Comparing of check lists of species of geometrid moths (Lepidoptera: Geometridae) collected on the Askold Island (Peter the Great Bay, Russian Far East) in 1878– 1873 and in 2021, revealed a low level of their intersection at 43.4%. An attempt to explain the significant historical change in the moth fauna by the impact on the ecosystems of the island of the local population of sika deer (Cervus nippon Temminck, 1838) was made. These deer here trends to episodic sharp increases in numbers, leading to significant damage to the vegetation cover on the island. Based on comparative areaological and ecological analyses of the old and new lists of geometrid moths, no changes have been identified that can be linked with the direct influence of deer on the population of the moths on the Askold Island. However, strong decline numbers of individuals during periods of high deer abundance, which draw indigenous populations of moths into an "extinction whirlpool", can explain the high rate of change of the moth fauna on the island.