[MARMAM] Extreme physiology and climate change in narwhals
williams at biology.ucsc.edu
Fri Sep 3 03:03:48 PDT 2010
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.
Terrie M. Williams
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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