Seed Storage Superpowers!
Updated: Feb 1, 2021
Did you know that most rodents don't actually have cheek pouches for food storage? Some (like hamsters) have separate pouches inside their mouths to store seeds, but most rodent species (like rats and house mice) just have very elastic skin and muscles in their regular cheeks that allow the cheeks to bulge outwards for increased food capacity. In rodents that do possess cheek pouches there are two kinds: internal pouches and... external pouches!?!?
There are a few families of rodents in the world that have developed cheek pouches with openings outside their mouths instead of inside. Two species can be found here in the Okanagan and Similkameen: the Northern Pocket Gopher, and the Great Basin Pocket Mouse, which is a Blue-listed species in BC. External cheek pouches function in much the same way as internal ones- the opening can be controlled using special muscles in the cheeks and the pouch extends down the face and towards the neck. One unique feature of external pouches though is they are completely lined with fur! This adaptation is thought to have perhaps evolved to preserve moisture loss from storing food in skin-lined pouches. Many rodents with external pouches live in dry desert areas, so it is important to preserve even the small amounts of saliva that would be lost when emptying internal cheek pouches. The photo below of a Prairie Pocket Mouse (close cousin to our Great Basin Pocket Mouse) shows its nose, mouth and chin in the middle of its face/head and the two "flaps" on either side are the external pouch openings.
Please note: The person holding the mouse in this photo is a professional biologist and is trained in safe and humane handling of wild rodents. This mouse was held for mere seconds before being released.
Harassment of wildlife without specific permits is an offense under the BC Wildlife Act and can invoke some very hefty fines.
Bonus fact: Platypuses and some monkey species also have internal cheek pouches!