Mammals of Coronado NMem

Domestic cows feed on grasses, stems, and other herbaceous plant material. An average cow can consume about 70kg of grass in an 8 hour day. Cows twist grasses around the tongue and cut them with their lower teeth. Domestic cows are ruminants. Ruminants have a special system of digestion which allows for the breakdown of the relatively indigestible plant material which they consume. Cows have a four chambered stomach including a rumen, reticulum, omasum, and abomasum. Grass passes through the rumen where it is mixed with specialized bacteria. From the rumen it moves to the reticulum, where it is broken down further. The partly digested food, known as cud, is regurgitated and chewed. It is then swallowed and moves into the omasum and abomasum, where digestive enzymes break it down further and nutrients are absorbed. The process of digestion takes 70-100 hours, one of the slowest passage rates of all animals. This method of digestion permits ruminants to obtain the most nutrients possible from these plant materials.

(Rath 1998; Hindsaw 1993; Walker et al. 1975)

Plant Foods: leaves; roots and tubers; wood, bark, or stems

Primary Diet: herbivore (Folivore ) less ↑

Mule Deer live in a broad range of habitats - forests, deserts, and brushlands. Mountain populations migrate to higher elevation in warmer months, looking for nutrient-rich new-grown grasses, twigs, and shrubs. They maintain separate summer and winter ranges, connected by a migratory pathway. In milder climates, they do not migrate. They live in small social groups of about three, except during the winter, when large groups may come together to feed in open meadows. Females tend to stay close to where they were born. Males disperse farther, establish their own territories, and compete for access to females during the October and November breeding season. The males lose their antlers after breeding and grow new ones yearly, with each set becoming larger than the previous one. Newborns, with spotted coats, are well-camouflaged.

Adaptation: The remarkable evolution of running adaptations is evident in comparing the same (homologous) wrist and hand bones of the Mule deer, Odocoileus hemionus (image on the left), with a primitive type of versatile hand, like that of a Hedgehog, Erinaceus europaeus (image on the right).

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The White-tailed Deer is distinguished from the Mule Deer by the smaller size of its ears, the color of its tail, and most strikingly, by antler shape. In Whitetails, the main beam of the antlers grows forward rather than upwards, and each tine develops as its own separate branch rather than being split into a forked pair. The two species also run differently when they are alarmed. Mule Deer stot, a boing-boing-boing motion in which all four feet leave and hit the ground with each bound, whereas White-tailed Deer spring forward, pushing off with their hind legs and landing on their front feet. Today White-tails are very widespread in North America: there may be as many as 15 million in the United States. These Deer are adaptable browsers, feeding on leaves, twigs, shoots, acorns, berries, and seeds, and they also graze on grasses and herbs. In areas where they live alongside Mule Deer, the species naturally separate ecologically, the Whitetails staying closer to moist streams and bottomlands, the Mule Deer preferring drier, upland places.

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  More images, video and sound of the Key deer, a subspecies less ↑

There are only three species of Peccaries in the world, all in South America. Only Collared Peccaries also live in North America. Their range includes a great variety of habitats, and they eat all kind of vegetation, including cactus. They live in highly social and communicative groups. Grooming is an important social behavior, and they have at least 15 different types of calls signaling alarm, submission, and aggression. Territorial groups of 15-50 animals stay together, and cooperate to defend the herd, but they form subgroups that disperse to feed. An alpha male is the dominant animal in the herd. Peccaries often have twins.

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Coyotes are among the most adaptable mammals in North America. They have an enormous geographical distribution and can live in very diverse ecological settings, even successfully making their homes in suburbs, towns, and cities. They are omnivorous, eating plants, animals, and carrion. Socially, coyotes live in a variety of arrangements. Some live alone, others in mated pairs, and others in packs, which may consist of one mated pair, their new young, and offspring from the previous season that have not yet left their parents. Packs are an advantage when preying on larger mammals such as deer, or defending food resources, territory, and themselves.

Adaptation: The upper and lower cheek teeth of a Coyote, Canis latrans, are blade-like, with sharp shearing edges that cut food in scissors-like fashion. The foremost shearing teeth, known as carnassials, are clearly larger than the others.

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Gray foxes are adept at climbing trees. They are active at night and during twilight, sleeping during the day in dense vegetation or secluded rocky places. Nursing mothers and pups use a den— a hollow log, abandoned building, tangle of brush, or cracked boulder—for shelter. When she is nursing small pups, the female stays within a few hundred meters of the den, but otherwise adults may range over a 2—5 square km area. Pups begin to forage on their own at about four months of age, and maintain close ties with the mother until they are about seven months old. By about ten months, both males and females are old enough to reproduce, and most females will have a litter annually from then on.

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The kit fox has been thought by some to be a subspecies of the swift fox. This fox currently inhabits desert and semi-arid regions between the Sierra Nevada Mountains and the Rocky Mountains and on down into Baja California and the North Central states of Mexico; it is also found in the San Joaquin Valley of California.

Several features distinguish the kit fox from the swift fox. Kit fox ears are larger and set closer together than the swift fox. The head of the kit fox is slightly broader between the eyes and the snout is narrower. The kit fox has a longer tail, relative to the body, than the swift fox.

Their diet consists of the most readily available small mammals in the region, especially rodents and rabbits. The relationship of kit fox populations to populations of banner-tailed kangaroo rats (Dipodomys spectabilis) in the San Joaquin Valley and to black-tailed jack rabbits (Lepus californicus) in Utah have been well documented.

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"The Bobcat is the most widely distributed native cat in North America. Bobcats occupy many habitat types, from desert to swamp to mountains. They are mostly nocturnal predators, taking quarry ranging in size from mouse to deer. Rabbits and hares make up a large part of the bobcat's diet. Like Lynx, male and female Bobcats maintain territories by scent-marking. An individuals territory does not overlap with another Bobcats of the same sex, but females home ranges can fall within the territories of males. Females breed sooner than males, at about one year of age; males are ready to breed when they are about two. One litter, with an average of three kittens, is born each year."

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"The Hooded Skunk is a desert animal, preferring rocky canyons and valleys, and the vegetation along stream edges. It lives at elevations of less than 2,000 m above sea level. It forages at night for meals that may include small mammals, birds, and some plants, and it digs for beetles and other insects, which seem to be its preferred food. Striped, Spotted, and Hog-nosed skunks are all found within the Hooded Skunk's range. The four species coexist by adopting different behavioral and ecological strategies."

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The Striped Skunk is the most common skunk in North America, yet most of what we know about it comes from studies of captive individuals. Like all skunks, it has a superb defense system, the ability to spray a foul-smelling fluid from two glands near the base of its tail. Skunk musk is oily and difficult to remove. If sprayed in the eyes, it causes intense pain and temporary blindness. Skunk kittens can spray when they are only eight days old, long before they can aim, a skill they exhibit only after their eyes open at about 24 days. Skunks attempt to give a warning before they spray: both Hooded and Striped skunks stamp their front feet before turning around and spraying. Like all skunks, Striped Skunks are nocturnal and eat a variable diet, mostly of insects, but also including small mammals, carrion, and some vegetation.

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Spotted skunks are smaller than Striped skunks and more weasel-like in appearance. Like all skunks, they have anal scent glands and can emit a foul-smelling spray to protect themselves. The Spotted Skunk usually sprays as a last resort, if stomping with its front paws or doing a handstand is not sufficient to warn off an intruder. Spotted Skunks are good climbers, able to scurry up and down trees like squirrels, and prefer forested areas to open countryside. They sometimes dig burrows to use for denning, and sometimes choose such places as barns, haystacks, dens abandoned by other mammals, or crevices in trees. Usually they live alone, although in cold weather, several skunks may den together.

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"Badgers look like short, shaggy, medium-sized dogs. They are powerful diggers. One, taken to a football game as a mascot, escaped and dug its way under the field. They dig after and feed on ground squirrels and pocket gophers, and also eat toads, frogs, birds, snakes, insects and insect grubs, wasps, bees, and worms. They sleep through most of the winter in a den, spending about 29 hours at a time in a state of torpor, rousing briefly, and then sleeping again. In torpor, which is not true hibernation, the Badger's heartbeat slows to about half the normal rate and its temperature drops. Humans are the Badgers' worst enemy, trapping and poisoning them, but they are now protected in some states and provinces."

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Ringtails are nocturnal, cat-sized carnivores. They are good climbers and are found in habitats that range from dry canyons to wet woodlands, in highland and lowland terrain. They prey on small mammals, but their varied diet also includes other vertebrates, insects, nuts, and fruit. These animals are solitary and territorial, marking their home ranges by depositing urine and feces.

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White-nosed Coatis are the most diurnal members of the family Procyonidae. They often sleep curled up in trees, and come down at dawn to forage, rooting with their long, mobile snouts and digging with long, curved claws for insects, larvae, eggs, and small vertebrates. Adult males often live alone, but females and young coatis travel together in bands, vocalizing and grooming each other. They do not hunt cooperatively or share food, but they join forces to defend against male coatis and other intruders. Females raise their young alone, in a nest. Mortality can be high when the young first leave the nest, from predators—including male coatis, big cats, monkeys, and boa constrictors—and accidents and disease.

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Habitat and Ecology

• Terrestrial
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"Raccoons are among the most adaptable of the Carnivora, able to live comfortably in cities and suburbs as well as rural and wilderness areas. They use small home ranges, as small as 1—3 square km, and show flexibility in selecting denning sites, from tree hollows to chimneys to sewers. A varied diet is at the root of their adaptability. Raccoons eat just about anything, finding food on the ground, in trees, streams, ponds, and other wet environments, and from unsecured trash cans, which they open adroitly by hand. They can live anywhere water is available, from the deep tropics well into southern Canada. Even in the suburbs, Raccoons can occur at densities of almost 70 per square km. Females can breed when they are not yet a year old, and typically have litters of four young, which they raise themselves. The female nurses her cubs for about 70 days. The cubs' eyes open at 18—24 days and they begin exploring the world outside the den when they are 9—10 weeks old. By 20 weeks of age they can forage on their own."

Adaptation: As an adaptation to an omnivorous diet, the molars of the Northern Raccoon, Procyon lotor, have lost their flesh-eating crests and have evolved a blunt-cusped crow, which is more efficient in crushing and grinding tough foodstuffs.

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Most Black Bears hibernate for up to seven months, and do not eat, drink, urinate, or exercise the entire time. In the South, where plant food is available all year, not all bears hibernate—but pregnant females do. The female gives birth to 1-6 cubs (usually 2 or 3) in January, while she is deep asleep in her den. The newborn cubs snuggle next to her for warmth and nurse while she fasts. They grow from a birth weight of 200-450 g each (about 7-16 pounds) to the 2-5 kg they will weigh when the family leaves the den in the spring. Black Bears eat a little meat, and some insects, but they rely on fruit, nuts, and vegetation for the bulk of their nutritional needs. They are not all black. Most are, with brown muzzles, but in some western forests they are brown, cinnamon, or blond, and a few, in southern Alaska and British Columbia, are creamy white or bluish-gray.

Adaptation: In the Black Bear, Ursus americanus, the evolution of typically carnivorous, sharp shearing molars into the flat crushing teeth, typical of bears, is evident.

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A member of the Molossidae family, the Brazilian free-tailed bat has the characteristic mouse-like tail protruding beyond the flight membrane stretched between its hind legs. Relatively plain when compared to many bats, this species has brown fur, large ears that are nearly square, and a strongly wrinkled upper lip. However, it is superbly adapted to its aerial lifestyle, having long, narrow wings with pointed tips to enable very fast flight, and long hairs on the toes to judge flight speed and turbulence. The hind legs are short and powerful, making this bat an excellent climber (3). less ↑

The Mexican long-tongued bat has short ears, a long, narrow rostrum, big eyes, a minute tail, and a leaf-like projection of skin above the nostrils called a nose leaf. It is a medium sized bat that weighs about 25 grams and is between 3 and 3.5 inches long. The fur is gray to brown above and lighter on the underside. The tongue of the Mexican long-tongued bat extends up to 1/3 of its body length.

Choeronycteris mexicana feeds and pollinates many different cacti species including saguaro (Carnegiea gigantea), organ-pipe cactus (Stenocereus thurberi), agaves (Agave spp.), and cardon (Pachycereus pringlei).

This bat lives in a variety of habitats, including desert, semidesert grassland, montane, riparian, tropical deciduous forests, and urban environments. The bat is most frequently found roosting in desert canyons, but also in deep caves, mines, rock crevices, and abandoned buildings.

This species is common throughout Mexico. Its range extends through Central and northern South America and to the southern parts of Texas, New Mexico, Arizona, and California. However, it is rare in the United States. less ↑

"The Mexican long-nosed bat feeds mainly on the nectar and pollen of agaves, and is found in Texas in June and July, when the plants are in bloom there. Then it migrates southward into Mexico, where it lives in pine-oak forests and deserts. It may be the main pollinator of a plant that has economic value in Mexico, the pulque plant. Little is known about the bat's pattern of reproduction. Nursing females and juvenile bats have been seen in Texas in June and July."

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Common throughout its range, the pallid bat occurs in arid and semi-arid regions throughout northern Mexico and the western United States. Pallid bats eat beetles, grasshoppers, and moths, and they forage for slow-moving prey, such as scorpions, flightless arthropods, and sometimes lizards, at and near ground level. They use echolocation to detect prey, but also use their large ears to listen for prey movements. Pallid bats visit flowers in their hunt for insects, and are natural pollinators of several species of cactus.

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Big brown bats make their homes in rural areas, towns, and cities, sometimes choosing barns, houses, or other buildings as roosts. Males usually live alone; females gather in maternity colonies in the spring and summer to give birth and raise their young. A maternity colony may include 20 - 75 adults and their offspring. Females in the eastern United States usually give birth to twins; those in the West usually have a single pup each year. Females may return to the same colony year after year. On warm, dry evenings, the bats leave the roost shortly after sunset to forage for insects especially flying beetles which they catch and eat in the air. When the weather is cold or wet, they may stay in the roost, dropping their body temperature and living on stored fat. In the winter, they hibernate. Many migrate a short distance (less than 80 km) to find mines or caves for hibernation, but some spend the winter in attics or walls where the temperature is cool but stays above freezing.

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Southwestern myotis live in a variety of southwestern mountain habitats, from desert grasslands up into pine and mixed coniferous forest in the United States, and in desert and grassland in Mexico. These bats and two other myotis species, the long-eared myotis and the fringed myotis, are able to hover and pluck insects from surfaces; most myotis bats catch their prey on the wing. The three species are known as hovering-gleaning bats. The southwestern myotis probably hibernates in caves, but has not yet been found in hibernation.

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"California myotis are found in deserts and arid basins. They drink at small waterholes, and when they forage, they fly low and slow over water and other open areas, and at forest edges. Many California myotis are active in winter, but some that live at higher elevations or farther north hibernate. Mating usually occurs in the fall, and sperm is stored in the female's uterus until spring, when ovulation and fertilization occur. A single pup is born in June or July, when food is plentiful. The young develop rapidly and can fly in about a month."

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The eastern small-footed myotis is one of the smallest North American bats. It has a limited range, occurring only in eastern deciduous and coniferous forests. This bat tolerates colder temperatures than many bats, entering hibernation later than many (November to December) and leaving it rather early (in March). It has a slow, erratic flight that is characteristic and can be used to help identify the species. Rather remarkable for a mammal of such small size, this bat is known to live to 12 years. By comparison, most small rodents and shrews live only about 18 months or less.

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"The fringed myotis belongs to the long-eared myotis group, all of which tend to be high-elevation forest bats. This species has the shortest ears and occupies the lowest elevation of the group. Its wings are short and broad, indicating maneuverable, low-speed flight, and it seems to be a specialist at gleaning small beetles from vegetation surfaces. Beetles may make up 70 percent of its diet. Fringed myotis have one baby a year, and it is huge in proportion to the mother's size. A newborn's weight is 22 percent, and its length is 54 percent, of the mother's. Newborn bats are left hanging in special roosts, where 2-10 adult females are always present to care for them. The other females fly out at dusk to forage and return at dawn, but are there as necessary to nurse their young.  Before they are three weeks old, the young can fly, and by three weeks, they are as large as adults."

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Western pipistrelles sometimes leave their roosts before sundown, and can be mistaken for late-flying butterflies, because they are so tiny and fly slowly and erratically, with much fluttering of their wings. Most common at low elevations in desert scrub and arid grassland habitats, they are also found in adjacent woodlands. Although they range over the arid West, western pipistrelles require a ready source of water—a lake, stream, or even a swimming pool. They—and some shrews—are the smallest mammals in North America, with weights ranging from 2—6 g. In spite of their tiny size, western pipistrelles usually give birth to twins, which are born and raised in small maternity colonies. The largest colony yet found comprised just four female bats and their eight young.

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Sporting prominent ears that look almost like wings, Townsend’s big-eared bat largely preys on moths over open pasture and forest canopy. For females, foraging increases during pregnancy and lactation, from one or two foraging bouts per night to three, and the distance traveled also increases, from 1.0 km to more than 4.0 km per night. Females form maternity groups in the spring, in caves and shelters, where they give birth to a single pup. In addition to winter hibernation, these bats also experience daily periods of torpor during cooler weather, a sleeplike state of reduced motor and metabolic activity. Townsend’s big-eared bat occurs in the western United States, northward to British Columbia, as far east as the Rocky Mountain States from Idaho to Texas, including Kansas and Oklahoma, and there are also populations in Arkansas, Missouri, Kentucky, Virginia, and West Virginia.

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The most well-known adaptation for evading predators is known as "playing dead" or "playing opossum." An opossums will lie on its side as if dead with its tails rolled up, eyes and mouth open, and its paws partially closed. (Parker, 1990) Common predators of southern opossums include owls, snakes, and mammalian carnivores.

Known Predators:

• screech owls (Otus)
• snakes (Serpentes)
• mammalian carnivores (Carnivora)
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"The Virginia Opossum, the only marsupial found north of Mexico, is an adaptable omnivore at home on the ground and in the trees. Opossums prefer forested habitats, but they are quite successful even in urban areas. They are active at night, year-round: in freezing weather, an unlucky opossum can lose its ear-tips and the end of its tail to frostbite.  Like all marsupials, opossums give birth to tiny, undeveloped young. The embryos develop in the mother's womb for less than two weeks, then the newborn opossums crawl from the birth canal to the mother's pouch, where they fasten tight to a nipple. They stay there, attached to the nipple, for 55 or 60 days. A female opossum usually has 13 nipples, and litters are usually smaller than that, but a baby that cannot attach to a nipple dies. After about 60 days the young opossums leave the pouch, but they stay close to their mother—sometimes riding on her back when they are out at night—and nurse for another month or more."

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Antelope Jackrabbits are nocturnal and crepuscular, and almost never vocalize. They are probably the fastest runners of their genus, with a top speed of 72 km per hour. They flash their white rumps somewhat as pronghorns do when they are running. Their ears are white on the outside, and longer than average. Typical of hares, and in contrast to rabbits, Antelope Jackrabbits give birth to well-developed young who are fully furred, with their eyes open, and able to hop.

Adaptation: As seen from the front and side, the spool-like shape of the main gliding surface of the elbow of the Antelope Jackrabbit, Lepus alleni, controls the movement of the forearm so that it can easily flex and extend but not twist. This is an adaptation to cursorial locomotion similar to what is found among other, very distantly related, running mammals.

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Black-tailed Jackrabbits are tremendous leapers, able to jump more than 6 m horizontally. They live in some of the hottest and driest regions of the continent, can survive on poor-quality foods, and get most or all of the water they need from their food. Where they can, they eat green vegetation, but they can survive in parts of the Southwest where creosote-bush forms a large part of their diet. They cope with extreme heat by lowering their metabolism and resting in the shade during the day, which conserves water. They get rid of extra salt through their urine, and blood flows close to the skin in their enormous ears, a cooling mechanism. Although mostly nocturnal and solitary, large groups sometimes form near a good food supply. With their typically high reproductive output, Black-tails can be agricultural pests, and there were periods in the 1800s and 1900s when aggressive rabbit drives herded and destroyed 5,000-6,000 animal in a single day. In spite of this, they are quite common and widespread.

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"Living well below sea level in Death Valley and also in woodland and grassland up to 2,000 m elevation, Desert Cottontails are able to tolerate diverse habitats. They are most active at dawn and dusk, and spend hot days resting in a burrow or in a ""hide,"" which is a shallow depression in the ground or in vegetation. Like all rabbits, they are vegetarians, feeding on grasses, shrubs, and forbs. They also eat acorns. When they can, they forage under shrubs, and when they venture out from under shelter, they move cautiously, and freeze when alarmed. They breed year-round, and mature quickly: breeding is seen in individuals as young as three months of age."

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"Pocket gophers dig with their front claws and with their teeth. A pocket gopher can close its mouth behind its front teeth, so it can dig without getting a mouthful of dirt. Its ""pockets"" are fur-lined, external cheek pouches, one on each side of its mouth, which it uses to transport food. Botta's Pocket Gopher has an extremely broad geographic range, and individuals vary widely in appearance: they can be nearly white, gray, brown, or blackish-brown. They vary in size, too. Males are larger than females. Males grow throughout their lives, whereas females stop growing after their first pregnancy, so older males can be much larger than females. Pocket gophers live in small, local populations, spending almost their entire lives underground in their network of burrows."

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Because most Southern Pocket Gophers live at high elevations in the mountains of Mexico, they are less accessible, and have been less-studied, than some other species. Like all pocket gophers, they are vegetarians, consuming both aboveground and underground parts of plants. Southern Pocket Gophers are active all year long and appear to have no set pattern of daily activity, excavating tunnels at any hour of the day. The average life span is probably 2-3 years. Most young are probably picked off by predators, which include hawks, owls, snakes, weasels, badgers, bobcats, and coyotes, before they are old enough to reproduce.

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"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 include semi-arid grasslands, mixed-grasslands, and scrublands. This ecological variation, together with the considerable geographic range, has contributed to the fact that more than 30 subspecies have been named. Ord's Kangaroo Rats are most active on cloudy nights. They usually stay in their burrows in bad weather and especially on clear, moonlit nights when owls can spot them most easily. Other predators include foxes, coyotes, badgers, and long-tailed weasels."

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"The Banner-tailed Kangaroo Rat confines its activities to small areas near the large earthen mounds that contain its complex burrow systems. Usually gentle and timid, this Kangaroo Rat will fight furiously to defend its territory from invasion by other Banner-tailed Kangaroo Rats. Foot-drumming on top of the mounds is used as a warning signal. Like other kangaroo rats, it sandbathes, both to clean its fur and to scent-mark its territory. The white tip on the end of its long tail waves as the animal moves around, giving this Kangaroo Rat both its common name, Banner-tailed, and its Latin scientific name, ""spectabilis,"" which means visible, worth seeing, notable, admirable, or remarkable."

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The smallest Perognathus species of all, the Silky Pocket Mouse is among the smallest rodents in North America. These Mice are most active on cool, humid nights, typically foraging for fallen seeds by sifting sand with their tiny forepaws. Sometimes they climb the stems of grasses to harvest seeds that have not yet fallen. They carry nesting materials and seeds back to the burrow in their fur-lined cheek pouches, and store seeds within the burrow. The Mice do not hibernate in winter, but remain active within their burrows, fueled by a cache of seeds. Silky Pocket Mice have not often reproduced in captivity, so knowledge about their reproductive habits is somewhat sketchy. They are known to have one or two litters a year, depending on climate and food availability. Two to six young are born in a litter, after a gestation of about four weeks.

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Northern Pygmy Mice are the smallest rodents in North America. They live in a variety of habitats where there is dense ground cover, and eat grass seeds and leaves, prickly pear cactus fruit and stems, mesquite beans, and granjeno berries (granjeno is an evergreen shrub). They will also eat snakes, snails, and insects if presented with them. They cope with desert heat by entering torpor. Males help care for the young, grooming them and returning them to the nest. Nests have been found under fallen logs or in thick clumps of grass. Young Mice reach sexual maturity quickly, females at about 60 days and males at about 70-80 days. The median life span is only 23 weeks, although captives, in laboratories, have been known to live as long as 170 weeks. Snakes and owls prey on them.

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"Woodrats are also known as Packrats, because they cache various manmade objects in their dens. This habit of collecting foreign objects is useful to scientists, who can place numbered sticks throughout an area and later open a den, record the numbers of the sticks the woodrat has carried home, and determine the size of the animal's home range. White-throated Woodrats occur on forested hillsides, rocky mountainsides, and on flat scrubland. They especially like prickly pear cactus, but also eat cholla, yucca, grass, catclaw, soapweed, and various parts of juniper trees and mesquite. They make their dens of some of these plants, which they can use as a food supply when fresh food is not available. Fossilized woodrat dens can supply information about ancient vegetation and therefore, what the climate must have been like at different times."

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Northern Grasshopper Mice are highly predatory, and their skulls and teeth resemble those of flesh-eating carnivores such as cats and dogs. Their forelimbs, equipped with elongated fingers and claws, have developed great dexterity, so they are able to manipulate captured prey. These Mice have a complex social system, using howling vocalizations to broadcast information on sex, identity, body size, and location. Grasshopper Mice prey primarily on grasshoppers, crickets, and beetles, yet they incorporate some seeds into their diet, presumably a dietary preference retained from a seed-eating ancestry.

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Southern Grasshopper Mice are also known as scorpion Mice: they are able to kill (and then eat) scorpions, by first immobilizing the venomous tail and then biting the head. They also prey on beetles that secrete defensive chemicals from the tip of the abdomen, by jamming the pointed barb into the ground and then striking a deathblow to the head. Of the three species of grasshopper mice, the southern Grasshopper Mouse inhabits the driest regions. Although it does not have the physiological adaptations of some other desert rodents, such as kangaroo rats or pocket mice, it may be able to get enough water from the bodies of its prey - arthropods and small mammals - to live without drinking water.

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Brush Mice occupy rocky and brushy or forested environments in which rock ledges, piles of brush, fallen trees, and boulders offer shelter and denning sites. Although they are reportedly good climbers, they only occasionally build their nests in tree cavities. Within their enormous range, these Mice are found only at elevations above 2,000 m. They consume many kinds of nuts, seeds, and fruit, including grass seeds, acorns, pine nuts, hackberries, juniper berries, and fir seeds.

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The White-footed Mouse has a very wide distribution. It is the most abundant rodent in mixed deciduous and coniferous forests in the eastern United States, and is probably equally abundant near farms. Its habitat preferences are very different in southern Mexico, however, as it prospers in semi-desert vegetation. White-footed Mice are excellent swimmers, and so are able to colonize islands in lakes with relative ease. They are not agricultural pests, and they are important ecologically because owls, weasels, snakes, and many other predators eat them. Individuals may live several years in captivity, but an almost complete turnover occurs annually in wild populations. In some places they carry the tick that transmits Lyme disease.

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Deermice rarely leave their homes during the day, but feed opportunistically at night on whatever is available: seeds, nuts, fruit, berries, insects and other animal matter, and whatever they find tasty in houses. Deermice have the most extensive range of any North American rodent, and are found in almost every kind of habitat. They climb easily, tunnel through snow or scurry about on its surface, and find shelter everywhere from mattresses to tree cavities to burrows in the ground. Populations fluctuate in cycles of three to five years, sometimes correlated with the amount of food available. The Deermouse is important as a laboratory animal, and can be a factor in the spread of some human diseases, including hantavirus, plague, and Lyme disease.

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The fulvous Harvest Mouse is a nocturnal species that lives in grassy fields where there are shrubs. These Mice are good climbers, and build baseball-sized nests up off the ground, in vegetation. Winter nests are sturdier than summer nests. When a nest is occupied—often by two Mice—the one or two entrances are plugged. Fulvous Harvest Mice eat invertebrates when they are available, during the spring and summer, and switch to seeds in fall and winter. Along the Texas coast, where invertebrates are available year-round, they are the dominant item in the diet. Males and females seem to travel together, which suggests they may pair-bond in monogamous relationships, a rarity for mammals. These Mice live for about a year, and seldom longer than 14 months.

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Western Harvest Mouse are adaptable, widespread, and abundant, especially in meadows, prairies, old pastures, stream valleys, and marshes. They eat seeds, insects, and plants. They rarely live for more than a year, but under optimal conditions, a female can produce more than 50 young in her lifetime. Their nests are built of plant material, usually on the ground, but sometimes in burrows or in vegetation slightly above the ground. Each mouse may have several nests, which it uses at different times. The Mice are nonterritorial and show a great deal of tolerance for one another, even huddling together when it is cold. Such intimate contact carries risks: they are afflicted with many parasites, including protozoans, worms, fleas, chiggers, mites, and lice. They are a vector for a hantavirus that can cause acute respiratory illness and hemorrhagic fever in humans.

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Plains Harvest Mice are found in grassy areas, including hay and wheat fields. They seem to prefer shorter grasses, and build round nests of grass on or near the ground. Newborns are blind and hairless, and weigh about a gram, but are weaned at about two weeks and are adult-size in five weeks.

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Voles and cotton rats usually live in different geographic regions, but both groups of small rodents eat grass and make runways. Yellow-nosed Cotton Rats are especially vole-like because they are small and live in grassy patches of habitat in mountains. They are found on isolated mountains at all elevations, sometimes using surface nests and sometimes building them underground. They have 2-6 young in a litter, at almost any season of the year except during the driest part of the summer. The young nurse for about 15 days, but in just over a week, they are also beginning to eat grass.

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Walnuts are a favorite food of Arizona Gray Squirrels, and when they find an abundance, the squirrels soon stain their faces, paws, and undersides a distinct brownish-orange from walnut juice. Other foods eaten may include fungi, acorns, juniper berries, pine seeds, and tree flowers and buds. This species is quiet and secretive and rarely seen. It is not very common and has a limited geographic distribution. Within its range, Arizona Gray Squirrels prefer broadleaf forests along rivers, which commonly occur in canyon bottoms.

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"Rock squirrels, with their long, bushy tails, look very much like tree squirrels, but seldom climb trees. They are most commonly found in rocky habitats—canyons, cliffs, and hillsides. Occasionally a nest is found in a tree, but they usually dig burrows, choosing a place that offers a near-by lookout where they can watch for danger. Other mammals and even burrowing owls are known to use their dens if the squirrels abandon them. The rock squirrel's geographic range is large, and it is found at elevations from sea level to 2,900 m. Females produce one litter a year in places or at elevations where winter weather lasts longer, and two in warmer parts of their range."

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These shrews live in deserts, but they seek out moister microhabitats within them, such as brushpiles or fallen logs. They have been found in beehives, and their tiny, golfball-sized nests have been found in dens built by—and sometimes still occupied by—woodrats. Captive individuals ate a variety of insects, including cockroaches, beetles, mealworms, and moths, and also accepted carrion. They would not attack live rodents, or eat salamanders, earthworms, or scorpions. Crawford’s Gray Shrews give birth to litters of 3 to 5 relatively helpless, but rapidly maturing, young, which leave the nest by six weeks of age.

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