The Sarlacc, according to the Star Wars Encyclopedia, is not a native of Tatooine, but seems to function in the desert climate just fine, digging itself into the ground and waiting for prey to come. We can't be sure how big the Sarlacc is, but it must be fairly large to have such a huge appetite. While burrowing seems limited to smaller animals on Earth, the Sarlacc somehow manages to get its huge bulk into the ground. For a terrestrial model for this kind of behavior, we look to a much smaller animal, the ant lion.
Ant lions live in a variety of climates and are common in the southwest United States. In their larval stage, ant lions have a large head, spiny jaws, and a bristly body about 1/2 inch long. Moving backwards, the larval ant lion traces out a circular pattern, spiraling steadily inward, digging deeper and deeper, until it creates a steep, conical pit in the sand and buries itself at the base of it. All that remains visible are long, curved jaws that lie open waiting for prey.
When an unlucky ant comes up to the edge of the pit, the sand collapses, and it falls down into the trap. The ant—much like Lando Calrissian—finds it can't climb out of the pit. The sides are angled so they crumble when the victim tries to crawl out, which is just what happens when Lando tries to climb out of the Sarlacc's pit. In the rare event that the prey looks like it might escape, the ant lion flicks sand at it, triggering an avalanche that brings the victim tumbling into its hungry maw. The ant lion snaps its jaws shut, injects a paralyzing poison and digestive acids into the victim, then sucks out its vital juices. When the ant lion is finished, it flings the carcass out of the pit with a flick of its head.
Although the body of the prey isn't digested inside the ant lion for one thousand years, as is said of the Sarlacc, any juices it has extracted from the prey do remain in the ant lion's body, since it has no method of excreting waste products. It's not until the ant lion transforms into its pupal stage —the inactive stage between larva and winged insect —that it can eliminate waste. This means that the ant lion must hold all its waste for its entire larval lifetime: three years. And I thought sitting through a movie could be tough.