Rediscovery after thirty years since the last capture of the critically endangered Okinawa spiny rat Tokudaia muenninki in the northern part of Okinawa Island

概要

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The Okinawa spiny rat, Tokudaia muenninki, is a critically endangered species endemic to the northern part of Okinawa Island and may be extinct in the wild as there have been no recent sightings of the animal in its natural habitat. We initiated the present search to determine whether the spiny rat still exists in the northern part of Okinawa Island. Sensor cameras and traps were distributed across areas in which past studies had identified the location of occurrence of spiny rats. From a total of 1,276 camera-nights and 2,096 trap-nights from 2007 to 2009, we captured 24 spiny rats; however, we were only successful in identifying spiny rats in the northernmost of the areas sampled, with no indications of the spiny rat in the more southerly areas. The area in which the spiny rats were still present was estimated to be only 1-3 km2 and is comprised of forest dominated by Castanopsis sieboldii, Lithocarpus edulis, Distylium racemosum and Schima wallichii. The trees range in age from about 30 to more than 100 years old, and have an average height of 12 m (range 7 m-16 m). Our rediscovery of the spiny rat in 2008 comes after an interval of 30 years since the previous trapping study in 1978 and seven years since indirect survey evidence from analysis of feral cat feces 2001. Measures for conservation of the location of the spiny rats are urgently required.