Harvest-based estimation of population size for Sika deer on Hokkaido Island, Japan

摘要

We devised a new method to estimate game populations using relative population sizes and numbers harvested in a population management program for Sika deer (Cervus nippon) in eastern Hokkaido, Japan. The Government of Hokkaido estimated the absolute deer population to be between 74,000 and 166,000 individuals (90% CI) as of March 1994. We took the ratio of the population index obtained by a spotlight census in year t to that in 1993. We estimated the relative population size in 2000 to be between 58 and 101% (95% CI). We analyzed a stage-structured population dynamics model that included uncertainty and yearly changes in parameter values. We assumed that ranges of biological parameter values were consistent with the 16-21% rate of natural population increase per year estimated by a field survey. The population dynamics model suggested that if the population size in 1993 was below 170,000, miles would have, become extinct. The model also suggested that if its size in 1993 was larger than 330,000, the population would not have subsequently decreased. Therefore, we estimated the population in 1993 to be between these two extremes. We provide a method of reviewing estimates of absolute population size by monitoring subsequent census and harvest data.