A survey of the results of pond projects for rare amphibians in Denmark

Published source details Fog K. (1997) A survey of the results of pond projects for rare amphibians in Denmark. Memoranda Societatis pro Fauna et Flora Fennica, 73, 91-100.
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This study is summarised as evidence for the following.

	Action	Category
	Release captive-bred frogs Action Link
	Release captive-bred toads Action Link
	Restore ponds Action Link
	Create ponds for amphibians Action Link

Release captive-bred frogs

A before-and-after study of projects in 1986–1997 that released captive-bred amphibians into restored and created ponds in Denmark (Fog 1997) found that released European tree frogs Hyla arborea established populations. European tree frogs established populations in 10 restored and 13 created ponds. A questionnaire was sent to all those responsible for pond projects across Denmark to obtain data. Animals were reared in captivity and then released into ponds as tadpoles or juveniles. For a pond to be defined as ‘colonized’ a species had to be present but not breeding.
Release captive-bred toads

A before-and-after study of projects in 1986–1997 that released captive-bred amphibians into restored and created ponds in Denmark (Fog 1997) found that European fire-bellied toads Bombina bombina and green toads Bufo viridis established populations. Released fire-bellied toads established populations in 18 restored and 22 created ponds and green toads in three created ponds. A questionnaire was sent to all those responsible for pond projects across Denmark to obtain data. Animals were reared in captivity and then released into ponds as tadpoles or juveniles. For a pond to be defined as ‘colonized’ a species had to be present but not breeding.
Restore ponds

A replicated, controlled, before-and-after study in 1986–1997 of 3,446 ponds restored and created for amphibians in Denmark (Fog 1997) found that pond management was effective for maintaining and increasing populations. Populations survived five years after restoration in 92% (74–100%) of cases, compared to just 40% (32–52%) of cases without restoration. A total of 175 (39%) restored ponds were naturally colonized by rare species and 28 colonized by released animals. Approximately 2,000 ponds were restored or created for rare species, over half of which were for the European tree frog Hyla arborea. The national population of the species doubled as a result. A questionnaire was sent to all those responsible for pond projects across Denmark to obtain data. Over a third of projects dredged existing ponds and 7% had other types of restoration. For a pond to be defined as ‘colonized’ a species had to be present but not breeding.
Create ponds for amphibians

A replicated before-and-after study of projects in 1986–1997 that created and restored 3,446 ponds for amphibians in Denmark (Fog 1997) found that pond management maintained and increased populations. The national population of European tree frog Hyla arborea doubled. A total of 387 (42%) created ponds were naturally colonized by rare species and 38 colonized by captive-bred animals. Alpine newt Triturus alpestris was the most efficient colonizer (72% of new ponds). Approximately 2,000 ponds were created or restored for rare species, over half of which were for the European tree frog. A questionnaire was sent to all those responsible for pond projects across Denmark to obtain data. Over half of the projects created new ponds. For a pond to be defined as ‘colonized’ a species had to be present but not breeding.