why zebras don't get ulcers?

why zebras don't get ulcers?
Why Zebras Don't Get Ulcers is a 1994 (2nd ed. ... The title derives from Sapolsky's idea that for animals such as zebras, stress is generally episodic (e.g., running away from a lion), while for humans, stress is often chronic (e.g., worrying about losing your job).
Full answer in: en.wikipedia.org
More questions like: why zebras don't get ulcers?