Energy demands for maintenance, growth, pregnancy, and lactation of female Pacific walruses (Odobenus rosmarus divergens)
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Full Publication: https://doi.org/10.1086/678237Product Type: Journal Article
Year: 2014
Authors: Noren, S. R., M. S. Udevitz, and C. V. Jay
Suggested Citation:
Noren, S. R., M. S. Udevitz, and C. V. Jay. 2014. Energy demands for maintenance, growth, pregnancy, and lactation of female Pacific walruses (Odobenus rosmarus divergens). Physiological and Biochemical Zoology 87(6). doi:10.1086/678237
Abstract
Decreases in sea ice have altered habitat use and activity patterns of female Pacific walruses Odobenus rosmarus divergens and could affect their energetic demands, reproductive success, and population status. However, a lack of physiological data from walruses has hampered efforts to develop the bioenergetics models required for fully understanding potential population-level impacts. We analyzed long-term longitudinal data sets of caloric consumption and body mass from nine female Pacific walruses housed at six aquaria using a hierarchical Bayesian approach to quantify relative energetic demands for maintenance, growth, pregnancy, and lactation. By examining body mass fluctuations in response to food consumption, the model explicitly uncoupled caloric demand from caloric intake. This is important for pinnipeds because they sequester and deplete large quantities of lipids throughout their lifetimes. Model outputs were scaled to account for activity levels typical of free-ranging Pacific walruses, averaging 83% of the time active in water and 17% of the time hauled-out resting. Estimated caloric requirements ranged from 26,900 kcal d-1 for 2-yr olds to 93,370 kcal d-1 for simultaneously lactating and pregnant walruses. Daily consumption requirements were higher for pregnancy than lactation, reflecting energetic demands of increasing body size and lipid deposition during pregnancy. Although walruses forage during lactation, fat sequestered during pregnancy sustained 27% of caloric requirements during the first month of lactation, suggesting that walruses use a mixed strategy of capital and income breeding. Ultimately this model will aid in our understanding of the energetic and population consequences of sea ice loss.
Keywords: Pacific walrus, climate change, sea ice loss, energetics, foraging
Annotation
Decreases in sea ice have altered habitat use and activity patterns of female Pacific walruses and could affect their energetic demands, reproductive success, and population status. Pregnant and lactating female walruses have increased energetic demands, some of which may be met by fat reserves deposited prior to reproduction. This increased energetic demand prior to and during reproduction may make female walruses especially vulnerable to changes in sea ice and access to foraging grounds.