A rat can compress and squeeze through which size opening?

• A. 1/4 inch
• B. 1/2 inch
• C. 1 inch
• D. 2 inches

Answer: (B)

Rats can squeeze through surprisingly small openings because their skeletons are highly flexible and their heads are narrow relative to their bodies. The smallest gap they can typically pass through is about half an inch (roughly 12.7 mm). So an opening of this size can admit a rat, making it a critical threshold for exclusion. A quarter-inch opening is generally too small for a rat and is more in the range of what mice can fit through; openings of an inch or two would also allow entry, but they’re larger than the minimum size a rat can maneuver through. The key idea is that the rat’s ability to compress and slide through narrow spaces makes the half-inch opening the practical limit to watch for when sealing entries.