Cuniculidae

A paca is a member of the genus Cuniculus of ground-dwelling, herbivorous rodents in South and Central America. It is the only genus in the family Cuniculidae. They are large rodents with dots and stripes on their sides, short ears, and barely visible tails. They are also referred to as 'gibnuts' or 'royal rats'. The Smithsonian Tropical Research Institute in Panama has studied the possibilities of developing the paca as a viable high-priced food supply for the tropics. Pacas originated in South America and are one of the few mammal species that successfully emigrated to North America after the Great American Interchange 3 million years ago. They were formerly grouped with the agoutis in the family Dasyproctidae, subfamily Agoutinae, but were given full family status because they differ in the number of toes, the shape of the skull, and coat patterning. 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. Pacas inhabit rainforests, cloud forests, and sometimes more open habitats. They are great swimmers and prefer to be near water. They dive when threatened and can stay submerged up to 15 minutes. They can also jump up to 1 m (3 ft 3 in) and freeze up to 45 minutes. They normally move along well-established paths and will create new paths when old ones are disturbed. They are normally passive in daytime and forage in the morning and afternoon, but can be strictly nocturnal in areas with many predators. They live in burrows up to 3 m (9.8 ft) deep, normally with two entrances covered with leaves to hide the burrow and to serve as an early warning system. Burrows are often near water, but always above the seasonal flood line. Predators except humans include jaguar, puma, ocelot, margay, jaguarundi, bush dog, boa constrictor, and caiman. Pacas have resonating chambers in their cheeks and their growling noise, at about 1 kHz, is surprisingly loud for their size. Aside from making noises, territories are marked with urine. Population density can reach up to 70 adults per 0.2 km2 (0.077 sq mi), and pacas often constitute some 20% of the biomass of terrestrial mammals.