89 ACTA ZOOLOGICA BULGARICA Acta zool. bulg., 66 (1), 2014: 89-108 * Corresponding author Introduction A detailed understanding of the climate develop- ment throughout the past depends on suitable proxy data and their translation into quantitative climate information. Small mammals are especially prom- ising in this respect. Several factors make them a good indicator group for the ecological conditions. Their remains and especially their teeth are well preserved in Quaternary cave sediments. Their oc- currence here is a result of the feeding activity of raptors using the caves as shelters where they bring their prey. It is widely accepted that in caves with large entrances birds of prey and especially owls are the main agent for accumulation of small mammal bones (ANDREWS 1990). These birds produce large numbers of pellets containing bones of their victims, which can be identified to species in most cases and recovered from sediments in quantities sufficiently large to permit estimation of relative abundance. Because of their small size and imperfect thermoreg- ulation the small mammals are habitat-dependent, Late Quaternary Small Mammals and Paleotemperatures in Bulgaria and Italy Vasil V. Popov 1 *, Emanuele Di Canzio 2 , Biagio Giaccio 3 1 Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, Tsar Osvoboditel 1, 1000 Sofia, Bulgaria; E-mail: vsl_popov@yahoo.com 2 Università Di Roma “La Sapienza” Dipartimento di Scienze Della Terra, Piazzale Aldo Moro n.5 CAP 00185 Roma, Italia 3 IGAG-CNR, Area della Ricerca di Roma 1, Via Salaria Km 29,300 00016 Monterotondo Stazione, Roma, Italia Abstract: The aim of the study was to analyze the capacity of fossil remains of small mammals in the cave sediments for quantitative climate reconstructions. We have developed a number of small mammal-climate inference models using modern owl pellet samples from 144 sites. Canonical correspondence analysis was used to reveal the factors (climate parameters, agent of accumulation) that best reflect the main patterns of variation in the modern small mammal assemblages. Annual Mean Temperature, Maximal Temperature of Warmest Month, and Minimal Temperature of Coldest Month capture a large and statistically significant fraction of the overall variance in the recent small mammal data. Four inference models were tested. The results of cross-validation showed that Modern Analog Technique and Weighted Averaging Partial Least Squares (WAPLS) were the best in terms of performance statistics. Using these models it was possible to produce quantitative records of past temperatures based on small mammal stratigraphic cave sequences from Bulgaria (Cave 16 and Cave 15) and Italy (Castelcivita, Mura, and Continenza). For each locality both methods revealed similar trends in climate change, but differ somewhat in terms of specific values of the reconstructed temperatures. The differences between them were larger in non-analog situations. In this sense, WAPLS was considered more reliable in the reconstruction of climate features during Late Pleis- tocene. Reconstructions made on the basis of this method have important implications for understanding paleoenvironmental changes during Late Quaternary. The reconstructions support the previous qualitative interpretations and reconstructions based on other proxies. Keywords: modern small mammal data; pellets; numerical analysis; paleoclimatic reconstruction; transfer functions; fossil small mammals Palaeozoology Research Article