My studies of primates: Sex, affinity, and competition

Abstract

In this essay, I summarize my research career, with reference to the early days of the Laboratory of Physical Anthropology (LPA) at Kyoto University led by Kinji Imanishi and Junichiro Itani. When I started conducting research on the sexual behavior of Japanese macaques in 1975, I made some unexpected observations. High-ranking males did not obtain high mating success. Estrous females often rejected the courtships of high-ranking males and chose to mate with lower-ranking males. Some male–female dyads exhibited long-lasting affinitive relations, but they avoided mating. Females frequently showed ‘excessive’ sexuality. Clear explanations for some of these observations do not exist. After that, I changed my study subjects several times from chimpanzees, Yakushima macaques (a subspecies of Japanese macaque), and ringtailed lemurs. It is difficult to summarize my findings into a consistent story. Instead, I review my research and experiences. Throughout my career, I kept two things in mind. The first was established by Imanishi at the Laboratory of Physical Anthropology at Kyoto University: to explore the evolution of human society. Second, I tried to understand seemingly incomprehensible phenomena using evolutionary theory. Despite adhering to these foundational concepts, things did not always work out as planned.

Anthropogenic Pressures on Gorillas: A Case of Grauer’s Gorillas in Maiko National Park, the Democratic Republic of Congo

“…Large-bodied, slow-breeding mammals like gorillas are more likely to disappear in severely disturbed areas than smaller and faster-reproducing species. For the Grauer's gorillas, survival prospects worsen, adult-adult playful interactions are reduced, and their sexual behaviors or affinity are affected by increasing human disturbances [55,56]. Because of that, the Grauer's gorilla population, numbers of sexually mature individuals, and geographic ranges have decreased [57].…”