Why do pufferfish inflate?

Answer: Defense against predators

Looking attractive to mates — Wrong. Inflation is a threat response, not courtship. Some pufferfish do create circular sand patterns to attract mates, but inflating is for defense.

Warming cold water around them — Wrong. Inflation doesn't generate heat. It's a defensive mechanism to appear larger and harder to swallow.

Defense against predators ✓ — Correct! When threatened, pufferfish rapidly pump water into their elastic stomach, inflating like a balloon to 2-3x normal size. This makes them too large and round for predators to swallow. Many pufferfish also have spines that stick out when inflated and contain tetrodotoxin poison. Triple defense!