Why do Kangaroos jump instead of walk?

Question

This might be a really weird question, but why do Kangaroos jump instead of walk?

As a human jumping takes a lot more energy than jumping, so it must be something biological, but they are like the only animal family that does that (I’m sure there are more kangaroo-like animals I don’t know about)?

Edit – After seeing a few comments, this post isn’t about why the evolved to do so (even though it is an interesting question), I was asking what is the anatomical reasoning for it.

In: 418

Answer 1

Many animals in Australia evolved to fill a niche that is very different from the niche their ancestors filled when Australia was connected to other landmasses. Today, Kangaroos are basically trying to fill the same niche as Deer. They are large herbivores, often the largest herbivore in their environment, with exaggerated and mostly useless sexual dimorphism. (compare deer antlers to kangaroo forearm strength, both relatively useless for an herbivore)

Kangaroos are in the family Macropodidae, and looking at other species in this family and other Marsupials gives us an idea of what niche their common ancestor originally tried to fill. Most Marsupials are small tree dwelling creatures. Being able to jump from limb to limb would be their most important mobility metric.[The Tree-Kangaroo is a good example of what their common ancestor likely looked like.](https://en.wikipedia.org/wiki/Tree-kangaroo) This is noteworthy as many tree dwellers don’t have the ability to move their legs independently. All that matters is that the legs can push with enough force to boost the creature up the tree.

You may already know this, but[Kangaroos cannot move their legs independently.](https://youtu.be/Hch24lsvvyo) Now knowing their ancestry, this makes sense, but why didn’t they evolve out of it? Well let’s go back to Deer. They are part of the family Cervidae. What’s relevant here is that none of the animals in this family live in trees. Walking instead of hopping was just came easier to Deer because their ancestor already walked. Deer don’t walk because it’s what’s best for their niche, they walk because it was easier for them. Same reason that Kangaroos hop.

tl;dr Kangaroos cannot walk because they cannot move their legs independently. This was because their ancestors lived in trees. Learning to walk instead of hopping isn’t a big enough advantage for them to evolve that way. Hopping was easier for them and it works good enough.