The diet of Sika deer is dominated by non-leafy plant material in a Japanese cedar-dominated landscape

Abstract

Rapidly expanding Sika deer populations in Japan are increasingly affecting forest vegetation. Deer populations have had particularly negative effects in Tottori Prefecture in western Japan, an area with extensive plantations of Cryptomeria japonica (Japanese cedar). We assessed understory conditions and damage to forest vegetation in both plantation and deciduous broad-leaved forests in this region. Fecal analyses indicated that living leaf tissue accounted for only 13.26% of the diet of the deer, even during the summer, and less nutritious materials including woody fiber, plant culms, and dead leaves comprised as much as 80%. Understory vegetation was in poor condition in both the plantation and deciduous broad-leaved stands. Deer exclusion fencing and subsequent assessments indicated that biomass indices were 9 and 39 times greater within the exclosure in the plantation and broad-leaved forest, respectively. Our results indicate that the diet of deer in areas dominated by Japanese cedar plantations is comprised largely of non-leaf plant material, even during the summer months, due to sparse understory vegetation.