The long-term drive count and culling data of the sika deer (Cervus nippon) population introduced on Nakanoshima Island in Lake Toya, Hokkaido, Japan, during 1980-2023

Cervid populations introduced to favorable habitats in confinement often increase excessively without predators and hunting. Overabundant deer populations impact the ecosystems and may cause damages to agriculture and forestry. Long-term count data on the changes in a deer population is essential to understand the relationship between the population dynamics and the natural vegetation. The introduced sika deer (Cervus nippon Temminck, 1836) population without predators on Nakanoshima Island, Hokkaido, Japan, showed repeated irruptions and declines with mass mortality and irregular culling between 1980s and 2000s. The overabundant deer significantly altered the natural vegetation, and density-dependent changes in population parameters such as body size and reproduction were observed. Here, we present the drive count and culling data to examine the population dynamics during 1980-2023. Deer were counted by 20-30 walking drivers and 2-3 observers on boats once per year in February or March. The number of counted deer rapidly increased from the original three introduced around 1960 to >270 deer (the first peak) in two decades and decreased by half due to starvation and the first culling. Thereafter, the number of counted deer continued to increase with a lower growth rate, reached a higher peak (>400, the second peak) than the first irruption in two decades, and decreased again by half due to starvation and the second culling. Although the number of counted deer increased again up to >300 in several years, it decreased and was maintained at around 100 deer with the annual culling program since 2012. The complete data set for this abstract published in the Data Article section of the journal is available in electronic format in MetaCat in JaLTER at http://db.cger.nies.go.jp/JaLTER/metacat/metacat/ERDP-2024-06.1/jalter-en.