Someone Surrendered a Guinea Pig — Here's the Intake That Keeps It Alive

It comes in on a bag of colorful muesli, in a cage barely bigger than a shoebox, usually alone. Maybe a kid lost interest, maybe a family is moving, maybe someone bought two from a pet store not knowing one was pregnant and now there are six. Guinea pigs are one of the animals rescues are quietly worst at, because almost everything the average owner "knows" about keeping them is wrong, and because a guinea pig will sit there looking fine right up until it crashes. The intake you run in the first 48 hours decides whether this animal lives a healthy seven years or dies of something preventable in three weeks.

Here's how to run it.

Assume It's Sick Until It Proves Otherwise

Guinea pigs are prey animals, and prey animals are built to look healthy. A cavy will keep eating, keep moving, keep acting normal while a serious problem builds underneath, because over evolutionary time the ones that showed weakness got picked off. A refusal to eat is often the first sign you'll get, and by then the clock is already running.¹

So the master signal at intake is the same one it is for rabbits: appetite and droppings. Offer hay the moment the animal arrives and watch. Is it eating? Are there normal fecal pellets in the enclosure within a few hours? A guinea pig that stops eating or stops pooping is not a "see how it looks in the morning" case — it's GI stasis, a digestive emergency where the gut slows or stops, and it can progress to death within 24 to 48 hours. The common guidance is blunt: if a guinea pig hasn't eaten or passed stool in 12 hours, treat it as an emergency.²

Write down what you see, with the time. "Ate hay 3pm, several droppings by 6pm" is a baseline you'll be grateful for if the animal goes quiet on day four.

Fix the Diet on Day One — It's Almost Certainly Wrong

Whatever this guinea pig came in eating, it was probably making it sick, because the pet-store default — a bowl of colorful muesli and a couple of carrots — is close to the worst possible diet.

The foundation of a healthy guinea pig is unlimited grass hay, available free-choice all the time. Hay should make up roughly 85% of the daily diet, with a small ration of plain pellets (about 10%) and fresh leafy greens (about 5%).³ There are two separate reasons hay is non-negotiable. First, it's the fiber that keeps the gut moving and prevents the stasis above. Second, guinea pig teeth never stop growing — the cheek teeth and incisors grow continuously, on the order of 1 to 2 mm a week — and the only thing that wears them down is the sideways grinding chew that long-strand hay forces. Feed mostly pellets and grain and the teeth wear unevenly, overgrow, and can eventually trap the tongue. Guinea pigs with established dental disease may need corrective procedures every one to two months for the rest of their lives, so preventing it with hay from day one is enormously cheaper than treating it.⁴

So your day-one diet is simple: unlimited grass hay (timothy or orchard for adults, not alfalfa), fresh water, a measured portion of guinea-pig-safe greens, and a small ration of plain pellets. Ditch the muesli mix and the sugary treats.

Supplement Vitamin C — Every Single Day

This is the one that catches even experienced dog-and-cat rescues off guard. Guinea pigs, almost uniquely among common companion animals, cannot make their own vitamin C — they lack the enzyme, exactly like humans do — so it has to come from the diet every day. Without it they develop scurvy, and the symptoms read like a checklist of things you might otherwise misdiagnose: rough coat, loss of appetite, difficulty eating, a stiff or limping gait, swollen joints, poor wound healing, and greater susceptibility to other infections.⁵

A healthy adult needs roughly 10 to 30 mg of vitamin C a day, and a sick or pregnant animal needs more.⁵ Pellets are often sold as "fortified," but the vitamin C in them degrades quickly once the bag is opened and exposed to light and air, so you can't rely on pellets alone. Provide it directly: vitamin-C-rich greens like bell pepper daily, plus a dedicated supplement (a tablet or liquid dosed by weight — not the drops that dissolve in the water bottle, which degrade and make the water taste bad enough that the animal drinks less). Put the daily C dose on the same care record as feeding, because "did anyone give the vitamin C today?" is exactly the kind of thing that falls through the cracks in a busy foster home.

Never Adopt Out Just One

Guinea pigs are herd animals. In the wild they live in groups and depend on constant companionship; kept alone, they're prone to stress, loneliness, and depression. This isn't sentiment — Switzerland's animal welfare law treats keeping a single guinea pig as a form of abuse and requires owners to keep at least two.⁶ You don't have to adopt them out in the exact pair that came in, but a lone guinea pig should be bonded with a compatible companion, and your adoption policy should reflect that. A bonded pair is also easier to place well, because you're handing the adopter a stable social unit instead of an animal that will pine.

One caution that runs the other way: intact males and females left together breed relentlessly, and you may not know a female's history. Sex every animal at intake, separate by sex, and get them neutered/spayed before pairing anything that isn't already a stable same-sex or altered group — otherwise your intake of two becomes an intake of eight.

Quarantine Before the Animal Meets Your Others

Guinea pigs from pet stores, homes, or Craigslist should be quarantined for two to three weeks before going anywhere near your resident herd, and there are specific things you're watching for.⁷

The big one is mange, caused by the Trixacarus caviae mite. Guinea pigs frequently carry these mites with no symptoms at all, and it's precisely the stress of being surrendered and moved that triggers an outbreak — so an animal that looks clear on arrival can erupt in intensely itchy, painful, sometimes seizure-triggering mange a week later. Many rescues simply treat every incoming guinea pig for mites in quarantine rather than risk seeding it through the whole population.⁷ Also watch for ringworm (a fungus, transmissible to humans, so wash hands or glove up), and listen for respiratory trouble — clicking, wheezing, or crackly breathing can mean an upper respiratory infection or pneumonia, which is one of the most serious diseases in pet guinea pigs and needs a vet, not a wait.⁷

Quarantine also protects the incoming animal: a stressed, immune-compromised new arrival is exactly who catches whatever your resident group is carrying.

Keep One Record Per Animal From Day One

The thing that quietly breaks small-animal rescue is lost information. A guinea pig passes through surrender, intake, quarantine, vetting, foster, and adoption, and at every handoff the knowledge — when it last ate normally, what its droppings looked like, whether it got its vitamin C today, the mite-treatment date, that it's bonded to the other sow and shouldn't be split — tends to live in one person's head and evaporate. With an animal whose first symptom of a fatal problem is "ate a little less today," that history is the difference between catching stasis on day one and finding the animal collapsed on day three.

Keep one record per guinea pig from the moment it arrives: intake date and circumstances, weight, sex, daily appetite and droppings, vitamin C given, quarantine and mite treatment dates, vet notes, diet, bond partner, and temperament. This is exactly the kind of per-animal record Pawsies is built to hold — one profile per animal with medical events and daily notes attached, viewable by your whole team from a phone, so the history follows the animal to its next home instead of dying in a notebook. (It's animal-agnostic; guinea pigs, not just cats and dogs.) A binder works too. What matters is that the next person doesn't start from a muesli bag and a guess.

A guinea pig can live five to seven years or more with the right care. The one someone handed you in a shoebox didn't fail — it was set up to. A careful intake — assuming illness, fixing the diet, supplementing vitamin C daily, never leaving it alone, quarantining before contact, and writing it all down — is what turns one more impulse-buy cavy into the home where it finally stays.