African vlei rats, also known as groove-toothed rats, live in many areas of sub-Saharan Africa. Most species live in marshlands, grasslands, and similar habitats and feed on the vegetation of such areas, occasionally supplementing it with roots and seeds. The name "vlei" refers to the South African term for intermittent, seasonal, or perennial bodies of standing water.
Otomys are compact rodents with a tendency to shorter faces and legs than other types of rats. The tails also are shorter than most Muridae, typically between one third and two thirds of the body length. The coat colour varies according to species, but generally they have the brown-to-grey agouti coats typical of mice and other small wild rodents. Species living in warm or temperate regions tend to have unusually large ears for murids (e.g. Otomys irroratus), whereas some of the alpine species, such as Otomys sloggetti have markedly smaller ears. (However, the latter species may no longer belong in the genus Otomys.)
Depending on the species adult Otomys have a body length between 12 and 22 cm (5–9 inches) and weigh 90 to 260 grams (3–9 oz).