Chinchillas come from a cold desert. It is a harsh environment with harsh plant material that chinchillas rely on for food. As herbivores in this type of environment, chinchillas have developed many mechanisms to succeed. They have unique and modified organs, modified behavior, and specific gut bacteria all to aid their digestion.
A viscacha, a chinchilla relative, in an environment similar to where you would find wild chinchillas. Source
All kinds of herbivores face a certain difficulty in their diet. Although plant life is abundant and usually easy to obtain, plants are hard to digest. Herbivores of all kinds have to possess a sophisticated digestive system just to get everything they need from their diet. They need the aid of beneficial bacteria to break down plant material and have specific places in digestive tract where their food ferments. Chinchillas digest plants using hindgut fermentation. This type of herbivore is monogastric with a simple, one-chambered stomach. Chinchillas house the bulk of their beneficial bacteria in the cecum. After eaten food leaves the stomach and small intestine, it goes into the cecum. The cecum is where fermentation takes places. It houses the bacteria that breaks down cellulose, a large component of plants that is otherwise indigestible.
A diagram comparing human and rabbit (another hindgut fermentor) GI tracts. Note the large cecum. Chinchillas also have a well developed cecum. Source
The large intestine absorbs what it can but much of the nutrients now made available by fermentation are lost in feces. This is why chinchillas eat some of their poops! The cecum makes a certain poo called cecotropes. Cecotropes are nutritionally concentrated and full of beneficial bacteria. This is the kind of poop chinchillas will ingest. Coprophagy might seem gross but it is important for chinchillas to do. They get more nutrition and it helps maintain their gut flora populations! The whole process takes about 15 hours from start to finish. Chinchillas rely so much on this system that any imbalance can cause major issues. How does a chinchilla's digestive system become unbalanced?
What can cause an imbalance?
Gastrointestinal stasis or GI stasis is one of the deadliest things a small herbivore can get. It can have many causes and can be a result of another issue or the instigator to other problems. GI stasis occurs when the digestive system slows down or stops. Chinchillas should have food available at all times. Chinchillas won't overeat their pellets and need a grass hay- usually timothy- to eat throughout the day. Their GI system is designed to be working on food at all stages. If the chinchilla is out of food for a time or otherwise has stopped eating, the digestion may slow down or stop. This will lead to a build up of gas that is difficult to eliminate. In fact, chinchillas do not have mechanisms to deal with gas and will need you or your vet's help.
Any imbalance in the gut flora of a chinchilla can cause bloating which can then lead to GI stasis and vice versa. Beneficial bacteria can become unbalanced from stress, illness, sudden changes in food, and introduction of inappropriate foods. If you are switching your chinchilla's food, be sure to do so slowly. If you are wanting to give your chinchilla a new treat, use in moderation and do not use treats high in sugar or fats. Seeds, nuts, and most dried fruits- including raisins- are best avoided.
Remember to always support your chinchilla's digestion by provided good quality pellets and hay at all times. Use chinchilla safe treats in moderation and keep your chin stress free!