Dear Colleagues, I would like to bring to your attention two manuscripts that were recently published on the bioenergetics and body condition of Pacific walruses.This research was undertaken in an effort to quantify important physiological parameters that will be important for incorporating into population models to predict how loses of sea ice in the Arctic may affect the sustainability of this species. I have never posted to MARMAM before.However, I felt that it was important to share these papers because they provide a template that may be modified and applied to other marine mammals that are faced with limitations in food availability.The abstracts and citations are provided below. If you are unable to access these journals, please contact me for a PDF. Best Regards, Shawn Shawn R. Noren, Ph.D. Associate Research Scientist Institute of Marine Science University of California, Santa Cruz snoren@ucsc.edu Early View for Marine Mammal Science: DOI: 10.1111/mms.12186 *Identifying a reliable blubber measurement site to assess body condition in a marine mammal with topographically variable blubber, the Pacific walrus* SHAWN R. NOREN, MARK S. UDEVITZ, LISA TRIGGS, JESSA PASCHKE, LISA OLAND, CHADWICK V. JAY Abstract Pacific walruses may be unable to meet caloric requirements in the changing Arctic ecosystem, which could affect body condition and have population-level consequences. Body condition has historically been monitored by measuring blubber thickness over the xiphoid process (sternum). This may be an unreliable condition index because blubber at other sites along the body may be preferentially targeted to balance energetic demands. Animals in aquaria provided an opportunity for controlled study of how blubber topography is altered by caloric intake. Morphology, body mass, blubber thickness (21 sites), and caloric intake of five mature, nonpregnant, nonlactating female walruses were measured monthly (12 month minimum). Body condition (mass 9 standard length--1) was described by a model that included caloric intake and a seasonal effect, and scaled positively with estimates of total blubber mass. Blubber thicknesses (1.91--10.69 cm) varied topographically and were similar to values reported for free-ranging female walruses. Body condition was most closely related to blubber thickness measured dorsomedially in the region of the anterior insertion of the pectoral flippers (shoulders); sternum blubber thickness was a relatively poor indicator of condition. This study demonstrates the importance of validating condition metrics before using them to monitor free-ranging populations. Physiological and Biochemical Zoology 87(6):837--854. 2014. *Energy Demands for Maintenance, Growth, Pregnancy, and Lactation of Female Pacific Walruses (Odobenus rosmarus divergens)* Shawn R. Noren, Mark S. Udevitz, Chadwick V. Jay 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 d21 for 2-yr-olds to 93,370 kcal d21 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.