Reproductive Hormone Levels within Captive Female Northern Fur Seals (Callorhinus ursinus) with and without Chemical Contraceptives

Northern fur seals (Callorhinus ursinus) are held in only a few institutions within the United States and the world. The Seattle Aquarium was the first institution to successfully breed and raise captive Northern fur seals from conception to adulthood. The captive group that was the focus of this study consisted of one adult male and five adult females. One female was related to the adult male and was placed on chemical contraceptives to prevent inbreeding. Another female was exposed to a chemical spill in the wild while in utero, had some health problems throughout the study period, and never became pregnant. The remaining three females were thought to be reproductively normal throughout most of the study period, although only one became pregnant and gave birth. Serum estrogen, progesterone, and testosterone levels were measured using standard competitive binding antibody radio and enzymeimmunoassay techniques. Individual animal longitudinal data are reported for samples collected over the 7-year study period. The hormone data revealed changes associated with chemical contraceptives, pregnancy, and animals becoming sexually mature and senescent.