Abstract 10.1002/zoo.1430100608.abs Between February 22 and August 10, 1986, 200 h of systematic observation were conducted on a male and female golden monkey (Rhinopithecus roxellana) at Seattle’s Woodland Park Zoo and Portland’s Washington Park Zoo. The pair was moved to Portland on May 6, and on July 24 the female unexpectedly gave birth to a male infant, the first such birth in the United States. Dramatic behavioral changes occurred immediately after the pair was moved to Portland, the midpoint of the female’s pregnancy, including the disappearance of sexual behavior and a sharp decline in time spent in contact. Explanations for these changes are discussed.