Landscape distributional pattern and craniometry of suncus etruscus (Mammalia: Insectivora, Soricidae) in South-East Bulgaria

The distribution of S. etruscus in South-East Bulgaria was traced on the basis of Barn Owl pellet collections. The species was found at 39 out of the 41 collecting sites. The effect of eight environmental variables, describing the proportion of the main habitat types within the owl's hunting territory and the climatic and landscape context, on the structure of the shrew prey spectra was investigated by means of redundancy analysis. It has been found out that the percentage of moist areas within the hunting territory and the temperature sums affect significantly the structure of the shrew prey spectra. The percentages of S. etruscus were positively related to the temperatures. On the basis of the obtained results and comparisons with published data, it was hypothesized that S. etruscus was a recent invader in the area. The spreading route probably follows the valleys of the Maritsa and the Tundzha rivers and curves eastward north of the Sakar and Strandzha Mountains reaching the Black Sea shore. The proportion of S. etruscus in the Barn Owl's food spectra tends to be lower compared with the true Mediterranean areas in Europe. Comparisons with craniometric data from literature indicate that the SE Bulgarian population represents a relatively large form in agreement with a well expressed size cline from south to north that complies with Bergmann's rule. Within the analyzed data set from S Europe the palatal length and zygomatic breadth increase significantly with decreasing of the mean annual temperature.