Development of a Method for Estimating the Monthly Age of Japanese Wild Boar (Sus scrofa) Using Head-body Length Data for Its Risk Management

Abstract

In this study, we developed a simulation method to estimate the age in months based on data on the month of capture and head-buttocks length of wild boars captured in the Nakajima area of Matsuyama City, Ehime Prefecture. As a result of the simulation, the average head and body length was estimated to be 95 cm at 12 months of age. This means that the 95 cm head and body length of captured animals can be used as a boundary value to easily distinguish between juveniles (age 0) and adults (age 1 or older) at the capture site. The proportion of age-0 individuals (aged 11 months or younger) to the total number of animals captured in this area was estimated to be 64% by simulation. In addition, the proportion of age-0 animals captured in April and May was 42% and 33%, respectively, which was less than 50%, indicating that adult animals were more likely to be captured in these months. This data will contribute to the planning of the annual trapping plan by clarifying the appropriate season to focus on the trapping of adult animals and to consider the efficient trapping of targeted animals depending on the season. The measurement of head-body length is a relatively simple and socially applicable monitoring method that can be used, for example, by government officials when confirming the number of pests captured.