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Order Description


Order Description

Rodents are found in almost every habitat around the world. In fact, there are more species in the Order Rodentia than any other Mammalian order. Rodents also have larger populations than any other Mammalian order. The Order Rodentia includes 2 suborders, 29 families, 443 genera, and 2021 species world-wide. Seven families, including 25 genera and 41 species, are represented in the southern United States. Each of these families is found in Georgia.

A distinguishing characteristic of rodents is the single pair of incisors coupled with the absence of canine teeth. The incisors have a hard front surface made of enamel and a soft rear surface made of dentine. This difference causes the teeth to wear unevenly, resulting in a characteristic chisel shape with a sharp front edge. Rodent incisors continue to grow throughout the animal's life, and have been recorded to grow as fast as one inch (2.5 cm; 1 in) per month. These fast-growing, sharp teeth prove very useful for gnawing plants, a favorite food for most rodents.

The smallest U.S. rodent, the Harvest Mouse, weighs only a few ounces (less than 100 g (3.5 oz)), while a Beaver may weight over 80 pounds (36.3 kg). Even though rodents come in a variety of sizes and individual species are adapted to exploit a wide variety of habitats, they all have a fairly similar body form and most produce large litters of offspring.

Family Castoridae

There is only one living genus (Castor) and one North American species in this family. The Beaver is easily recognized by its large size (about 1 m, or 3.3 ft, long), massive head, webbed hind feet, and large flat tail. It has small eyes, short ears, very dense thick fur, and 5 clawed fingers on both its front and hind feet. With these characteristics, it is well-equipped for its aquatic lifestyle.
Species in this family:
    American Beaver (Castor canadensis)

Family Geomyidae

This family includes several species of pocket gophers. Pocket gophers live in underground burrows and rarely come to the surface. They are easily distinguished from other rodents by their short furless tails, large cheek pouches, and front legs enlarged for digging. They have small eyes and ears, and 5 clawed toes on each limb. Two species of pocket gophers occur in Georgia.
Species in this family:
    Southeastern Pocket Gopher (Geomys pinetis)

Family Muridae

This is the most diverse family of mammals, with 1,326 species of rats and mice world-wide. Species from this family can be found in almost every habitat, and include some of the world's most common mammals. They are small to medium in size, with short to long tails. They have 4 clawed toes on the front feet and 5 on the rear feet. Most species have large eyes and ears. Sixteen species are found in Georgia (excluding the introduced Old World rats and mice).
Species in this family:
    Black Rat (Rattus rattus )
    Common Muskrat (Ondatra zibethicus )
    Cotton Mouse (Peromyscus gossypinus)
    Deer Mouse (Peromyscus maniculatus )
    Eastern Harvest Mouse (Reithrodontomys humulis)
    Eastern Woodrat (Neotoma floridana)
    Golden Mouse (Ochrotomys nuttalli)
    Hispid Cotton Rat (Sigmodon hispidus)
    House Mouse (Mus musculus )
    Marsh Rice Rat (Oryzomys palustris)
    Meadow Vole (Microtus pennsylvanicus )
    Norway Rat (Rattus norvegicus )
    Oldfield Mouse (Peromyscus polionotus )
    Round-tailed Muskrat (Neofiber alleni)
    Southern Red-backed Vole (Clethrionomys gapperi )
    White-footed Mouse (Peromyscus leucopus)
    Woodland Vole (Microtus pinetorum )

Family Myocastoridae

This family has a single species, the Nutria, which resembles a large aquatic rat. The Nutria is almost as large as a Beaver but has a long, round, scaly tail. It is nocturnal (active at night), and feeds on aquatic vegetation. It has small ears, short limbs, and webbed toes. The Nutria is a native of South America that has been introduced into the United States.
Species in this family:
    Nutria (Myocastor coypus)

Family Sciuridae

This family includes squirrels and marmots. Species in this family have 5 clawed fingers on their front feet and 4 on the hind feet. They have relatively large ears and thick body fur. Their tails are furry and often bushy. They range in size from the African Pigmy Squirrel, 12 cm (4.7 in) to the Giant Squirrel, 1 m (39.4 in) long. Some species are arboreal (tree-dwelling), while others are ground-dwelling and dig burrows. There are even species that can glide. Six species of squirrels occur in Georgia, including one flying squirrel, 2 species of ground squirrels, and 3 species of tree squirrels.
Species in this family:
    Eastern Chipmunk (Tamias striatus)
    Eastern Fox Squirrel (Sciurus niger)
    Eastern Gray Squirrel (Sciurus carolinensis)
    Red Squirrel (Tamiasciurus hudsonicus )
    Southern Flying Squirrel (Glaucomys volans)
    Woodchuck (Marmota monax)

Family Zapodidae

Species in this family:
    Meadow Jumping Mouse (Zapus hudsonius )
    Woodland Jumping Mouse (Napaeozapus insignis )