They grows to a length of about 8 - 10 in and weigh between 1.5 - 2.5 lb. They have an average life expectancy of 4 - 5 years, but can live up to 7 - 8 years. According to the Guinness Book of Records, the longest living guinea pig lived for 14 years and 10.5 months.
These rodents are born with their eyes open. They sport a fur coat at birth. Although, they are small enough to fit into your palm at birth, they grow very fast. They can start running within four hours of birth.
The most common breeds are the American, Abyssinian, and the Peruvian guinea pigs. These breeds are differentiated on the basis of their fur coats. The American breed has a short and smooth fur coat, while the Peruvian breed sports long hair.
Guinea pigs have also been used in medical research. One such instance came in 1890, when they were used to test an anti-toxin developed for diphtheria. Even today, they are used in research work pertaining to human ailments such as tuberculosis, scurvy, and juvenile diabetes.
They don't require vaccination, but they can suffer from ailments such as respiratory infections and diarrhea. Mange is observed to be a common cause for hair fall and excessive scratching in Guinea pigs. They also suffer from lice and fungal infections.
Cavies are easy to domesticate because they have a good memory. Their sharp senses of smell, hearing, and touch, compensate for their poor eyesight. When they are attacked by a predator, they tend to run haphazardly; it's their defense mechanism to confuse the predator.
Guinea pigs were domesticated for meat by ancient tribes. Come today, they have become an integral part of the diet in many parts of South America. People of Peru alone consume around 65 million guinea pigs every year.
Pro Tip: When selecting one as a pet, choose an alert and active individual, as the ones which are very quiet and calm are likely to be ill. A healthy pet guinea pig can give you company for 7 - 8 years.