Preliminary data on the diet of a population of Speleomantes italicus from the Republic of San Marino

During the last few decades, the trophic niche of the European plethodontid salamanders (genus Speleomantes) has been intensively studied. Adopting a harmless technique (i.e., stomach flushing) researchers have been able to collect stomach contents from plethodontid salamanders and analyze multiple traits of their feeding habits, from assessing the diversity of the consumed prey to evaluating if and how many individuals from a specific population show a specialized diet. The Italian cave salamander, Speleomantes italicus, is the species with the widest distribution that covers most of the Apennine chain from Tuscany to Abruzzo. It is considered to be endemic to the Italian peninsula and it also occurs in the Republic of San Marino. The trophic niche of this species has been investigated multiple times, but none of such studies were performed on any population occurring in the Republic of San Marino. Here we present the first data on the consumed prey by an epigean population of S. italicus from the Republic of San Marino. We performed two surveys at night, one in November 2022 and one in April 2023. This population occurs in a forested area and in dry walls nearby a small, urbanized area. We captured and photographed the salamanders to estimate their size (snout-vent length; SVL), and to sex them (males, females, juveniles) on the basis of both secondary sexual male character (i.e., mental gland) and SVL. Before their release we performed the stomach flushing; stomach contents were preserved in 70% ethanol until their recognition under the stereo microscope. Analyzing the stomach contents of 67 individuals, we recognized 1,018 prey items belonging to 28 prey groups (autumn, N = 46, prey groups = 27, prey items = 921; spring, N = 21, prey groups = 17, prey items = 97). Larvae of Diptera, Collembola Entomobryomorpha and Hemiptera were the most consumed prey in autumn, while adult Diptera and Araneae were the most consumed in spring. Considering the full dataset, We did not find any significant effect of both size and sex (male, female, juvenile) on the number or diversity (Shannon index) of consumed prey. Overall, we identified a significant high proportion of generalist individuals in this population. This is the first study performed on the diet of S. italicus from San Marino, and it also represents one of the fewer studies of epigean populations of Speleomantes compared to those occurring in caves. Our findings identified some divergences from previous studies on this species, for example the lower number of flying preys consumed by individuals, which always represented the larger proportion of prey. These results must be considered a starting point for the study of the trophic niche of S. italicus from San Marino, as further repeated samplings are needed to provide a more complete information on the dietary habits of this population.