Article ID: 1923
We investigated the population dynamics of Japanese sika deer (Cervus nippon) in the absence of hunting and natural predators in a warm temperate broad-leaved forest on Yakushima Island (World Heritage Area), southern Japan, from 2001 to 2018. We established two study sites 1.3 km apart (Hanyama and Kawahara) and counted the number of deer encountered while walking 5-km-long census routes at each site three times each year from late July to August to obtain a deer density index (the number of deer observed/km). We also set 15 trap cameras at Hanyama in August-September 2014, 2015, 2016 and 2018 and measured the deer photo rate of each camera (the number of deer photographed/day). At both sites, the deer density index increased by 9.1% annually from the initial survey in 2001 to 2014, after which it decreased by 15.2% annually until 2018. The density indices at the sites did not differ during the increase (2001.2014) or decrease (2014-2018) phases. The deer photo rate also decreased by 10.0% annually from 2014 to 2018. During the decrease phase, we observed 19 individually identified deer (six males and 13 females) at Hanyama. The annual migration rate was, at most, 3.5% and most individuals did not move from Hanyama. These findings suggest that the sika deer population declined gradually in the absence of hunting because of some ecological factors at the study sites.
