Dogs chase efficiently, but cats skulk counterintuitively

Dec 03, 2008

A Duke University study suggests that evolution can behave as differently as dogs and cats. While the dogs depend on an energy-efficient style of four-footed running over long distances to catch their prey, cats seem to have evolved a profoundly inefficient gait, tailor-made to creep up on a mouse or bird in slow motion.

"It is usually assumed that efficiency is what matters in evolution," said Daniel Schmitt, a Duke associate professor of evolutionary anthropology. "We've found that's too simple a way of looking at evolution, because there are some animals that need to operate at high energy cost and low efficiency."

Namely cats.

In a report published online Nov. 26 in the research journal Public Library of Science (PLoS), Schmitt and two former Duke co-researchers followed up on a scientific hunch by measuring and videotaping how six housecats moved along a 6 yard-long runway in pursuit of food treats or feline toys.

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. In contrast, the maximum for cats is about 37 percent and much lower than that in a stalking posture, the report found.

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

In other words, they found that 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 centers 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."

Source: Duke University

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drel
4.3 / 5 (4) Dec 03, 2008
I would say in one way of looking at it the cat has a more energy-efficient style. Stalk for 30 yards (at high energy cost) and then pounce on bird vs pursue prey for miles (at low energy cost).

Bottom line question is... Who spends more of their daily lives in restful activities such as sleeping, and less time hunting? Feral dogs or Feral cats. IDK. Anyone have answer with data to back it up?
Mayday
4.6 / 5 (5) Dec 03, 2008
I think that it was quite some time ago that cats figured out that if they park themselves close to humans, then they can give up stalking, running, climbing and pouncing altogether.

Dogs have yet to achieve this intellectual breakthrough.

It doesn't take much observational analysis to see that the efficiency crown goes to the cat.
Corvidae
5 / 5 (2) Dec 03, 2008
I've heard figures in the past saying cats spend about 60-80% of their time resting. Anecdotaly they are known as some of the most efficient hunters on the planet.

I'd guess it would depend on how you look at it. Alligators and crocodiles can lay in wait using far less energy for far longer than either dogs or cats. On the other hand, reptiles are screwed in cold weather. Judging by how long they've been around though, that doesn't seem to be a huge problem for them.

Personally I'd say it just shows that energy efficiency isn't the only, and often not the most important, factor in natural selection.
earls
3 / 5 (1) Dec 03, 2008
I don't see how the same isn't true for dogs, Mayday. Though I do feel cats ARE superior to idiot dogs, I'd think humans would have domesticated dogs far before cats, simply because of their pack mentality.

Perhaps I'm misunderstanding.
GrayMouser
3 / 5 (1) Dec 03, 2008
Conversely, look at the hunting style of dogs and cats...

Dogs hunt in packs and will run down their prey. When individuals run out of energy other pack members can fill in for them.

Cats, generally, are solo predators and only run fast for short distances. And when they run out of steam there is no one (other than a compeditor) to fill in.
Roj
4 / 5 (1) Dec 03, 2008
Perhaps small cats initially got along with hungry humans & their scraps, because humans didn't find the taste of the scrawny fur balls a worth-wile meal.
nkalanaga
not rated yet Dec 03, 2008
One of the leading theories on the domestication of cats is that they domesticated themselves. Everywhere in Europe, North Africa, and the Middle East, it seems that cats started living with humans shortly after the development of agriculture. As Roj says, people don't generally eat cats, but we do raise, store, and eat grain. Rats and mice also eat grain, and are favorite foods of the cat. With a concentrated food supply, and little competition, the villages became an ideal habitat for cats. Eventually, the cats and the humans learned to like, rather than simply tolerate, each other, and we've been together ever since. One piece of evidence for this theory is that the cat is the only obligate carnivore commonly kept as a domestic animal. Wild canines do well on an omnivorous diet, similar to humans but a little higher in protein, but the cat's natural diet is almost entirely fresh meat.
Nik_2213
not rated yet Dec 03, 2008
Um, did those researchers get their cats up to full-gallop ?? One problem comparing 'apples & oranges' like this is these cats may not have had enough space to apply other gaits...

nkalanaga
not rated yet Dec 04, 2008
Or may not have wanted to. There was a study a few years back trying to determine if exercise helped a cat's heart. The problem was getting the cat to exercise. Put it in an exercise wheel, it went to sleep. Put it on a treadmill, it went to sleep. On a motorized treadmill, it fell off the end and went to sleep. Finally, they put it in a harness on a motorized treadmill. It retracted all four legs, hung in midair by the harness, and went to sleep. The conclusion was that exercise is not a natural condition for a cat, and the study was ended.
superhuman
not rated yet Dec 04, 2008
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


Allowing the body to rise and fall is not enough to save energy, this energy has to be stored in elastic tissue like tendons so that it may be reused.
So just studying the gait is certainly not enough to know the efficiency.

This might be why they he talks about maximum possible recovery not the actual recovery, but this is pretty misleading, if the energy stored is lower then 37% then both species are equally efficient.

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


Claim that humans recover as much energy as dogs is also pretty unsubstantiated, the difference in mass, anatomy and the fact that we are bipedal all have to be taken into account. Basing such claims only on the fact that we also rise and fall as we walk is laughable.

And finally *everything* that rises or falls exchanges potential and kinetic energy, even rocks, so saying its an "evolutionary miracle" implies a complete misunderstanding of physics and evolution.

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