Nicknames: Pack rat, trade rat

Claim to fame: Many people have used the term “pack rat,” but most don’t know what a pack rat is or where it lives. “Pack rat” is the most common name used for this long-tailed rodent, which is found in parts of Missouri. On a lesser-known basis, the eastern wood rat was the first of many wildlife species discovered by Lewis and Clark.

Species status: The range of the eastern wood rat in Missouri primarily occupies the southern half of the state.

Discovered: The discovery of this creature is something of a curiosity. Though the eastern wood rat is found in several areas of the eastern and southeastern United States and had likely been seen by trappers and early settlers, no reference of the species exists until its mention in the journals of Lewis and Clark. (Three were sighted on May 31, 1804, in what is now Osage County and wood rats were noted again on July 7.) The first detailed taxonomic description was written by American naturalist George Ord in 1818.

Family matters: Eastern wood rats belong to the mammal family Cricetidae and are one of several rat species referred to as “New World rats.” They’re called this because they are native to North America. One of the continent’s most abundant rat species, the Norway rat, is called an “Old World rat” because it originated in Europe and Asia. It was transported here by passenger and cargo ships.

Length: Eastern wood rats have a body length of 12 to 17 inches (and a tail that measures between 5 inches and 8 inches).

Diet: Wood rats are nocturnal and almost entirely vegetarian. They eat all types of plant foods such as buds, leaves, stems, bark, roots, fruits, nuts and grasses. Bones are gnawed to sharpen and wear down teeth and to obtain certain minerals. It’s theorized the eastern wood rat may drink little — if any — water. It’s thought the creature gets almost all its moisture from the foods it eats.

Weight: 6 to 12 ounces

Distinguishing characteristics: The eastern wood rat is a medium-sized brownish-gray rodent with prominent short-haired ears; bulging black eyes and long, conspicuous whiskers. A unique characteristic is the one that’s the source of its common name — pack rat. Eastern wood rats have the peculiar habit of picking up a variety of objects and taking them back to their nests. These collections are often diverse, featuring things such as coins, bottle caps, gun cartridges, nails, sticks and small stones.

Life span: In the wild, wood rats probably live approximately three years

Habitat: Wood rats occupy rocky, timbered regions and, to a lesser extent, swampy, open lands. They often build their nests in crevices or caves in limestone bluffs and outcroppings. Sometimes, they build a nest on the ground in brushpiles or tangled vines or in abandoned barns or outbuildings.

Life cycle: In Missouri, the breeding season occurs primarily from February to September. (In the warmer southern states, it may encompass the whole year.) Probably two or three litters are produced annually, each containing between one and six offspring. Young are born blind, deaf and slightly haired. Between the age of 15 and 21 days, the eyes open. At that time, the young are well-furred and active. Weaning occurs around four weeks after birth. The young reach adult size at approximately eight months.