Funding for this research was provided by:
Japan Society for the Promotion of Science (17J09827)
Text and Data Mining valid from 2018-12-10
Received: 9 October 2018
Accepted: 29 November 2018
First Online: 10 December 2018
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: This study was approved by the Research Centre for Ecology and Forestry and the Ministry of Scientific Research of the Democratic Republic of the Congo, and followed all laws in the Democratic Republic of the Congo. This study was conformed to the Guidelines for Field Research established by the Ethics Committee of the Primate Research Institute, Kyoto University.