Use of human chorionic gonadotropin in a male Pacific walrus (Odobenus rosmarus divergens) to induce rut and achieve a pregnancy in a nulliparous female.
Walrus in US zoos have a very low reproductive rate of 11 births in 80  years, and little is known about Pacific walrus (Odobenus rosmarus  divergens) reproductive biology. To address this, we initiated a program  in which detailed biological data were recorded on captive walrus. As part of  a 7-year study, 1 male and 1 female 16-year-old captive Pacific walrus were  carefully monitored with weekly serum hormone analysis, daily glans penis  smears for spermatozoa, and abdominal ultrasound for pregnancy. The female  ovulated once annually from late December through mid-January and then  exhibited 9 months of sustained elevated progesterone. This nonconceptive  estrous cycle profile is consistent with reports from wild walrus females. In  contrast, the male's seasonal rut routinely occurred in late February through  May with a serum testosterone peak in March. This profile differed from the  reported adult male cycle in wild walrus of November through March. During the  period of the female's ovulation, the male had nadir testosterone levels and  was consistently azoospermic. Likewise, during the male's spermatogenic rut in  the spring, the female was anovulatory with elevated progesterone. On this  basis, the male was treated for 14 weeks with human chorionic gonadotropin  (hCG) in an attempt to increase testosterone levels in synchrony with the  female's annual ovulation. The treatment successfully induced rut  characterized by sustained elevated serum testosterone levels and production  of spermatozoa. The male and female successfully bred, and the female became  pregnant. Upon discontinuation of hCG treatment, the male resumed baseline  testosterone levels. We theorize that the lack of synchronization of rut and  ovulatory cycles is a primary reason for reproductive failure in these captive  walrus.
Six Flags Discovery Kingdom, 1001 Fairgrounds Dr, Vallejo, CA 94589, USA. holley@muraco.biz
Holley S
HS
Muraco
Leah D
LD
Coombs
Dianna G
DG
Procter
Paul J
PJ
Turek
Michael J
MJ
Muraco
D000818:Animals; D000836:Animals, Zoo; D053713:Azoospermia / Q000097:blood / Q000188:drug therapy / Q000503:physiopathology / Q000662:veterinary*; D015415:Biomarkers / Q000097:blood; D006063:Chorionic Gonadotropin / Q000008:administration & dosage*; D030762:Estrous Cycle; D005260:Female; D005303:Fertility Agents, Male / Q000008:administration & dosage*; D006801:Humans; D008297:Male; D010060:Ovulation; D010298:Parity / Q000187:drug effects*; D011247:Pregnancy; D011374:Progesterone / Q000097:blood; D027724:Reproductive Techniques, Assisted / Q000662:veterinary*; D013076:Sperm Count / Q000662:veterinary; D013091:Spermatogenesis / Q000187:drug effects*; D013739:Testosterone / Q000097:blood; D016216:Ultrasonography, Prenatal / Q000662:veterinary; D014856:Walruses / Q000097:blood
D015415:Biomarkers; D006063:Chorionic Gonadotropin; D005303:Fertility Agents, Male; D013739:Testosterone; D011374:Progesterone