**Acknowledgements**

We thank Dr Y. Itoh of the Osaka Prefecture University and Dr O. Takano of JAPEX, who gave us the opportunity to submit this manuscript to this publication. Research in Samburu Hills and Nakali was permitted by the Government of Kenya and was supported by many local people. This study was supported by a grant in aid from the Ministry of Education, Japanese Government (17740335 for TS, 19207019 for MN and 14253006 for YS).
