Dogs Chase Efficiently, But Cats Skulk Counterintuitively?

I don't see that there is a puzzle here. Surely the "energetic efficiency" that "is the currency of natural selection" would apply to how much energy needs to be expended to obtain a certain amount of energy from food. This study looks at how much energy is expended per step, or per a unit of distance. However, a cat may spend more time waiting until prey comes close by, and thus have to travel a shorter distance to obtain it. So even thought each step, or each inch, might need more energy, that doesn't mean the total amount of energy used is greater.

http://www.sciencedaily.com/releases/2008/12/081203184533.htm

ScienceDaily (Dec. 4, 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.
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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.
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"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."