5.2.4. Fencing and reinforcements for small vertebrates

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Last update: June 2023

To avoid small animals (hedgehogs, mustelids, amphibians, reptiles etc.) accessing the infrastructure at sections where it crosses particularly vulnerable habitats, additional reinforcements must be installed at the lower exterior part of a standard fence for large mammals. These fences can also be installed alone (Figure 5.2.14).

The entire fenced length of the infrastructure does not necessarily have to be impenetrable for small fauna, because in some sections the verges can be used by these animals as habitats for living or moving.

Fence sections with specific additional precautions to prevent small wildlife access are generally to be reserved for:

  • Intersection of ecological corridors that wildlife use to move across the landscape and where safe crossing structures must be provided to prevent mortality.
  • Habitats of high risk which are ‘ecological traps’ attracting wildlife to areas where they will experience high mortality and which could even jeopardise the long-term viability of a population.
  • Road sections where median safety concrete barriers are installed (Figure 5.2.6) which are potential traps for small and medium-sized animals.

To provide fencing which is effective and safe for amphibians, reptiles and other small fauna, smooth opaque and durable materials should be used, such as metal, concrete or recyclable resistant polymers (Figure 5.2.10 and Figure 5.2.14). These fences could be added as a reinforcement to standard fencing or be used alone, fixed on small poles. Some manufacturers provide small fauna fencing which is smooth at the exterior part to avoid climbing but rough on the interior, allowing the small fauna trapped in fenced sections to escape to adjacent habitats. Combinations of amphibian fencing which guides the animals to suitable crossing points are described in Section 5.5.13 – Amphibian passages.

Figure 5.2.14 – Opaque fences adequate to deter amphibians, reptiles and other species of small fauna. A: Reinforcement at the base of a large mammal fence; B: Exterior of small fauna fence with smooth surface to deter amphibian from climbing over. C: Interior of small fauna fence allowing amphibians to climb and escape from fenced section (Photos by: Animex International).

A high-density welded mesh anchored to the lower part of a fence for large mammals is a frequent practice to prevent access by hedgehogs, badgers or other small and medium size animals. Reinforcements must be installed at the exterior side of the standard fence. Height (40 cm to 1m) and mesh density size (3×3 cm or 4×4 cm) must be defined according to the species to be stopped (Table 5.1). Mesh fences are not suitable for amphibians and reptiles because they can easily climb over mesh fences (Figure 5.2.15). Amphibians may also be harmed if they get trapped in the mesh.

Figure 5.2.15 – Small fauna fencing which are not effective or could pose a risk for amphibian. A: Temporary fence which is not effective because amphibians and other animals can climb easily (Photo by: B. Beasley – Association of Wetland Stewards for Clayoqout & Barkley Sounds); B: Reptiles such as tortoises, lizards and snakes can also climb mesh fences (Photo by: BrightSource); C: Welded mesh reinforcement added to a large mammal fence which deters small fauna but not amphibians and reptiles that can climb over or be trapped on the net (Photo by: C. Rosell). To avoid Less favourable / More research required Optimal

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