Diet composition of sika deer in the Shiiba Research Forest in Miyazaki Prefecture, Japan

Abstract

Abstract: The diet composition of sika deer (Cervus nippon) in Kyushu, Japan, has been poorly studied to date. Therefore, we analysed the seasonal diet composition of sika deer in the Shiiba Research Forest of Kyushu University. The deer population has increased since the 1970s and the forest ecosystem has been heavily affected by deer browsing; for example, the broad-leaf bamboo (Sasa borealis) disappeared from the study area around 2000. Faecal composition analyses of samples collected in 2022 and 2023 showed that fibre and culm were predominant, with green leaves accounting for only about 30% of the sika deer diet even in summer; thus, the deer appear to consume poor-quality food throughout the year. A comparison of the diet composition of sika deer in the study area with those of other habitats throughout Japan during the 2000s suggested that they had a very poor diet, probably because of deterioration of forest floor vegetation as a result of heavy deer browsing during the last few decades.