Diet composition of sika deer in Kasuya Research Forest of Kyushu University in northern Kyushu, Japan

Abstract

We analyzed the diets of sika deer from Kyushu University’s Kasuya Research Forest based on point-frame fecal surveys conducted between February 2023 and January 2024. Leaves, mainly from evergreen species, accounted for 42.1% of the fecal contents in February, with the remainder comprising fiber and culms. In April, the leaf component decreased, whereas the fiber component increased to 45.8%. In August, grass leaves comprised only 11.2%, and culms increased to 56.5%, suggesting that deer ventured out of the forest to feed on grasses. In October, the leaf component decreased further, while culms decreased to 12.0% and the fiber content again increased to 39.0%. Acorns of Castanopsis cuspidata and seeds of pokeweed (Phytolacca decandra) seeds were recovered from fecal samples in October. In January, the leaf component decreased to 16.8% and the proportion of unidentifiable materials increased to 35.1%. The deer population in our study area increased rapidly over several years around 2010, profoundly affecting the local vegetation. The small occupation of green leaves in the deer diets (23–33%), even during the plant growth season, reflected the vegetation deterioration caused by the increase in deer.