チゴガニの個体間の相互関係(II) : 集団の高密度調節機能について

概要

論文の詳細を見る
The effects of high population density on the behavior, distribution of nests and dispersal of individuals of a fiddler crab, Ilyoplax pusillus DB HAAN, were studied by using the experimental cages set on the natural habitat of this crab. Two kinds of cages, each five in number, were used ; one had the basal area of 40×40cm^2 and the other of 20×20cm^2. Two series of populations, each having 2,4,8,16 and 32 individuals, were introduced into these cages. The results of observations are as follows : 1. The crabs begin their daily activity when the ground appears above the ebb-water in the daytime. Then , the number of active crabs in each cage gradually increases until it reaches an equilibrium density. It was ascertained that the ratio of the equilibrium density of active individuals to the total population density in the cage falls with the rise of population density, suggesting the interruption of activity of individuals due to the mutual interference (Figs. 1 and 2). 2. By the marking of individuals, it was clarified that, at the high density some individuals disappear from the ground surface after a short period of activity and nearly the same number of crabs newly appears from the nests alternately (Table 1). Namely, at high density, the individuals of the crab utilize the habitat area alternately. The higher the population density becomes, the more frequent the alternation takes place. 3. A statistical treatment revealed that the crabs aggregate on the border area of the cage at low density, but both of border and inner area are utilized at high density (Fig. 3). The utilization of the unfavorable inner area is considered to be caused by the high population pressure in the border area. .The distribution of individuals in the border area was not at random but uniform, indicating the existence of mutual interference among individuals. 5. Fightings between individuals, either between two nest owners or between nest owner and wanderer, the latter having no nest, were often observed (Table 2). In most cases, the fighting near a nest ended by the retreat of the invader. The frequency of fighting per individual (Fig. 4) and also the number of wanderers (Table 2) were density dependent as was seen in the proportion of active individuals to the total inhabitants. 6. It seems that the regulatory mechanisms of the crab population, represented in the uniform nest distribution, limitation of the number of active individuals and dispersal of individuals to the unfavorable inner area, are controlled by the territorial character of the crab intermediated by the fighting behavior among individuals (Fig. 5).
日本生態学会の論文
1960-08-01

チゴガニの個体間の相互関係(II) : 集団の高密度調節機能について

スポンサーリンク

概要

著者

関連論文

スポンサーリンク