Based on the importance of conserving endangered species and of long-term ecological research, the second-year objective of the extensive study was designed to monitor the relative abundance of large mammals and acorn production for understanding the complicated interaction between Formosan black bears (Ursus thibetanus formosanus) and the oak forest ecosystem in Yushan National Park. The acorns of ring-cupped oak (Cyclobalanopsis glauca) in Daphan started to fall off and consumed by wildlife since October until February, but the peak occurred in Nov. and Dec. (70 % of the fallen acorns). The acorns were mostly used by wildlife, which caused 85% of the fallen acorns collected by 200 seed traps. Both of the visual survey methods indicated that the acorn production in 2007 was greater than, or twice of, that in 2006. We also found the greater the oak trees produced acorns, the more bears used the trees (r = 0.311, P<0.001, n = 498). The camera trapping identified 13 species of larger mammals out of 2,448 effective animal photos, with the Occurrence Index (OI, photos taken in 1,000 hours) of 31.6 (excluding unidentified small mammals). The camera data (2006–2007 Oct.) showed that 87% (n = 15, OI = 0.19) of bear photos were taken mainly in Nov. and Dec., which coincided with the acorn peak. The most abundant large ungulates was muntjacs (Muntiacus reevesi), followed by Sambar deer (Cervus unicolor), wild boars (Sus scrofa), and serow (Naemorhedus swinhoei). The occurrence of these animals, including bears, in the acorn forest indicated a obviously seasonal variation expect for serow. The relative abundance of large mammals in the acorn season was more than twice of that in the non-acorn season.