Kangaroos are freaking scary.

[u/Odd-Difference-1483]

[u/CorvidCuriosity]

Actually, their tail really does act as a third leg. When they "gallop", they use their tail like a rear leg and spring off of it, putting as much pressure on their tail as they put on their feet combined.

It's basically a 3-legged gait.

[u/professionalchutiya → u/CorvidCuriosity]

The tail must be crazy muscular

[u/CorvidCuriosity → u/professionalchutiya]

Their tail has 6 large muscles, which look and function a lot like muscles in our legs, which gives power and flexibility.

[u/professionalchutiya → u/CorvidCuriosity]

The tail must be crazy muscular

[u/holyrolodex → u/CorvidCuriosity]

If they are sprinting isn’t it more like 5-legged? I’ve heard the term pentapedal used in reference to kangaroos

[u/CorvidCuriosity → u/holyrolodex]

I've never seen a kangaroo sprinting on all 5 legs. Usually, they are just doing the hopping sprint with their hind legs and tail.

They say "pentapedal" because they are counting the tail as fifth leg, but not because they are using all 5 at once.

[u/holyrolodex → u/CorvidCuriosity]

Gotcha

[u/ddraig-au → u/CorvidCuriosity]

Its also the most efficient of all forms of animal locomotion

[u/coffeebribesaccepted → u/ddraig-au]

First, you certainly must be only referring to land animals. Second, how is that more efficient than greyhounds or cheetahs that run the same speed or faster with smaller muscles.

[u/CorvidCuriosity → u/coffeebribesaccepted]

Cheetahs use crazy amounts of energy to sprint. Not efficient at all.

Kangaroos can maintain their gait for miles and miles.

[u/coffeebribesaccepted → u/CorvidCuriosity]

So your measurement of efficiency is only over a certain distance? Many animals including humans can maintain their gait for miles and miles.

[u/CorvidCuriosity → u/coffeebribesaccepted]

Yes, the measurement for locomotion efficiency is "how much energy are you spending" per "how much distance can you travel". That's not "my" definition.

I would agree that humans are probably the most efficient runners (but usually this discussion is about non-human animals).

However scientists have shown that because of a spring-like action in their tail muscles, Kangaroos are incredibly efficient - moreso than any other land-animal (possibly besides humans - I've never seen a side-by-side comparison there).

(To be clear, Cheetahs are so inefficient with their speed, they can only manage high speeds for a couple of seconds. And if a cheetah sprints at high speed and doesn't catch prey a couple times in a row, that Cheetah will certainly die from simply using up all their energy.)

[u/coffeebribesaccepted → u/CorvidCuriosity]

per "how much distance can you travel"

Then by definition the animal that can travel the most distance is the most efficient, regardless of how much energy is used. An animal can be more efficient over a short distance, even if a different animal is more efficient over a longer distance. And larger muscles use more energy than smaller muscles, even at rest. So the base energy used will be less for a smaller animal.

this discussion is about non-human animals

My original comment was a response to the ridiculous statement that kangaroos are the most efficient of all animals.

[u/CorvidCuriosity → u/coffeebribesaccepted]

Then by definition the animal that can travel the most distance is the most efficient, regardless of how much energy is used.

Huh? That's not how ratios work.

If animal A can run 10 miles but uses 10,000 Calories of energy, that is less efficient than an animal that can run 5 miles using 500 Calories of energy.

[u/ddraig-au → u/coffeebribesaccepted]

Oh yeah, of course land animals, oops. And usually speed is the enemy of efficiency.

That being said, that giant heavy tail and the big legs store a lot the energy when they land, and it is used to then make the next jump.

https://www.nature.com/scitable/blog/student-voices/why_walk_when_you_can/#:~:text=Red%20kangaroos%20hopping%20at%20speeds,a%20pitiful%206%20km%2Fh.