Green Toad Reintroduction
To breed and reintroduce green toads to supplement stocks in Sweden
The green toad (Pseudepidalea viridis) is the most threatened amphibian species in Sweden. Its natural habitats often include sandy or rock-dominated environments near the coast. Encroachment and drying out of breeding pools due to draining of wetlands are believed to have caused part of the heavy decline of the toad. Other reasons may be changes in agricultural and forestry practices resulting in deterioration of water quality, and the use of pesticides. The changes in land use patterns have resulted in a shift in the balance of competition between the green toad and the common toad (Bufo bufo) in favour of the common toad.
Earlier the distribution area included some 50 localities in the counties of Skåne and Blekinge in southern Sweden, as well as on the islands of Gotland and Öland. Today the occurrence of the green toad has diminished to some 10 sites in Skåne, most of which hold very small populations, and to the island Utklippan near Karlskrona. The only viable populations are found at the limestone quarry of Limhamn and the coastal meadows of Eskiltorp.
According to the national Red List, based on the IUCN classification system, the green toad is considered Critically Endangered in Sweden. It is also one of the species listed in EU's Habitat directive. The Swedish Environmental Protection Agency (SEPA) has set up and approved a National Action Plan for the green toad.
The goal is to establish 10 free-ranging populations of at least 100 adults each, and therefore a long-term conservation project was initiated in 1990. The project is based on ex situ hatching of eggs collected from the wild, rearing the larvae and juveniles, habitat restoration and release of the ex situ reared toads.
From the single remaining viable populations at Limhamns limestone quarry and Eskiltorp, eggs are collected in April or May and reared at Nordens Ark, first in aquaria up to metamorphosis, and then in terrestrial enclosures. A number of different breeding and rearing methods are currently being tested. The goal is to find out which methods are most suitable and will yield a high survival rate. Some hundreds of toadlets are then released in late September or early October at restored sites within their historical range with a potential breeding pond within a few hundred meters distance. Some individuals are kept at Nordens Ark for one or two years before release, to test if the release of older animals can increase the chance of surviving in the wild. Since 2009 each toad is photographed prior to release for future identification.
From 2003 to 2006, some 12,000 toadlets and 53 adult toads that had hatched at Nordens Ark were released on the island of Öland at a restored site near the limestone quarry of Horns Manor. A second batch of toads, 1,200 reared at Nordens Ark and 670 reared at the educational centre Universeum in Gothenburg, were released on the island of Gotland.
From about 10,000 eggs collected in Skåne in 2007, about 3,300 hatched and developed into toadlets. Some 2,500 of these were released at suitable places, and about 900 were retained at Nordens Ark to hibernate and to be released in 2008.
From 2009 onwards Nordens Ark has had a fruitful co-operation with a European Union LIFE project together with the regional conservation authority in Kalmar, with the aim to restore green toad localities and restock them with toads reared at Nordens Ark. Each year 300–500 toads have been released at the southern tip of Öland at Ottenby bird sanctuary. In 2011 reproduction was observed as well as many recaptures of Nordens Ark reared toadlets.
The breeding and reintroduction project is part of the Swedish Action Plan for the conservation of the species, which also includes monitoring, habitat restoration and environmental improvements.
WAZA Conservation Project 06019 is implemented by Nordens Ark, the Swedish Environmental Protection Agency, County Administrative Boards, local landowners and Gothenburg University. Nordens Ark's part of the project is funded by the Swedish Environmental Protection Agency, LIFE, Hasselblad Foundation and Fondation Segré.
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