Michiels, N. K.; Hohner, A.; Vorndran, I. C.: Precopulatory mate assessment in relation to body size in the earthworm Lumbricus terrestris: Avoidance of dangerous liaisons? Behavioral Ecology 12 (5), pp. 612 - 618 (2001)
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.