Debarking behavior by deer may impact forest renewal and succession, particularly when a deer population is overabundant. The sambar deer (Rusa unicolor) population in Taiwan has expanded rapidly in the last 20 years, and its debarking behavior has been observed for approximately 10 years. This study surveyed 83 sampling plots in four protected areas to reveal the status of debarking by sambar in Taiwan. A total of 153 species of trees was sampled and 94 of them were debarked by sambar. The debarking frequency was high in Yushan National Park (19.9%), but very low in the other three protected areas. The best-fitting generalized linear model shows that sambar has a significant preference for tree species and range of diameter at breast height (DBH) for debarking. Pinaceae species were most preferred by sambar except that Taiwan red pine (Pinus taiwanensis), a pioneering canopy species in forest succession, was the least preferred in all the species in our sample. Without considering species, trees with a DBH around 20 cm were preferred the most by sambar for debarking. We hypothesize that the preference of debarking by sambar for specific species and younger trees may eventually impact forest regeneration and succession.