Among Avatar’s most wondrous sequences are those showing Jake Sully’s first encounter, in his avatar body, with the rich environment of the Pandoran forest. OK, it ended up with a lot of running away from a thanator. But who could forget Jake’s discovery of those big spiral trumpet-like plants (the helioradians) that, at a touch, shrank down into the ground?
How did Avatar’s designers dream up such a marvellous and convincing world?
First impressions: the ecosphere we see on Pandora is evidently a kind of rain forest, dominated by the tremendous trees that are so important to the Na’vi. Various other flora include what look like Earth’s ferns, palms, bamboos and grasses. Pandora is evidently an environment as rich in resources and energy flows as tropical Earth, and natural selection has produced an ecology as diverse and complex as anything on Earth.
However Pandora’s conditions differ from Earth. The lower gravity, thicker air, strong magnetic fields and different day–night cycles have all shaped the evolution of life, as we will see. One obvious example is gigantism; thanks to the lower gravity, many of the plants we see are like terrestrial forms grown huge. As for magnetism, the anemonid is a carnivorous plant that absorbs metals from the soil, giving it the ability to use Pandora’s magnetic field for movement, a feature RDA’s biologists refer to as “magnetonasty.” And a plant called sol’s delight, or Calamariphyllum elegans—“elegant squid-like plant”—is “magnetotropic,” that grows in the direction of magnetic fields. The “delight” name comes from the fact that the plant helps RDA’s miners detect unobtanium deposits by conveniently straining towards them.
But in devising this ecology, as with other aspects of the movie, the designers have always kept in mind the audience’s needs. They have given us a world that is strange, but with elements of the familiar from Earth, twisted and distorted to give an impression of the alien. That’s why Pandora is green! Plants on Earth are green because of the chlorophyll in their cells, the chemical compound that supports photosynthesis, processing the energy of sunlight for growth. Maybe, as sunlight is such an easily accessible energy source, on worlds with transparent atmospheres like Pandora and Earth some kind of photosynthesis is always likely to evolve. But there are different chemical ways to achieve photosynthesis; leaves don’t have to be green. The greenness of Pandora is a design choice.
The trees are the single most important element of the Pandoran forest, as in all forests on Earth. The main canopy tree is called the beanstalk palm, growing as much as a hundred and fifty metres tall. To the Na’vi it is tautral, the “sky tree.”
Earth’s greatest trees, the sequoias, don’t grow as high as this, but they are remarkable organisms in themselves. Today, sequoias are confined to a strip of the Pacific coast of North America. They flourish in the mountains, which trap moisture coming off the ocean; the tallest specimens grow in valleys and gullies where streams flow year-round and there is regular fog drip, which helps keep the trees’ upper leaves supplied with moisture. The sequoias are part of a habitat which supports many species of plants and animals. In the 1990s, tree-climbing biologists discovered a treetop ecology based on soil that had formed high above the ground from leaf mulch and other decayed vegetable matter.
Sequoias can be as tall as a Saturn V rocket, and older than Christianity. They are remarkable inhabitants of planet Earth.
Meanwhile in the undergrowth, deep, rich, dense and luminous, visually the Pandoran forest has something of the feel of the underwater world—you might be reminded of a coral reef, perhaps. In fact on some coral reefs there is a shrinking-trumpet plant like the helicoradians Jake encountered, the “Christmas tree worm,” Spirobranchus giganteus, that does indeed withdraw into a tube when disturbed. The woodsprites, “seeds of the sacred tree,” look a lot like jellyfish. Much larger jellyfish-like beasts float by like natural airships. The Mother Tree in the Tree of Souls has tendrils that resemble the tentacles of sea creatures. This oceanic influence is no surprise. After James Cameron completed the very aquatic movies The Abyss and Titanic, he made six deep ocean expeditions, filming in 3D. At the time of writing he is planning an expedition to the Pacific’s Mariana trench, the deepest point on Earth, a point nobody has visited since 1960.
And Cameron did base his vision of the forests of Pandora (partly) on the coral reefs he encountered in the ocean’s depths. This is appropriate because a coral reef, like a rain forest, is an example of a “climax ecosystem,” a complex and rich environment in which large numbers of animals and plants have coevolved.
It was Charles Darwin himself who first figured out how coral reefs work. Corals themselves are tiny anemone-like organisms that leave behind tough little skeletons. (In the past, reefs have also been built by other organisms such as algae, sponges, molluscs and tube worms.) With time these skeletons can heap up into huge reefs; Australia’s Great Barrier Reef stretches for two thousand kilometres around the north-east coast of Australia.
The secret of a reef as a habitat for life is that it “fills in” what would otherwise be an empty column of water above a flat ocean floor. A reef is a highly complicated three-dimensional structure, full of crevices and folds and cracks, ripe for colonisation by other life forms. On land, forests do the same thing, the tall trees rising up from the ground to vastly increase the effective surface area available for life. And so coral reefs are thick with fish, molluscs, sponges, echinoderms (starfish and sea urchins) and other forms of life, all shaped by evolution into complex chains of symbiosis, competition and cooperation—just as we glimpse in the Pandora forests. (Ironically, on Earth the coral reefs that are such an inspiration for Avatar are dying back. This is an ecological disaster but also a human one, as there will be economic losses for fisheries and tourist resorts, and coastlines will be left less protected from the ocean.)
But on Pandora, within that intricately interconnected biosphere, there are a rather large number of living things that bite.
The first truly spectacular animal that avatar-Jake confronts is a hammerhead titanothere. This is a massive six-legged quasi-rhino, heavily armoured, with a “hammerhead” muzzle reminiscent of another aquatic creature, a hammerhead shark. And the beast has a spectacular threat display, designed to scare off any ambitious predators, and indeed would-be rivals from within the titanothere’s own species; these are very territorial animals.
But the hammerhead, a herbivore, is somewhere near the bottom of Pandora’s land-based food chain. The hammerhead eats the Pandoran equivalent of grass, shrubs, leaves, and in turn is eaten by predators like the viperwolves. These scary beasts are six-legged pack hunters that run like dogs, but are also nifty climbers thanks to their ape-like paw-hands. And they are highly intelligent, as you can tell from onscreen evidence of communication as they hunt Jake. There are evidently creatures that prey on the viperwolves in turn, such as the thanator, a beast like a lion or a panther, a relative of the viperwolf.
Similarly there is a food chain of the air. The mountain banshees, graceful pterosaur-like flyers, are also pack hunters, aerial equivalents of the viperwolves—and again an even scarier hunter preys on them, the mighty leonopteryx.
We always see the thanator alone, like the leonopteryx, and this makes sense from what we know of food chains on Earth. On our planet each step of consumption up the chain is only about ten per cent efficient, in terms of nutrient value. A thousand tonnes of grass can support a hundred tonnes of hammerhead meat, which can only support ten tonnes of viperwolf meat, which can only support one tonne of thanator meat… So if you are an “apex predator,” as a thanator or a leonopteryx is believed to be on Pandora—or a lion, or a tyrannosaurus rex on Earth—the land can only support a small number of your kind. It’s thought that the range of a single tyrannosaur might have been hundreds of kilometres; a thanator’s range is three hundred square kilometres. On Pandora or Earth, for six limbs or four, the rules of the natural economy are set in stone.
This dog-eat-dog (or viperwolf-eat-viperwolf) aspect of life on Pandora is reflected in something else we see onscreen: arms races between predator and prey.
To escape a big fast scary predator, you either evolve to run fast, like the slender deer-like hexapedes, or you evolve heavy armour, like the hammerheads—or you do both, like the direhorses. Another possibility is to use threat displays like the hammerheads, effectively startling away the hunter, if you’re lucky. Meanwhile your hunter in response is evolving to run ever faster, brandishing ever sharper teeth… The end result of an evolutionary arms race is a killing monster like a thanator or a tyrannosaur hunting down a tank-like prey animal like a hammerhead or a styracosaurus—which was a rhino-like dinosaur with a horn on its nose, bony bosses over its eyes and cheeks, and a bony frill over its neck with even more long and pointy horns.
Although Pandora is presented to us as a world of natural harmony, nature is evidently red in tooth and claw here: a world so tough that even apex predators like the thanators need to be armoured. And while the forest has a dreamy oceanic visual feel, the ferocious predators and their heavily armoured prey drew inspiration from the mighty creatures of Earth’s dinosaur age.
But there are gentler elements too. Many of the animals are social, the direhorses, the buffalo-like sturmbeests in their herds, the banshees in their flocks. And we glimpse family groups, the sturmbeest on the move protecting their calves, the direwolf cubs playing.
You’ve no doubt observed that many of Pandora’s animals share common features: six legs, two neural whips (called “queues” in the Na’vi, as they are wrapped in braids of hair), supplementary breathing holes, and four eyes. This applies to flying creatures like the banshee and leonopteryx, as well as to the ground animals from the hammerheads to the thanators. (The exceptions to the general plan are the Na’vi and their apparent relatives the prolemuris, as we’ll see in the next section.) This convincing consistency is a testament to the disciplined imagination of the movie’s designers, and to their inventiveness, such as in the plausible-looking gait of the many six-limbed animals, and the sensible-looking flapping of four wings.
The antenna-like neural whips are used to link the nervous systems of animals, and to link Na’vi to animals, and indeed to link Na’vi to Na’vi. While a Na’vi has just one queue, many animals have two whips. The equine direhorses connect with each other through their whips, bonding emotionally but also passing on information about food sources and threats. We’ll look more closely at neural queues when we come to consider the Na’vi themselves, as well as the Eywa neural network.
What of the multiple breathing holes shown on many of the animals? On Earth some insects have “spiracles,” additional body vents to take in air. On Pandora the vents are for supercharging—taking in more oxygen quickly, a feature that is particularly useful for flying creatures, and we do see prominent vents on the banshees, which, like birds, burn up a lot of energy and need efficient heat-loss systems. But the vents are also a relic of an early stage of the movie’s design process; Cameron wanted some of the animals he envisaged to have the feel of automobiles, and the air vents are a trace of that source of inspiration!
Those multiple eyes are another striking feature. Why would you need two sets of eyes? On Earth, though insects may have many sets of eyes, one pair seems standard issue across the animal kingdom—though a bivalve mollusc known as the “thorny oyster” (Spondylus) has multiple eyes scattered around the edge of its shell. There is a South American fish called the anableps that rises to the water’s surface to seek prey in the air, but while it hunts it is in constant danger of threats from below. So each of its eyes works as two separate optical systems, an upper one for aerial vision and a lower one for aquatic vision; the creature can watch for danger from below while it stares up into the air for its food. These systems have separate retinas, but there is only one optic nerve per eye—two eyes acting as four.
On Pandora the multiple eyes have primarily evolved because of the varying light conditions. Maybe there is no single eye design that can handle the brilliance of a double-sun open sky, the bioluminescent shade of the forest, and the occasional deep dark night. For example a banshee’s primary eyes see in full colour, with vision roughly equivalent to a human’s. Its secondary eyes see in the near infrared, for night hunting: they are like military night-vision technology, capable of detecting prey through its body heat.
Perhaps the most visually impressive of all Pandora’s creatures are the flyers.
The banshees are reminiscent of pterosaurs, the flying reptiles of the past, or of bats, rather than birds. But they are also a little like stingrays or manta rays, another oceanic visual reference, and have jaws rather like fishes’, indicating a possible line of evolutionary descent. Flying is aided on Pandora by the lower gravity and the thicker air, which gives the flyer’s body more impetus with each stroke. But a downside is that the thicker air is harder to move through, and good streamlining is needed to achieve high speeds.
On Earth, flight seems to have evolved independently among three groups of vertebrates (backboned creatures), the birds, the dinosaur-age pterosaurs and the bats (the insects also evolved flight, again independently). All these three groups descended ultimately from the same four-legged bony fish that crawled out of the ocean some four hundred million years ago, to become the progenitor of all vertebrate life on land and in the air. Each of the three groups used adapted forelimbs as wings—but in each group a different evolutionary strategy was used, as if the primordial skeleton was pulled this way and that into new forms. In the birds, the whole forearm flaps; a reduced hand with lost or fused fingers is an anchor for feathers. In the pterosaurs, the wings were sheets of membrane that stretched from a grossly extended fourth finger and were attached to the rear legs. And the bats don’t flap their forearms at all; their wings are membrane sheets attached to a frame made of hugely extended fingers. A bat’s wing is essentially its hand.
The wings of a banshee consist of membranes stretched over a framework of bones, a little like a tent over a frame; they look something like the wings of a bat or a pterosaur. Each main fore-wing has three sail-like structures on the end, stretched over struts of bone. These vanes are used to generate extra lift and give fine control in flight. The wing also has an impressive claw.
But there is the complication that the banshees also have hind wings. There are no vertebrate four-winged animals on Earth, though some insects have four wings—some of the Lepidoptera, for instance, the big group that includes moths and butterflies. These insects have various kinds of coupling mechanisms to ensure the wings work together. Those extra rear wings, plus the wing-tip panels, give the banshee additional control over its flight, as well as providing additional power when required.
Flying animals have differing wing shapes, described by a number called the “aspect ratio”—the ratio of wing length to wing breadth. A long, narrow wing is aerodynamically efficient, but is energy-consuming to flap. So long wings are best suited to creatures that can fly in open airspaces, especially where you can just jump off a ledge to get your lift: these include the albatrosses, and the big pterosaurs of the dinosaur age, and the mountain banshees of Pandora. If you live in wooded country, the ability to take off from the ground, powered lift and manoeuvrability are paramount, so shorter wings are favoured. Thus the forest banshee has a much shorter wingspan than its mountain cousin.
When Jake, undergoing the Iknimaya initiation trial, is taken to the banshee rookery to choose his mount, we see the banshees on the ground, where they look big, clumsy, ill-adapted; with their hind limbs having been adapted to wings they have no “legs” and must stump about on folded leathery wings. The great pterosaurs were similarly poorly adapted to the ground. The banshees have given up everything else for the sake of efficiency in flight, even their manoeuvrability on the ground. But then nothing will prey on them on the ground.
Nothing save the leonopteryx.
The “Last Shadow,” as the Na’vi call it, has a superficial similarity to the banshees, but a quite remote evolutionary relationship. The banshees evolved from four-limbed creatures, but the leonopteryx’s ancestors were six-limbed; it has two sets of wings like a banshee, but also a set of true legs, which the banshee does not. And its wings are composed of individual panes that can separate like a Venetian blind, or close over to form a solid surface; the vanes are a little like the big flight feathers of a bird on Earth.
On a world where even great creatures like the banshees have something to fear, at least on Pandora you rarely need be afraid of the dark.
The first time we really become aware of the ubiquitous bioluminescence of the Pandoran forest, the glowing of the living things, is during Neytiri’s first encounter with Jake as she saves him from the viperwolves. When she douses his torch it turns out he doesn’t need it to see, for almost everything around him shines of its own accord.
The Greek roots of the word bioluminescence are “living” and “light.” Living creatures can emit light by releasing stored energy through chemical reactions, though the details differ from species to species. On Earth, bioluminescence is common in the deep sea, below around a thousand metres. Down there in the eternal dark, too deep for sunlight to penetrate, it’s thought that some eighty per cent of creatures exploit bioluminescence. On land, by comparison, it is used by very few—fireflies, glow-worms, a few fungi.
In our oceans, bioluminescence is used for a variety of purposes. Some creatures use the living light to attract mates. But mostly bioluminescence is used in the endless game of predator versus prey. Many prey animals use the dark to hide in; they will descend into the deep dark during the day, and ascend to the food-laden surface waters only at night. So if you are a hunter, having a built-in headlight, as do many predators among the shrimps, fish and squids, can be very useful in tracking your elusive prey.
Meanwhile some prey creatures like the benttooth bristle-mouth use bioluminescence as a kind of camouflage, to muddle their own silhouettes if they are shadowed against light from above. Another tactic is to raise a “burglar alarm,” to lure an even bigger predator to chase off the guy attacking you. And still another tactic, used by some shrimps and squids, is to startle a would-be predator by releasing bioluminescent material into its face.
On the other hand, some predators use bioluminescence to attract prey. In the ocean, some of the decaying matter drifting down from above can be riddled with glowing bacteria; if you can mimic that glow, your prey animal can swim right up to you expecting to find lunch, only to become your lunch.
In the Pandoran forest, bioluminescence is common among plants, and animals, such as the direhorses, exploit it too. Even the Na’vi have glowing skin-spots, yellow on blue, and they light up their Hometree with sacs of bioluminescent life forms.
Why it is that so many land-based creatures on Pandora have chosen to exploit bioluminescence, compared to so few on the Earth? The answer is that so few nights on Pandora can rarely be truly dark in the first place, thanks to the spectacular light show put on by the two suns of Alpha Centauri, Polyphemus and the other moons. While the banshees for example have developed good night vision with their secondary eyes—and perhaps other animals have developed echolocation, a sound-based detection system like that of bats—many creatures have joined in a kind of cooperative light-based “arms race.” If everybody is kept flooded with light all the time you don’t need to evolve night vision or echolocation.
Visually, the living lights of Pandora are one of the most charming aspects of the movie, even if bioluminescence isn’t used quite the way it is on Earth.
There’s a great deal more detail on Pandora’s flora and fauna available in sources like the online encyclopaedia Pandorapedia. If you check it out you’ll find that Pandora’s invented biosphere has both intellectual and emotional depth.
Intellectually, the designers have given all their creations formal species names: thus the hometree species is Megalopedians giesei, Latin meaning the Great Tree. (And of course the tree has a Na’vi name, Kelutral.) This mirrors the biologists’ classification of life forms on Earth, which sorts out living things into hierarchies: you belong to a species, which belongs to a genus, which belongs to a family, which belongs to an order, which belongs to a class, which belongs to a phylum, which belongs to a kingdom. The five kingdoms, including animals, plants, fungi and bacteria, are at present the highest level of division; all living things on Earth are supposed to belong to one of them. Biologist Peter Ward has suggested that if we do ever discover life on another world we may need to extend the hierarchy upwards to include super-kingdoms, each covering all life on Earth, Mars, Titan, Pandora, the details depending on whether or not life on the different worlds is in any way related.
And emotionally, the designers have tried to give us a visual sense of the interconnectedness of the Pandoran biosphere. Think of the ubiquity of the touch response we see in many of Pandora’s creatures, such as the helicoradian, and the way the mosses on the tree branches and light up in response to Jake’s footsteps, like a Michael Jackson video. Everything reacts to everything else, everything is connected.
This quick tour of Pandora’s flora and fauna has shown us that some aspects of Pandoran life have parallels with Earth life—there are predators and prey, carnivores and herbivores—and some don’t have such parallels, such as the ubiquity of bioluminescence. But we’re in another star system here, on an entirely alien world. Why should life on Pandora have any similarities with life on Earth at all?
And why, indeed, is there life here in the first place? Pandora is evidently habitable. Was it necessary that it should be inhabited?