[MARMAM] Extreme physiology and climate change in narwhals

Terrie Williams williams at biology.ucsc.edu
Fri Sep 3 03:03:48 PDT 2010

Dear Marmamers:

We have a new, exciting manuscript online at Marine Mammal Science. In 
addition to describing the physiological limitations of a unique cryptic 
Arctic species (the narwhal), this paper presents a "Biological Achilles 
Heel" approach for assessing the vulnerability of marine mammals to 
climate change. Often we examine the behavioral response of wild animals 
and subsequently try to infer the impact of environmental perturbation. 
Here we first examine the physiological capacity of the animal and use 
it to predict the species ability to respond. Such a method enables 
investigators to predict rather than just react to the effects of 
environmental disturbance on an animal population.

The paper is online at Marine Mammal Science 26 Aug, 2010. DOI: 
and will be in print in October.

Best Regards,

Terrie M. Williams
McMurdo, Antarctica

Extreme Physiological Adaptations as Predictors of Climate-Change 
Sensitivity in the Narwhal, Monodon monoceros
Terrie M. Williams*1, Shawn R. Noren1 and Mike Glenn2

Rapid changes in sea ice cover associated with global warming are poised 
to have marked impacts on polar marine mammals. Here we examine skeletal 
muscle characteristics supporting swimming and diving in one polar 
species, the narwhal, and use these attributes to further document this 
cetacean’s vulnerability to unpredictable sea ice conditions and 
changing ecosystems. We found that extreme morphological and 
physiological adaptations enabling year-round Arctic residency by 
narwhals limits behavioral flexibility for responding to alternations in 
sea ice. In contrast to the greyhound-like muscle profile of acrobatic 
odontocetes, the longissimus dorsi of narwhals is comprised of 86.8  
7.7% slow twitch oxidative fibers, resembling the endurance morph of 
human marathoners. Myoglobin content, 7.87  1.72 g (100 g wet 
muscle)-1, is one of the highest levels measured for marine mammals. 
Calculated maximum aerobic swimming distance between breathing holes in 
ice is <1450 m, which permits routine use of only 2.6 - 10.4% of 
ice-packed foraging grounds in Baffin Bay. These first measurements of 
narwhal exercise physiology reveal extreme specialization of skeletal 
muscles for moving in a challenging ecological niche. This study also 
demonstrates the power of using basic physiological attributes to 
predict species vulnerabilities to environmental perturbation before 
critical population disturbance occurs.

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