Population Dynamics of Roe Deer (Capreolus capreolus, L. 1758) in the Ticino River Natural Park (Northern Italy): from the reintroduction to nowadays

though in Northern Italy was absent in the Po Plain since the last centuries. Between 1991 and 1994 a reintroduction project was carried out in the Ticino River Natural Park (province of Milan), with the release of 43 individuals in the first phase (capture and immediate release) and 47 individuals in the second phase (capture, acclimatization, and release) [1]. The aim of this study was to assess the reintroduction success after more than twenty years after the reintroduction by defining the habitat occupancy by the species and its population level and structure. The study area extends 147.28 Km2 and is placed in the south-western part of the Lombardy, in the Ticino Valley. The data were collected during the years 2015 and 2016 using two census techniques: camera-trapping and direct observations by car. Data collection was planned by a Tessellation Stratified Sampling design (TSS, [2]), within 56 sampling units represented by cells of a 2-km grid. Camera-traps were posed at 292 random points localized into the 56 cells, monitored twice a year, both in autumn-winter and spring-summer. The data about the age and sex structure of the population were analyzed by the Chi-square goodness-of-fit test and Likelihood Ratio (G test) for contingency tables. Furthermore a Population Viability Analysis (PVA) was run in order to define the probability of persistence (or on the contrary, of extinction) of the population within a specified future time interval (in this case thirty years) [3]. The PVA was conducted with the software Vortex 10.0 [4] and the parameters used in the analysis derived from data collected during the census and literature. The PVA was performed running seven simulations, considering an initial population size of 30, 50, 200, 400, 600, 800 e 1000 individuals. Overall 94 Roe Deer were observed, distributed widespread in the Park, but for only 79 individuals it was possible to determine the sex and/or age. The global sex ratio (SR) was equal to 0.75, not significantly different from the expected sex ratio of 1:1 (Table 1). Moreover the sex ratio did not vary significantly between age classes (LR = 0.120; df = 1; P = 0.729). The reproduction success, calculated as the percentage of female which rear a fawn successfully, was equal to 33.0% (SD = 4.43). The PVA simulation showed that the population will increase over the next 30 years with a negligible extinction risk (Figure 1). Although the population is growing, the Roe Deer will not reach the carrying capacity (K) in the next 30 years, unless the initial population size was equal to 1000 individuals.