Here's why it happens:
* Muscle Stiffness: After death, the body's cells stop producing energy. This causes the muscles to become stiff and rigid due to a lack of ATP (adenosine triphosphate), the molecule that fuels muscle contractions.
* Rigor Mortis Timeline: Rigor mortis typically sets in a few hours after death and reaches its peak stiffness around 12-24 hours later. After that, the muscles start to relax again as the proteins in the muscles break down.
Important Note: While you might observe this stiffening in a deceased gerbil, it's important to handle the body with care and respect.