What kind of circumstances came about for marsupials to evolve as hoppers? Brachiation is the most efficient form of acquiring leaves, so that unorthodox travelling style makes sense, but on the ground there are many methods of transportation to acquire vegetation, some of them much more practical than hopping. Walking is a good example. Kangaroos don’t exactly “hunt” vegetation, which is the only reason I could think of. Fleeing? Running works just as well, probably even faster and probably a bit more natural to their ancient ancestors. Does it give them any great agility for eluding predators?
I don’t think their terrain was spectacularly different from the rest of the world. So what was in Australia that made hopping a good idea? (Or do hoppers date back to Pangea?)
Evolution tends toward greater diversity, not toward any abstract ideal animal. So there’s no reason that more than one basic mode of locomotion evolved; as soon ask why fish don’t fly or bats don’t burrow.
Each has its benefits, obviously. That marsupial hoppers have a height-to-mass advantage that makes it easier to see for greater distances is one that occurs to me off the top of my head. I’m sure other could be (surely have been) posited.
For high-speed hopping, the metabolic cost of locomotion actually decreases for the animal as speed increases. This makes hopping rather efficient as locomotion goes. However, to get to high-speed hopping requires something of a high, up-front (so to speak), metabolic cost (that is, until they reach a given speed, locomotion tends to be somewhat less efficient for them than simple four-legged running).
Many marsupials tend to have a high capacity for aerobic activity, so seem well-suited (or at least, better suited than most other mammals) to adopt a hopping mode of locomotion; they seem better adapted to overcome the up-front metabolic cost. Since, as I mentioned, once they get going, the cost begins to decrease with increased speed, it appears to be a worth-while evolutionary effort to adopt this mode of high-speed travel. But, obviously, it’s not for everyone.
WTF? Unless a close relative recently died of anal scurvy, you’re an ass. So you don’t like my sense of humour, fine. You have the noble option of ignoring me instead of condescending.
Let’s remember what forum we’re in. If you have a problem with someone’s username, take it to the Pit. If you want to call someone an ass for something they said in GQ, take it to the Pit.