[MARMAM] New Publication on Pacific Walrus Reproduction

Holley Muraco holleymuraco at yahoo.com
Wed Jan 4 16:24:41 PST 2012

Dear All


The following paper has been e-published ahead of print in the Journal of
Andrology. Contact: holley at muraco.biz


Title: Use of Human Chorionic Gondadotropoin in a Male Pacific Walrus

rosmarus divergens) to Induce Rut and Achieve a Pregnancy in a Nulliparous


Authors: Holley S. Muraco, Leah D. Coombs, Dianna G. Procter, Paul J. Turek,

Michael J. Muraco


Published-Ahead-of-Print on December 29, 2011 by Journal of Andrology

Copyright 2011 by The American Society of Andrology



Walrus in United States 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 seven year study, one male and one 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 nine months of
sustained elevated

progesterone. This non-conceptive 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.

Based on this, the male was treated with 14-weeks of 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

the reproductive failure in these captive walrus. Key Words: endocrinology,

reproduction, testosterone, progesterone, ultrasound




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