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Most animals that glide are rather light and small. Flying squirrels, Colugos, and sugar gliders all weigh but a few ounces. The largest gliding predators are snakes of the Chrysopelea genus. Flying Snake Again, they weigh but a few ounces. But could it be possible for a larger animal to glide? After all, there are eagles that weigh nearly twenty pounds, could a gliding animal not rival that size with proper adaptations and selective pressure?

My idea is that this animal is not optimized for going long distance like these real animals, but being able to make jumps it otherwise couldn’t, and to safely land from great heights instead of splattering when it falls out of the tree.

This animal glides primarily to attack prey moving on the forest floor, by jumping and silently gliding with relatively little horizontal gain it is still able to safely and silently land on the back of its prey and kill it with a swift and strong bite (think of a leopard) It does most of its actual movements in the trees through basic climbing assisted by a prehensile tail.

So is a large (+10 Kilograms) gliding predator feasible?

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    $\begingroup$ I wouldn't call a golden eagle or a condor small -- and they are exceptionally good gliders. $\endgroup$ – AlexP Jan 22 at 9:08
  • $\begingroup$ @AlexP very good point sir $\endgroup$ – NixonCranium Jan 22 at 9:10
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    $\begingroup$ Gliding with very little horizontal gain is probably better called diving. In my understanding gliding is when horizontal moving rate is higher then vertical moving rate $\endgroup$ – L.Dutch - Reinstate Monica Jan 22 at 9:21
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    $\begingroup$ Ever heard of a drop bear? $\endgroup$ – Starfish Prime Jan 22 at 13:57
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    $\begingroup$ @jamesqf so the glide ratio is low. Ticks all the other boxes though. $\endgroup$ – Starfish Prime Jan 23 at 7:49
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to attack prey moving on the forest floor, by jumping and silently gliding with relatively little horizontal gain it is still able to safely and silently land on the back of its prey and kill it with a swift and strong bite (think of a leopard)

Gliding with very little horizontal gain is probably better called diving. In my understanding gliding is when horizontal moving rate is higher then vertical moving rate.

What you describe is exactly what ambush predators like felids and humans, weighing more than 10 kg, do: they dive on the prey and strike. I think it was in Castaway where the main character kills a boar by jumping on it with a wooden spear which pierces through its body.

You don't want to do a gentle landing in such case, because you want to prevent your prey from escaping, and a blow at full speed will put it on the ground.

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  • $\begingroup$ What about from very significant heights? Like 70 feet? But your answer does make a lot of sense in that imparting energy from a fall is a powerful weapon $\endgroup$ – NixonCranium Jan 22 at 9:53
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Yes it is possible. Such a situation might be encouraged where the environment was dark. In this way the prey would not be able to see the predator coming. If the creature could echo locate its prey it would then be able to fall on it without being detected.

Another encouraging factor would be a fairly open understory without lots of crisscrossing branches and vines; this might be expected at the mid-lower level under a very high and dense upper canopy.

It would also be very useful to have the ability to move horizontally to some extent to allow it to home in on its prey during descent, it would also need the ability to vary its rate of descent, slowly falling until at a specific point when directly above the prey it folds its “parachute” and drops a lot more quickly to make the final kill.

Another useful attribute would be silence so perhaps owl like feathers or features that do not make any noise and the ability to expand or modify its flying surface perhaps like an octopus with a membrane stretched between its tentacles.

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It existed! The larger species could only glide, and easily surpass your minimum size.

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  • $\begingroup$ Pterosaurs don't glide, they fly. Many of them are thought to have caught thermals like birds of prey but they were perfectly capable of flying without them (though it would have been exhausting to do it long-term). $\endgroup$ – user2352714 Jan 22 at 18:16
  • $\begingroup$ Some species flew, some could only glide, as referenced in the link! $\endgroup$ – ColonelPanic Jan 22 at 18:41
  • $\begingroup$ The link specifically states that hypothesis was based on outdated models and is no longer accepted as valid. Those models were based on seabird-like muscular systems which it is now known that pterosaurs did not have. All currently known pterosaurs are considered to have been capable of powered flight. books.google.com/… $\endgroup$ – user2352714 Jan 22 at 20:08
  • $\begingroup$ Pterosaurs were active fliers rather than mere gliders $\endgroup$ – NixonCranium Jan 22 at 20:42
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Depends on the Environment

The big issue to overcome with gliding is the initial height. Gliding is defined as horizontal movement through the air without any significant gain in elevation beyond maybe an initial jump (like in flying fishes and flying squid), where the rate of horizontal movement is greater than the falling speed due to gravity. Thus, because there is no way to gain altitude, the best thing to do is jump from the highest structure possible. For big animals finding structures tall enough for efficient gliding that also can support your weight are rare. Maybe in a redwood forest, or the Hork-Bajir homeworld. A small, raccoon-sized animal (10 kg) like you're proposing would have plenty of things to climb though. And the other question is how well does the creature stick the landing, bigger sizes mean harder landings which can be dangerous for larger animals.

Southeast Asia has lots of gliding species (colugos, gliding snakes, gliding frogs, Draco lizards, flying geckos, big flying squirrels) because of its unusual forest structure. Forests in southeastern Asia have a lot of tall trees but not a lot of lianas or vines between them, leaving big gaps in the understory open that make it easy to glide but also make it very difficult for climbing animals to get around as easily as they would in African, Australian, or South American rainforests, promoting the evolution of gliding in different lineages. So environment is key.

Your predator doesn't seem infeasible, but I suppose the best way to figure it out would be to determine the size of the gliding membrane. The gliding membrane might have to be too large and cumbersome to be able to support the animal's weight and effectively glide. The largest gliding mammal is the woolly flying squirrel (Eupetaurus cinereus) which weighs a maximum of 2.5 kg and glides pretty well. Sifakas (Propithecus) have been suggested to do a "fall with style" glide, and they weigh 3-6 kg, but I think this is controversial. Many animals with powered flight (e.g., eagles) do glide, but they can switch from powered flight to passive gliding whenever they want.

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