Spotted Ground Squirrels are among the smallest ground squirrels in North America. They inhabit arid and semi-arid regions of Mexico and the Southwest and are found in scrubland and grassland as far north as Wyoming and Nebraska. Learn...

The Mohave Ground Squirrel occupies a relatively tiny part of the Mohave Desert and is rarely seen since it spends more than half the year underground in a burrow. Estivation, the hot-weather equivalent of hibernation, and hibernation...

Wyoming Ground Squirrels are found in three separate regions of the western United States at elevations above 1,500 meters. Their geographic centers are in southwestern Montana, central and southwestern Wyoming, and southwestern Idaho,...

Eastern and Western Spotted Skunks were for years thought to be one and the same species, but they differ in an important detail of the reproductive process. In the Western Spotted Skunk, a very long period of delayed implantation...

Schools of spinner dolphins leap out of the water, twirl, and reenter with large, noisy splashes that can be heard for long distances underwater. Usually they make several such spinning leaps in a row. Learn more about the Stenella...

Marsh Rabbits live only in marshy areas, and like Swamp Rabbits, are good swimmers. They are often found in habitats with pools of brackish water and plants such as cattails, water hyacinth, rush, centella, and marsh pennywort. Learn...

At dawn and dusk in the mountainous regions of the western United States, the Mountain Cottontail forages for sagebrush, western juniper, and grasses, almost always close to cover. As befits a rabbit that lives where it gets very cold,...

Southern Bog Lemmings are born with whiskers and a scattering of hairs on their heads and backs. They are well-furred when they are a week old, and look like miniature adults at two weeks of age. Learn more about the Synaptomys cooperi,...

Merriam's chipmunk's calls are distinctive. Perched on top of a stump or rock, the chipmunks vocalize long and vigorously, and the "chip" sound is often followed by a burst of sound called a "terminal pulse. Learn more about the Tamias...

The range of the Long-tailed Pocket Mouse is mostly within the Mojave Desert, Colorado Desert, and the Great Basin. On cold nights, this animal becomes inactive and usually remains within its burrow system during winter. Learn more about...

Siskiyou chipmunks have their own, distinct vocalization: a long, intense, one-syllable call that starts low, rises, and then falls again. It starts at a frequency of about 300 kHz, rises to more than 1,600 kHz, then falls to about 400...

Swift foxes are primarily nocturnal, but can sometimes be seen sunning themselves near the entrance to a den. They live on prairie grasslands just east of the Rocky Mountains. Learn more about the Vulpes velox, more commonly known as a...

This free-tailed bat prefers warm climates and is most commonly found in northern South America, Central America, and the Caribbean Islands. It is believed that several colonies that have been found roosting in buildings in the Florida...

The right whales have been driven nearly to extinction as the species preferred by commercial whalers and have been hunted in spite of international bans. There are perhaps several hundred in the western Pacific, and perhaps only a...

Southern Red-backed Voles, like other voles, are active year-round. They do not hibernate or reduce their metabolism and enter a state of torpor to conserve energy against the cold. Learn more about the Clethrionomys gapperi, more...

No other mammal in the world looks like the star-nosed mole, which has 22 fingerlike appendages surrounding its nostrils. It has recently been discovered that these very sensitive tactile organs are used for object manipulation, and...

Notable for its running speed, the Texas Antelope Squirrel has the longest hindlimbs and tail of any antelope squirrel. In the field, the squirrels are noticeable because of the way they carry the tail arched forward over the back. Learn...

Stephen's Kangaroo Rat is endangered, chiefly due to habitat loss. It lives only in isolated populations in three counties of southern California. Learn more about the Dipodomys stephensi, more commonly known as a Stephen's Kangaroo Rat,...

Pronghorn are endemic to North America and are the only living members of the family Antilocapridae. In the Pleistocene, about a dozen species roamed the continent. Learn more about the Antilocapra americana, more commonly known as a...

The Panamint Kangaroo Rat lives where vegetation includes creosote bush, cactus, yucca, juniper trees, and Joshua trees. A seed eater, this Kangaroo Rat makes particularly efficient use of its external cheek pouches, as it removes the...

Like all members of the family Heteromyidae, Merriam's Kangaroo Rat is found only in the New World. Many kangaroo rats have rather specific habitat preferences, but Merriam's Kangaroo Rat is not one of these. Learn more about the...

By occupying the short grass prairie of the Great Plains, and a variety of habitats where there are fine-textured, sandy soils, Ord's Kangaroo Rat has managed a truly enormous geographic distribution. The varied habitats that it occupies...

Texas Kangaroo Rats live in only a few counties of north-central Texas, although the species was once also present in Oklahoma. They prefer to live where soils have a high percentage of clay. Learn more about the Dipodomys elator, more...

The Sea Otter is the largest member of family Mustelidae, and the smallest marine mammal. Sea Otters are more aquatic even than seals and sea lions, because they mate and give birth in the water. Learn more about the Enhydra lutris, more...