Analyzing the spatial distribution of Lynx lynx in Switzerland
Müller, L.A., 2018: Analyzing the spatial distribution of Lynx lynx in Switzerland. Master thesis. 44 p.
Müller, L. A., 2018: Analyzing the spatial distribution of Lynx lynx in Switzerland. Master Thesis ETHZ, D-USYS. Supervisors: PD Dr. J. Bolliger, Dr. Robert Pazur.
Since the first release in 1971, two lynx populations have evolved in Switzerland consisting of about 134 individuals in the Alps and 58 individuals in the Jura Mountains. However, the return of the lynx is controversially discussed and management conflicts appear. It is therefore of high importance to identify major drivers of the potential lynx distribution in order to assess further expansion potential and to devise effective conservation plans. Accordingly, this Master thesis was designed to explain lynx occurrences in Switzerland as a function of eleven environmental variables. For this, spatially and temporally highly resolved GPS-tracked resident lynx locations and a quantitative modelling approach relying on Boosted Regression Trees (BRT) was used. Consequently, the present study allows to delineate important environmental drivers of lynx occurrence, allowing to define management recommendations based on identification of sensitive areas. State-of-the-art remotely sensed environmental variables such as snow information, vegetation height and night light emission were found particularly important for lynx occurrence. In general, lynx preferred areas located higher than 600 m a.s.l. and forests with a relatively low vegetation height up to 10 m. In open land, a vegetation height below 1m had a negative effect on the occurrence of lynx, suggesting that lynx avoid such landscape. On the other hand, lynx preferred vegetation heights in open land from 1 m up to 5 m. Regarding night light emission, females with cubs showed a preference for dark environments while males and females without cubs were much less sensitive to night light emission. In summer, snow cover fraction was completely insignificant. However, in winter, it played a major role in the distribution of lynx. Also in winter, lynx tended to avoid areas with cumulative snowfall of the last 72 hours greater than 40 – 45 mm. Overall, cumulative snowfall of the last 72 hours appeared to be the most important explanatory variables for habitat selection by lynx.
In summary, the results of this study clearly indicate that snow may be a key factor in the spatial distribution of lynx in Switzerland. Consequently, the observed relationship between snow information and lynx occurrence raises new questions and will hopefully inspire new studies. Based on this assessment, environmental managers may gain new insights into the habitat choice of lynx and identify sensitive areas for lynx in a more differentiated way.