Brown Bear Use of Ant Mounds in Scandinavia

Brown bears (Ursus arctos) in Scandinavia forage in early spring on ants (Formicidae) they excavate from large ant mounds. We collected information on the selection and handling of ant mounds by bears by following their tracks in snow during 3 consecutive spring seasons in 1970-72 in the Vassfaret area of central southern Norway. The density of large ant mounds in the study area was about 9/km of bear track or about 3 mounds/ha. Approximately half of the 143 ant mounds recorded were excavated by bears. The excavations ranged from superficial to complete; 9 completely excavated ant mounds were used as day beds, the others for food. The excavated ant mounds were relatively large, spanning 60-190 cm in base diameter and 40-150 cm in height. Excavated mounds were smaller, had more ants present, and had greater vegetative cover than untouched mounds.