Pacas are 50–77 cm (20–30 in) in length, excluding the 13–23 cm (5.1–9.1 in) short tail, weigh 6–14 kg (13–31 lb), and are the sixth-largest rodents in the world. Similar to guinea pigs, they have square heads, small ears, sides patterned with spots and stripes, and virtually invisible tails. With large hind limbs, small fore limbs, and cone-shaped bodies, pacas are similar in appearance to the deer-like, ungulate chevrotains, and like them have four to seven horizontal lines of blotches and stripes along their flanks. They have a heavy and robust appearance, though their legs are long and relatively tiny. Their small ears are set high on their heads. They have four toes on their fore feet and five on their hind feet (of which two are short and hardly touch the ground) and they have stout nails that resemble small hooves. In young pacas, the skin is covered with horny scales about 2 mm (0.079 in) in diameter perhaps these scales have a protective function against smaller predators. There is virtually no difference between sexes. They can live up to 13 years in the wild.