Meinwald, J.; Boriack, C. J.; Schneider, D.; Boppré, M.; Wood, W. F.; Eisner, T.: Volatile Ketones in the Hair-pencil Secretion of Danaid Butterflies (Amauris and Danaus). Experientia: interdisciplinary journal for the life sciences 30, pp. 721 - 723 (1974)
Scientists studying a rare population of tool-using chimpanzees have found that aging can have a profound impact on their abilities—but not all chimps decline equally.