What Kind of Rodent Has No Tail?

The largest of the large when it comes to rodents, capybaras (Hydrochoerus hydrochaeris) are native to South America. Like several other tailless rodents, the capybara belongs to the family Caviidae. Averaging around 100 pounds, 1 to 3 feet tall and 4 feet long, their bodies are short, squat and stout. Capybaras thoroughly enjoy the water and use it as protection from predators such as jaguars and anacondas. These large rodents are herbivores, feeding primarily on grasses and the aquatic plants growing in the water they wallow in.

Cuddly, gentle guinea pigs (Cavia porcellus) have become extinct in nature, but are more than common in the pet trade. Sometimes referred to as "cavies," guinea pigs may be the most thought of when it comes to tailless rodents. Guinea pigs have been domesticated since around 5,000 B.C. because of their gentle nature and their popularity as a food source. Originally native to South America, these medium-sized rodents inhabited grasslands. While still generally accepted as a rodent, some experts believe guinea pigs are not true rodents, according to the University of Wisconsin's BioWeb.

Belonging to the same taxonomic family as guinea pigs, some other cavies also are tailless. The common yellow-toothed cavy (Galea musteloides) is one such example. Approximately the size of a hamster, these smaller rodents are native to South America and live in a wide range of habitats. Like guinea pigs, these cavies are herbivorous and feed primarily on grasses. The southern mountain cavy (Microcavia australis) also has no tail. The rock cavy (Kerodon rupestris) is closely related to the capybara, although much smaller.

While the first tailless rats in captivity were an unfortunate gene mutation that led to several other health problems, the tailless rats of today tend to have distinct personalities and outgoing, fun, playful temperaments. The true tailless rats have modified vertebrae and a noticeable dimple where a tail would normally come out. Because of their modified backbones, tailless rats have a distinctively rounded rear end. Some pet stores and breeders may dock the tails of baby rats and call them "tailless"; these rats, however, still have a stub where the tail was and the same body shape of more common fancy rats.