The great crested newt (Triturus cristatus) is Luxembourg's largest and rarest newt species, and is the only amphibian species other than the yellow-bellied toad listed in appendices II and IV of the European Fauna-Flora-Habitats Directive. While the great crested newt is relatively widespread in Gutland, it is extremely rare in Ösling: its presence is limited to a single, very small population in the extreme north-west of the country, in the Trëtterbaach basin. The main reason for the great crested newt's absence in Ösling is the lack of suitable standing water and the loss of existing biotopes.
Given the small size and isolation of the existing population, it is of the utmost importance for the protection of the great crested newt in Ösling to preserve and strengthen this population and thus enable it to spread throughout the region. As part of the great crested newt action plan, new stagnant waters will be created in the north of the country, and existing ponds will be optimized in a first phase. In a second phase, the newly-created aquatic habitats will be networked by suitable terrestrial corridors.