Bioenergetics model for estimating food requirements of female Pacific walruses Odobenus rosmarus divergens

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 460:261-275 (2012) - DOI: https://doi.org/10.3354/meps09706 Bioenergetics model for estimating food requirements of female Pacific walruses Odobenus rosmarus divergens S. R. Noren1,*, M. S. Udevitz2, C. V. Jay2 1Institute of Marine Science, University of California, Santa Cruz, Santa Cruz, California 95060, USA 2US Geological Survey, Alaska Science Center, Anchorage, Alaska 99508, USA *Email: snoren@biology.ucsc.edu ABSTRACT: Pacific walruses Odobenus rosmarus divergens use sea ice as a platform for resting, nursing, and accessing extensive benthic foraging grounds. The extent of summer sea ice in the Chukchi Sea has decreased substantially in recent decades, causing walruses to alter habitat use and activity patterns which could affect their energy requirements. We developed a bioenergetics model to estimate caloric demand of female walruses, accounting for maintenance, growth, activity (active in-water and hauled-out resting), molt, and reproductive costs. Estimates for non-reproductive females 0–12 yr old (65−810 kg) ranged from 16359 to 68960 kcal d−1 (74−257 kcal d−1 kg−1) for years with readily available sea ice for which we assumed animals spent 83% of their time in water. This translated into the energy content of 3200–5960 clams per day, equivalent to 7–8% and 14–9% of body mass per day for 5–12 and 2–4 yr olds, respectively. Estimated consumption rates of 12 yr old females were minimally affected by pregnancy, but lactation had a large impact, increasing consumption rates to 15% of body mass per day. Increasing the proportion of time in water to 93%, as might happen if walruses were required to spend more time foraging during ice-free periods, increased daily caloric demand by 6–7% for non-lactating females. We provide the first bioenergetics-based estimates of energy requirements for walruses and a first step towards establishing bioenergetic linkages between demography and prey requirements that can ultimately be used in predicting this population’s response to environmental change. KEY WORDS: Pinniped · Foraging · Metabolism · Energetics · Arctic · Ice · Climate change Full text in pdf format PreviousNextCite this article as: Noren SR, Udevitz MS, Jay CV (2012) Bioenergetics model for estimating food requirements of female Pacific walruses Odobenus rosmarus divergens. Mar Ecol Prog Ser 460:261-275. https://doi.org/10.3354/meps09706 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 460. Online publication date: July 24, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.