Why should you never trust a pig with a secret?
Why this joke works
A Pig That Is Bound to Squeal
Pigs squeal as a normal vocalization. Informally, “squeal” also means revealing secret information, especially by informing on someone. A pig entrusted with a secret is therefore “bound to squeal” in both senses: the animal will make its characteristic sound, and the untrustworthy confidant will talk. The phrase “bound to” means certain to happen, letting the animal behavior serve as supposed proof of future betrayal.
A closer look
The Question Treats Animal Behavior as Character Evidence
The setup frames secrecy as a matter of trust and invites a reason tied to personality. Instead, the answer uses the pig’s expected sound as if it proves the animal cannot keep quiet. “Bound to” makes the prediction sound inevitable, strengthening the mock warning. The question-and-answer form also lets a brief pause create anticipation before the single revealing verb.
Fact behind the joke
Pigs Communicate With More Than Squeals
USDA’s feral-swine guide describes a varied vocal repertoire that includes contact, nursing, and feeding grunts as well as squeals and growls. Pigs can also communicate through teeth clacking and scent glands. The punchline picks their best-known high sound, but real pig communication changes with activity and social context rather than relying on one universal noise.