family has dispersed — and check the den is empty before you start.
6. Get proper advice if the den is affecting a building, or if you are simply not sure what you are looking at.

Urban foxes are adaptable, unbothered by our schedules, and remarkably good at living alongside us. Knowing where they den takes most of the mystery out of it — and usually turns a worry into something closer to interest.

Photo: Brett Jordan / Pexels