Facets of the reproductive biology of wild cetaceans are often inferred from observations on the presence or absence of calves ' from the examination of beached/ stranded animals or from animals taken directly or indirectly in fisheries. Reproduction by cetaceans in captivity provides a unique opportunity to document the behavioral and physiological aspects of reproduction that are difficult or impossible to study in the field.

The killer whale reproductive program at the several Sea World parks includes biweekly to monthly blood sampling to document progesterone levels and daily observation of reproductive behavior. The progression of a pregnancy is also documented with ultrasound examinations and biweekly body measurements of the pregnant female. A round the clock behavior watch is initiated about 1 month prior to estimated date of parturition.

Since 1985, 7 (6 full term) killer whale calves have been born to 4 different females. Mean gestation time was 515 +/- 7 days. 5 calves were born head-first and 2 tail-first. Delivery ranged from 1 to 3 hours. The placenta was passed 3-12 hours post-partum. Five calves began consistent nursing 3-9 hours post-partum and started taking solid food at 2-3 months. The overall nursing patterns of different calves are similar. The pattern of progesterone levels was similar for all pregnancies, although progesterone levels differed between females and between successive pregnancies in the same female. Five of the 6 fullterm. calves are still alive. The sixth was stillborn.