There’s also a scaling argument you can make here. The power an animal’s muscles can generate is proportional to their cross-section, and therefore scales as the animal’s size squared, i.e. P ~ L[sup]2[/sup]. However, the power required to climb a hill at a constant velocity scales as the animal’s mass times its velocity, i.e. P ~ v L[sup]3[/sup] (since mass scales as volume.) So equating the two, we find that the velocity at which an animal can climb a hill scales inversely with it’s size, i.e. v ~ L[sup]-1[/sup].
Maybe not what the OP is asking, but I understand that cows (and several other animals) can easily climb stairs but not descend them. I am not sure exactly why this is, but here is hoping someone with better knowledge will find this interesting and explain it.
Are you sure that’s for power, not force? I can understand why force is only dependent on cross-section, but I’d think the work that can be done by the muscle is also proportional to its length.
Anyway… I think most marine animals are close to being neutrally buoyant, and therefore they can walk up a slope (underwater) just as easily as across a flat surface.
This was explained away as an urban legend quite nicely in a few recent threads:
http://boards.straightdope.com/sdmb/showpost.php?p=7498665&postcount=60
Of things not to know by someone who grew up around cows. In my defense, it was always on flat land and one storey buildings. Funny that my FIL has plenty of cows on very hilly terrain and I see them going up and down and I never thought of putting those two notions together.
Ignorance fought.