The things you learn when researching!
My current WIP involved shapeshifters, and Michelle brought up a good question: Why doesn’t a shapeshifter just pick up the protagonist and fly her off, Hobbit-style, to where he needs to go?
I considered it a simple issue of physics: in order to pick up and carry an adult human, you’d need enormous wings, and eventually you get big enough that muscles wouldn’t be able to move them.
For reference I used the albatross, which is enormous but can only carry very small loads, and the extinct Haast’s eagle, which was believed to eat moa birds and occasionally human children before its main food source was hunted to extinction by the Maori several hundred years ago. Though it was relatively huge (roughly 45 lbs), it looks like it didn’t carry off its pray so much as dive at it, maul it like a tiger, and then eat it where it had fallen.
Now, I was under the impression that the Haast’s eagle was the largest predatory bird.
Turns out I was wrong.
Meet the Argentavis Magnificens, with a wingspan between 23-40 feet, which weighed between 150 and 550 lbs (since it’s been extinct for millions of years, scientists are a bit iffy on the specifics).
Scientists believe it picked up its prey off the ground and swallowed it whole without landing, because actually getting off the ground was nearly impossible– they believe it didn’t have the muscle strength to take off the ground without a running start, a high surface to jump off, and a running start.
So now why doesn’t the shapeshifter in my story become one of these monstrosities?
I can’t just sit back and say ‘because I said so’. In fiction especially, ‘just because’ isn’t enough. So here’s my reasoning:
Shapeshifters could create new bodies according to their own specifications– after all, they frequently changed personal details like size, skin color, and body shape as fashion suited them. However, they were still bound by the limits of physics and physiology. So a creature like Argentavis magnificens, which lived at a time when there was more oxygen in the environment, would need much larger lungs to be able to oxygenate its enormous body. Messing up proper lung-to-body ratios was considered especially dangerous: a leading cause of death among shifters was getting that ratio wrong and suffocating before they could revert into a more familiar form. Even if they got that right, they would also need to do several experiments with proper ratios of muscle mass and wingspan to figure out how to get that much mass off the ground in the first place.
In the end, those sorts of experiments would be disregarded as unnecessarily dangerous and impractical. Anyone you wanted to transport could either fly or turn into something small enough to be carried by a regular-sized eagle. Non-shifters could take slower methods of getting from place to place, like horses and trains. Most damningly, very few shifters would demean themselves by carrying around a complete stranger. It would be the rough equivalent of giving a random tourist piggyback rides around town.