Asian elephant microsatellite genotypes: Nakai Plateau and Sepon mines region, Lao PDR

Habitat loss and fragmentation are leading contributors to the endangered
status of species. In 2006, the Nakai Plateau contained the largest known
Asian elephant (Elephas maximus) population in the Lao People’s Democratic
Republic (Lao PDR), and the population was among those with the highest
genetic diversity reported for Asian elephants. In 2008, completion of the
Nam Theun 2 hydroelectric dam inundated much of the Plateau, resulting in
the loss of 40% of elephant habitat. We studied elephant presence,
movements, and the incidence of human–elephant conflict (HEC) on the Nakai
Plateau and surrounding areas from 2004-2020, before and for 12 years
after dam completion. To examine contemporary population dynamics in the
Nakai elephants, we used genetic sampling to compare minimum population
numbers, demography, and levels of genetic diversity from the wet and dry
seasons in 2018/2019, 10 years after dam completion, with those reported
in a pre-dam-completion genetic survey. After dam completion, we found a
major increase in HEC locally and the creation of new, serious, and
persistent HEC problems as far as 100 km away. While we were unable to
compare estimated population sizes before and after dam completion, our
data revealed a decrease in genetic diversity, a male-biased sex ratio,
and evidence of dispersal from the Plateau by breeding-age females. Our
results raise concerns about the long-term viability of this important
population as well as that of other species in this region. Given that
hydropower projects are of economic importance throughout Laos and
elsewhere in southeast Asia, this study has important implications for
understanding and mitigating their impact.