Abstract

Limited information exists on the reproductive biology and growth and development of beluga whales (Delphinapterus leucas). Accurate information regarding length of gestation, delivery presentations, and growth and development at known ages over time from belugas in the wild is impossible to obtain. The data that is available on animals in wild populations cannot be accurately interpreted due to lack of known age reference points. Since August, 1992, SeaWorld San Antonio, San Antonio, Texas has had fifteen beluga calves born. From those births, we have developed a better understanding of the length of gestation, delivery presentations, and growth and development.

The earliest known age of initiation of a successful pregnancy in a beluga whale is 5 years and 9 months. Gestation (based on serum progesterones and progesterone metabolites in urine) ranges from approximately 435 days to 491 days. Deliveries have been quick and uneventful as well as extended requiring physical assistance. Dystocia (abnormal labor or delivery) in beluga whales does not appear to be an uncommon condition.

The following table compares various stages of parturition in hours as well as time elapsed from delivery to observed nursing. The observations are in hours and minutes.

Causes of pregnancy failure and neonatal mortality are varied. Loss of calves due to abortion or preterm delivery has been identified in two cases. In one of these instances, twin male fetuses measuring 96.5 cm long and weighing 13.6 and 12.5 kg were delivered. Whaling records archived in Barrow, Alaska did not indicate any multiple fetuses in 100 pregnant belugas examined between 1990 and 1995, suggesting that multiple fetuses in belugas are rare.

Two other pregnancies have resulted in delivery of non-viable calves. One full-term calf with immature pulmonary development was delivered in a fresh state. One calf was delivered in an autolytic condition suggesting in utero death with subsequent abortion. No cause was determined.

Delivery associated mortality has occurred in two beluga calves. One case was due to large fetal size and malposition, and the second due to an elongated umbilicus with fetal entanglement and subsequent vascular occlusion.

One case of a congenital malformation was observed. This case involved a one day old calf from a multiparous dam. On necropsy examination, an atrial septal defect was identified in the heart.

Neonatal mortality from infectious diseases has occurred in two calves at less than five days of age. In both instances, failure of passive transfer has been considered a predisposing factor.

From our observations, it appears that the average range for birth weight is 55 to 65 kg and a length of 150 to 163 cm, with 64 kg and 155 cm observed most often. The smallest surviving calf weighed 53.6 kg and was 140 cm long. The average weight gain through the first 180 days was approximately 0.32 kg/day. In calves less than 200 days old, their gain in length ranged from 0.15 to 0.24 cm/day. Overall growth rate in calves greater than 800 days of age was 0.2 kg/day and 0.1 cm/day. The youngest age we have seen a beluga conceive was 5 years and 9 months. Gestation ranges from 435 to 491 days. The calves were first noted to consume solid food from 172 to 328 days of age.

Acknowledgements

I want to extend my appreciation to all the Animal Care and Training staff at SeaWorld San Antonio for the many hours spent observing the calves and collecting data. I also want to thank Dr. Judy St. Leger for her input and direction in the preparation of this paper.