Dogs have evolved to chase prey, cats to creep

Washington, Dec 4 : While dogs depend on an energy-efficient style of running over long distances to catch their prey, cats seem to have evolved with profoundly inefficient gait to creep up on their mouse in slow motion, say researchers.

Although it is believed that efficiency is what matters in evolution, Daniel Schmitt, associate professor of evolutionary anthropology at Duke University, suggests that there are some animals that need to operate at high energy cost and low efficiency, just like the cats.

During the study, the researchers looked at six housecats moved along a 6 yard-long runway in pursuit of food treats or feline toys.

They found that long-distance chase predators like dogs can reduce their muscular work needed to move forward by as much as 70 percent by allowing their body to rise and fall and exchanging potential and kinetic energy with each step.

However, the maximum for cats is about 37 percent and much lower than that in a stalking posture.

"An important implication of these results is the possibility of a tradeoff between stealthy walking and economy of locomotion," said the researchers.

"These data show a previously unrecognized mechanical relationship in which crouched postures are associated with changes in footfall pattern, which are in turn related to reduced mechanical energy recovery," they added.

The team found when cats slink close to the ground they walk in a way that "the movements of their front and back ends cancel each other out," Schmitt said.

While that's not good for energy efficiency "the total movement of their bodies is going to be even and they'll be flowing along," he added.

"If they're creeping, they're going to put this foot down, and then that foot down and then that one in an even fashion. We think it has to do with stability and caution," Schmitt said.

Walking humans recover as much energy as dogs, said Schmitt, who studies gaits of various mammals.

"Our centres of mass rise and fall when we walk. And when we do that, humans and other animals exchange potential and kinetic energy. It's an evolutionary miracle in my view."

"But cats need to creep up on their prey. Most scientists think that energetic efficiency is the currency of natural selection.

"Here we've shown that some animals make compromises when they have to choose between competing demands, " he added.

ANI