The Flying Giraffe

So today I learned why pterosaurs could get so much larger than birds. I wondered about that. How could it be that an Azdarchid like Quetzalcoatlus could be the size of a giraffe (!!) while the largest bird was much, much smaller.

I’ve been watching presentations by the Royal Tyrell Museum and found one on pterosaurs.  It turns out that birds are stuck using only their two hind limbs to leap into the air to begin their flight. This limits them. They only have two legs to accomplish sufficient heights to begin flapping. If the hind legs get stronger so they could leap higher, it would add weight and that would require a stronger stroke and larger wings for flapping, which would require more muscle, which would add more weight… this works up to a certain point, but after that you just can’t balance the ratio of the weight to be overcome with the wing load. Eventually the situation degrades into a positive feedback loop.  Birds can only get so big and still be able to fly.

Pterosaurs, however, walked on all four limbs as modern bats do when they are on the ground. And like modern bats, the evidence is that they used all four legs to push themselves up into the air. So the muscles of the wings did add weight, but they also provided extra strength to the wings. This allowed them to leap higher into the air, and still maintain an adequate wing load. They could grow to the size of a giraffe and still fly.

(So why can’t bats get that big? It is peoposed that the answer is due to the fact that bats simply can’t find enough food if they get much larger.  That does not mean that, in the future, bats might not evolve to be as big as, well, a giraffe.)

I found this to be a very satisfactory explanation. I love it when science manages to answer a perplexing question.

I remember teaching science class. I always told the children science was like a never ending mystery story. Every time a mystery was solved it opened up the door for more questions to be answered. It’s one of the things I most love about science. One of the greatest mysteries which fascinated my generation when we were children was how the dinosaurs died out. Paleontologists were also obsessed with the problem, but never could come up with a good answer. A new hypothetical solution would be proposed every few years, only to be quickly be debunked by other scientists.

I remember my excitement when the now accepted impact proposal was first made by Luis Alvarez. Watching it slowly become more and more proven and finally accepted was intellectually exciting and engaging. So also with the mysterious moving rocks of Death Valley or the mystery of how a bumblebee could fly. On the one hand it’s very sad to see the mystery solved, but on the other hand it’s so exciting to learn that there is indeed a resolution and watch the process of that resolution being calculated and determined, and to see how it is finally proven.

My inability to function mathematically put an end to childhood dreams of a scientific career, but my love of science continues.

Unfortunately, I cannot figure a way to post the illustration here. But if you will Google simply three words you’ll get to see it. Type in azdarchid, giraffe, man: and you will see an amazing picture.