The bottleneck in suburban hedgehog surveys
Most garden hedgehog records stop at presence. A volunteer finds droppings beside a shed, logs the sighting, and the dataset says “hedgehog here” without showing whether the animal can reach the next garden. That omission matters because hedgehogs forage across several hectares in a night and a single blocked fence line can cut off food, water, and mates. The problem is not a lack of sightings; it is a lack of route evidence.
Why fence gaps are the critical data point
A hedgehog needs a gap roughly the width of a CD case—about 13 centimetres—to pass under a fence without injury. Gravel boards, brick plinths, and close-boarded gates often close that gap without appearing on a standard garden map. The cause is survey design: records are built around animals, not around barriers. When a street has ten hedgehog sightings but no gap inventory, the records cannot show where movement is concentrated or where a single repair would reconnect two colonies.
On a recent street survey in Bristol, the wildzy habitat layer flagged six fence gaps within 90 metres; three were blocked by gravel boards and one opened onto a busy road. That changed the recommendation from “add more log piles” to “clear two gaps and add a kerb ramp,” a cheaper and more targeted intervention.
A three-step gap survey with wildzy
The method works best at dusk, when torchlight shows gaps without disturbing daytime wildlife. Start with a boundary walk: record every fence line, gate, and wall on the garden edge, then mark gaps below 15 centimetres as potential bottlenecks. Next, classify each gap by surface—soil, concrete, gravel, or tarmac—because hedgehogs prefer soft ground and a hard sill can turn a passable gap into a trap. Finally, log the destination: a gap into a neighbour’s garden is useful; a gap onto a road is a liability.
The value of the wildzy checklist here is consistency. A shared checklist keeps volunteers from recording “gap present” without noting width, surface, or connectivity. In a trial of 24 gardens, surveyors using the checklist found 31 passable gaps and 18 blocked ones; the blocked list became the work plan for a weekend fence-fix session.
What changes after the survey
The result is not a map for its own sake. It is a priority list. A street with three blocked gaps along one terrace can usually solve the problem with a few 13-centimetre cuts and a note to residents about keeping them clear. The takeaway is simple: hedgehog conservation in suburbs depends less on adding habitat than on removing barriers between existing habitat. Once the gaps are recorded, the next sighting becomes a route confirmation rather than an isolated dot.