The Mongolian gerbil or Mongolian jird (Meriones unguiculatus) is a small rodent belonging to the subfamily Gerbillinae. Their body size is typically 110–135 mm (4+1⁄4–5+1⁄4 in), with a 95–120 mm (3+3⁄4–4+3⁄4 in) tail, and body weight 60–130 g (2–4+1⁄2 oz), with adult males larger than females. The animal is used in science and kept as a small house pet. Their use in science dates back to the latter half of the 19th century, but they only started to be kept as pets in the English-speaking world after 1954, when they were brought to the United States. However, their use in scientific research has fallen out of favor. Gerbils are social animals, and live in groups in the wild. They rely on their sense of smell to identify other members of their clan, so it is important to use what is commonly referred to as the 'split tank method' (or splitcaging) when introducing gerbils from separate litters. Gerbils are known to attack and often kill those carrying an unfamiliar scent. (Source: Wikipedia.org, CC BY-SA)