Evol Ecol Res 5: 1103-1109 (2003)     Full PDF if your library subscribes.

How supplemental food may induce abnormality

in wild Japanese macaque populations

Jin Yoshimura,1,2,3* Takayuki Fujiki,1 Takahisa Kawai1 and Hiroyasu Amagai1

1Department of Systems Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu 432-8561, Japan,  2Department of Environmental and Forest Biology, College of Environmental Science and Forestry, State University of New York, Syracuse, NY 13210, USA and 3Marine Biosystems Research Center, Chiba University, 1 Uchiura, Amatsu-Kominato, Chiba 299-5502, Japan

Address all correspondence to Jin Yoshimura, Department of Systems Engineering, Shizuoka University, 3-5-1 Johoku, Hamamatsu 432-8561, Japan.
e-mail: jin@sys.eng.shizuoka.ac.jp


Food has been supplied to many wild Japanese macaque (Macaca fuscata) populations in Japan since the 1950s. Since then, the monkeys have often exhibited various physical abnormalities such as anomalies and malformation of the limbs and other body parts. No conclusive explanation exists for these anomalies. Here we propose a new population-level hypothesis: feeding relaxes selection intensity such that abnormal babies tend to be born and survive to adulthood. We build a discrete population dynamic model and use it to simulate successfully the macaque population of Mt. Takasaki. Contrary to our usual intuition that a bad effect is caused by a bad factor, in some situations frequent abnormalities could be caused by the shift to a good environment.

Keywords: abnormalities, feedings, Japanese macaque, selection intensity.

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