Verbreitung und Gefaehrdung der Geburtshelferkroete (Alytes obstetricans) in der Schweiz

Borgula, A.; Zumbach, S.

Zeitschrift fuer FeldherpetologieMaerz; 10(1): 11-26


Accession: 024106526

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In Switzerland, the midwife toad occurs in the Jura mountains, the Midlands and the prealpine zone on the north side of the Alps. The main altitudinal distribution (highest relative frequency) is between 600 m and 900 m in the hilly and prealpine zone. Sixty-three of 1196 records are from above 1000 m. The highest finding is from 1900 m, the highest reproduction site is at 1670 m. More than 87 % of breeding sites are permanent ponds. More often colonized than expected based on their frequency are artificial ponds, whereas temporary water bodies are underrepresented. Habitats and population trends of the midwife toad in the well documented central Swiss cantons Lucerne, Nidwalden and Obwalden are presented (54 breeding sites). Natural and fairly natural habitats (16 %) existed only in the prealpine zone. In the past 20 years the number of breeding sites declined dramatically (49 %). Twenty-eight extinct populations contrast with only 3 natural colonizations. The decline was most pronounced in the Midlands (75 %), below 600 m (79 %), and mostly not linked to the destruction of the habitat (71 %). The causes of local extinction vary and are in many cases unknown. The remaining populations (number of calling males) tend to be smaller than 20 years ago. Breeding sites with more than 50 calling males have not been recorded recently. Possible causes of the decline are discussed. On a national level the available regional data also show, with one exception, significant to drastic declines with a resulting loss of breeding sites and a decrease of population sizes, although no large reduction of the distribution area has been recorded yet. Some requirements for conservation concepts and an example of a species conservation program are presented for discussion.