What accounts for the vastly different energy levels in different species?

Dude, hang out with a two year old for a little while. Kids’ main mode of ambulation seems to be running. I’m not sure why that changes we become adults, though.

This article from Cornell says: In both endothermic and ectothermic animals, the normal metabolic rate is inversely related to body size; the smaller the organism, the higher the relative metabolic rate——that is, the higher the metabolic rate per gram of body tissue.

So mice and squirrels—and notably children!—seem to have boundless energy because of a higher metabolic rate, while elephants don’t get around as much. But take heart in your stately lethargy: longevity seems roughly inverse to basal metabolic rate of the species—we sluggards live longer than mice.

“Energy” here is in the informal sense of “motion.” This is not the strict usage that a physicist uses for that word (though it indeed takes caloric energy to be energetic). Obviously the organism’s nervous system has to be organized to support behaviors involving continuous movement, but metabolic rate is ultimately the constraining throttle.

@nikipedia Hahaha, good point.
@gasman Interesting, thank you!

How about diet? We’re not exactly eating our ideal diet, at least not most of us (myself included, sitting here chomping down on Chinese food). Lifestyle is also probably part of it. We’re sedentary.

Either way, take a look at existing hunting and gathering peoples. It’s fairly common for adults in those cultures to walk ten miles or so a day. Play continues throughout life.

I’d say it’s not a matter of being more energetic, but seeming to be more energetic.

@incendiary_dan True, I once heard a report, I think it was on NPR, about how humans are actually better adapted for long distance travel than any other animal. Better than horses, even. I can’t imagine being able to go farther than a horse, but my lifestyle could use a lot of improving. Perhaps it is as @bob_ said, and we just use our energy differently. Toy dogs’ energy manifests in overwhelmingly frantic bursts; perhaps we just use our energy at a slower rate.

@Mariah There was an experiment done with long distance runners to see if they could chase down an antelope until it was exhausted. They almost got it, but to be fair none of them were hunters.

It seems our ability to endure gives us a certain edge over animals that are fast but wear themselves out. Plus, we can transport water, which is always good.

Dogs are carnivores. If their prey doesn’t come from a can, they need to be energetic. They even need play before doing the real thing.