Human-animal interactions and Pleistocene animal extinctions are important topics in prehistory. In the Ryukyu Islands, several species of endemic deer became extinct around the time of first human arrival. However, it is not clear whether people impacted the survival of deer on the islands due to insufficient chronological data on the timing of deer extinction, and the absence of direct evidence for human predation on deer fossils. In contrast to the deer, many other animals were not affected by human hunting. The hunting impact on the animals is related to the life history and ecology of the animals. We therefore conducted palaeodietary reconstructions of extinct deer using isotopic and microwear/mesowear analyses, and reconstruction of the age profile based on the tooth-wear rate with palaeodietary data. Results showed the extinct deer had a long life span due to island adaptation and were susceptible to predation pressure. New excavations have revealed that deer have been extinct for thousands of years since the first human arrival at least on Okinawa Island, and was the result a considerable hunting impact. The vulnerability of deer on the Ryukyu Islands was increased by their long isolation, and their behavioural and ecological adaptations to island habitation.