Integrated and novel survey methods for rhinoceros populations confirm the extinction of Rhinoceros sondaicus annamiticus from Vietnam

Abstract

Javan rhinoceros (Rhinoceros sondaicus) is among the most threatened large mammal species in the world. Development of rigorous, non-invasive survey techniques is a high priority, to monitor populations and develop informed conservation management strategies. The critically endangered javan rhinoceros until recently survived in two separate populations, one in Vietnam and one in Indonesia, representing distinct subspecies. The range of the annamiticus subspecies around Cat Tien National Park (CTNP) has declined significantly since its re-discovery in 1989, and no accurate estimate of population size had ever been obtained. We employed integrated survey techniques and analyses to determine the population status of the javan rhinoceros in Vietnam. We conducted a comprehensive field survey of the Cat Loc sector of CTNP using scat detection dogs to detect javan rhinoceros dung between October 2009 and April 2010. Twenty-two dung samples were collected for microsatellite DNA analysis, seventeen of which were of sufficient quality to be analysed. The genotyping work confirmed that only a single rhinoceros was present at the start of the survey in 2009 and that this was the same individual that was found dead in April 2010. Although far less definitive than host genotyping, stool bacterial diversity assays also supported the hypothesis that all samples collected by the survey were from one individual. This empirical data combined with field survey data indicate the extinction of the javan rhinoceros in Vietnam. We conclude by discussing the developmental progress of these non-invasive survey techniques to monitor other endangered rhinoceros populations.