Tunnels greater than 0.5m in diameter, lined with soil or gravel, with a 0.6–0.9 m high drift fence was considered most effective for four frog and turtle species tested in the USA

  • Published source details Woltz H.W., Gibbs J.P. & Ducey P.K. (2008) Road crossing structures for amphibians and reptiles: informing design through behavioral analysis. Biological Conservation, 141, 2745-2750


This study is summarised as evidence for the following.

Action Category

Install barrier fencing along roads

Action Link
Amphibian Conservation

Install culverts or tunnels as road crossings

Action Link
Amphibian Conservation
  1. Install barrier fencing along roads

    A replicated study in 2005–2006 of different height barrier fencing in a Wildlife Management Area, New York, USA (Woltz, Gibbs & Ducey 2008) found that fences of at least 0.6 m excluded most green frogs Rana clamitans and leopard frogs Rana pipiens. Fences 0.6 m high were more effective at excluding frogs (97–100%) than 0.3 m fences (77–80%). Only one leopard frog climbed over the 0.9 m high fence. Opaque, corrugated plastic fences were used to construct three nested, circular enclosures of heights 0.3, 0.6 and 0.9 m. Local green frogs (n = 135) and leopard frogs (n = 187) were placed in the centre of each arena and left for 15 min to attempt to scale the fences.


  2. Install culverts or tunnels as road crossings

    A replicated study in 2005–2006 of tunnels in a Wildlife Management Area in New York, USA (Woltz, Gibbs & Ducey 2008) found that green frogs Rana clamitans and leopard frogs Rana pipiens showed some preference for particular tunnel types. Green frogs showed a significant preference for soil (40%) and gravel (38%) linings, compared to concrete (13%) and PVC (9%). Leopard frogs showed no preference (19%, 32%, 29%, 19% respectively). Leopard frogs tended to prefer larger diameters (0.8 m: 35%; 0.6 m: 12%; 0.5 m: 28%; 0.3 m: 25%) and avoid the longest tunnels (9 m: 15%; 6 m: 40%; 3 m: 22–24%). Green frogs showed no preference for diameter (0.8 m: 33%; 0.6 m: 24%; 0.5 m: 27%; 0.3 m: 16%) or length (9 m: 32%; 6 m: 23%; 3 m: 19–26%). Tunnels with the greatest light permeability were preferred (4% light permeability: 39–41%; 1.3% light: 14–17%; 0.6% light: 24–26%; no light: 17–24%). Choice arenas had four different PVC culverts radiating out, which local green frogs (n = 135) and leopard frogs (187) could select to exit through. Frogs were tested in groups of 1–17 individuals, once per arena. Trials lasted 15 minutes, after 5 minutes acclimatization, in June–August 2005–2006. Pitfall traps captured animals at the end of each tunnel.


Output references

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