Circulating Gestational Progesterone and Estradiol Concentrations, Parturition, and Placental Descriptions of Two Beluga Whales (Delphinapterus leucas)
Paul P. Calle, VMD; Robert A. Cook, VMD; Catherine McClave, BS; Shelagh Palma,
BS, AAS
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.