Blood samples were obtained on an irregular sampling interval in 1990 and 1991 from two pregnant beluga whales (Delphinapterus leucas) housed at The Aquarium for Wildlife Conservation, Brooklyn, New York, USA. Samples were opportunistically collected utilizing a trained fluke presentation behavior or obtained in conjunction with physical restraint for medical procedures. The whales were eleven and twenty two years old at parturition. The younger whale was nulliparous and the older one was a primiparous female which had delivered a healthy calf ten years previously. The sire was twenty one years old and had sired the calf born ten years earlier.

Serum or plasma samples were analyzed by radioimmunoassay for progesterone and estradiol concentrations by a veterinary diagnostic laboratory (New York State College of Veterinary Medicine, Endocrinology Laboratory, Ithaca, New York 14851-0786, USA). Due to the irregular sampling interval, precise gestation lengths could not be determined, but were estimated to be between fifteen and sixteen months. Progesterone values peaked (60-66 ng/ml) in the first four months, declined to a plateau in the middle half of gestation (7-24 ng/ml), and decreased again in the last four months (6-9 ng/ml); one week prepartum the older female had a circulating progesterone level of 6 ng/ml; 28 days postpartum her progesterone levels were undetectable. These gestational progesterone values are similar to those of other pregnant beluga whales (Dr. Jim McBain, personal communication). Estradiol levels rose through the first four months of gestation and reached peak values (30-31 pg/ml) in the second quarter of gestation. Circulating estradiol values remained elevated in the latter half of gestation (14-22 pg/ml). The estradiol levels had declined to 6 pg/ml 28 days postpartum in the older female.

Late gestation and the prepartum period were characterized by progressive enlargement of the abdomen, mammary glands, and nipples. Fetal movements, spraying of milk from the mammary glands, increased defecation, partial anorexia, and occasional rubbing of the urogenital slit on the pool bottom were also observed. Abnormal arched back postures, which were thought to reflect uterine contractions, were noted one week prepartum in the older whale.

Healthy male calves were born one week apart (7 & 14 Aug. 91). Both calves were dorsosacral posterior presentations. Labor lasted 2 hrs and 16 min. in the younger whale and 12 hrs and 30 min. in the older whale. Birth and the immediate postpartum interval were accompanied by moderate hemorrhage from the urogenital slit in the older whale while the younger whale exhibited minimal hemorrhage.

The placentas were passed intact at seven hours and thirty minutes, and seven hours and forty five minutes, respectively, postpartum. The umbilical cords consisted of four vessels. Histologically, the placentas were classified as a diffuse epitheliochorial placentation. To date, 18 months postpartum, both calves remain with their mothers and are healthy, although the older calf experienced a neonatal illness.¹

Acknowledgements

The authors thank the trainers, especially Martha Hiatt-Saif and Kevin Walsh, and the staff of The Aquarium for Wildlife Conservation for their assistance. Drs. John Trupkiewicz and S. K. Liu performed histologic evaluation of the placentas. We also acknowledge and thank Dr. Jim McBain, Sea World, San Diego, California, USA for sharing his knowledge, experience, and valued advice with us.

References

1.  Cook, R.A.; P.P. Calle; C. McClave; S. Palma. 1992. Health care and medical problems of a captive bred and mother reared beluga whale (Delphinapterus leucas). Proc Int. Assoc. Aq. An. Med 23: 107-110.