Squirrel Monkey Reproduction: The "Fatted" Male Phenomenon and Seasonal Spermatogenesis

Records of reproduction in a Miami colony of squirrel monkeys living in a seminatural state and of monkeys in the field indicate that the male undergoes an annual testis cycle. The spermatogenic phase is associated with the seasonal acquisition of a secondary sexual characteristic which we have termed the "fatted" condition. Body weights, measurements of subcutaneous fat, and testicular histology studied over a 12-month period further establish this cycle. Climatological analyses suggest that this cycle is associated with the precipitation cycles of the respective environments.