Funding for this research was provided by:
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (31003A-144210)
A.H. Schultz-Stiftung zur Förderung Primatologischer Forschung
Received: 16 January 2019
Revised: 12 April 2019
Accepted: 17 April 2019
First Online: 30 May 2019
Compliance with ethical standards
: The authors declare that they have no conflict of interests.
: All sources of data were from the literature or the web and did not involve ethical approval.
: The dataset and all additional analyses supporting the conclusions of this article are available in this published article and in the supplementary information files.