1,721,012 research outputs found
Diet of the asp viper Vipera aspis in woodland habitats of the Po plain (NW Italy)
No full textThe diet of Asp viper Vipera aspis was studied in forested habitat of Northern
Italy The species feeds on a low number of preys, possibly reflecting the reduction
of small mammal richness in woodland habitats
Thermal ecology of a grass snake (Natrix natrix) population of Northwestern Italy (Reptilia, Serpentes, Colubridae).
No full textThis paper records body temperatures of
grass snakes captured near Pavia, northwest Ital
A methodological approach to feral pigeon (Columba livia) census in urban areas
No full textCorrection coefficients (CCs) are used to improve censuses of Feral
Pigeons, Columba livia, within large urban areas, because most of individuals are not
directly visible. However, a satisfactory analysis of procedures of quantifying CCs has
not been thoroughly addressed. In this study we investigated, by capture-recapture
methods, the effects of structural heterogeneity of buildings, non complete closure of
population, and heterogeneity in bird’s capture probability, on the procedure commonly
used for the computation of CCs. Our results indicate that either heterogeneity of capture
as structural features of different areas of the city differently affected pigeon
sightability, and consequently CC values. Two main solutions might be applied: 1) using
capture-recapture methods based on partial closure of population and heterogeneity of
capture (e.g. the Bowden index) instead of the Petersen-Lincoln index, and 2) sampling
more than one site in order to remove the effects of structural variability of buildings
Morphometric differences between extant and extinct Italian populations of the adder, <em>Vipera berus</em> (Linnaeus, 1758)
Full text linkVipera berus (Linnaeus, 1758) is the terrestrial snake showing the widest distribution in the world, occuring from Great Britain, France and Northern Italy to the Sakhalin Island and North Korea (Nilson, 1980; Saint Girons, 1980; Nilson et al., 1994; Nilson & Andrén, 1997a). However, adders do not occur uniformly over their distribution area, but are scattered in several isolated populations (Nilson & Andrén, 1997a). Frequently, ecological traits of borderline and isolated populations differ from those living in the core area of the distribution range of the species, and might be subjected to higher risks of stochastic extinction and higher differentiation rates (Mayr, 1970). For example, meadow vipers (Vipera ursinii) show a highly fragmented distribution, many of isolated groups being different
subspecies (Nilson & Andrén, 1997b, 2001)
Species distribution modelling as a conservation tool: the case study of Vipera aspis in a highly exploited region
Full text linkVipera aspis is quite common in hilly and mountainous area of Northern Italy but is becoming rare in the Po plain with few exceptions along main rivers. The reasons for such a distribution seem related to the progressive reduction of suitable habitat due to human landscape modifications, rather than to specific ecological needs. In this scenario, the knowledge of the exact distribution of this species and the identification of the factors which still make some planitial areas suitable would be very useful for conservation strategies. So the aims of this work are: i) modelling a distribution map of the potential suitable areas to focus surveys efforts and spatial relations with protected areas; ii) identifying the most important factors which affect suitability. The study area was the plain area of Lombardy that covered about 14100 km2 and was defined by 300 m a.s.l. contour line. The 45 occurrence data came from various research projects from 2000 to 2009. Fourteen non-correlated potential predictors were included in the model: six bioclimatic variables (http://www.worldclim.org/); five environmental (land use; density of cultivated fields); three anthropic (fresh water level of fungicide and organochlorine, roads density). All the variables were resampled to 100 m spatial resolution. Potential distribution was modelled using the maximum entropy method, and performed by the software MAXENT 3.3.1 (http://www.cs.princeton.edu/~schapire/maxent/). We used the bootstrap procedure to generate ten different models each with 25% of localities as test sample. We then averaged single model results. The models fit well (mean training AUC: 0.981 ± 0.008; mean testing AUC: 0.942 ± 0.032). The suitable area at the 10th percentile threshold is 3.4% of the study area and is reduced to its North-Western part, with few and isolated spots elsewhere. Fifty-six percent of suitable cells falls within protected areas, and most of the remaining part is nearby. The most informative variables are land use and roads density, which together explain 56.1% of observed variance. Suitability is positively affected by woods and meadows, and negatively by anthropic structures and increasing roads density. Our results demonstrate that asp viper is a species at risk in the Po plain, due to habitat fragmentation and modifications caused by anthropic activities. The north-western part of the study area plays a key role in its conservation thanks to more natural conditions and to a higher protection level. It is fundamental to preserve this territory and to increase the connectivity among existing natural parks
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