1. Females possess mammary glands which provide milk

    for their young.


2. Possess hair or fur.


3. Most have varied teeth for cutting, tearing or grinding.


4. Warm-blooded and back-boned (also in birds).


5. Ends of digits usually have claws, nails or hoofs.


6. External ear flap.


7. Movable upper eyelids.


Mammals keep warm under a coat of hair or fur. To protect against winter temperatures, many mammals develop thicker, longer fur. This extra fur is shed in the spring with the onslaught of warmer weather. Deer get extra insulation from the trapped air inside their hollow hairs. Mammals can control body temperature so that it stays fairly constant by panting, sweating, and confining activity to the cooler hours. Not all mammals have the same body temperature. It generally varies quite a bit among different groups of mammals. Mammals, in any environment, that are active by night and quiet by day are called nocturnal.


Antlers and Horns

Some mammals have antlers or horns growing from their skulls. Male members of the deer family produce antlers. Antlers grow externally from calcium deposited by blood-filled capillaries underneath furred skin. By late summer, growth stops and the furry skin, called velvet, is rubbed off against tree trunks and small saplings. Antlers are sharpened for use and display during the fall mating season. They are shed in winter with regrowth starting in the spring.


Evergrowing Teeth

Rabbits and rodents have incisors that grow continuously, an adaptation to grit in their diet which would otherwise wear their teeth to the gumline. Evergrowing teeth are kept under control normally by grit, or by gnawing action. If these animals don’t have enough grit in their food, or are unable to gnaw regularly, their incisors will grow outside of their skulls and protrude from their mouths. If unchecked, these teeth will continue to grow until they turn backwards towards the skull, preventing the animal from eating. Starvation and death result.


Skin Glands

Mammals have five different kinds of skin glands, which serve specific purposes. Mammary glands in females produce milk to nurse young. Sweat glands help to cool mammals and get rid of waste products through the pores of the skin. Oil glands lubricate skin and hair. Scent and musk glands produce chemicals used for marking territories and communication.



Parasite Hitch-hikers

Wild mammals support a wide variety of hitch-hiking parasites like fleas, ticks, bloodsucking flies, and lice. Parasites can weaken their hosts, but rarely kill them. Because some of these parasites can transmit diseases like plague and tularemia to people, it is a good idea to avoid handling dead animals, especially rodents and rabbits.


Coyote (Canis latrans)


Color and size variable. Mountain coyotes are larger, have longer fur than desert coyotes. Coyote is vocal at night; a series of yaps, a long howl, then short yaps. Holds tail between legs when running. Can reach 40 mph. Track like a dog’s. Population, range increasing despite hunting, poisoning campaigns. Widespread. Dens along river banks, well drained sides of canyons, gulches. May enlarge badger or squirrel burrows. Chiefly nocturnal, but active any time. Often hunts in pairs. Omnivorous, but mostly eats small rodents, rabbits, squirrels. Droppings gray, with some seeds, but mostly fur, bones, insect parts, reptile skin, feathers; occasionally solid foil, plastic, or grass, which helps remove tapeworms. Mates January-February. Six to seven pups born April to May, raised by both parents. Livestock losses blamed on coyotes often the work of dogs. Coyotes kill many grass-eating rodents, earning them protection from some ranchers.         






Gray Fox (Urocyon cinereoagenteus)

Salt-and-pepper gray with rusty neck, legs, feet. Less vocal than other foxes. Can run, in short bursts, 28 mph. Only fox which climbs trees to escape or to hunt. Mainly in woodland, chaparral. Dens in hollow trees, logs, under rock ledges, or in culverts; may have several escape dens nearby. Den area often marked by accumulation of droppings, bones. Gray fox is nocturnal, but often seen in day. Eats small rodents, insects, birds, eggs, fruit, acorns; in some areas, diet is largely cottontail rabbits, ground squirrels, berries. Two to seven pups are born March-April, dark brown, eyes closed. Hunt on their own at four months. Afflicted with many diseases, parasitic worms. Enemies: domestic dogs, bobcats, lions, people. Poison bait intended for coyotes kills many gray foxes.




Droppings: 50mm, 10mm, smaller than

Coyote’s- almost always black with stringy

Ends, berry seeds, fur, etc.




Mule Deer or Black-Tailed Deer (Odocoileus hemionus)

Coat varies; reddish in summer, grayish in winter. Have large ears that move independently and almost constantly and account for the common name. Tail white with black tip, to all black. Rump patch white. 100-475 pounds. Antlers branched; number of branches and rack size increase with age, decline after peak; are shed in winter; grown again in early spring, are covered with velvet until late summer. Buck damages saplings and branches by rubbing off velvet. Black-tailed deer are  active most hours except mid-day. Chiefly a browser; fond of clover, alfalfa, fruit, acorns, many herbaceous plants.


Coastal deer lose weight June-November, followed by natural die-off. Survivors gain weight after fall rains. Shrubs resprouting after fires in the fall, combined with available acorns, supply deer with essential food for recovery.


Bucks solitary; may form bands before and after mating season. Harems form in October. After gestation of 6-7 months spotted, odorless fawns are born May-June, hidden for one month. Young does have singles, older does twins. Fawn yearlings travel in family groups with mothers. Bucks will urinate in beds as they stand; does step to one side first. Chief enemies; lions, bobcats, coyotes, domestic dogs, people and cars.



Striped Skunk (Mephitis mephitis)


Bold coloring warns predators. When threatened may snarl, stamp feet, raise hindlegs, click teeth, arch tail, turn toward enemy, This failing, shoots a jet spray of musk (to 4.5 meters) as final defense. Adult skunk needs about l0 acres. Uses abandoned burrows of other animals, digs its own or may use protected spaces under houses (unless repelled by mothballs). Nocturnal. Does not hibernate; may be inactive for weeks in winter. Males solitary; females may den together in winter. Eats variety of vegetable matter, insects, grubs, mice, eggs, frogs, and also yellow jackets and their nests, leaving large holes in ground. Four to seven young born in May, follow mother single-file until June or July. Chief carrier of rabies. Predators: great horned owls, golden eagles.







Raccoon (Procyon lotor)


Color salt-and-pepper. Playful, curious, good swimmer. Feeds mostly along streams, lakes, ponds, but will wander from water. Dens in hollow trees, logs, rock crevices, or ground burrows. In cold weather, may sleep for several days; does not hibernate. Chiefly nocturnal, but occasionally about in day. Especially active in autumn. Solitary except when breeding, caring for young. Diet varied: fruits, nuts, grains, insects, frogs, fish, crayfish, birds’ eggs. Washing food enhances sense of touch in toes, helps raccoon discern non-edible matter. Leaves droppings at base of den tree, on large branches, rocks, logs across streams. Mates in February or March. Two to seven young born April or May. In fall, young raccoons may disperse up to 160 miles, but mostly less than 30 miles. Chief enemies: dogs, hunters, autos. Raccoon can defend self well against a single dog.



        hind feet tracks: 95mm                                                 droppings: 30 – 50mm




Opossum (Didelphis marsupialis)


Only pouched mammal in U.S. Scruffy, gray body with prehensile tail. Thin, black, hairless ears and part of tail may be missing in north range due to freezing. Opossum feigns death when threatened. Thrives in urban, rural, and woodland areas. Nests in hollow trees, logs, culverts, brush piles, under houses. Eats fruit, vegetables, nuts, insects, carrion, eggs. Nocturnal. Solitary. Does not hibernate; stays in den for several weeks in cold weather. Has one to two litters, January to October. One to 14 embryos crawl out of womb to pouch covering 13 teats. All could fit in a teaspoon. Nurse for two months. Five to seven normally survive to juvenile stage. Lifespan about seven years.






Mountain Lion, Cougar, Puma (Felis concolor)


Yellowish, grayish, reddish-tawny. Habitat generally wilderness but may hunt in rural hills. Male may travel 25 miles in one night. Strongly territorial. Mostly nocturnal. Rarely seen. Voice like tomcat’s, greatly magnified. Uses tree trunks as scratching posts. Solitary, except in two week breeding season. Eats large mammals; one deer per week forms half of diet. Has more success catching old, weak, less alert deer, thus keeps herd healthy. Also eats coyotes, porcupines, beavers, rabbits, marmots, raccoons, birds, sometimes livestock. Covers remains of large kill with branches, leaves. Droppings often left like bobcat’s. Adults breed every two-three years. One to six furry, spotted kittens

Born midsummer, raised by female for one to two years. Only enemies are human. Before lions were legally protected, a man was found with 52 lion skulls, from animals killed in the Kern River Canyon—a tragic waste. Protection should be permanent, even though population is reported to be increasing.





Hind tracks: 101 mm   Droppings: 76 – 228 mm

Bobcat (Felis rufus)


Gray-brown to reddish. Ear tufts used like antennae to aid hearing. Good climber. Gets name from “bobbed” tail. Found in most every habitat, life zone. Range is usually within two miles, may be up to 50 miles. Mostly nocturnal, also seen in daytime. Solitary. Often rests on branches, atop large rocks to watch for passing prey. Eats rabbits, mice, squirrels, porcupines, woodrats, bats, small, weak deer. Caches large kills. Droppings are like dog’s or coyote’s, but often partially buried, with scratch marks on ground. One to seven (average two to three) kittens born April-May in den of dry leaves in hollow log, under rock ledge or fallen tree. Southern animals may have two litters per year. Lifespan 25 years. Marks territory by urinating on rocks or tree trunks, making scent posts. Uses tree trunk as scratching post. Often killed by poison bait intended for coyotes.











There are about 11 species of ground and tree squirrels. Most do not hibernate, but sleep for short periods. Eat variety of green vegetation, seeds, nuts, fruit, flowers, bulbs, roots, fungi, bird eggs, insects, baby birds, and occasionally fresh road kills. Most store food for use after awakening from sleep periods and in spring. Enemies include coyotes, foxes, bobcats,  hawks, owls, and large snakes.


Western Gray Squirrel  (Sciurus griseus)


Large, gray (occasionally all black), has bushy tail with white-tipped hairs. Belly white, or sometimes rust colored. In oak and pine forests. Home range one half to two acres, two squirrels per acre. Being displaced by introduced fox squirrel near urban areas. Most active in mornings. Feeds heavily on fungi, robs acorn woodpeckers’ caches of acorns, eats pine nuts. Makes nests of sticks, leaves, shredded bark in tree cavities or among outer branches more than five meters above ground. Young born February, three to five per annual litter.





Fox Squirrel (Sciurus niger)


Rusty, reddish gray, lower parts rusty yellow or orange; some pure

Gray, no rust. Melanistic forms occur. Introduced from east to

City parks and campuses, now widespread in urban areas. Replaces native western gray squirrel as range extends. Like western gray squirrel, buries acorns and pine nuts, some of which are not retrieved and grow into trees. Young born February-March, sometimes June-July, two to four per litter, with two litters per year. Lifespan about seven years.





Desert Cottontail (Sylvilagus audubonii)


Dark ear tips, larger size, and white-tipped hairs on underside distinguish it from Brush Rabbits. In open plains, foothills, low valleys, coastal areas; in grass, sage, moist chaparral. Home range one acre for females, up to 15 acres for males. Active in late afternoon, night and early morning. Stays close to thickets. Eats green vegetation and a variety of fruit, but rarely tree bark. Young born naked and blind, in fur nests, throughout the year. May

Live two years in wild. Vulnerable to marauding domestic dogs.


Brush Rabbit (Sylvilagus bachmani)


Occupies chaparral and thick brush of coastal and foothill areas. Stays close to thickets, often clearing vegetation to bare ground along edges between brush and grass areas.  Home range ¼ to one acre, with one to three rabbits per acre. Least active in middle of day, but feeds on vegetation at any time. Basks in morning sun. Young born with short, fine hair, but blind; two to six per litter, sometimes three to four litters per year, January to June. Same enemies as other rabbits; also vulnerable to dogs. Some tick species are specifically attracted to the ears of pregnant females for their blood meal, which provides the hormones the ticks

Need for reproduction.



Dusky-Footed Woodrat (Neotoma fuscipes)


Woodrat often builds a second “escape” nest in tree branches near

Ground nest. Presence of wood rats is indicated by bulky nests

Of twigs at bases of trees, shrubs, in rock crevices, in cactus or

Tree branches. They earned name ”packrat” by stashing anything

They fancy in their nests. Nocturnal, territorial, they respond to

Disturbance by drumming or thumping with hind feet or tails.

Woodrat tails have hairs, unlike “old world rats”. Feed on green

Plants, nuts, seeds, fruit, fungi. Most species give birth to one to

Four young per annual litter. Enemies include owls, foxes, coyotes, bobcats and large snakes.








California Vole

California Meadow Mouse

(Microtus californicus)


Many of the grass-covered hills, and often pastures and marshes as

Well, are scenes of constant rodent activity. The grass is honeycombed with neat tunnels, built and maintained by meadow mice. The floors of these tunnels are smooth and well packed from daily use, and any debris in them is cleared away, for a vole’s life often depends on a speedy and unobstructed retreat.


Meadow voles are about 6 ½” long with a short (1 ½”) tail and small ears. Voles have large families and they have them often. They can produce 12 litters a year, 4-8 in a litter. They are weaned at 10 days and the females can breed again. Young females 4 weeks old and males 6 weeks old are ready to breed. Fortunately, many predators – hawks, owls, snakes, weasels, skunks, badgers, foxes, coyotes and bobcats – aid in keeping the vole population in check. Without a high reproduction rate, the species would not survive.


Voles usually eat their own weight every day—roots, grains, vegetables. Life span, barring predation, is 11/2 years.








Botta Pocket Gopher (Thomomys bottae)


Have large, external, fur-lined cheek pouches for carrying food. Squeeze contents out with fore paws; turn pouches inside out for cleaning. Burrowing area may cover 2,000 square feet. Gopher’s lips close behind the upper incisors to keep dirt out of mouths while they dig. Enamel covers fronts of incisors, creating sharp, beveled edges as backs of teeth wear faster. Gophers are active day, night, year round. Eat roots, tubers, greens. Solitary. Males fight other gophers on contact, except females in breeding season. Two species rarely live in same field. Sexually mature at three months. Young born mainly in spring, one or two litters per year, 2 to 11 per litter. Predation low. Enemies: badgers, weasels, snakes, owls, hawks, coyotes, foxes.









The insectivores, or insect-eating mammals, found in the bay region are shrews and moles. Although there are six species of shrews in the bay region, they are so much alike that positive identification of specimens should be sought from an expert.


Shrew Mole (Neurotrichus gibbsi)

The shrew mole, smallest of North American moles, spends much of his time above ground in a network of trails and tunnels beneath the leaves and tangled vegetation.

Identification Black, forefeet longer than broad; tail relatively short, scaly, and haired. Head and body 3 to 3 1/2" long; tail 1 to 1 1/2" long.

Habitat Moist ground litter at edges of forest, around wet meadows,

and along streams.

Range Restricted chiefly to redwood forests.

Young Possible several litters a year; 4 to 9 in a litter.

Food Earthworms, sow bugs and insects.









Broad-Footed Mole (Scapanus latimanus)


Fur blackish-brown or gray-brown, velvety, flexible; allows forward or backward movement in tunnels with equal ease. Eyes pinhead size. Earholes concealed. Naked nose is most vital sense organ. Mole digs with broad front feet in breast-stroke motion. Can tunnel 30 cm.  per minute. Mounds appear to erupt from earth. Tunnel ridges collapse in time; improve soil aeration, rain penetration, reduce erosion. Mole feeds on worms, insects, centipedes, snails, slugs, some root crops. Young born March-April, two to six per litter. Active day and night. Rarely above ground, thus low predation rate.


A mole run is often used only once. Thus a mole is hard to trap unless the trap is set in one of his main tunnels, which are deeper and more often used (see sketch). The dirt from these deeper tunnels is pushed to the surface in a “molehill”; unlike a gopher’s mound, a molehill is never open.


Except in the mating season, gophers are rarely found in the open, preferring to remain in safety underground. Strong claws and chisel teeth equip them for a life of burrowing. In hard soils they literally gnaw their way through the ground.




Little Brown Bat

ORDER: CHIROPTERA (“hand-wing”)

Myotis lucifugus

L. 31/2”  Wing Span 9”


The Little Brown Bat is one of the most common in North America and can live up to 30 years.  It is usually found near people’s homes and in buildings near a creek,, river, marsh or lake.  Little Brown Bats mate in the fall just before hibernation.  The females arouse the following spring and at that time allow fertilization to take place.  The young, usually one per female, are born and reared in June and July.  Bats are slow to reproduce and 50% of the babies die their first year.


Rainforests need bats for their survival to pollinate fruit flowers and disperse seeds.  Bats are responsible for 95% of rainforest regeneration.  If not for bats we would not enjoy bananas, mangoes, plaintain, avocadoes, cashews, dates, figs, allspice and many other fruits.


Nearly 40% of American bat species are threatened or endangered.  California has 24 species of bats with 12-13 species in the Bay Area.  Almost 1,000 species of bats are found around the world and each species makes its own electronic sound.  Bats use sonar at night but have good eyesight in daytime.




Carrion - Dead and decaying flesh.


Diurnal - Active during the daytime rather than at night.


Melanistic - Dark coloration of the skin, hair, fur, or feathers because of a high concentration of melanin (dark pigments).


Nocturnal - Most active at night.


Omnivorous - Eating both animal and vegetable foods.


Prehensile - Adapted for seizing, grasping, or holding by wrapping around an object.


Species - A group of plants or animals composed of individuals that interbreed and produce similar offspring.




Mammal Finder, Ron Russo and Pam Olhausen, Nature        Study Guild, Berkeley, CA. 1987


Mammals of the San Francisco Bay Region, William D.and Elizabeth Berry, University of California  Press, Berkeley, CA. 1959


The Audubon Society Field Guide to North American Mammals, John O. Whitaker, Jr. Chanticleer  Press, Inc., N.Y., 1980


A Field Guide to the Mammals, Peterson Field Guide Sereies,

William H. Burt and Richard P. Grossenheider

Illustrations scanned from Mammal Finder, Ron Russo and Pam