Flightlessness

Flight.

Powered flight (in the biological world, flight that comes from the mechanical flapping of wings as opposed to passive drifting or gliding) can be found in a wide range of animals on our planet. It is has evolved independently in insects multiple times, leading to a biologically diverse menagerie of colorful blotches on our windshields. While insects are far and away the first creatures to master the air (by a solid 200 million years), and the only invertebrates to do so, they share the skies with the much larger vertebrate fliers like birds, bats, and at one time, the reptilian pterosaurs. Aerial locomotion provides an animal with obvious advantages; ease in avoiding predators, access to new habitats and food sources, and the nullification of the game of Monkey in the Middle. There definitely are interesting correlations concerning the success of flying; it appears as though once evolved, flight is an incredibly successful strategy. Bats account for a fifth of all mammal species, birds have the most species of any land-lubbing vertebrate class, and the class containing insects is more speciose than all other animal groups combined. So it obviously pays to take to the skies, on a numbers and diversity level. That, and flying is quite clearly the most badass way to get around.

And yet, some representatives of these flying lineages drop the practice altogether. One explanation is that they are ungrateful, arrogant pricks who wouldn’t know the value of an honest day’s wingbeat if it bit them in the ass.

“Soaring elegantly through the heavens is sooooo mainstream.”

The other explanation, of course, is that under some conditions, regaining flightlessness is a relatively useful evolutionary strategy. One such scenario that keeps popping up, almost exclusively in flightless birds, is that of geographic isolation through island colonization. A familiar example of this is that of the dodo. Basically, a species of pigeon colonized the island of Mauritius some 10 million years or so ago. This pigeon, faced with a new environment completely devoid of anything that could conceivably eat it, and fully stocked with food, suddenly possessed a relatively unneccessary trait; flight. You see, evolution is a fucking merciless accountant. Traits that are expensive to maintain that aren’t an essential part of an organism’s fitness are generally cut by natural selection, and very quickly so. Flight, with the massive amounts of bone and muscle devoted to the wings, is about as energetically expensive as it gets. So, over many generations, this pigeon species diverged into various small-winged, big-bodied, big-legged flightless animals we called dodos. Without the pressures from predators, and little competition for food, wings (and the flight associated with them) became superfluous and were dropped…which is the approach many Americans took towards their legs after the advent of delivery pizza and a Burger King every third block.

Arms, you’re next.

The dodo’s strategy was only good given the conditions of its island haven. Once Europeans showed up in the 16th century, dodos were screwed, because they were essentially lightly feathered bags of delicious, delicious flesh. They were also completely unafraid of humans, or of any of the dogs and cats that were brought along to the island, and they couldn’t move much faster than a burdened shuffle. One Portugese sailor simply stopped using a gun on them because they were “too fucking pathetic, bro.”

So, of course, we see flightlessness pop up in birds whenever the opportunity presents itself, evolutionarily. We’re all familiar with kiwis, which gave up the flying game long ago and live their days happily on the islands of New Zealand. Penguins and ostriches have more complicated evolutionary reasons for their flightlessness, but are successful all the same. Our recent past is also littered with now extinct flightless fowl. There are the Madagascan “elephant birds” which survived until the Middle Ages, and were heavy as a cow and were tall enough to stuff a shot from Yao Ming with their faces. There were also the great auks of the Arctic, which were the closest thing to a penguin a polar bear had ever seen. Europeans robbed polar bears of this privilege by killing and eating all of the great auks by the middle of the 19th century, presumably after gaining a taste for fat, defenseless birds from their dodo encounters.

But, there are extinct flightless birds (and living other non-related animals) that aren’t as well-known.

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Meet Dromornis stirtoni. I know, you’re probably chuckling at the big goofy schnoz, the dorky, lanky neck and Nemo-esque coloration. But consider the following…

Ol’ Dromy was big.

Dromornis, and its close relatives, lived in Australia between 15 million and 30,000 years ago. While they were first believed to be chiefly herbivores, the structure of some species’ beaks suggests meat-eating, or at least occasional scavenging…like if Big Bird and a hyena had hot, childhood-destroying sex and somehow generated unholy demon-spawn progeny. Whatever their diet consisted of, one thing’s for sure, that beak probably smashed human skulls like grapes, whether Dromornis was defending itself or making din-din. Despite this impressive repertoire of pants-shittingly horrifying characteristics, Dromornis and its kin had a humble pedigree. Its closest relatives were ducks and geese. No joke. One member of the family, Bullockornis, is unofficially referred to as the Demon Duck of Doom by paleontologists. I’m completely serious. The cute, quacking bird paddling around in the water feature at your local park had dinosaur-sized cousins with hatchets where their faces should go.

Somehow imagining this thing squealing like Donald Duck as it lumbers after you doesn’t make it any less terrifying…

Another example of island-induced flightlessness coupled with gigantism is the relatively recently described Ornimegalonyx that lived on Cuba until as recently as 10,000 years ago. Ornimegalonyx was a very, very large owl.

If I had to stand next to that thing, I’d have a gun too, buddy.

While its true flightlessness is currently debated (it may have just had markedly reduced flying abilities, like wild turkeys), there’s a lot of evidence to suggest it was large enough to look an eight-year old in the eyes. The length of its legs means it likely spent a lot of time running around on the forest floor, pinning down unfortunate animals with its size 12 feet, and ripping them to shreds. Undoubtably, Ornimegalonyx was considered the wisest animal in Cuba…or else.

Most flightless bird lineages considered here are isolated and unique anomalies, rarely lasting more than a few tens of thousands of years before they are usurped by changing climate, new predators, or hungry white dudes. But in the case of South America between about 60 million and 2 million years ago, as far as the food web power structure is concerned, bird was the word.

This is Kelenken, the largest in a long line of super-predatory flightless birds known as phorusrhacids. Phorusrhacids were the apex predators over the entire South American continent during the majority of the time between the when the dinosaurs kicked the bucket, and when modern humans emerged in Africa. This is a very long time. It’s no wonder their reign was so lengthy, considering that many had bladed beaks as long as your refrigerator is wide and could potentially run at 30 mph. They filled the ecological vacuum left by the extinction of nightmares like T. rex and Velociraptor on the island continent. Phorusrhacids were apparently such big fans of their dead cousins, that they re-evolved clawed hands from their stubby, deformed wingtips as an homage. Due to their inherent badassatry and Castroian ability to maintain power, scientists often affectionately refer to phorusrhacids as “terror birds.”

It’s safe to assume that any mammalian whining about term limits was quelled with a hooked beak to the spine.

The shining star example above, Kelenken, was particularly large. It was tall enough to scratch its noggin on a basketball hoop, which it only would have done after eating the basketball, disemboweling all the players, and presumably crapping in the shape of a pentagram on the floor.

While the fossil record is ripe with flightless bird examples, one group that is often overlooked as possessing examples of flightlessness is the one that invented flight in the first place; insects.

This is the velvet ant. There are over 400 species, and are found in arid tropical and subtropical regions worldwide. Much of their diversity is concentrated in the Southwestern US and Mexico. The “velvet” refers to their dense hairs covering their entire body. Simple enough, right?

Except it isn’t an ant.

Velvet “ants” are highly-derived wasps. The females of the group are completely wingless, and thus run around on the desert ground and resemble large, fuzzy, orange or red ants. Other then their luxurious coat, there isn’t a lot “velvety” or “anty” about them. Females have an incredibly painful sting. Supposedly, the pain is so excessive, that it can kill a cow, hence leading to their other common name; “cow killer.” Charming. They reproduce by raiding the nests of their fellow, flighted wasps, and laying eggs next to their brethren’s pupae or larvae. These eggs hatch, and the cow killer larvae digs into the body of the other baby wasp, eventually killing and eating it from the outside in. So not only did the cow killer abandon the family business of flying around and spelunking into soda cans, but started actively Benedict Arnold-ing its waspy relatives. The entire reason they are so fuzzy is to protect themselves from the stings of the wasps whose nest they raid.

I had encounters with cow killers when I lived in semi-arid eastern Idaho. I was smart enough to cruelly pin them down with a twig for closer observation, which instigated an awful chirping/screeching noise to erupt from flaps on its back. Apparently, this is caused by a structure known as a stridulitrum, and is supposed to deter predators. I eventually would let the cow killer go, mostly because that noise is fucking annoying, but partly because I was afraid it was summoning help from its friends…

Absolute flightlessness is all fine and dandy, but sometimes we can see flightlessness in the process of developing, evolutionarily, in an organism. One example of this is the vampire bat.

Vampire bats feed exclusively on the blood of other mammals (some species upon birds), including pigs, cows, goats, and humans. Vampire bats are, of course, quite capable of flight, but where many bats have nearly completely lost the ability to move around on the ground, vampire bats excel. Maneuvering around big, hooved animals isn’t as simple as a drop out of the sky onto the back. A certain level of ninja stealth is involved, and this requires bounding around on the ground in order to reach the bloody, bloody promised land. So, bats have sort of re-evolved the capability to nimbly navigate on the forest floor.

But since bats have shrunken their hind legs over the tens of millions of years, it just made more ‘sense’ to utilize those big, powerful wing limbs as makeshift legs. As if vampire bats weren’t unsettling enough, they can quickly pursue a host, silently, by lunging creepily behind them in the last place you’d expect a bat…by your feet. While this is isn’t legitimate flightlessness, the conditions are in place for these little guys to eventually give up flying altogether and just hop around in the leaf-litter, looking for fresh blood with their heat-sensitive nose flesh and hearing that is keyed in specifically on the sounds of breathing in sleeping animals. However, it is possible that flight isn’t on its way out, and that this hybrid lifestyle of the vampire bat isn’t changing anytime soon.

So, flying around is a pretty awesome way to get by, but there are plenty of reasons to give up the craft. Flightlessness has been a part of the biosphere’s past, it’s present, and will most definitely be a part of its future, long after we’re gone and we’ve eaten all the slow and stupid grounded birds…

* artwork by Peter Trusler

© Jacob Buehler and “Shit You Didn’t Know About Biology”, 2012-2013. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Jacob Buehler and “Shit You Didn’t Know About Biology” with appropriate and specific direction to the original content.

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One thought on “Flightlessness

  1. Pingback: Angry Birds: Part 1, Barbarism from Above | Shit You Didn't Know About Biology

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