Studer, F., V. Amrhein & T. Roth
(* = Kurzbeitrag)
Verbreitung und Bestandsentwicklung der Geburtshelferkröte Alytes obstetricans im Kanton Basel-Landschaft.
(von 1994 bis 2006 vergeben)
Bestand, Bestandsentwicklung, Population, Verbreitung, Chytridpilz, Wanderdistanz, Ausbreitung, Artenschutz, Artenförderung, Teich, Weiher
Distribution and population trend of the Common Midwife Toad Alytes obstetricans in the canton of Basel-Landschaft. In Switzerland, about 50 % of the populations of Common Midwife Toads have disappeared in the last 25 years. Such a decrease was not yet found in the canton of Basel-Landschaft, where new populations have been continuously discovered since the survey in 1978. For the present study, we summarized the last four canton-wide surveys and revisited most of the known populations. Since 2011, 85 populations out of 114 known populations have been confirmed; in 24 surveyed populations, no toads were found. Within the populations, there was a trend towards decreasing numbers of adults over the period 1978–2017. We examined whether the population trend is related to the occurrence of a pathogenic chytrid fungus or of water frogs, and to the elevation and the size of the area inhabited by a toad population. A relatively clear correlation was found only for the size of the area: Populations where locations of individual observations were less than 100 m apart showed a trend towards decreasing numbers of adults, while populations with larger areas remained quite stable. This finding should be taken into account in management projects: In the case of shrinking populations, new habitats should be created in the immediate vicinity. Populations that are close to each other should be connected so that suitable habitats can be found at distances of about 500–1500 m.
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