Frog Fencing

The life cycle of frogs dictates that females lay their eggs in water. Some species live most of their lives in and around water and are relatively sedentary. Terrestrial frogs, however, live most of the time in other environments, such as forest, but still need to visit water to breed. They are more mobile than their aquatic counterparts and are prone to movements at the start and end of the breeding season. Therein lies a problem for conservationists. In spring, adults make their way to a favored pool, later returning to the environment where they spend the rest of the year. Juveniles also move away from their natal pool to suitable terrestrial habitat; tens of thousands of froglets may migrate from a single pool in late summer.

If there is an artificial obstruction between the two environments – a construction site or a new road, for example – mortality will be greatly increased. Every year there will be two adult migrations and one juvenile migration across it – with resultant development site deaths and road-kill. New developments fragment habitats and obstruct migration routes. They often also involve the removal and relocation of breeding ponds; fencing can be used both to guide them away from development sites and towards newly constructed breeding ponds. Fencing can also be used to aid population assessment prior to any development.

It is the responsibility of planning engineers to reduce the ecological impact that construction sites and roads have, and to use mitigation measures as tools in ecological conservation. Fencing, along with other mitigation measures, such as tunnels, has been shown to reduce deaths on construction sites and road-kill – without disrupting the animals’ life cycle. But it has to be the right kind of fencing or frogs will climb over it, find their way through it or become entangled in it.