I was walking through San Francisco yesterday, trekking up and down our famously arduous hills and got to wondering: is it this hard for all animals? For example: does a dog have to expend that much extra energy to climb a hill? How about a snake? A caterpillar? An ant? I can’t shake the suspicion that this is an incredibly stupid question, so feel free to mock me as you see fit.
Would it necessarily cost more energy to go uphill than to go downhill or stay flat, since you have to fight gravity in addition to moving forwards? I can’t imagine that any animal - or any thing for that matter - would have it easier going uphill.
Now, there might be degrees of difficulty between different animals. But that seems to be a different question.
That’s supposed to be “Wouldn’t it.” Duhr.
(bolding mine)
My question isn’t whether traveling uphill would be easier, per se, but whether it would actually be harder. So, in plain English, I suppose the question is: is there any animal which does not require additional energy to travel uphill? The more I ask it, the stupider it sounds, too.
I don’t think that there is any getting around the fact that it takes ‘work’ to raise something in height. But I think you’re on the right track that something like an ant, with a very high strength to weight ratio would probably not notice a huge difference in the effort needed to walk uphill. Ants can walk straight up a wall and don’t seem to go much (if any) slower than on level ground.
Anecdotal evidence — my dog gets tireder much faster on walks if we include hills. It’s fairly obvious / almost exaggerated on steep hills that she has to lean way forward and drive her little legs harder to keep moving at her normal pace.
Unless the animal is really inefficient at walking on level surfaces, it will almost always cost more energy to go uphill, since you’re increasing your gravitational potential energy, and that energy has to come from somewhere.
However, there’s also the question of how difficult it is, which is different from the question of how much energy it takes. I’ve heard that some cats can actually run uphill easier than they can run downhill, due to the way their legs are set up (if they tried to run downhill, they would be likely to trip, tumble, or have some other such mishap).
Balloon-like creatures would have no problems going uphill. Unfortunately, not everyone believes they could evolve on Earth.
The haggis.
I’d suspect even they would end up obeying the laws of thermodynamics. Whatever they use to generate buoyancy would require a lot of energy to create and maintain. Of course, once they do this by generating methane or hydrogen, they’ll have a very easy time floating around.
As has been noted, physical laws dictate that going uphill requires energy. But that energy need not come from the animal. A good example would be a circling hawk, which gets the needed energy from rising air.
In response to the OP: it is not harder for a hawk to go “uphill”.
Richard Adams, in watership Down, hasome wonderful little piece about how it’s harder for a man to haul that “walking tower of flesh” uphill along a direction that most of his mass isn’t moving, and keeping it upright, while for a rabbit it’s easier to propel the its mass uphill along the direction it’s concentrated (and with powerful legs pushing it).
No. The mountain haggis (which comes in two different breeds that aren’t cross-fertile, haggis montis dexteris and haggis montis sinistris) is adapted to travelling around mountains, not straight up or down. They have to spiral; if they tried to go straight up, they’d topple over to left or right, the short-legged side.
Assuming you understood Mr. Adams, could you explain the bit about going “uphill along a direction that most of his mass isn’t moving”? 
Most of a human’s body is a vertical tower. In order to move in the direction of your mass, you’d have to be jumping up (or dropping down). But we don’t – we propel ourselves along a direction mostly perpendicular to the direction our flesh is laid out along.
Rabbits are built horizontal, and push themselves forward , mostily in the direction their bulk is already facing.
Or to look at it another way, in humans the point of propulsion is under the centre of mass; in a rabbit, it’s behind the centre of mass. Whether Adams’s explanation makes mechanical sense is open to debate, but that’s what he meant.
don’t know who’s Richard Adams, but it sounds like center of gravity to me. like running with a rock in your hand vs a long pole of the same weight held straight up.
He’s the author of Watership Down, a moderately famous novel about rabbits.
If you had a dog with forelegs half the length of its hindlegs, could it walk up a 45 degree hill roughly as easily as a normal dog could walk along a flat surface?
IIRC, he goes on to say that rabbits have difficulty running downhill as their long back legs mean that they have a tendancy to go head over heels.