Zoo residents Cubby and Takoda are helping scientists learn how bears get around
Not all walking is created equal.
Fleet-footed mammals like horses, deer and wolves travel with heel-up gaits to increase their speed and support long-distance travel. But the world's first mammals actually stood with their heels flat on the ground — a positioning called "plantigrady."
Flat-foots are far less studied than their tiptoe counterparts, and scientists are now trying to understand them by looking at a few living plantigrades: the bears.
"You would think we'd understand how and why animals move by now, but we really don't."
—Craig McGowan, Ph.D.
"You may notice that when bears walk they rotate their foot inward," said Katie Shine, whose paper on grizzly bear locomotion appeared last summer in the Journal of Experimental Biology.
By measuring the force of four grizzly bears from Washington State University's Bear Center as they stepped across a runway equipped with sensors, Shine found that the grizzlies' unusual wrist motion and limb anatomy cause their feet to push outward as they move — not what you would expect for an animal of a bear's stature.
"Most animals that stand up straight don't seem to be pushing out at all," Shine said.
This could be related to grizzlies' dirt-digging lifestyle, but Shine can't be sure. To find out, she and her Ph.D. adviser, University of Idaho biologist Craig McGowan, recently traveled to the Oregon Zoo, where keepers helped them lead black bears Takoda and Cubby through the same walking trial as Washington State's grizzlies. They're hoping to put polar bears to the test as well.
"We want to see whether this is just a grizzly bear thing or a general bear thing too," said Dr. McGowan, who has been studying animal movement for nearly 20 years. "You would think we understand how and why animals move by now, but we really don't."
McGowan, who has looked at energetics and movement in everything from wallabies to emus, thinks Shine's research on bears could lay some of the groundwork for understanding the evolution of flat-footed locomotion as a whole — badgers, civets and mongooses included. There's a lot of future research to be done in this field.
"Locomotion is a fundamental aspect of survival in all animals," Shine said. "It's required for finding food, catching prey, avoiding predators and finding mates. Determining the way animals move can help us to understand how they utilize their habitats to perform these required behaviors. In bears, there are only eight living species, but they occupy a wide range of ecological niches, and therefore by studying the way they have evolved to move in these different habitats, we can help to understand how their ecosystems need to be preserved to maintain their natural locomotor patterns."
Oregon Zoo conservation and research manager Nadja Wielebnowski agrees.
"As the climate changes around them, the availability of food and the distances bears must travel to get it may be altered," Dr. Wielebnowski said. "Researchers in the field are trying to get a handle on energy costs of wild bears to help estimate what conservation challenges they may be facing."