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In the story I'm writing, there is an island of mostly lizards (like the Australian dragon lizard) which have diversified into a variety of ecological niches, including flight acting as pseudo-wyverns (mostly because my actual wyverns barely resemble traditional wyverns). Now these bootleg wyverns (as I'll call them) are rather small; the size of a cat at most. I was wondering, is warm bloodedness a necessity for the energy demands of flight?

NOTE: magic does not exist in my story.

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  • $\begingroup$ You are aware, are you not, that the dinosaur lineage that led to modern birds was warm blooded? Feathers evolved first as insulation (same reason as hair on mammals); their function for flight was an offshoot. $\endgroup$ – Zeiss Ikon Mar 13 at 13:57
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    $\begingroup$ Does this answer your question? Would cold-blooded dragon be suitable for flying? $\endgroup$ – user2352714 Mar 13 at 15:15
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Strictly speaking, no. But there are huge energy requirements for powered flight, so a cold-blooded animal (hence with slower metabolism) would necessarily either not spend much time in flight, or it would have huge wings and its flight would consist almost entirely of gliding.

However, I would suggest that evolving endothermy isn't as big as a hurdle as you might envision - at a fundamental level it's just a faster rate of metabolism.* Just make your wyverns warm-blooded and there's no issue. The reason why most animals aren't warm blooded is because it's a high-cost way to live, it isn't actually a complicated thing to do in principle. It means you have to eat more food and more frequently. Basically, it allows you to do energy intensive tasks more easily, but at the cost of forcing you to live an active lifestyle.

A warm blooded lizard isn't a stretch at all. Endothermy has appeared multiple times in vertebrates, including in mammals, dinosaurs (maybe not all dinosaurs but they got there eventually since birds are endothermic), pterosaurs, ichthyosaurs, and even some species of fish. In fact, some species of lizards are partially endothermic, discussed in an interesting short paper by Glenn Tattersall. If your wyverns have an active, flying lifestyle, it's scientifically much more believable that they would be warm-blooded reptiles than that they would be ectotherms like most lizards. You needn't make them as warm as mammals or birds. Endothermy is a spectrum, your wyverns could be somewhere between lizards and mammals and still be believable.

*It's a little more complicated than this; you also need some extra insulation to maintain the heat generated by the increased metabolism. Hence why mammals have hair, dinosaurs had feathers, and pterosaurs had pycnofibres. But you did mention in your other question these wyverns have feathers.

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Given that insects fly, and given that they aren't warm blooded. I'd say that warm bloodedness isn't a requirement for flight.

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  • $\begingroup$ Insects are not as large as cats, nor shaped like dragons. $\endgroup$ – Renan Mar 13 at 3:12
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    $\begingroup$ @Renan: Prehistoric flying insects got up to pretty good sizes. Meganeuropsis permiana was pretty close to the size of a small cat: eartharchives.org/articles/… $\endgroup$ – jamesqf Mar 13 at 4:41
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    $\begingroup$ @jamesqf good point, +1 to the answer. $\endgroup$ – Renan Mar 13 at 5:02
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No

Well, no, warm-bloodness isn't necessary to fly given a few restrictions. To fly, you need muscles, and cold-blooded animals can have muscle power to spare. Just take, for instance, the crocodile, which has incredibly powerful bite strength. Cold-blooded animals can have the strength to fly.

The problem is just that being cold-blooded gives you two restrictions. The first is that cold-blooded animals frequently run into problems regulating body temperatures and thus aren't creatures capable of endurance activities. The second is that cold-blooded animals can't range across the same climates that warm-blooded animals can, they need a very consistent climate.

Given these limitations, it's possible to have a cold-blooded reptile capable of flight, but it's restricted to very specific climates and can't fly for very long periods of times or distances. Not to mention that it'll be very lazy, constantly seeking to be in the sun to soak up those sweet heat rays.

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  • $\begingroup$ it's possible to have a cold-blooded reptile capable of flight... Not to mention that it'll be very lazy... That's so sorta self-contradictory in the practical sense (why fly to warm up when you could do it lazier on the ground?) that the possibility is almost just theoretical (i.e. improbable... until proven otherwise :) ) $\endgroup$ – Adrian Colomitchi Mar 13 at 3:16
  • $\begingroup$ @AdrianColomitchi It wouldn't fly to warm up. It would fly for the same reason birds do - to catch their prey or to escape from predators. After all, why else do birds fly? $\endgroup$ – Halfthawed Mar 13 at 3:21
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    $\begingroup$ Given that we had zillions of years of evolution and the best evolution selected so far in regards with cold-blood-flight is some gliding lizards, I'd say it's quite unlikely for those cold-blooded reptiles to use flight to catch their prey. Because if you come empty handed for a bit, all it takes is a cold wind to become catatonic in mid-flight and tumble to the ground - sorta evolution saying "Well, at least I tries. Doesn't quite works". $\endgroup$ – Adrian Colomitchi Mar 13 at 3:29
  • $\begingroup$ @AdrianColomitchi The question wasn't whether or not such a creature could evolve, it was whether or not such a creature could exist. And there's only been an estimated 300 or so million years for reptiles to evolve. Give it time. $\endgroup$ – Halfthawed Mar 13 at 3:38
  • $\begingroup$ The set of tags qualifying the question tends to contradict your "not asking about evolution". As for giving it time: well, I'm quite tempted by the idea, just that nagging problem I don't know how to exactly. And I'm running out of time waiting for a positive answer :) $\endgroup$ – Adrian Colomitchi Mar 13 at 3:43
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No

A picture is worth a thousand words, and this bugger was photographed midflight:

A flying lizard in midflight

This is just one species of the real world draco genus.

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    $\begingroup$ Midglide. That is not powered flight, nor are they capable of significant distance. $\endgroup$ – rek Mar 13 at 4:38
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I'm not sure but seems Pterodactylus wasn't warm blood animals.

In this wikipedia article show this image too about the size:

enter image description here

However, in wiki says:

"Soemmerring (1755 - 1830) did not change his opinion that these forms were bats and this "bat model" for interpreting pterosaurs would remain influential long after a consensus had been reached around 1860 that they were reptiles. The standard assumptions were that pterosaurs were quadrupedal, clumsy on the ground, furred, warmblooded and had a wing membrane reaching the ankle. Some of these elements have been confirmed, some refuted by modern research, while others remain disputed.."

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  • $\begingroup$ Pterosaurs were probably warm blooded. From a bit of cursory research, it seems this is even less controversial among paleontologists than the claim that dinosaurs were warm blooded. $\endgroup$ – Dark Malthorp Mar 13 at 13:15
  • $\begingroup$ @DarkMalthorp Thanks! This text was unclear about it. $\endgroup$ – Rodolfo Penteado Mar 13 at 13:20

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