Holocene brown bear (Ursus arctos L.) from Norwegian caves

Norwegian caves contain stratigraphical information regarding the historical faunal composition valuable in the assessment of postglacial colonization and phylogeographical structure. In some of these limestone caves, brown bear ( Ursus arctos L.) remains have been excavated and radiometrically dated. We present osteology (95 traits defined) from 29 brown bears found within 22 Norwegian caves above 658N. Our data span the time interval 6210–420 ¹⁴C yr BP. The sex of individuals was based on dimorphic canines, while age was determined by cementum analysis and body size estimated from regressions between morphological traits compared to a contemporary reference collection. Five females and 14 males were recognized, while the remaining bears could not be sexed because of their small size, low age or lack of canines. The ages of 26 bears (tooth cementum age and estimates) ranged from juveniles (<0.5 year) to adults (23 years), the majority being old animals. Both sexes have used these caves for over-wintering lairs, as seen in several caves, where denning is also suggested based on the observations of adult females and cubs. There were no signs of predator or human transported bear remains, suggesting natural mortality. The age of the bears suggests that young or old bears may have died from insufficient nutrient storage, environmental harshness, or may have drowned in spring or autumnal flooding. We conclude that Norwegian brown bears have used these caves sporadically for thousands of years, which suggests that caves are not a preferred site for the brown bear during hibernation or denning.     

Vertebrate remains in Holocene limestone cave sediments: faunal succession in the Sirijorda Cave, northern Norway

The faunal composition and temporal species succession dynamics during the Holocene are poorly known in Norway, and interpretations are often biased because of the potential overrepresentation of game species in the archaeological finds. Pitfall traps in limestone caves represent less biased long-term records of fauna, often being excellently preserved for thousands of years and thus providing an opportunity for reconstruction of the postglacial distribution history. We excavated fossiliferous sediments at the bottom of a 40-m entrance shaft, functioning as a pitfall trap, in the Sirijorda Cave, northern Norway, comprising 3467 identified vertebrate bone fragments. Radiocarbon-dating of mammalian bones at stratigraphic levels in excavated trenches was used for calibrating the time scale during the last 8000 ¹⁴C years BP, with a reconstruction of local vegetation history from a pollen profile in the cave deposits. At least 20 species were identified: one frog, two birds (plus 1-2 to genus level) and 17 mammals. Most of the species appeared more or less continuously during the covered time periods of the Atlantic, Subboreal and Subatlantic chronozones. With the exception of one species, Sorex isodon, which seems to have disappeared during the past 2000 years, all the registered species in the time profile are present in the area today. The possible immigration routes and time periods for (re)colonization of the recorded species are discussed.