Design News: There are enormous lifeforms that exist on the Ugnaught’s rather barren desert planet. How could such large animals be sustained on a planet with such seemingly limited resources?
Patrick Johnson: Let’s consider just a single animal, the Mud Horn (the rhino-like beast). It's my understanding that it's based off of an actual pre-historic Earth animal called the Elasmotherium. It is thought that creatures like dinosaurs grew larger than creatures we see today because of a more oxygen-rich atmosphere. Perhaps on Arvala-7, the atmosphere has a higher mix of oxygen. It'd also require a lot of food. The Elasmotherium was an herbivore (like a rhino), so there didn't seem to be a lot of plant life shown, so perhaps this was a carnivorous creature. There easily could be a food chain where the sparse plants could feed small creatures which would in turn feed the medium creatures which would then feed the largest creatures. There are apparently plenty of Jawas around for the Mud Horn to consume as they try to obtain the eggs.
Mark Brake: According to Star Wars legend, another enormous lifeform, the exogorth, reached its size by swallowing spaceships whole. That’s why they lurked about in asteroid fields. They also burrowed into an asteroid and fed off stellar energy emissions, mineral-rich deposits within the asteroid, and floating space debris. This seems an unlikely scenario!
But with regard to the huge lifeforms on Ugnaught’s desert planet, perhaps a better clue can be gotten from that other famous of desert planets: Arrakis, in Frank Herbert’s celebrated 1965 classic sci-fi novel, Dune. The huge sandworms of Arrakis are like our Terran whales. They too have their own enclosed ecosystem, in which they thrive. The sandworms effectively swim through the sands of Arrakis, swallowing huge pockets of spice, getting their sustenance from the plankton that live within it. The worm then excretes a more refined version of the spice, which the plankton then feed upon, allowing the lifecycle and spreading the spice over the desert planet. One imagines the ecosystem of Ugnaught may function in a similar fashion.