奄美大島におけるハブ捕獲数の周期的変動(第二報)

抄録

The existence of cyclic fluctuation in the number of habu, Trimeresurus flavoviridis, caught on Amami Oshima was examined with a computor. The spectral analysis represented statistically periodical properties of a time series. Regarding the yearly fluctuationof the number of habu caught in the period from 1954 through 1977 as a realization of a stationary time series, we tried to obtain estimates of the spectral density by two methods: (1) Blackman and Tukey's estimate, and (2) fitting to an autoregressive model. Through the latter method, we found peaks appearing at about 4 and 8 year cycles. The existence of these cycles was ascertained by simulation, notwithstanding our limited data of only 24 observations. It appears that a change of sugarcane yield at a given time negatively correlates with the number of captured of habu 7 years later.