Sex-specific energetics of Pacific walruses (Odobenus rosmarus divergens) during the nursing interval

Physiological and Biochemical Zoology
By: , and 

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Abstract

Habitat use and activity patterns of Pacific walruses (Odobenus rosmarus divergens) have changed with climate-induced reductions in sea ice. Increases in the time active in water could result in negative energy balance, precluding females from sustaining lactation, which could impact population demographics. Little is known about lactation costs in walruses. We examined the energetics of 0–2-yr-old walrus calves by using Bayesian hierarchical models based on longitudinal husbandry records of growth (n = 6 females and 7 males) and caloric intake (n = 5 females and 6 males) as a proxy for maternal lactation costs. Males and females had similar growth patterns; mean mass increased from 68 kg at birth to 301 kg by 2 yr. Females had a 2,000 kcal kg−1 higher mass storage (growth) cost than males; females typically synthesize and deposit greater amounts of adipose, which is more energy dense than lean tissue. In contrast, males had higher metabolic (basal and activity) costs, ranging from 600 to 1,800 kcal d−1 greater than similarly sized females; males are typically leaner, and muscle is more metabolically active than adipose. Yet total daily energy requirements (storage plus metabolic components) were similar across sexes, summing to approximately 190,000 kcal over the first month postpartum. Based on these estimates and assuming that 8,103 kcal is recovered from 1 kg of mass loss in adult female walruses, suckling calves could deplete 23 kg of their mother’s body mass over the first month after parturition if none of the lactation costs is met through ingested prey.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Sex-specific energetics of Pacific walruses (Odobenus rosmarus divergens) during the nursing interval
Series title Physiological and Biochemical Zoology
DOI 10.1086/685454
Volume 89
Issue 2
Year Published 2016
Language English
Publisher University of Chicago Press
Publisher location Chicago, IL
Contributing office(s) Alaska Science Center Biology MFEB
Description 17 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Physiological and Biochemical Zoology
First page 93
Last page 109
Online Only (Y/N) N
Additional Online Files (Y/N) N