Fundacja Przyroda i Nauka » Fir trees stripped of their bark. Who did this?

During May hikes in the Bieszczady forests, one can find fir trees with freshly stripped bark. The trees are most often wounded in the ground level, and the bare trunks show parallel depressions, as if made by a double-edged chisel. This is the work of bears. The bark is stripped off with claws, and the parallel grooves on the bare trunks are incisor marks. It is no coincidence that fir trees are stripped of their bark during this period. This is when trees transport nutrient-rich sap containing mainly sugars up the trunk. Bears "harvest" the phloem (conducting tissue), with the sap it contains, most often from medium-sized fir trees. Usually these trees are no more than 2.5 meters in circumference. The bear-injured fir trees we found this year in the Bieszczady Mountains were between 80 and 180 cm in circumference. In comparison, the oldest, and therefore largest fir trees growing in these mountains have girths measuring more than 3 meters, and the most magnificent of them have girths measuring even more than 5 meters. Old, large fir trees with ground-level spacious hollows can serve as a denning place for bears and breeding sites for wolves and lynxes. It is interesting to note that it is only since 2003 that bears have been observed stripping fir trees of their bark more frequently. Previously, this mainly affected larches and spruces, trees much less common in the Bieszczady than firs. Trees wounded by bears are colonized by microorganisms, fungi, wood-feeding insects, and after a few years become a feeding ground for woodpeckers. Some researchers believe that bears, by stripping the bark from fir trees, prepare future dens for themselves.

Author: Wojciech Śmietana

P.S. For those more interested in this issue, I recommend the articles listed below.

- Zyśk-Gorczyńska E., Jakubiec Z. 2014 Ranienie drzew przez niedźwiedzia brunatnego (Ursus arctos) w Bieszczadach. Sylwan 158 (5): 377-382.

- Zyśk-Gorczyńska E., Jakubiec Z., Wuczyński A. 2015. Brown bears (Ursus arctos) as ecological engineers: the prospective role of trees damaged by bears in forest ecosystems. Canadian Journal of Zoology 93 (2): 133-141.

- Zyśk-Gorczyńska, Jakubiec Z., Wertz B. , Wuczyński A. 2016. Long-term study of damage to trees by brown bears Ursus arctos in Poland: Increasing trends with insignificant effects on forest management. Forest Ecology and Management 366: 53–64.

- Zyśk-Gorczyńska E., Jakubiec Z. 2018. Multi-scale approach to brown bear (Ursus arctos) foraging on trees: characteristics of damage to trees and stands in the north-eastern Carpathians. Forestry: An International Journal of Forest Research 91 (2): 185-192.

© 2023 Fundacja Przyroda i Nauka

Fir trees stripped of their bark. Who did this?