(A) The location of Dzanga Bai in Central Africa. (B) Dzanga bai, showing the location of the observation platform and bisecting stream. The stippled areas could not be seen from the platform. (C) Observation days per year during the 20-yr study. (D) The distribution of days between successive sightings of identified adults. For females (open bars; 49,235 intervals) median=3, mean=42, max=15.5 yrs. For males (black bars; 21,843 intervals) median=4, mean=64, max=16.8 yrs.