Research in Indonesia, 1975: Survey of border areas of Sulawesi macaque species

1980 Speciation in Macaca: the view from Sulawesi. In Donald D. Lindburg (ed) The Macaques: studies in ecology, behaviour and evolution, pp. 84-124. Van Nostrand Reinhold Company, New York.

Hybridisation occurs on the borders between Macaca tonkeana and M.hecki , and between M.nigra and M.nigrescens . I interpreted this to mean that hecki should be reduced to a subspecies of M.tonkeana , and that nigrescens should be a subspecies of M.nigra . I would not do this today.

Juvenile macaque, hybrid between M.tonkeana and M.hecki, photographed at Biromaru, said to have been caught at Pandere.