About 40% of mammal species are rodents, and they are found in vast numbers on all continents other than Antarctica. Rodents use their sharp incisors to gnaw wood, break into food, and bite predators. Most rodents eat seeds or plants, though some have more varied diets. Some species have historically been pests, eating seeds stored by people and spreading disease.
Cotton Rat

A cotton rat is any member of the rodent genus Sigmodon. They are called cotton rats because they build their nests out of cotton, and can damage cotton crops. Cotton rats have small ears and dark coats, and are found in North and South America. Members of this genus are distributed in the Southwestern USA, Mexico, Central America and South American countries of: Venezuela, Ecuador, Colombia, Peru, Brazil, Guyana and Suriname. Many of the species are found in Mexico.

They are primarily herbivores. The molars of cotton rats are S-shaped when viewed from above. The genus name literally means S-tooth.

Sigmodon hispidus was the first model organism to be used in polio research.

Deer Mice

The genus Peromyscus contains the animal species commonly referred to as deer mice. This genus of New World mice is only distantly related to the common house mouse and laboratory mouse, Mus musculus. Although superficially resembling Mus musculus, Peromyscus species have relatively larger eyes, and also often two-tone coloring, with darker colors over the dorsum (back), and white abdominal and limb hair-coloring. In reference to the coloring, the word Peromyscus comes from Greek words meaning "booted mouse".

They are also accomplished jumpers and runners by comparison to house mice, and their common name of "deer mouse" (coined in 1833) is in reference to this agility.

The most common species of deer mice in the continental United States are two closely related species, P. maniculatus, and P. leucopus. In the United States, Peromyscus is the most populous mammalian genus overall, and has become notorious in the western United States as a carrier of hantaviruses.

House Mice

The house mouse (Mus musculus) is a small mammal of the order Rodentia, characteristically having a pointed snout, small rounded ears, and a long naked or almost hairless tail. It is one of the most numerous species of the genus Mus. Although a wild animal, the house mouse mainly lives in association with humans.

House mice usually run, walk, or stand on all fours, but when eating, fighting, or orienting themselves, they rear up on their hind legs with additional support from the tail - a behaviour known as "tripoding". Mice are good jumpers, climbers, and swimmers, and are generally considered to be thigmotactic, i.e. usually attempts to maintain contact with vertical surfaces.

Mice are mostly crepuscular or nocturnal; they are averse to bright lights. The average sleep time of a captive house mouse is reported to be 12.5 hours per day. They live in a wide variety of hidden places near food sources, and construct nests from various soft materials. Mice are territorial, and one dominant male usually lives together with several females and young. Dominant males respect each other's territory and normally enter another's territory only if it is vacant. If two or more males are housed together in a cage, they will often become aggressive unless they have been raised together from birth.

House mice primarily feed on plant matter, but are omnivorous. They will eat their own feces to acquire nutrients produced by bacteria in their intestines. House mice, like most other rodents, do not vomit.

Norway Rat

The brown rat, common rat, street rat, sewer rat, Hanover rat, Norway rat, brown Norway rat, Norwegian rat, or wharf rat (Rattus norvegicus) is one of the best known and most common rats.

Thought to have originated in northern China, this rodent has now spread to all continents except Antarctica, and is the dominant rat in Europe and much of North America—making it by at least this particular definition the most successful mammal on the planet after humans. Indeed, with rare exceptions, the brown rat lives wherever humans live, particularly in urban areas.

The fur is coarse and usually brown or dark grey, while the underparts are lighter grey or brown. The Brown Rat is a rather large true murid and can weigh twice as much as a Black Rat and many times more than a House Mouse. The length is commonly in the range of 20 to 25 cm (8 to 10 in), with the tail a further 18 to 25 cm (7 to 10 in), thus being roughly the same length as the body. Adult body weight averages 350 g (12 oz) in males and about 250 g (9 oz) in females. Exceptionally large individuals can reportedly reach 900 to 1,000 g (32 to 35 oz) but are not expected outside of domestic specimens. Stories of rats attaining sizes as big as cats are exaggerations, or misidentifications of other rodents, such as the coypu and muskrat. In fact it is common for breeding wild Brown Rats to weigh (sometimes considerably) less than 300 g (11 oz).

Brown rats have acute hearing, are sensitive to ultrasound, and possess a very highly developed olfactory sense. Their average heart rate is 300 to 400 beats per minute, with a respiratory rate of around 100 per minute. The vision of a pigmented rat is poor, around 20/600, while a non-pigmented (albino) with no melanin in its eyes has both around 20/1200 vision and a terrible scattering of light within its vision. Brown rats are dichromates which perceive colors rather like a human with red-green colorblindness, and their colour saturation may be quite faint. Their blue perception, however, also has UV receptors, allowing them to see ultraviolet lights that some species cannot.

Roof Rat

The black rat (Rattus rattus) is a common long-tailed rodent of the genus Rattus (rats) in the subfamily Murinae (murine rodents). The species originated in tropical Asia and spread through the Near East in Roman times before reaching Europe by the 1st century and spreading with Europeans across the world. Alternate names include ship rat, roof rat, house rat, Alexandrine rat, and old English rat.

A typical adult black rat is 12.75–18.25 in (32.4–46.4 cm) long, including a 6.5–10 in (17–25 cm) tail, and weighs 4–12 oz (110–340 g). Despite its name, the black rat exhibits several colour forms. It is usually black to light brown in colour with a lighter underside. In the 1920s in England, several variations were bred and shown alongside domesticated brown rats. This included an unusual green tinted variety. The black rat also has a scraggly coat of black fur, and is slightly smaller than the brown (Norway) rat.

Black rats are considered omnivores and eat a wide range of foods, including seeds, fruit, stems, leaves, fungi, and a variety of invertebrates and vertebrates. They are generalists, and thus not very specific in their food preferences, which is indicated by their tendency to feed on any meal provided for cows, swine, chickens, cats, and dogs. They are similar to the tree squirrel in their preference of fruits and nuts. They eat about 15 grams (0.53 oz) per day and drink about 15 millilitres (0.53 imp fl oz; 0.51 US fl oz) per day. Their diet is high in water content. They are a threat to many natural habitats because they feed on birds and insects. They are also a threat to many farmers since they feed on a variety of agricultural-based crops, such as cereals, sugar cane, coconuts, cocoa, oranges, and coffee beans.

Pocket Gopher

The pocket gophers are burrowing rodents of the family Geomyidae. These are the "true" gophers, though several ground squirrels of the family Sciuridae are often called gophers as well. The name "pocket gopher" on its own may be used to refer to any of a number of genera within the family.

Pocket gophers are widely distributed in North America, extending into Central America.

Gophers are heavily built, and most are 12 to 30 cm (4.7 to 12 in) long, weighing a few hundred grams. A few species reach weights approaching 1 kg (2.2 lb). Within any species, the males are larger than the females and can be nearly double their weight.[1] Most gophers have brown fur that often closely matches the color of the soil in which they live. Their most characteristic features are their large cheek pouches, from which the word "pocket" in their name derives. These pouches are fur-lined, and can be turned inside out. They extend from the side of the mouth well back onto the shoulders. They have small eyes and a short, hairy tail, which they use to feel around tunnels when they walk backwards.


Moles are small cylindrical mammals adapted to a subterranean lifestyle. They have velvety fur; tiny or invisible ears and eyes, reduced hindlimbs; and short, powerful forelimbs with large paws positioned for digging. The term "mole" is especially and most properly used for true moles of the Talpidae family in the order Soricomorpha found in most parts of North America, Asia, and Europe although may refer to other completely unrelated mammals of Australia and southern Africa which have also evolved the mole body plan; it is not commonly used for some talpids, such as desmans and shrew-moles, which do not quite fit the common definition of “mole”.

Moles have been found to tolerate higher levels of carbon dioxide than other mammals, because their blood cells have a special and unique hemoglobin protein. Moles are able to reuse the oxygen inhaled when above ground, and as a result, are able to survive in low-oxygen environments such as underground burrows.

A mole's diet primarily consists of earthworms and other small invertebrates found in the soil, and a variety of nuts. The mole runs are in reality 'worm traps', the mole sensing when a worm falls into the tunnel and quickly running along to kill and eat it. Because their saliva contains a toxin that can paralyze earthworms, moles are able to store their still-living prey for later consumption. They construct special underground "larders" for just this purpose; researchers have discovered such larders with over a thousand earthworms in them. Before eating earthworms, moles pull them between their squeezed paws to force the collected earth and dirt out of the worm's gut. The star-nosed mole can detect, catch and eat food faster than the human eye can follow (under 0.3 seconds).