Guinea pigs, like other cavies, are stout and short-legged. Full-grown adults range in length from approximately 8 to 19 inches (20 to 50 cm). Adult guinea pigs are about 5 inches (13 cm) tall. The average adult weight is 30 to 35 ounces (850 to 1000 g). Their normal body temperature is 102°F to 104°F (39°C to 40°C). The guinea pig life span varies, but on average they live 6 to 8 years ( see Table: Guinea Pigs at a Glance Guinea Pigs at a Glance ).
There are currently at least 13 recognized breeds of guinea pigs. Some of the more common breeds include the American, which has short, smooth hair; the Abyssinian, with short hair that grows in whorls; and the Peruvian, which has longer, silky hair. Hairless breeds have also been developed. Guinea pigs come in several colors and color combinations, including black, tan, cream, brown, and white.
Guinea pigs' eyes are located on the sides of the head, allowing them to see both forward and backward, although they may have trouble seeing directly ahead. Their heads are blunt and have small ears. Guinea pigs have 4 digits (toes) on each front foot and 3 on each hind foot. Each toe has a very sharp claw. Their hind legs are longer than their front legs. They have no external tail.
Guinea pigs have 20 teeth, including upper and lower incisors (for cutting and tearing), premolars, and molars. A guinea pig’s teeth are “open rooted” and grow continuously throughout its life. Guinea pigs wear down their teeth by eating, chewing, and grinding food. Thus, it is important that your guinea pig’s diet contain a sufficient amount of hay, grass, and abrasive foods to maintain healthy teeth at the proper length. Fat pads in the cheeks, which are normal, can make examination of guinea pig teeth difficult.