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Abstract The paper presents a study regarding the aggregations of the Lesser Horseshoe bat Rhinolophus hipposideros in Latium, Central Italy, based on data collected during 27 years in natural caves (limestone) and artificial buildings (abandoned mines, ancient monuments and others). Furthermore some parameters including size, dynamics, sex ratio and age structures are investigated. The number of bats that occur at the hibernacula in winter is low over the whole territory of this region, the most numerous aggregations being 18 individual bats with an average of about 4 bats/visit. In the shelters of the area, the highest numbers of R. hipposideros, a stenotherm thermophilous species, is reached at the end of January, while at the beginning of spring (April) few bats are generally observed. As in many other European populations, males are more commonly represented in winter samples; some caves harbour only adult males over a long time span, about 20 years. The results would suggest that some conservation measures should be introduced to protect this widespread but uncommon and threatened species.

Abstract The present paper summarizes the results of 3 years of observation made at six month intervals for six months at a time (18 field surveys) in a man-made cave in Northern Latium (Central Italy) from April 1992 to April 1995. Its aim is to analyze the main structural and dynamic features of a bat community which hibernates at the shelter. Rhinolophus ferrumequinum and especially Rhinolophus euryale are the most abundant species. Population dynamics of both species as well as that of Rhinoluphus hipposideros show higher levels of abundance between December and February of each semester. In mid-winter, large and sometimes mixed aggregations of Rhinolophus ferrumequinum and Rhinolophus euryale in deep hypothermia occur. A small number of Rhinolophus hipposideros, mainly adult males, was observed. The paper compares the structure of this community to the structure of another community of the same district which has been previously analyzed, in which Vespertilionidae, especially Miniopterus schreibersi, are much more abundant. Despite the difference in species composition, body size was found to be a significant and common feature (as highlighted by forearm length), of the dominant species in both communities, Rhinolophus euryale and Miniopterus schreibersi respectively.