1 Yunnan Asian Elephant Field Scientific Observation and Research Station of the Ministry of Education, Kunming 650091, China and Asian Elephant Research Center of Yunnan University, Kunming 650091, China.
2 Yunnan Asian Elephant Field Scientific Observation and Research Station of the Ministry of Education, Kunming 650091, China and Asian Elephant Research Center of Yunnan University, Kunming 650091, China. mychen1108@ynu.edu.cn.