The study of the dietary changes which have intervened over the years in generalist and opportunist predators may provide useful information on the temporal modifications of their prey communities, especially under a climate change scenario. In this study, we analyzed the quantitative changes in the small mammals portion of the diet of two generalist and opportunist predators, the Barn owl (Tyto alba) and the Asp viper (Vipera aspis), in a forest zone in central Italy, for the period respectively 1987-2010 and 1975-2008. Concerning the Barn Owl, studied through the analysis of its pellets, there was no apparent change over the years, except for an increasing trend of syn-anthropic species Mus musculus domesticus and Rattus rattus. Similarly Microtus savii, a typical rodent of agroteriocoenoses, doesn’t show significant variations over the years. However, since I did not obtain a longitudinal long-term dataset on Barn owl pellets, I tested the methodology through a longitudinal sampling (for 30 years) at two Spanish areas. In this case it was possible to record a significant increase in two termoxerofilic species, Mus spretus and Crocidura russula, during the period analyzed. However, correlating this increase with thermopluviometric data for the same Iberian areas there wasn’t a significant correlation. As regards the analysis of the diet of the Viper, this issue was also studied through the analysis of ingesta, for a longitudinal period of 20 years. Among the various taxa eaten by vipers, only two showed significantly consistent trends over the years, with Myodes glareolus increasing and Sorex spp. declining in the viper diet. Despite being temperate-zone forest-associated species, hence likely adversed by global warming, Sorex spp. and Myodes glareolus showed opposite trends over the years, thus suggesting that such trends may reflect more local scale perturbations (local forest overgrowth and diminution of logging). I also found a significantly positive relationship between small mammals abundance in the field and their relative frequency of occurrence in the viper’s diet, thus demonstrating that vipers really sampled the small mammal species in relation to their local availability. However, global warming has certainly had an effect on the activity rhythms of predators: for example, some aspects of the annual phenology of the same populations of Viper studied for the diet have changed over the years according to patterns related to the global warming. This work therefore show the effectiveness of some indirect sampling methods in the study of temporal variations in small mammals highlighting some relevant limitations. We also tried to investigate the human impact through mutagenetic tests (micronucleus test on peripheral blood) and investigations in relation to bioaccumulation of trace elements in wild rodents. For this kind of analysis we made three different trapping sessions of small mammals in two areas: Canale Monterano and Civitavecchia. These areas are characterized by different conditions of anthropic impact: - about Civitavecchia (Santagostino) we are in a mostly urbanized and man-made environment in relation with the presence of the largest european energy hub consisting of the Torvaldaliga power plants. - about Canale Monterano there is a situation of greater naturalness, with agricultural areas, pastures and forest patches. With regard to the accumulation of trace elements analysis were conducted on the hair of small mammals captured and on the bones from barn owl’s pellets. The results show some significant differences for the two locations examined, in particular for the site of Canale Monterano readings are significantly higher in bone samples for the following elements Tl, Th and U due to the geology of the area, while, on the hair is confirmed a difference to Tl as well as a higher concentration of Pb in samples of Civitavecchia. This result is very interesting because it is directly attributable to the higher vehicular traffic and industrial pollution of Civitavecchia. The other important data concerne the concentrations of Mn, which could be due to use of fungicides in agriculture. With regard to micronucleus test, on erythrocytes from circulating blood, analysis showed a generalized genetic damage (from 0 to 8 MN in 1000 MNE) for both locations, according to the Mackey & MacGregor (1979) index used as reference (MNE/1000 ≥ 2), suggesting an alteration of the overall environmental situation
Variazioni temporali nella struttura di vertebratocenosi nei Monti della Tolfa: influenza di cambiamenti climatici e impatto antropico / Milana, Giuliano. - (2013 Nov 08).