The European tree frog Hyla arborea Anura in the canton de Vaud Present state of knowledge La Rainette verte Hyla arborea; Anura dans le canton de Vaud Un etat des lieux
Pellet, J.; Neet, C.
Bulletin de la Societe Vaudoise des Sciences Naturelles. Decembre; 874: 287-303
2001
Document Number: 341621
Highly endangered in Switzerland, the European tree frog (Hyla arborea L., 1758) has been widely disappearing from its distribution range over the last two decades. During spring 2000 in the Canton de Vaud, 3 distinct metapopulations have been identified summing up to 58 calling sites. The south shore of the lake of Neuchatel represents the biggest reservoir of individuals with 42 calling sites, whereas the small population of the Grangettes in Noville, constituted of only 4 sites, owes its survival to specific dispositions. The third metapopulation, situated along the Aubonne river, represents 12 calling sites. The counting of calling males in the first two areas indicates that the species is expanding or at least has stabilized. In the third area, evaluation of the probability of survival of the populations is prevented by the lack of standardized countings. Since 1970, two regression zones have been identified in the study area: the plain of the Orbe river and the western part of the south shore of the lake of Neuchatel, between Yverdon and Forel. The regression observed during the last 20 years can be partly explained by the tree frog habitat fragmentation. Analyses based on a connectivity index indicate that the presence of the tree frog in a pond between 1985 and 1990 was significantly dependent on the number of potential sites within a defined range. Between 1995 and 2000 however, this index no longer indicates the presence of the species. Human activities, such as urbanization and road constructions could partly explain these results describing non-equilibrium populations. Recent literature provides many examples of dense biotope networks as a way to preserve the species. Recommendations for tree frog friendly dispositions are presented.