Transcript for the text on the image under the cut:
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Spectember 2020 #03 | nixillustration.com | alphynix.tumblr.com
Concept suggested by:
anonymous
Plunge-Diving Bats
(Enchonycteris praecipitis)
Although there are several present-day species of fishing bat, surprisingly none of them were the ancestors of the GANNETBATS.
[Image: three views of a long-winged pointy-nosed bat folding its wings back and dropping headfirst into a plunge dive.]
This species actually evolved from fruit bats.
Their ancestors were a large day-flying island species of flying fox that fed mainly on fruit but also snacked on insects for additional dietary protein – and occasionally even opportunistically fed on carrion, particularly beached fish.
They were already very capable swimmers, sometimes ending up in the water when swooping down to drink or to collect dropped floating fruit. Naturally highly buoyant, they were able to float at the surface and propel themselves back to land with rowing motions of their wings.
Eventually some of these bats began intentionally dropping into the water to actively pursue fish visible just beneath the surface, and over the next few million years these piscivorous diving bats became increasingly specialized.
Gannetbats have developed proportionally long and narrow wings, spanning up to 2m (6’6”), giving them a better ability to glide and soar than their ancestors. Their skulls and necks have become heavily reinforced and shock-resistant for plunge diving, and their snouts have become pointed and streamlined with retracted nostrils and an underslung jaw full of sharp needle-like teeth for gripping slippery aquatic prey. Their eyes face forwards and downwards, allowing them to spot fish shoals from above.
They’re also one of the few bat species to practice biparental care. During the first few weeks of a pup’s life it’s carried around clinging to an adult’s body – and to avoid submerging it during dives both parents take turns carrying and guarding it while the other hunts.
[Image: two different close up views of the head of a gannetbat, showing its narrow pointed snout, needle-like teeth, and downwards-facing eyes.]
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[Image: a gannet bat using its wings to launch itself into the air from the water’s surface.]
By folding their wings back and diving at high speed gannetbats are able to overcome their natural positive buoyancy and access prey up to 10m (33’) below the surface, using powerful wing strokes to propel themselves underwater.
Dives last less than a minute before the bats float back up to the water’s surface. From there they can launch themselves back into the air using several rapid pushes with their wings, “hopping” along for several strokes before gaining enough momentum to get fully airborne.
[Image: a gannetbat swimming underwater, chasing several small fish.]
Sounds great. Plunge-Diving bats could fish at night in the open ocean, where no birds do (even some fish tend to ascend to the surface at night, as they are free from bird predation). This is plausible at the niche level. However, it presents many more constraints for bats than simply the adaptation of their face, wing shape, and behavior.
First, the membrane (patagium) of bat´s wings is very fragile and could easily be torn by strong winds on the coast and open ocean. It’s also no good at protecting the bat from the water (essential on the open ocean) and is a disaster if the bat tries to swim (bats tend to drown if they fall into the water) or even float to rest like a seagull does. Furthermore, it is very thin and would considerably limit its prescence in cold climates and with the cold breezes of the open ocean. Although one might think diving bats could simply live in warm tropical or subtropical climates, they would need to take advantage of wind currents (something no bat does, but a diving bat would be required in order to get to the ocean in time and use theri narrow wings like sea birds do (narrow wings are used for endurance)), and at such altitudes, the air is very cold and could damage their membrane. They would need to insulate their body and wings, perhaps with fur, but it would have to be simimlar (an evolutionary analogy) to feathers in order to improve its aerodynamics, protect it´s body and wings… and be covered with oil… lots of oil…
Also, bats are quick flyers. They can fly quicker than birds by flapping their wings (Shure, a large bird can dive-fly faster than any bat can, but it needs to gain height firts and is far less agile than a bat) BUT they can´t fly on long distances (Something a Plunge-Diving bat has to do)… They rely a lot on body fat… And a bat based on endurance flights would require more fat… And fat is heavy… And a heavy body is no good for flying. I think fat could either evolve to be blubber-like (filled with air to be lighter) and be used as marrow. Now… Birds have air sacks… ALL over their bodies. This not only makes them lighter, but also greatly increases their air input (and their endurance). Bat´s lungs can only get so big in their torsos… BUT maybe if the sternum is elongated… Into the abdomen like the Keel of a bird… It would serve to purposes. Larger chest muscles, more strenght at the flapping of the winds, less flaps are required, less energy is wasted AND a larger diaphragm that sort of “invades” into the abdomen, so it can have larger lungs. As for their energy storage… Maybe a more eficient liver at storing glucogen and lots of blubber.
Finally. Either it goes back to land in the day and rests… Like a seagull, or it flyes endleslly on the open ocean. Like an albatros. Eitherway it would need to rest every so often on the water by floating and of course swim if it´s Plunge-Diving. And maybe siwm on the surface to eat… And it would need to have… Palmed feet like a beaver… Or use it´s tail… Wich would need to be modified to do so. Maybe like the feet of a platypus (large fin like structures at the end of each finger that can sort of bend inwards when it flyes), so it can have free large claws that assist on grabbing prey or hanging from clifts… And since you are telling that it evolves from mega bats it has a reduced tail. So maybe just use the feet? Idk.
Anyway, sorry for adding so much text. And sorry if it´s not so clear. And thank you for the art. It´s great.