Pull a loaded sled and the weight wants to tip you over backward. For a dog, the fix is to carry that weight lower, and Arctic sled dogs appear to have been built that way.
A team led by Kletzerman measured five long bones in 60 canids, including sled dogs, wolves, village dogs and spitz breeds. Relative to overall body size, sled dogs had a radius, ulna and tibia about 6 percent shorter than the others, Earth.com reports. The team modeled what that buys. Halve the height of the center of mass and you roughly double the pulling force available before the dog tips backward.
The old bones agree. The team scored 82 loose bones and three deliberately buried dogs from three sites on the Chukchi Peninsula, across the Bering Strait from Alaska. Eighty-nine percent matched the sled dog pattern, and all three buried dogs did too.
Nobody thinks prehistoric Arctic communities bred for short legs on purpose. Kletzerman’s reading is that dogs which pulled better kept pulling, and their descendants stayed in the team. Most of those bones were loose, so each score is a probability rather than a verdict.
What this means for your dog: if your dog pulls, where the load sits matters more than how strong he looks. A fitted harness with a low, straight line of pull lets a dog drive off the back end instead of fighting to stay upright, whether he weighs 15 pounds or 70. If you add weight to a pack, keep it low and snug, because a high, loose load is the thing that tips a dog. Our guide to dog boots before the first freeze covers winter fit, and the same rule applies: nothing strapped on should change how the dog stands.