Low occurrence of the great crested newt Triturus cristatus at the limits of its range: an alarming preliminary study

摘要

The lower Rhone valley constitutes the southern limit of the great crested newt's (Triturus cristatus) global distribution range. The initial objectives of this study were to confirm historical presence data, to identify potential new great crested newt populations and to characterise their habitats (with a Habitat Suitability Index) in order to assess their status in the lower Rhone valley. Despite the use of four different survey methods (eDNA, Ortmann traps, collapsible nylon traps, amphibian dip net), great crested newts were not detected except for one known population in Arles. HSI value results highlight the poor quality of wetlands in the studied area. Furthermore, the invasive crayfish Procambarus clarkii (detected in 60% of ponds) and the presence of fish (detected by sight in 50% of ponds) are known to have a negative impact on habitat quality and amphibian populations. These limiting factors might be one explanation for the critical conservation state of the T. cristatus Rhone populations.