[MARMAM] New publication-Endocrine profiling of reproductive status and evidence of pseudopregnancy in the Pacific walrus

Jenell Larsen larsenjenell at gmail.com
Tue Sep 22 19:00:15 PDT 2020

Dear MARMAM Colleagues,

My co-author and I are pleased to share with you our publication in Plos

Larsen Tempel JT, Atkinson S (2020) Endocrine profiling of reproductive
status and
evidence of pseudopregnancy in the Pacific walrus (Odobenus rosmarus
divergens). PLoS ONE 15(9):e0239218.

This publication is open access.

Endocrine profiling is an increasingly utilized tool for detecting
pregnancies in wild populations of mammals. Given the difficulty in
calculating reproductive rates of Pacific walruses (*Odobenus rosmarus
divergens*) the use of endocrine techniques for determining pregnancy rates
could be particularly useful for management of the population. The goals of
this study were to 1) determine if progesterone and total estrogen
concentrations in ovarian tissues of female walruses could be used to
determine reproductive state and 2) determine if walruses undergo a
functional postpartum estrus, as is seen in other pinnipeds. Ovaries were
collected from female walruses (n = 13) hunted in subsistence hunts by
Alaska Native communities. Females were categorized as postpartum,
full-term pregnant, pregnant diapause or unbred. Total estrogen
concentrations were greatest in unbred (n = 2) and pregnant (n = 2)
females. Progesterone concentrations were also nominally larger in unbred
(n = 2) than pregnant (n = 2) and postpartum (n = 9) animals. Small samples
sizes precluded the use of statistical comparisons among groups. Corpora
lutea tissue samples in this study did not reflect the presence of a
postpartum estrus in the month of May as postpartum females yielded lower
total estrogen concentrations than unbred or pregnant animals. Both unbred
animals were in a state of pseudopregnancy, which has not been
physiologically described for this species before. The progesterone
profiles in late (59 ng/g) and early (140 ng/g) pregnancy were lower than
expected and fell within the range of the postpartum females (36-210 ng/g),
suggesting low production of the hormone by the corpus luteum during these
phases of pregnancy. Profiling reproductive hormones in free-ranging
walruses demonstrates that an endocrine approach may be a valuable tool for
determining reproductive status of females, however increased sample sizes
and time of year must be considered to accurately separate pregnant versus
pseudopregnant individuals.

Jenell Larsen Tempel, Ph.D.
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