What Can We Learn From Sled Dogs?

This is why I love reading the NY Times Science pages. Tuesday's issue has an article that describes how the Defense Advanced Research Project Agency (DARPA) is studying sled dogs to find out why the heck they don't collapse with fatigue despite maintaining an extended caloric burn rate that puts Tour de France cyclists to shame.

Researchers Seek to Demystify the Metabolic Magic of Sled Dogs

The dogs endurance abilities are legendary, but even so the details are staggering: when competing in the Iditarod, a multi-week trek over 1100 miles of Arctic trail, the dogs burn 240 calories per pound per day, 2.4 times the metabolic burn rate Lance Armstrong maintains when touring the Pyrenees, and yet somehow they do not exhaust their reserves of fat and glycogen.

Dr. Michael Davis that there is a biological "switch" that the dogs turn on that makes them such great athletes on the trail. He also believes that other species might have the same ability to activate this switch.

"They have a hidden strategy that they can turn on," he said. “We are confident that humans have the capacity for that strategy. We have to figure out how dogs are turning it on to turn it on in humans."

Or is it possible the dogs are just more motivated than other species?

As I read, I couldn't help remembering the incredible passage from Jack London's "Call of the Wild," describing a dog who kept wanting to pull the sled, even unto death:

"He pleaded with his eyes to remain there. The driver was perplexed. His comrades talked of how a dog could break its heart through being denied the work that killed it, and recalled instances they had known, where dogs, too old for the toil, or injured, had died because they were cut out of the traces. Also, they held it a mercy, since Dave was to die anyway, that he should die in the traces, heart-easy and content. So he was harnessed in again, and proudly he pulled as of old, though more than once he cried out involuntarily from the bite of his inward hurt. Several times fell down and was dragged in the traces, and once the sled ran upon him so that he limped thereafter on one of his hind legs.

But he held out till camp was reached, when his driver made a place for him by the fire. Morning found him too weak to travel. At harness-up time he tried to crawl to his driver. By convulsive efforts he got on his feet, staggered, and fell. Then he wormed his way forward slowly toward where the harnesses were being put on his mates. He would advance his fore legs and drag up his body with a sort of hitching movement, when he would advance his fore legs and hitch ahead again for a few more inches. His strength left him, and the last his mates saw of him he lay gasping in the snow and yearning toward them."

I've known runners like that.