Rabbits live on a nutritional knife edge: nonstop grazers that cannot vomit, yet built to process unstable plants. Their stomach is locked down by an unusually strong cardiac sphincter, and their diaphragm and esophagus are arranged so that the reverse contractions needed for emesis simply do not fire.
Survival, for them, is outsourced to motion. Powerful gastric and intestinal peristalsis push food in one direction only, while the cecum acts as a biochemical sorting hub that relies on microbial fermentation and volatile fatty acid production to strip calories from low‑value fiber. Instead of purging, the system double‑handles nutrients: soft cecotropes, packed with vitamins and amino acids, are expelled, then immediately re‑ingested and routed back through the upper gut for a second harvest.
This is not a cautious design; it is an efficiency play with no safety valve. Toxins or hair can form obstructive masses because there is no emetic reflex, leaving rabbits dependent on continuous gut motility, balanced microbiota, and constant access to abrasive, high‑fiber forage to keep ingesta moving. The price of that elegant grazing machine is simple. When the one‑way conveyor jams, there is no reverse gear.
