Many rodents have cheek pouches, and hamsters’ get impressively big for such a tiny animal. When full the cheek can expand across the shoulder blades.
For a Syrian hamster, a larger species, entire baby carrots can disappear into the cheek pouch.
Hamster cheek pouches are extremely elastic, expanding to nearly triple their size, an adaptation that has to do with the cold climate and harsh terrain they live in, making food storage important. Their elasticity and the fact that they have their own blood vessels are among the traits that make them popular for research on transplants and microcirculation.
How do hamster cheeks work?
Hamster cheeks contain pouches that resemble two small deflated balloons. If you watch your hamster closely enough, you will notice that once it places food inside its mouth, it rotates around these pockets in order to make it easier to slide back.
Once the snack is positioned correctly, the pouch expands, and the retractor muscles squeeze the pouch pulling the food back with it.
Dine & Dash
Hamsters can both eat and run with their cheeks full. They can stuff the cheeks with up to 20% of their body weight, but as the cheeks are extremely elastic and stay in place along the shoulders, they don’t noticeably affect the speed of the hamster or how far they can travel.
Fresh all-day
To keep the food fresh and dry during foraging trips, the hamster’s mouth doesn’t release any saliva into the pouches.
Built-in luggage
Hamsters do not only carry food in their pouches, but they can also bring bedding or building material back to the burrow for nesting or decorating. Wild hamsters may also place their babies inside their cheek pouches if they feel threatened or anxious.
SOURCE
SCIENCE DIRECT: “Veterinary science and veterinary medicine – cheek pouch.”