A hedgehog can cover more than a kilometre between dusk and dawn. It has no map, and no idea that the fence at the end of your garden is about to stop it dead. For an animal that needs to roam, a solid boundary between two gardens is a locked door.

That is where a hedgehog highway comes in: a gap roughly 13cm square left at the base of a fence, or a short tunnel under a wall or gate. It costs nothing but half an hour, and it turns a row of separate gardens into a single, usable territory.

Why One Gap Matters So Much

Hedgehogs are not really garden animals. They are wild animals that happen to use gardens, and they need far more space in a night than most of us can offer. A small back garden, however lovely, will run out of beetles, worms and nesting corners by midnight. Hedgehogs need to move between feeding patches, find mates, and locate somewhere safe to sleep and hibernate.

Hedgehog numbers in Britain have fallen sharply over recent decades, and the fragmentation of the landscape is part of the reason. Tidy fences, paved front gardens and solid boundaries cut a once-connected patchwork into isolated islands. One gap will not fix that. Do it across a whole street, though, and you start to rebuild something real.

Thirteen centimetres square, sitting on the ground, never blocked. That is the whole specification.

Thirteen centimetres is about the size of an old CD case: wide enough for a hog, narrow enough that most dogs cannot follow and a fence panel keeps its strength.

Cutting a Gap in a Wooden Fence

Timber is the easiest boundary to work with. You need a tape measure, a pencil, a jigsaw (or a drill and a handsaw), eye protection and a pair of gloves. Before you cut anything, work out who owns the fence and ask if it is not yours. If you rent, check with your landlord or letting agent. Most neighbours say yes straight away, especially when you mention that hedgehogs eat slugs.

Then:

  1. Pick the spot. Stay at least 30cm away from a post, and avoid any panel that is rotten or already loose. On fences with a gravel board along the bottom, notching that board is usually the neatest option, because the panel above it stays untouched.
  2. Mark a 13cm square on the ground line. The bottom edge of the square must sit level with the soil, not above it. A raised gap is useless, because hedgehogs cannot climb. If the ground slopes, level a small area first.
  3. Check both sides of the fence. Look for hidden nails, cables, irrigation pipes, a raised bed or a paving slab on the neighbour's side.
  4. Cut. A jigsaw makes short work of it; drill a starter hole if you are using a handsaw. Do not be tempted to cut it smaller "just in case". Ten centimetres is a failure, fourteen is fine.
  5. Tidy the edges. Sand down splinters, pull any loose nails, and clear stones or gravel so the ground beneath the gap is flat and firm.
  6. Protect it from good intentions. Tell everyone who gardens or mows near it. A plant pot, a water butt or a bag of compost parked in front of the gap closes the road again, often within a week.

Tunnels for Walls, Gates and Concrete Panels

Not every boundary can be cut. Concrete posts and panels, brick walls, railings set in a kerb, a shared gate nobody wants to drill: all of these can still be crossed with a tunnel. Ready-made hedgehog tunnels, usually concrete or plastic, are sold by wildlife trusts and garden centres, and they are designed to be set into the ground at soil level.

You can also build one for very little:

  • A length of drainage pipe with an internal diameter of about 13cm, sunk under a gate so the floor of the pipe is flush with the soil on both sides.
  • A tunnel of bricks laid two courses high with a paving slab across the top, built without mortar so it can be dismantled later.
  • A gap left under a gate or at the base of a hedge, which is often all that is needed once the gravel board stops being replaced.

One caution. Never cut or tunnel under a wall that is holding something up — a retaining wall, a wall carrying a structure, or anything you are unsure about. Ask a builder or surveyor before you touch it.

Link the Whole Street

Your gap only becomes a highway if someone else has made one too. The most useful thing you can do after cutting it is knock on a couple of doors. Aim for a chain of four or five gardens in a row, and routes that cross the street rather than running along it. Offer to do the cutting yourself; the job is easier than the conversation.

It is also worth logging your gap on the Hedgehog Street map, run by the British Hedgehog Preservation Society and the People's Trust for Endangered Species. When you move house, your hedgehog highway stays on record. A small painted marker or a little sign by the gap helps too, so the next owner of your house does not block it when they replace the fence.

Keeping the Route Safe

Getting a hedgehog through the fence is only half the job. The other half is making sure the garden on the far side is worth arriving in. A few hazards are worth dealing with before you invite anyone in:

  • Slug pellets. Hedgehogs eat slugs, so poisoned slugs poison hedgehogs. Use nematodes, beer traps or hand-picking instead, and accept a few holes in the hostas.
  • Strimmers and mowers. Long grass is exactly where a hedgehog will be sleeping. Walk the area first, and cut from the middle outwards.
  • Netting. Football nets, fruit netting and pond netting all tangle hedgehogs. Lift nets clear of the ground at night, or store them.
  • Ponds. Steep sides are a trap. A gently sloping edge, a ramp or a half-submerged log gives them a way out.
  • Drains and pits. Window wells, open drains and gaps under sheds can become prisons. Cover them, or lean a rough plank inside as an escape route.
  • Bonfires. Build the fire on the day you light it. A pile left standing for a fortnight is a hibernation site.

A shallow dish of fresh water is a good idea all year, and in a dry summer it saves lives. If you feed, use meat-based cat or dog food or a proper hedgehog food; bread and milk will make them ill. And if you see a hedgehog out in daylight, assume something is wrong and ring a local wildlife rescue rather than trying to treat it yourself.

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Photo: katerinavulcova / Pixabay