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In the original version of Star Wars (or Episode IV), we saw Banthas on Tatooine, but nothing larger. Then in Return of the Jedi, we saw the Sarlacc (which, to be fair, isn't native to Tatooine). In later versions, we saw a number of dewbacks in Mos Eisley. (I've also read about the Krayt Dragon, which is even larger -- we do see a skeleton of one in Episode IV, but no living one or any indication how old the skeleton is.)

The reason this started to bother me is because the Dewbacks reminded me of dinosaurs and I remember reading about how larger dinosaurs were vegetarians because there just were not enough animals that could live in their range that they could eat to get the energy they need.

We see almost nothing growing on Tatooine. Luke's uncle is a farmer, but a moisture farmer, not a food or plant farmer, and there's no other evidence (at least in the movies) of many plants growing on Tatooine.

And on Hoth, Han comments, "There isn't enough life on this ice cube to fill a space cruiser." Again, there's almost no evidence of plant life on Hoth, but the Rebels are using tauntauns (that are native and likely from near where they are) and Luke is captured by a wampa, which is also kind of large.

On both Tatooine and Hoth, we see these animals in areas of little or no vegetation, so unless they all store food for extreme periods of time (to allow for long migrations), they're in or near their natural habitat.

On the other hand, on Dagobah, where there is plant life in abundance, and more than enough to support larger animals, we get only one hint of a big animal (when Artoo is presumably eaten up and spit out under water). (At least on Naboo, there's an abundance of plant life and large animals.)

Are these animals too big to realistically survive on ice and desert planets where there is so little plant life? Is there anything to give us reason to believe there is enough life at the lower end of the food chain, with plants (or maybe some kind of algae or bacteria) that can support such large life forms on these planets?

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We saw the Krayt Dragon skeleton in the original version of ANH too. –  dkuntz2 Dec 6 '11 at 5:54
    
Thanks -- added that in the question. I always kind of ruled that out in my head because we had no idea how old the skeleton was or if it had only recently been uncovered, so in my head, I always figured it could be explained from being from a previous era. –  Tango Dec 6 '11 at 6:00
    
Don't forget the rancor! –  Kevin Dec 6 '11 at 14:10
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Don't forget the womp rats either! –  Peter Cassetta Dec 13 '11 at 22:59
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@Kevin: The rancor was a rich Hutt's pet; we can assume it was imported. And clearly it was fed regularly. –  Tynam Jan 3 '12 at 13:54

7 Answers 7

up vote 21 down vote accepted

Hoth: : Lichens

Fields of lichens grew in Hoth's vast cave grottoes, providing an important source of food for wild tauntauns. These animals also sometimes found lichens on exposed outcroppings on the surface and just below the frost layer. (source: "Galaxy Guide 3: The Empire Strikes Back")


Tatooine::

This one has no explicit in-Universe explanations.

What is known is that:

  • Tatooine was originally modeled on either a desert planet from Flash Gordon, and/or Arrakis.

  • Like Arrakis, it was once a thriving ecology, NOT dessicated desert all around (source). The change was due to bombardment Rakatan Infinite Empire after a rebellion by native Kumumgah race.

  • Krayt dragons fed on banthas, of which there were plenty

  • Banthas were not necessarily native to Tatooine (origin disputed between many words) BUT they were able to survive in almost any extremes of environment and could go without food or water for several weeks, and often were used on desert worlds. Ecologically they might have been similar to camels.

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And presumably the wampa would live off of tauntauns. –  Kevin Dec 6 '11 at 14:13
    
@Kevin - yes. I think the question itself mentioned that which is why I didn't bother covering it –  DVK Dec 6 '11 at 22:06
    
I had initially thought so too, but I looked at the question and didn't see it. I still don't see it explicitly, just "the Rebels are using tauntauns... and Luke is captured by a wampa". –  Kevin Dec 6 '11 at 22:19
    
A planet-wide ecology based on (photosynthetic) lichens growing in caves? –  mu is too short Oct 26 at 1:05

And on Hoth, Han comments, "There isn't enough life on this ice cube to fill a space cruiser."

Han is not exactly a Xenobiologist. He is using hyperbole for dramatic effect to express that he does not feel that the recon patrols are worth wasting time on.

As for Tatooine, Camels have developed large humps to help them retain water and nutrients for long periods where they are unable to replenish naturally, The animals large size could allow them to retain large amounts of water to help keep them hydrated. In addition what you see on Tatooine is not the entire planet. In SW Galaxies there were areas that had water. There seems to be quite a bit of life underground as well. The evolution to large size could be an effective strategy for non meat eaters survival seeing as large creatures are going to be difficult to take down for the small predators that would thrive in a desert. And the areas where wildlife thrives is not in the open desert but in oasis that provide food, water, and shelter during the rain cycles. The key to the survival of the Banthas is that there are so few of them. The sand people have a herd that they have domesticated.

The Krayt is very rare and I am unaware of any live sitings in the EU just the rumors of a friend of a friend... The remnants we see in the desert could be from a period where there was more water and fauna above ground.

In a place like Dagobah being heavy would be a hindrance since the land is swamp. There is lots of water so it would make sense that any large creatures would be at most amphibious. Though I recall there are a few large avian creatures that inhabit dagobah as well.

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IIRC, humps aren't there to retain water (I think this was debunked on cracked.com). You may want to ask on skeptics.se –  DVK Dec 6 '11 at 22:04
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Yep, humps are fat reserves. Camels store water in the same places as human-beings (throughout the entire body). They've just adapted to be very efficient in using their body's water supply, and they're able to function on very little water as well as in a super-hydrated state. These extreme changes in fluid levels would normally cause an animal's red blood cells to rupture due to osmotic pressure, but Camels have specially adapted ovular blood cells that prevent this. –  Lèse majesté Dec 7 '11 at 1:11
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fat however is rich in water, so the net effect of the hump is to store water as well as nutrients. –  jwenting Dec 7 '11 at 8:32
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@DVK - Indeed it was a lapse in judgement to make a claim of a single function for the humps. My humps, my lovely camel humps... yep gonna be one of them days :) –  Chad Dec 7 '11 at 14:09
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@jwenting: Where did you hear that? Fat is made of lipids/oils, which are completely insoluble in water. Your adipose tissues do contain some water, so there is water in the camel's hump, but the water content of muscle & lean tissue is much higher. Additionally, it takes water to process fat for energy--much more than the adipose tissue actually holds, so the result is a net water loss when the camel consumes its hump fat. –  Lèse majesté Dec 8 '11 at 0:51

The polar bear is the largest land predator on earth, yet lives in an area similar to the ice wastes of Hoth. So an equivalent to the wampa exists on the real earth.
Deserts too are teeming with life, most of it underground or highly seasonal. The dew farms where Annakin grew up weren farming crops or animals (at least as their primary product) but drinking water, similar to dew collectors in Frank Herbert's Dune.
We don know if areas elsewhere are less arid. And of course even in deserts on the known earth large animals can survive. Camels, onyx, even crocodiles (albeit usually on the fringes).

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Sorry, wrong. Polar bears can exist where they do due to marine life (seals) –  DVK Dec 6 '11 at 11:14
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@DVK: What's to say that there aren't similar fat-rich prey animals on Hoth? The movie only gives you a very brief glimpse of the planet. If you watch nature documentaries on the arctic, you'd see polar bears and other animals roaming in equally inhospitable and apparently desolate areas. Many animals IRL can survive on a single meal a year, and many animals travel great distances to find food. Who knows, maybe there are giant prey animals underground analogous to whales on Earth--a single corpse feeding thousands of animals for months or years. –  Lèse majesté Dec 6 '11 at 13:55
    
@Lèsemajesté - not terribly plausible biologically due to assorted energy considerations, and not expressed anywhere in canon. –  DVK Dec 6 '11 at 22:08
    
@DVK: well, the food sources for a lot of other species aren't specifically named in canon either. And while it's not very plausible by real-life standards, it's not that much more implausible than giant space worms or other elements of the Star Wars universe. –  Lèse majesté Dec 7 '11 at 1:00
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well said. Nowhere is mentioned what the animals eat, so if we just take the canon literally they don't eat anything except hapless travelers. The canon only shows the very few top predators and maybe a few top herbivores (when those are used as beasts of burden or farm animals), doesn't mention anything smaller than the equivalent of that polar bear or giraffe at all. That doesn't mean such don't exist. –  jwenting Dec 7 '11 at 6:21

All good answers, but I think the worst offender is the Exogorth, of "This is no cave" fame. It is probably too big to survive at all, let alone on a barren asteroid.

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-1 Your assumption that a silicon based life form would exist with the same biological constraints as carbon based life forms is flawed sorry. –  Chad Dec 7 '11 at 14:44
    
@Chad: good point about it being silicon based. But there would still be a problem with surface area / volume relationships. (Correct me if I'm wrong.) –  Wikis Dec 7 '11 at 14:52
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This is true under earth like gravity. In the vacuum of space under the influence of asteroid microgravity I do not think this holds. I will concede I really doubt there is a space slug of that size out there, but that is not the same as saying it is impossible. –  Chad Dec 7 '11 at 15:02
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Actually that's an excellent point. I see someone downvoted your answer, but I think for someone to do that it shows they missed the entire point of my question. While the exogorth is in an almost null-gravity environment, which would make it not subject to the normal square-cube rule, but at least it eats minerals, which explains its food source. –  Tango Dec 7 '11 at 16:16
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our metabolism requires oxygen, that doesn't mean there are no other mechanims out there. There are for example bacteria whose metabolism is sulphur based. If that slug were to operate on those principles, all it'd need was a source of sulphur rich rock or interplanetary dust. –  jwenting Dec 8 '11 at 6:09

There are a number of biological strategies that could conceivably account for the apparent lack of food supply comparable to what earth-based fauna of comparable size would require.

While the lichens mentioned by DVK would likely be the key component of the lower levels of the food chain, a greatly reduced metabolism, particularly supplemented by hibernation behavior, would help account for the size of wampas and tauntauns.

Various forms of biological symbiosis could also help provide nutrition for either species. There are precedents for this in earth biology:

While most of the approximately 5,000–10,000 known species [of sponges] feed on bacteria and other food particles in the water, some host photosynthesizing micro-organisms as endosymbionts and these alliances often produce more food and oxygen than they consume.

While slower metabolism and hibernation seem less likely for hot-weather dewbacks and krayt dragons on Tatooine, again, there is precedent in earth fauna:

They emerge after the summer rains in order to feed and breed in large, temporary rain pools. During the rest of the year, Sonoran Desert Toads hibernate underground.

Biological symbiosis is also a possibility in Tatooine fauna.

Another possibility is supplemental nutrition through photosynthesis, either by symbiosis or through alien biology that crosses characteristics of earth plants and animals. This is particularly plausible for Tatooine, where the one element in abundance appears to be sun.

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Not to mention the symbiosis between man and domesticated animals. Maybe Tauntauns and Dewbacks were transplants or otherwise selectively bred from smaller sizes by humans (like domesticated camels, which can grow to over 1500lbs while wild camels went extinct in North Africa in prehistoric times). If humans can survive in those places, then they certainly have a food/energy source that could be used to feed their domesticated animals. –  Lèse majesté Dec 6 '11 at 14:07
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@Lèsemajesté: Wookiepedia says both tauntauns and dewbacks are native to Hoth and Tatooine, respectively. –  Tango Dec 6 '11 at 17:00
    
@TangoOversway: There's still a small chance that they could be transplated from a different region of Hoth/Tatooine though--just as horses and other domesticated animals have often been introduced into areas they're not native to. –  Lèse majesté Dec 6 '11 at 17:07

I will answer primarily for Tatooine, as Hoth has been covered:

Most answers for Tatooine have forgotten the womp-rat, apparently a two-meter creature indigenous to Tatooine. The video game Rogue Leader shows them moving in large herds in the training map. That would be a prime food source for large carnivores like the dewbacks and krayt dragons. Womp-rats could, in turn, feed on smaller fare; in ROTJ, there was a connecting shot showing a large frog-like animal capture a much smaller forager, and in Ep 1, Jar Jar gets in trouble with Sebulba over trying to steal a fresh frog or lizard of some kind from a shop vendor. It would stand to reason that such creatures would thrive in at least a captive situation on Tattoine, suggesting those animals may be native to the planet and are captured and bred, or simply hunted.

Even deserts have abundant life. There are not many places you could go on this planet and not find life on some scale. Granted, most true deserts don't have very large apex predators (coyotes, maybe cougars are probably as big as you'll see in the American Southwestern deserts, while the High Sahara's apex predators are small fox species and the very rare Saharan cheetah), but it's there. Introduce a few large domesticated species (such as the camel) and you have a food web.

Also, keep in mind that a lot of the large animals we see in Star Wars are domesticated. A domesticated animal is more or less dependent on its handler for its food; so, herbivores don't necessarily need large fields to graze in, and carnivores don't need a similarly large hunting range. It's the human handler that must provide the food, and they can do so by buying it, growing it, or hunting for it.

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One of the things I found most unbelievable about anything in all of the Star Wars films, was the series of ever-larger sea monsters swallowing each other as the blase Jedi descend to Jar Jar's underwater home town. Not only do they get huge (apparently to impress the audience with how big the CGI is), but huge creatures are consuming each other in a very short amount of time. This seems like a huge mathematical problem of scale, since unless this is an astronomically unlikely event, I would expect it to take many years for those animals, and much more consumption of smaller creatures, to get those large creatures to exist in the first place... in other words, it's hard for me to wrap my head around quite how extremely wrong that sequence seems.

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