Ursus arctos L., 1758 from Bukovynka Cave (W Ukraine) in an overview on the fossil brown bears size variability based on cranial material

Brown bear Ursus arctos is a permanent member of European Middle and Late Pleistocene carnivore assemblages, which shows great body size fluctuation over time. To study this subject we carried out extensive comparison of 37 cranial metric features based on 2954 measurements coming from 263 specimens. In the statistical analyses we included a new complete brown bear calvarium which was found in Bukovynka Cave in Ukraine and dated to postglacial period. The cranial material was divided into male and female sets and classified according to geographic and stratigraphic affiliation of the samples. Analyses revealed clear decrease in many skull dimensions from the Middle Pleistocene specimens through the Late Pleistocene and postglacial to the Holocene skulls. The trend is probably related with general climatic changes during this period. However, Late Pleistocene specimens from Iberian Peninsula were significantly smaller from other Late Pleistocene European skulls or even a bit younger from the Late Glacial and postglacial period for some dimensions. The deviation from the global trend could result from their isolation from other European populations. These conclusions can be drawn both for male and female skulls. The decrease in body size showed that U. arctos is dynamically evolving species. Thus, the size does not seem to be a perfect criterion in determining the biochronological age of the brown bear findings although a general decreasing trend in size with time is clearly visible. The size of brown bear is under the influence of many factors such as great sexual dimorphism, individual and population variability as well as global and local climatic conditions.