How to Make a Hedgehog Highway Through Your Garden Fence

A hedgehog's nightly wanderings take it across several gardens, and a solid fence stops it dead. If you have ever watched one pacing along the base of a panel, nose pushed against the gravel board, you have seen the problem. The fix is small and cheap: a 13cm square gap at ground level. Cut one and a dead end becomes a through route. Cut a few with your neighbours and you have a hedgehog highway — a chain of linked gardens where hedgehogs can feed, nest and find a mate.

Why hedgehogs need a gap

Hedgehogs are not territorial. They roam widely and need a lot of ground to find enough beetles, worms, caterpillars and slugs. One garden, however lovingly planted, is rarely enough on its own. A single patch may hold food for a night or two, but not the varied habitat a hedgehog needs across a season: short grass for foraging, dense hedges and leaf piles for nesting, compost heaps and log piles for invertebrates.

The distances are bigger than most people expect. An adult hedgehog may walk a kilometre or more in a single night, and over a summer it can use tens of hectares. Estimates suggest Britain's hedgehog population has fallen from tens of millions in the 1950s to around a million today, with rural numbers roughly halved since 2000. In towns the decline has been slower, and one of the main reasons is that gardens still give hedgehogs something farmland no longer offers: a dense, slightly messy mosaic of cover and food. But only if they can get from one garden to the next.

A 13cm by 13cm opening at ground level is the size most wildlife groups recommend — roughly the size of a CD case. It is wide enough for an adult hedgehog and small enough that you barely notice it from a few metres away. Much smaller and you risk blocking the larger adults; much bigger and it stops being a gap and starts being a hole in your boundary.

One garden is a room. A dozen linked gardens is a home range.

Where to put the gap

Hedgehogs follow cover. They move along fence lines, hedge bottoms and the edges of borders, so put the opening where they already travel rather than in the middle of a bare run of panels. A few things to look for:

• Good: the corner where a fence meets a hedge, a spot under a shrubby border, the bottom of a gate, the end of a gravel board beside a compost heap.
• Better: two gaps facing different ways, so a hedgehog has a choice of route if one is blocked by a new wheelie bin or a pile of timber.
• Avoid: directly onto a busy road or pavement, right beside a steep-sided pond, anywhere a dog is routinely tethered, or the base of a panel that is already rotting and needs replacing.

Keep the opening at ground level, sitting on soil rather than gravel, and make sure the ground on both sides is level enough to walk through. If you can, position it near a shrub or hedge so there is somewhere to pause and check for danger.

Before you commit, look at the other side. A gap that opens onto a paved patio or a wall of stored pots will not be used. A gap that opens onto a border or a lawn will.

Cutting the gap, step by step

1. Check whose fence it is. A boundary fence belongs to one property, and it may not be yours. Your deeds, or a quick word with the neighbour, will settle it. If you rent, or live on a managed estate, ask before you cut anything.
2. Look for hazards. Check both sides for low-voltage garden lighting, irrigation pipe, cables running along the base or a strap holding the panel. Cut nothing until you know what is behind it.
3. Mark a 13cm square with the bottom edge level with the soil. Use a set square or a straight edge and measure twice. On uneven ground, work from the highest point so the finished gap does not shrink.
4. Drill the corners. A hole at each corner, wide enough for a jigsaw blade to turn in, makes the cut far easier and stops the wood splitting.
5. Cut the wood. A jigsaw with a fine-toothed blade is ideal; a pad saw or an oscillating multi-tool works too. Support the panel from behind, cut slowly, and let the blade do the work. On a wooden gravel board, cut below the top edge of the board rather than through the panel above it — the gap is easier to hide and cheaper to repair.
6. Smooth the edges. Sand off splinters, then treat the fresh timber with a water-based, pet-safe preservative and let it dry completely. Hedgehogs will nose along the cut.
7. Clear the floor of the gap. Remove gravel, shingle and rubble, then level the soil on both sides. A 2cm lip of gravel is enough to put a hedgehog off, and a gap that holds water will soon be avoided.
8. Line it if you like. A short length of pipe, a purpose-made hedgehog tunnel or a couple of bricks set either side will keep the opening clear as plants grow and make it look deliberate.
9. Test it. Kneel down and look through. If you can see daylight and the ground is clear, a hedgehog can use it.
10. Tell the neighbours. A gap on one side of the fence is only half a highway. Knock on the door, explain what you have done, and offer to do the same on their other boundary.

Gravel boards, concrete and other awkward fences

Most fences are straightforward, but the base is where the complications live.

• Wooden panel over wooden gravel board: the easy case — twenty minutes with a jigsaw.
• Concrete gravel board: harder. A bolster chisel and club hammer, or an angle grinder with a diamond blade, will cut a 13cm notch, but the board can crack and the dust is unpleasant. Wear goggles and a mask, and consider whether swapping one board for a shorter one is cleaner than cutting it. Never cut a concrete post.
• Metal railings or welded mesh: often passable already along the bottom, but a concrete kick plate under a gate can be just as solid as a fence. Check the clearance before assuming.
• Hedges: leave a 13cm gap at the base when you trim, and never run a new fence tight against a hedge that hedgehogs use.
• A new fence: the cheapest gap is the one you ask for before the panels go in. Ask the installer to leave a hedgehog gap at each end, or fit a tunnel through the base.

Keeping the highway safe

A gap is only useful if what lies beyond it is not a trap. A few checks turn a route into a good one:

• No slug pellets. Metaldehyde and ferric phosphate pellets harm hedgehogs and the creatures they eat. Beer traps and evening patrols are kinder.
• Ponds need ramps. A gentle slope, a half-submerged log or a strip of mesh gives a hedgehog a way out. Steep-sided, smooth-lined ponds are a classic death trap.
• Water in dry spells. A shallow dish of fresh water at ground level is one of the most useful things you can put out.
• Food, if you feed. Meat-based cat or dog food and chopped nuts are fine. Bread and milk are not — hedgehogs are lactose intolerant.
• Check before you cut. Strimmers and mowers injure thousands of hedgehogs a year. Walk long grass before you start, and leave the edges.
• Bonfires. Build the pile on the day you light it, or move it completely. A leaf pile left for a week is a nesting site.
• Netting and drains. Keep netting taut and at least 20cm off the ground, and cover open drains and gullies.

Mapping your highway and getting neighbours involved

The real gain comes when several gardens join up. A useful target is eight to ten linked gardens — enough ground for a hedgehog to find food, shelter and, in spring, another hedgehog. Talk to neighbours on every side, not just the one whose fence you share. Two or three gaps in a row along the same boundary line are worth more than one wide opening.

It helps to make the gaps visible and repeatable. A small marker or sign beside the opening tells the next resident what it is for and stops someone blocking it with a planter or a shed base. Sketch your own rough map of which gardens link to which, and if you want to go further, log your gaps on the national Hedgehog Street map so the next household along can see where the route runs.

Maintenance is minimal: check the gaps once or twice a year, clear leaves and weeds, and make sure the ground has not risen or sunk. Do that, and a 13cm square of missing fence quietly turns a row of separate gardens into one continuous place to live.

Photo: Pixabay / Pexels