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Living at the extremes –
physiological adaptations of Inuit Sled Dogs in Greenland
by Nadine Gerth, Dept. Biology, University of Munich, Germany
Inuit Sled Dogs kept under traditional husbandry conditions in Greenland experience tremendous seasonal changes in living conditions. In winter and spring, teams of 3 to 20 dogs pull heavy wooden sledges in fan hitch formation. During this time they are fed regularly. In summer and fall the dogs remain chained to the rocks and are fed only 1-3 times per week. During this inactive period they often are heavily infested with intestinal parasites such as the northern dog hookworm, ascarids (roundworms), and tapeworms. (Endoscopic exams of the same dogs in winter found hardly a single worm even though parasiticides were not given.) Feeding conditions, lack of exercise and parasite infestation result in marked seasonal differences of up to 30% in body mass.
A fascinating aspect is that Inuit Sled Dogs switch from resting to heavy work without an obvious training period. In contrast, human athletes would have to train for weeks when aiming to reach a similar level of performance as Inuit Sled Dogs during winter. Therefore, we think that Inuit Sled Dogs provide an excellent model system to study the ceilings of exercise physiology, of energy metabolism, and seasonal up-and-down regulation of the internal working machinery of a midsized mammal. Ultimately, understanding Inuit Sled Dog physiology might help to understand why humans are so different and why athletes have to train so hard.
In 2005, I joined an international team around Prof. Dr. J. Matthias Starck at the University of Munich (LMU), Germany, to conduct my Ph.D. work on adaptations of Inuit Sled Dogs to changing external conditions. Other team members are: Dr. Sue Jackson, University of Stellenbosch, South Africa and Dr. vet. med. Steffen Sum, University of Georgia, USA. The project "Feeding and fasting, resting and exercise under extreme climatic conditions" has been funded by the German research council and has received logistic support from the Alfred-Wegener-Institut, Bremerhaven, Germany. Central theme of the project is the question how Inuit Sled Dogs cope with changing external conditions and which parameters of their physiology and anatomy are modified to optimize the adjustment to the current condition. My special research topic is how muscle size and structure change in adjustment to different work load, energy demand and fuel supply.
In summer 2005 and winter 2006, we went to the Arctic Station of the University of Copenhagen at Qeqertarsuaq, Disko Island (69°15`N, 53°32`W) West Greenland. There, we studied two teams of sled dogs kept by locals. In summer 2007, the project was moved to Qaanaaq, the northernmost community in Greenland. There, hunting of large mammals and traditional dog husbandry are still alive. We have access to three active dog teams of professional hunters who go out on week-long hunting trips to the north. In addition, we were able to screen dogs of other teams.
We use exclusively non-invasive or minimally-invasive methods (ultrasonography, respirometry, bio-impedance analysis, food input-output relationship, and micro-biopsy of muscle tissue) to repeatedly measure the same individuals. Key equipment in the project is a portable high-end ultrasonography unit that allows us to measure muscle size, different organ sizes and heart function without any impairment of the dogs. Our non-invasive and minimally-invasive methods warrant that our research does not affect the performance of the dogs.
To quantify how much energy an animal is using for maintenance and/or activity, one can measure the amount of oxygen consumed by an individual. For such measurements, we use a system that was originally designed for human athletes but has been modified by our team to measure dogs. In addition, we measure the input (food) - output (feces) relationship which allows us to determine how much of the energy contained in the food is actually utilized by the dogs. Putting these two measures in relationship ultimately allows us to see if the dogs are in a positive, neutral or negative energy balance.
The heart and blood circulation do not only drive the energy metabolism of an animal, they also serve to distribute oxygen and nutrients in the body to places where they are required. Therefore, we measure not only heart rate (with an external monitor unit as used by human athletes), but also perform a full echocardiographic exam.
In three seasons we have studied more than 60 dogs with different levels of detail. All dogs adapted quickly to the procedures and actually enjoyed the additional attention they received. Our future plans are returning to Qaanaaq during the hunting season in early spring 2008 to actually study "our" dog teams in full action. We are grateful for the hospitality our project receives from the Qaanaaq community, enthusiastic about working with Inuit Sled Dogs, and are looking forward to an exciting winter season.
Contact: Nadine Gerth (email@example.com) or Dr. Matthias Starck (firstname.lastname@example.org)