* Size: While a cat's throat is quite flexible, a gerbil is still significantly larger than a typical prey item like a mouse. The size and shape of a gerbil would likely make it difficult to swallow whole.
* Instinct: Cats are equipped with instincts to kill and eat their prey efficiently. This usually involves breaking the prey down into smaller pieces. A cat would likely be more inclined to bite the gerbil's neck and kill it before consuming it.
* Digestive System: Even if a cat somehow managed to swallow a gerbil whole, it's doubtful it could pass through the digestive system. The gerbil's bones, fur, and other components are unlikely to be easily digestible.
Important Note: While this information is based on general knowledge and behavior, it's always best to keep cats and gerbils separate. Cats are natural predators, and even if they don't swallow a gerbil whole, they could still harm it.