Pond modification for the fire-bellied toad (Bombina bombina)

LIVING MOHELNICE – Species Conservation Concepts in Gravel Mining Environments

As part of reclamation efforts in mining area Mohelnice, new ponds for amphibians are being created. This year, two more were excavated, and as part of the project, it was also possible to agree on the modification of an existing pond that had not originally been constructed optimally. The pond had an overly regular shape, steep banks, and uniform depth (approx. 0.8 m). Its banks gradually became overgrown with woody vegetation, particularly alder trees, which led to increased shading of the water surface and higher nutrient input in the form of leaf litter.

This condition, however, does not suit the fire-bellied toad (Bombina bombina) and significantly limits its breeding opportunities. The management plan for the Zátrže Nature Monument, in which the site is located, designates the fire-bellied toad as a flagship species. Ensuring suitable conditions for its occurrence and reproduction is therefore a primary goal of conservation efforts in the area.

The following measures were proposed to improve the pond:

  • Gentle bank slopes of 1:5 to 1:10 depending on feasibility, ideally up to 1:20. Slopes must not be steeper than 1:3.
  • Bank and shallow zone structuring, with irregular and gradual transitions between land and water. Proposed depths of up to 50 cm should be combined with raised areas and seasonally inundated or waterlogged zones.
  • Shallow zones (up to 50 cm deep) should cover at least one-third of the pond’s total surface area.
  • Bottom structuring – instead of a uniform bottom, a varied and irregular shape with multiple microhabitats should be created. Larger stones, branches, logs, or even a small island may be added.
  • Use of appropriate excavation tools – it is recommended to use a toothed bucket rather than a smooth grading bucket when shaping the banks.
  • Vegetation cover – natural regeneration of vegetation is expected, but the banks should develop a shallow, mosaic-like, and species-diverse plant cover that provides sufficient shelter from predators while allowing easy access to the water.
  • Adequate sunlight on the water surface is essential – shading reduces water temperature and limits the toad’s reproductive success. Dense and continuous reed beds or woody vegetation should therefore be regularly and selectively reduced to prevent excessive shading and preserve habitat diversity.

Despite certain spatial constraints and the existing water level, the pond was successfully modified to better meet the ecological needs of the fire-bellied toad.

The fire-bellied toad (Bombina bombina) is a critically endangered species dependent on lowland wetlands with shallow, sun-warmed water, gentle slopes, and diverse shoreline vegetation. It prefers habitats without fish, which would prey on its tadpoles. Reproduction takes place from May to July, with larval development lasting approximately one month. Due to its ecological sensitivity, the fire-bellied toad serves not only as a conservation target but also as an indicator of wetland habitat quality. Measures aimed at supporting its habitat requirements enhance the ecological value of the site and benefit other amphibians and aquatic organisms as well.