[rauljara]

Would love to see a pterosaur / bat version of this drone. Birds use one set of muscles to jump in the air and another to flap their wings, limiting how big they can get. That’s because, if you make your wing muscles bigger, then you need bigger leg muscles to support them, then you need bigger wing muscles to support your legs, etc. pterosaurs and bats have tiny little legs and use their “arm” (wing) muscles to do the initial jump into the air. It’s just one set of muscles that are used for both functions, which is why pterosaurs were able to get so big. It does beg the question, tho, why we haven’t seen any truly giant bats.

This pbs aeons video has a great explanation: https://youtu.be/scAp-fncp64?si=hjeWKGBI7riyjE1M

[type0]

> It does beg the question, tho, why we haven’t seen any truly giant bats.

They're mammals, birds have different respiratory system

"Flow-Through Ventilation

Unlike mammals, birds breathe through continuous one-directional flow of air through the respiratory system. We take air in and breathe it out, sort of like the tide moves in and out of a bay. As a result, our breathing system is said to be tidal. Avians have a non-tidal respiratory system, with air flowing more like a running stream."

https://birdfact.com/anatomy-and-physiology/respiratory-syst...

[vanderZwan]

That's why mammals can't breathe at high altitudes that birds can, but I'm not sure if that affects the body plan much in terms of size. The largest birds are smaller than the largest mammals on land or at sea. Then again, lower oxygen levels compared to the past seems to be a limitation for insect sizes too (who have an even less efficient respiratory system).

I also don't think it's the warmbloodedness. There are giant mammals in general after all.

Perhaps it is because bats form large, dense colonies? There is only so many resources available in any given ecological niche, so then for any species that fills a niche one would expect those resources to be divided either among many small individuals or a few large ones. Bat evolution chose the "big colony" route, which I assume favors smaller individuals.

[keyle]

Nature optimizes. The bigger you get, the more you need to eat. The harder it gets to fly. Fruit bats eat fruits.

Look at the food source and you'll understand the evolution.

[vanderZwan]

Robots and living animals have different limitations and constraints though: compared to separate legs and wings for animals, using one motor with some kind of gearbox to switch output from wings/propellers to legs might have a lower added cost in terms of weight . The legs can stay very skinny. The limitation would be how bulky such a gearbox would be, and how much extra kinetic energy loss it would introduce. At the same time creating functioning wings that can also work as legs sounds like it might be a huge challenge in robotics (unless there's a way to massively simplify it).

Definitely an interesting idea that should be investigated though! :)

(Also, I've seen so many "AI learns to walk" videos that I'm wondering if it could be used to find a design that would work for this task)