Animal Care/Guinea pig
Guinea Pigs (also called cavies after their scientific name) are rodents belonging to the family Caviidae and the genus Cavia. Despite their common name, the animals are not pigs, nor do they come from Guinea. Male guinea pigs are called boars, females sows and babies are called pups. They are originally native to the Andes, and while they are no longer extant in the wild, they are closely related to several species which are commonly found in the grassy plains and plateaus of this region. The guinea pig plays an important role in the folk culture of indigenous South Americans, especially as a food source, but also in folk medicine and in community religious ceremonies. Since the 1960s, the guinea pig has become increasingly important as a staple food in the Andes, and efforts have been made to increase consumption of the animal outside South America. See the cookbook entry for links to recipes.
In Western societies, the guinea pig has enjoyed widespread popularity as a household pet since its introduction by European traders in the sixteenth century. Because of its docile nature, the relative ease of caretaking, and its responsiveness to handling and feeding, the guinea pig remains a popular pet choice. Organizations devoted to competitive breeding of guinea pigs have been formed worldwide, and a large number of specialized breeds of guinea pig, with varying coat colors and compositions, are cultivated by breeders.
Choosing a Guinea Pig 
Taking care in choosing your guinea pig and its possible companions is the first, and possibly the most important, step in keeping guinea pigs. Make sure your guinea pigs are either of the same sex or neutered/spayed. Never trust a pet store employee to sex a guinea pig. Pet stores provide absolutely zero training in sexing their animals. As there have been several documented cases of major pet stores purchasing guinea pigs from breeders that later had their animals confiscated and were even convicted of animal cruelty, it is always better to first try and adopt from your local humane society or cavy-specific rescue. This reduces the possible risk of receiving an already unhealthy guinea pig. A lot of people argue that buying a guinea pig from a pet store would be "rescuing" it, when in fact, it just gives more money to the store, and opens up the space for one more guinea pig that they can sell. Guinea pigs from pet stores are often times pregnant, ill, and/or malnourished. To find a trustworthy guinea pig rescue or animal shelter near you, please visit Petfinder.com.
As prey animals, guinea pigs have evolved to hide any signs of illness, as long as possible in order to avoid becoming the main targets of the dangerous predation. This can make it difficult to recognize an illness or ailment. The best way to check for them is to place the cavy carefully on its back and check the belly. Their feet should be clean-looking and not red or irritated; with no broken or extraordinarily long nails. Check their teeth for length and evenness (see section below). It is also important to check their eyes and nose, to make sure that there is no mucus or crust there. These are signs of an upper respiratory infection, or URI, and can be deadly if left untreated.
The most common kinds of guinea pig (especially in pet stores) are the short-haired "American" or "Self" breed and the "Abyssinian", which has curly, cow-licked hair. Long-haired guinea pigs (the Sheltie/Silky and Peruvian breeds) are very beautiful pets, but they need daily grooming to be healthy, thus making them not usually suitable for children. The hair near the rear of the Guinea Pig must be cut and cleaned on a regular basis, or it will get caked with feces and the bedding from the cage. Short hair guinea pigs take less effort in the hygienic and cosmetic categories, but still need to be properly cared for. Therefore, the Peruvian guinea pig breed is the most difficult breed to care for due to the long hair. It gets tangled extremely easily, and is not recommended for anyone without extensive time to care for the cavy's hair every day.
How many? 
The vast majority of rescues, knowledgeable vets, household breeders and scientists will tell you that guinea pigs should be housed in groups of two or more. Not only is making sure your guinea pigs have companions important for their health and happiness, keeping multiple guinea pigs will improve the fun of having these animals as pets as you watch them interact. In practice, the best option is usually a pair of guinea pigs. Of course, the most important factor in choosing groups is to make sure you will not have any unwanted babies, so make sure your pets are either of the same gender or spayed/neutered. Once again, never trust a pet store employee to sex a guinea pig. If you are not confident in sexing guinea pigs, buy/adopt whatever guinea pigs you so desire, and then take it to your vet or a cavy-specific rescue to have its gender confirmed before introducing them at all.
While groups of boars might get along (provided no females are present and they are carefully introduced), and groups of females are often fine, the easiest combination is one neutered boar (neutering is cheaper and safer than spaying) and one or more females. The personality of individual guinea pigs varies; with some being very amicable to company and others incapable of showing anything but hostility to other cavies. This is where a guinea pig-specific rescue will come in handy, as they will have a better understanding of the sociability and general behavior of any guinea pigs at their shelter than would a pet store or high-volume shelter more concerned with the dogs and cats they will be dealing with.
Guinea pigs are active during the day, but are actually crepuscular (most active at dawn and dusk). Guinea pigs are very gentle, and even untamed guinea pigs will not bite unless you are causing them pain or they have been abused in the past.
Guinea pigs have a poor sense of sight, but well-developed senses of hearing and smell. Vocalization is the primary means of communication between members of the species.
- Wheek - A loud noise that is essentially onomatopoeic, also known as a Whistle. An expression of general excitement, it may occur in response to the presence of its owner or to feeding. It is sometimes used to find other guinea pigs if they are running. If a guinea pig is lost, it may wheek for assistance. listen (help·info)
- Bubbling or Purring - This sound is made when the guinea pig is enjoying itself, such as when being petted or held. They may also make this sound when grooming, crawling around to investigate a new place, or when given food. listen (help·info)
- Rumbling - This sound is normally related to dominance within a group, though it can also come as a response to comfort or contentment. While courting, a male usually purrs deeply, while swaying from side to side and circling the female. listen (help·info)
- Chutting and Whining - These are sounds made in pursuit situations, by the pursuer and pursued, respectively. listen (help·info)
- Chattering - This sound is made by rapidly gnashing the teeth together, and is generally a sign of warning. Guinea pigs tend to raise their heads when making this sound.
- Squealing or Shrieking - A high-pitched sound of discontent, in response to pain or danger. listen (help·info)
- Chirping - This less-common sound seems to be related to stress. listen (help·info)
The Cage or Living Environment 
While some older guinea pig resources may say that housing them outdoors is acceptable, this is simply not the case. Wind can blow a hutch over easily; it is also the perfect place for molds to grow. Spiders and insects may bite guinea pigs left outside. There is also no guarantee that temperatures will be acceptable for your guinea pigs to live in. It is also very hard to notice signs of disease in guinea pigs if they are constantly out of sight, and out of mind. Even indoors, sudden drafts or radical shifts in temperature may adversely affect the health of your guinea pig. Outdoors, guinea pigs may still be subject to predators such as raccoons, opossums, birds of prey and cats. Even a guinea pig physically protected from a predator may suffer from the ill effects of stress from the presence of a predator. Guinea pigs in the Andean region of South America are often kept outside on roofs or in milk crates. But these are livestock, not pets. A pet guinea pig is a member of your family and will benefit from the most interaction available. Being inside your home will make it easier and more appealing to care for and play with your guinea pig. Additionally, most secure hutches are designed for rabbits, and as such have mostly wood or wire floors that are unsuitable for guinea pigs. These wire floors are extremely painful for rabbits and cavies alike, and will damage their delicate feet.
Indoor housing can consist of a large cage, with a plastic base (not metal mesh, this can damage the guinea pig's feet; wood will soak up urine permanently) and a large metal top half. As guinea pigs are not climbers, a top is only absolutely necessary if other pets are present in the house. A pet store cage is nowhere near adequate size for a happy guinea pig, and will cost in upwards of $45-50. The minimum size cage for 1-2 guinea pigs is 7.5 square feet. A good cheap option is buying or making a "C&C" cage made of metal mesh cubes (the organizer kind with small plastic connectors, for the outside) and Coroplast (the floor and walls) which is basically plastic cardboard you can buy at any sign store for a very low price. There are instructions at Cavy Cages
The housing should be lined with bedding at a minimum of 1 inch deep, ideally deeper in the sleeping areas. You should never use softwoods such as pine or cedar shavings for bedding, as these emit harmful odors called phenols that cause your guinea pig respiratory problems. Hardwoods such as aspen are fine. Other options for bedding are recycled paper products such as Carefresh; these are more expensive, but also stay clean for longer than shavings and are easier on a guinea pig's feet. A cage needs to be cleaned generally every week at the very minimum, but more often as needed.
A newer form of guinea pig bedding is polar or anti-pill fleece. While this may seem strange at first, it is a very hygienic and cost-effective form of bedding. First, an absorbent layer must be in the bottom of the cage, because the function of fleece is to wick the urine away from the guinea pigs' feet. Most fleece users are happy to use 1-2 layers of towels on the bottom of their cage, topped with a single layer of fleece. So, when a guinea pig urinates on fleece bedding, the urine is wicked through the fleece and into the towels, where it is absorbed. Fleece needs to be washed at least once weekly, without fabric softener; it inhibits the fleece's ability to wick urine. It is also a good idea to wash it with an unscented detergent, and some white vinegar to absorb odors. For more information on using fleece as a bedding, please visit 
Other essential accessories 
Other items needed for your guinea pig's home will be a gravity-fed water bottle (cavies tend to spill and defecate in water bowls), a small bowl for pellets and other food, and "hidey houses". Wild cavy species and feral guinea pigs naturally use dens made by other animals, and all domestic guinea pigs should be provided a safe place to hide in. As they are prey animals, they will feel much more secure in their environments if they have places to hide. This can be a plastic "igloo" or wood house from a pet store, or simply a towel tent. Be aware that some cardboard is put together using glues that can be harmful to your guinea pig, so it is best to avoid these if you can. If you have more than one guinea pig, having both an entrance and an exit to any hiding places can prevent fights between cornered guinea pigs. The more hiding places, the merrier! It is also better for your guinea pigs to keep borders around the cage clear, so that they can run laps.
Unlike hamsters or rats, guinea pigs don't need fancy toys such as running balls or exercise wheels. Wheels and balls may have a picture of a guinea pig on the box, but you should not buy one for them to play with. A cavy's spine (and other bones) is much more fragile than other pet rodents, its feet are too soft, the balls are not properly ventilated for a larger animal such as a cavy. Mostly they like simple things like cardboard shoe boxes, towel tents, oatmeal tubes, paper bags and other tunnels or places to hide and chew on. Some owners give bird toys, but chewing the plastic is very bad for guinea pigs. Mirrors can be hung from outside the cage, however.
An item that is very dangerous and should be avoided is a guinea pig leash. Guinea pigs cannot be trained to walk, and it shouldn't be attempted. While this may seem like a good way to let them run about the yard safely, it is merely dangerous. They have very delicate spines and bones, which are easily damaged by a leash or harness.
An alternative way to get fresh air and fresh grass is an outdoor pen, but it should be used when you will be outside with the guinea pig the entire time. It is good to place their igloo/hut in there with them so if they become startled, they can hide. The igloo/hut will not suffice for sun protection, however, as it will keep in too much heat. You must be careful where you place the pen and must stay with the guinea pig at all times while they are outside in it. Also, it should be noted that if a guinea pig is to be outside, the grass it will be on cannot have had any pesticides or fertilizers on it. These chemicals will kill your guinea pig, and are very dangerous.
A guinea pig's diet should be comprised of three basic groups; grass hay, pellets, and fresh treats. Most importantly, a guinea pig cannot make their Vitamin C (just like people) and will need it either in vitamin supplements (not droplets, these don't work as the C dissolves too rapidly in water) or in plenty of the right fruits and veggies. Of course, every guinea pig needs a water bottle (they tend to poop in water bowls, and it could get very unhealthy).
You should give one adult guinea pig approximately 1/8 cup pellets every day, possibly more for young ones. Pellets should be Timothy hay-based (little green ones), and not a seed mix. They can easily choke on seeds, and seeds are too fatty. Alfalfa-based hay pellets have too much calcium, and should not be fed for guinea pigs over 6 months of age.
Providing your guinea pig as much Timothy hay or orchard grass as it can eat is very important for its health and happiness. Hay provides important digestive fiber and can prevent a condition in older boars where they lose the ability to defecate properly. Also, guinea pigs have a natural inclination to forage for food almost constantly, not giving them proper hay can cause them stress and result in barbering (chewing their own hair) and other behavioral problems. Alfalfa hay can be fed to guinea pigs younger than 6 months, but should not be fed to older guinea pigs other than the occasional treat. If you do not know the age of your guinea pig, or are unsure, use a different hay that is safe.
- Fruits and vegetables
If you ever have a question about whether your guinea pig can eat a certain vegetable or fruit, and in which quantities, please visit this link:  . It was made by a guinea pig dietary specialist, and is very helpful!
Guinea pigs like to eat lots of green veg, and on the whole this is very good for them, but there are a few things that should be left off your pets menu. Iceberg Lettuce causes bloat and gas, and so should be avoided, no exception. Tomato leaves are also not good for piggies. Carrot in excess can cause liver problems due to the excessive amounts of vitamin A, and in the pregnant cavy can cause birth defects. However, in small amounts to a non pregnant guinea pig, this is fine. Mushrooms and Rhubarb are poisonous. The best fruits and veggies for Vitamin C are Romaine lettuce, Carrot, Kale, Mustard greens, Red bell pepper, Spinach and many others. Oddly, oranges do not have very much vitamin C and can even cause the runs in guinea pigs. They need 10-20 MG of Vitamin C a day if they are healthy. If they are unhealthy, pregnant, or under 3 months, they should get 30-50 MG. For additional vitamin C, you can purchase vitamin C tablets. It is very important that you do not use vitamin C drops, as these can result in dehydration in guinea pigs. Do not give them multivitamins. These can be bad for them and even poisonous.
- Other things to avoid
- Mixes or treats with nuts, seeds, dried fruit and dyed pieces.
- Dairy and meat products (cavies are herbivores)
- Seeds in husks can be a choking hazard.
- Cruciferous vegetables (cabbage, collards, bok choy, broccoli) may cause gas in your pet and are best offered sparingly and infrequently.
- Mineral wheels. Never use Tang (which contains dyes, refined sugars, and very little vitamin C) in drinking water.
- Commercial treats marketed for cavies (like yogurt drops) which can even be detrimental to their health. Consuming these empty calories (many contain fat, sugars and even excess calcium) can result in decreased consumption of the basic foods they really need. Guinea pigs are very strictly herbivores; therefore, they are lactose intolerant. Yogurt and honey are not good for guinea pigs, and should be avoided.
Before you bringing home your new guinea pig, you should locate your nearest veterinarian, and go in to the practice to pick up any leaflets or advice sheets on basic first aid for guineas. Staff should be knowledgeable, and will be able to help you with any other queries you might have about your guinea pigs. Make sure to visit a knowledgeable exotic pet veterinarian, as many regular cat and dog veterinarians have limited knowledge of cavies and some may refuse to treat them altogether.
Pain As guinea pigs are naturally prey animals, they instinctively hide pain to prevent appearing as a weak animal within the group. As a result it may be difficult to tell if they are hurting. If you notice changes in behavior, or unusual avoidance of handling, call your veterinarian for advice.
Parasites Guinea pigs can occasionally harbor skin (ecto-) parasites, which may not always be visible to the naked eye. Fortunately these parasites are not zoonotic, meaning your guinea pig cannot give them to you. Treatment with a topical product called Revolution(R) (active ingredient, selamectin) is a very effective method of controlling ectoparasites. Ivermectin is also effective, and is given either as an injection or orally. These medications must be prescribed by your veterinarian. It is not uncommon for pet store bought guinea pigs will harbor lice or mites. For this reason, it is a good idea to have a newly acquired guinea pig examined by a veterinarian before introducing the new cavy to other cavies in your home.
Teeth As guinea pigs are rodents, their teeth grow constantly. The constant availability of roughage (grass hay) is of critical importance in maintaining your guinea pig's dental health. It is also helpful, and fun for your guinea pig, if you include a chew stick (available in most pet shops) or piece of fruit wood for them to gnaw on. Dental examinations are an important part of your guinea pig's health plan. You can easily monitor the incisors (front teeth), but it is difficult to see the premolars and molars (cheek teeth) without an oral speculum. To see the incisors, hold your guinea gently but firmly in one hand, with one finger behind the head to support, lean your pet back. If this doesn't expose the teeth, gently push on the lips to show them. The teeth should appear straight; the top and bottom teeth should overlap only slightly (top over bottom- if they are the other way round, you should consult with your veterinarian). Normal incisors are off-white to yellow in color. Normal mandibular (lower) incisors often appear quite long to the untrained eye. If the incisors curve away from each other or are excessively long, consult your veterinarian. Never attempt to trim or clip your guinea pig's incisors by yourself. This may result in a fractured incisor, which is painful, and may cause further dental problems in the future.
Guinea pigs and other pets Obviously, cats, dogs and ferrets are predators and may kill a small furry creature. However, there are cases of guinea pigs getting along with them, and often as not cats may not know what to think of a guinea pig or even be scared of it. Dogs may be trained to accept guinea pigs as well. Chiefly, never leave a guinea pig alone with any predatory animal, however well-trained. Cohousing of guinea pigs with other rodents such as gerbils, rats and hamsters may increase instances of respiratory and other infections, and such rodents may act aggressively towards the guinea pig. Opinion is divided over the cohousing of guinea pigs and domestic rabbits. Some published sources say that guinea pigs and rabbits complement each other well when sharing a cage. However, as lagomorphs, rabbits have different nutritional requirements, and so the two species cannot be fed the same food. Rabbits may also harbor diseases (such as the respiratory infections Bordetella and Pasteurella), which guinea pigs are susceptible to. Even a dwarf rabbit is much stronger and more aggressive than the guinea pig and may cause intentional or inadvertent injury.
Breeding Pregnant sows have a 25% chance of having a fatal pregnancy complication. It is advisable to not breed guinea pigs, unless you know 100% of what you're doing, you're able to find homes for them, and you know what breeds can cause problems if they cross.