Monitoring diversity and abundance of mammals with camera traps: a case study on Mount Tsukuba, central Japan

Abstract

To establish a standard procedure for monitoring wildlife diversity and abundance using camera traps, a three-year camera-trapping study of medium- to large-sized mammals was carried out on Mount Tsukuba, Ibaraki Prefecture, central Japan. A total of 412 photographs of nine target mammal species was obtained. The practical concept of "minimum trapping effort," defined as the amount of trapping effort required to record a set of target species in a particular area at a certain probability, was proposed. The minimum trapping effort for five major species in the study area was 40 camera-days with a 94% bootstrap probability. In the deciduous forests of Japan, studies should use five cameras for four days (20 camera-days) and be repeated twice between late spring and late summer. By counting a series of conspecific photographs taken repeatedly within a certain period of time as a single appearance, a camera-based encounter rate was calculated and its temporal changes were examined. The results suggest that an intermission length, that is the time required between two consecutive photographs of the same species for them to be counted as independent events, of more than one minute reduces the self-dependence of the data in camera studies.