Abstract

At Six Flags Discovery Kingdom, 1.2 18-year-old Pacific walrus have been a part of a long-term reproductive research program. The study has included serum endocrinology in the pregnant and non-pregnant walrus, identification of estrus and ovulation, and monitoring the annual rut cycle of the male. Additionally, studies of reproductive behavior and vocalizations, breeding frequency, semen collection, semen cryopreservation, anatomy, and ultrasonography of fetal development have been conducted. Artificial insemination requires the appropriate procedure, timing and sperm concentration to achieve the highest probability for conception. Knowledge garnered through our intensive clinical research program led to a successful methodology for performing artificial insemination in the Pacific walrus, and so, a female at the Indianapolis Zoo became the first walrus to be artificially inseminated through a collaborative effort. The female Pacific walrus ovulates once annually in the winter months followed by 9 months of sustained elevated progesterone in non-conceptive cycles.^1,2 The male walrus experiences a 3–5 month spermatogenic rut with elevated testosterone once annually.² For the walrus artificial insemination, weekly serum estradiol was used to identify estrus and ovulation. Vaginal cytology and behavioral observations conducted at Six Flags showed that walrus do copulate outside of estrus; however there is an increase in the frequency and concentration of spermatozoa during estrus. Based on natural breeding data, inseminations were performed over three successive days during peak estradiol levels and one following the initial progesterone rise. The male walrus only produces motile sperm during rut when testosterone levels are above basal levels. Because the male walrus at Six Flags does not go into rut until spring, well after most female walrus have ovulated, his rut was pharmacologically induced in the fall to ensure adequate spermatozoa for the winter inseminations.² Sperm collection was accomplished using a voluntary urethral massage technique which enabled a collection of 300–500 million sperm for each insemination. To ensure that a transcervical insemination procedure could be performed, in-situ and ex-situ examination of the reproductive anatomy was conducted including exploratory vaginal endoscopies on trained females. The female Pacific walrus reproductive anatomy is highly unusual as the species has a duplex uterus like lagomorphs and rodents not a bicornuate uterus like other pinnipeds.¹ The insemination technique required the walrus to voluntarily lie calmly in dorsal recumbency for the duration of the average 15 minute procedure. Because ovarian ultrasonography cannot confidently confirm which ovary has the dominant follicle at this time, both cervices were catheterized when possible and sperm deposited into each uterine horn. If catheterization wasn't possible, sperm was deposited into the external cervical os. During the months following the procedure, serum endocrinology looked promising for implantation and pregnancy. Ultrasonography of the uterine horn in the fall showed a possible post-implantation fetus, however the female did not carry to term. With continued efforts, we feel confident that artificial insemination in the Pacific walrus can lead to conceptions and allow zoological managers another option for breeding the walrus.

Acknowledgements

This project would not be possible without the outstanding behavioral training conducted by the Indianapolis and Six Flags walrus teams. Special acknowledgement goes to Indianapolis trainers Lisa Oland, Mandy Goin, Kelly Tabor, Katherine Pearson and Tom Granberry and Six Flags trainers Heather Carollo, Samantha Sanford, Jessa Paschke, Jennifer Cleaner, Abby Warner, and Dianne Cameron. Thanks to the veterinary staff at The Indianapolis Zoo, Dr. Jan Ramer, Dr. Michelle, Bowman and Jennifer Niederlander; and at Six Flags Discovery Kingdom, Dr. Vanessa Fravel, Kelly Smith, Eric Calvo and Dawn Robles. Additional thanks goes to the support from Dr. Rob Shumaker VP of Life Sciences at the Indianapolis Zoo, Dale Kaetzel Park President at Six Flags Discovery Kingdom, Dr. Scott Willard, head of the Department of Biochemistry and Molecular Biology at Mississippi State University and Dr. Peter Ryan, Associate Provost for Academic Affairs at Mississippi State University.

* Presenting author

Literature Cited

1.  Fay F. 1982. Ecology and biology of the Pacific walrus, Odobenus rosmarus divergens Illiger. North American Fauna. 74: 1–285.

2.  Muraco HS, Coombs LD, Procter DG, Turek PJ, Muraco MJ. 2012. Use of human chorionic gonadotropin in a male Pacific walrus (Odobenus rosmarus divergens) to induce rut and achieve a pregnancy in a nulliparous female. Journal of Andrology. 33(5): 789–797.