[MARMAM] 2 Recent Publications

Shawn Noren Kramer snoren at ucsc.edu
Thu Dec 4 09:09:32 PST 2014

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 R. Noren, Ph.D.

Associate Research Scientist

Institute of Marine Science

University of California, Santa Cruz

snoren at 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*



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 

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


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.

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