ツキノワグマの保護と森林への被害防除 (II)

Abstract

舞鶴大浦半島におけるツキノワグマ 舞鶴市大浦半島における年捕獲数は4 - 13頭であり, 森下・水野の推定法を利用して生息数を推定すると約30頭となり, 密度は0. 3頭/km_2となった。クマハギ被害木の分布と被害実態 芦生演習林のスギ人工林におけるツキノワグマによる被害率は16 - 60％にも及び, 同一林分内では直径の大きなものを選ぶが, 直径10cmでも被害を受ける。全周囲に対しての剥皮率50％で結実, 落葉などの異常を起こし, 70％で枯死する。産仔数 集積した103例のうち産仔数1頭の場合が32例, 2頭が圧倒的に多く70例, 3頭の場合が1例あった。産仔の性比は42例のうち, 雄1頭3例, 雌1頭4例, 雌雄1頭ずつ29例, 雄2頭1例, 雌2頭5例となり, 雌雄1頭ずつの場合が多いことがわかった。

Wild japanese black bear (Selenarctos thibetanus japonicus Schlegel) is the most destructive mammal especially to the coniferous tree in central Japan. In order to control their damages to forest trees and to conserve them, more detailed information about their population, age structure, habits etc, is required, The result obtained from the field research are as follows: 1. Bear population in Ōura peninsula in Maizuru City During the past several years, 4-13 bears were captured per year. By the estimation formula of Dr. Morishita & Mizuno, 30 bears were in the peninsula and their density was 0.3/km2. 2. Distribution of the damaged cryptomeria trees and their actual conditions 16 to 60% of the trees in 18 years old stands were damaged. The damaged trees were over 10 cm D. B. H. The trees those barks were stripped over 50% round became abnormal in physiology. The trees began to produce cones or to defoliate. Over 70% of them were dead. 3. Litter size Of 103 cases, in 32 cases a bear produced one cub and in 70 cases a bear did two cubs, only in one case three cubs. Sex ratio of 42 cases were as follows: 1♀-4, 1♂-3, 1♀-1♂-29, 2♀-5, 2♂-1. The case of one female and one male are aboundunt.