Pacarana: Dinomyidae

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PACARANA: Dinomyidae


Also known as Branick's giant rat after the Polish count who first described the species in 1873, the pacarana is the sole member of the Dinomyidae ("terrible mouse") family. The name pacarana comes from a Tupi Indian term meaning "false pig." Full-grown pacaranas weigh between 22 and 33 pounds (10 to 15 kilograms), and from nose to rump measure from 28 to 31 inches (730 to 790 millimeters). Their tails are usually 7.5 inches (190 millimeters) long. Sturdy and compactly built, their heads are broad and large in proportion to their bodies. They have short but extremely powerful limbs with four digits and formidable claws on each. Pacaranas have a thick coat of coarse, grayish brown or blackish hair with rows of white spots on the back half of the body. The animal has bushy, white whiskers on either side of its blunt snout and a deeply split upper lip. It is the third-largest rodent on Earth, after the capybara and the beaver, and some people say it looks like a gigantic guinea pig or spineless porcupine.


A South American rodent, pacaranas' sparse populations may be found in the mountainous areas of a band running through western Venezuela, western Colombia, central Ecuador, Peru, part of western Brazil, and into northwestern Bolivia.


In Peru, this species occupies suitable habitat from 800 to 6,600 feet in elevation (240 to 2,000 meters), but in Venezuela they occur up to 7,870 feet (2,400 meters). Pacaranas live in montane forests and rainforest valleys of the Andes Mountains. They prefer to live in cracks in rock walls or outcroppings, but caves are also attractive habitats.


Pacaranas are mainly vegetarian and especially favor palm berries and other fruits as well as the stems and leaves of tender young plants.


Because most pacarana behavior has been studied among captive animals, biologists know little about how these animals act in the wild. However, we do know that they are active mostly at night, when they spend most of their time in solitary searches for food. They occasionally climb trees to get to food sources, but spend most of their time on the ground, sitting up on their haunches to manipulate food with their forelimbs. They do not seem to dig, despite their sturdy claws. Although their Latin name indicates a placid nature and slow-moving ways, pacaranas are well equipped to defend themselves and have a strong will to do so. They can be surprisingly vicious in attacks on interlopers and predators, animals that hunt them for food, alike, including pet dogs and other pacaranas. They can climb well and walk on two feet occasionally for various purposes. Adults often live alone, but have also been observed cohabitating in pairs and family groups. Their communication with each other is fairly sophisticated and features seven different sounds, including singing, hissing, tooth chattering, stamping their front feet, and whining.


Although their ancestors' native land of Colombia is thousands of miles away, a thriving colony of pacaranas has been established at the San Diego Zoo. The animals can live for at least thirteen years in captivity, and are easily trained to perform in shows.

Pacaranas make a sound like crying to attract mating partners, and then engage in an elaborate courtship ritual during the breeding season in about November through January. The ritual has been described as a mixture of dancing and wrestling, with much sniffing, growling, and whimpering as a male and female stand on their hind legs to grapple with each other and interlock their front cutting teeth. Head-tossing is common prior to the male mounting the female, which he does after approaching her with dramatically trembling legs. Females gestate, or experience pregnancy, for about 222 to 283 days and can be quite aggressive during the pregnancy. Scientists have never observed pacaranas building nests. Litter sizes are usually one or two pups, each of which weighs about 32 ounces (900 grams). Young can move around independently almost immediately and are born with eyes open and fully furred.


Many native South Americans hunt pacaranas as a food source.


The IUCN has classified the pacarana as Endangered, facing a very high risk of extinction. Its normally low population levels, which in past years led scientists to believe the animals were extinct, are especially vulnerable to human predation and to habitat loss from human activities.



Anderson, Sydney. Simon and Schuster's Guide to Mammals. New York: Fireside, 1984.

Burton, John A. Rare Mammals of the World. Lexington, MA: Stephen Greene Press, 1987.

McKenna, Malcolm C. The Classification of Mammals. New York: Columbia University Press, 2000.

Nature Encyclopedia: An A to Z Guide to Life on Earth. Oxford, U.K.: Oxford University Press, 2001.


White, T. G. "Dinomys branickii." Mammalian Species 410 (1992).

Web sites:

"Animal Info-Pacarana." Animal Info-Information on Endangered Mammals. (accessed on June 23, 2004).

"Comparative Placentation." University of California, San Diego Medical School. (accessed on June 23, 2004).

"Dinomys branickii." Animal Diversity Web. (accessed on June 23, 2004).