The Role of Brown Bear (Ursus arctos) in the Plant Seed Dispersal of Golestan National Park

The brown bear (Ursus arctos) is the largest carnivore species in Iran which can be found in large parts of the Alborz and the Zagros mountain ranges but reaches remarkable densities in northern forest, ranging from Golestan National Park to western Gilan.  We investigated the potential of brown bear for endozoochory in Golestan National Park through greenhouse experiment. In order to detect temporal and spatial variability of emerged seedlings, abundance, species richness and composition of germinated seeds from faecal samples collected in different habitats and across seasons were analyzed. A total of 268 seedlings belonging to 33 plant taxa, 25 genera and 19 families germinated from 64 brown bear faecal samples. Based on the obtained results we show seasonal variability in the numbers (p=0.003) and composition (p=0.001) of the dispersed seeds, which can be attributed to plant species phenology. There were no significant differences for seed abundance and composition between the two types of habitats. Similarly, seed species richness did not significantly differ among seasons and habitats. Herbaceous growth form (24 taxa) represented the highest species richness in the germinated plants, while shrub plants were the most abundant germinated species (76% of the total germinated seeds). Fleshy fruits are the principal source of energy during the hyperphagia phase prior to hibernation. In contrast, seeds from dry fruits were observed in lower densities in the faeces, especially during spring and early summer. This result is in line with opportunistic feeding behavior of the brown bear.
Considering that co-occurring ungulates in Golestan National Park rather disperse annual species, we highlight the role of brown bear in specifically dispersing shrub and tree species.