Brown bear (Ursus arctos) diet composition and seasonal food habits were examined in the Central Forest Nature Reserve (CFNR) in West-European Russia. This territory has 2 landscape types: (1) a mostly intact and strictly protected CFNR core area with southern taiga forests, and (2) a human-modified buffer zone around it. We collected 758 bear scats between March and November 2008–2021. Fleshy fruits were the most important food category in the bear diet and represented 30% of the annual estimated dietary energy content (EDEC). Among fruits, the most important food items were apples (Malus domestica; EDEC = 22%). Bears highly preferred bilberry (Vaccinium myrtillus) in the late summer and early fall seasons (EDEC = 9%). During the hyperphagia period, bears fed on apples, hazel nuts (Corylus avellana; EDEC = 17%), oat (Avena sativa; EDEC = 9%), rowan (Sorbus aucuparia; EDEC = 5%), and cranberry (V. microcarpum and V. oxycoccos; EDEC = 4%). Herbaceous plants were also important (EDEC = 6%) from late spring to early fall. Among insects, bears actively consumed ants (Formicidae; EDEC = 3%) and social wasps (Vespidae; EDEC = 3%). Ungulates, especially adult moose (Alces alces) and calves, comprised the most important food item for bears during spring, contributing 15% of the EDEC. The CFNR core area, which presents natural foods for bears, had a prevalence of bilberry in scat amount (Cliff's Delta = –0.20). The buffer zone had a prevalence of apples (Cliff's Delta = 0.19) and oat (Cliff's Delta = 0.14), whose distributions were associated with abandoned orchards and cultivated fields. Brown bear food habits in the CFNR are similar to those in southern and eastern Europe, with a great dietary contribution of plant materials (especially fleshy fruits and hard mast). However, at the same time, CFNR bears have a significant dietary impact associated with boreal ecosystems (high Vaccinium berry consumption and active moose hunting), which makes it similar to populations from northern Europe.

The study of A.A.K. was performed within the framework of the state assignment FEWZ-2020-0009 from Ministry of Education and Science of the Russian Federation. During this work V.P. was supported by the I+D+i Project PID2020-114181GB-I00 financed by the Spanish Ministry of Science and Innovation, the Agencia Estatal de Investigación (AEI) and the Fondo Europeo de Desarrollo Regional (FEDER, EU).

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