Mammalia

• Class in the phylum Chordata
• Radiative evolution in the Cenozoic Era after extinction of dinosaurs, 65mya
• Includes: tiny shrews, bats, elephants, blue whales

Synapomorphies

Various Skeletal Modifications

Double-jointed Jaw Joint

• Dentary: Lower jaw
• Squamosal: Upper jaw
• Dentary and Squamosal are jointed

Three-Bone Middle Ear

• Three bones used in hearing
• Sounds pass from eardrum into three bones:
  1. Malleus: Outermost
  2. Incus: Middle, lengthy tunnel
  3. Stapes: Innermost, ring-like

Oral Teeth & Enamel

• A set of teeth
  • Teeth are replaced once in life in most mammals (except whales, rodents)
  • Heterodont: Different forms of teeth
  • Homodont: Identical form of teeth
• Teeth have an enamel coating on their surface
• Heterodont teeth have different notable forms:
  1. Incisor
     • Sharp, blade-like form
     • Cuts into food
     • Most anterior
  2. Canine
     • Strong, pointed form
     • Tears food
  3. Premolar
     • In-between form of canines and molars
     • Tear and grind into food
  4. Molar
     • Broad, flat surface of form
     • Crushes and grinds food
     • Most posterior
• Teeth dentition is adapted to diet
  • Carnivores:
    • Large, pointed incisors and canines
    • Smaller, jagged premolars and molars
    • Varying diastema
    • Predation
    • Dogs and cats
  • Herbivores:
    • Broad, ridged premolars and molars
    • Modified incisors and canines, or absent canines
    • Larger diastema
    • Horses and deer
  • Omnivores:
    • 32 teeth
    • Bladelike incisors, pointed canines, varying numbers of each toothform
    • Narrow diastema

Occipital Condyles

• Two knobs at the base of the skull that fit into the neck vertebrae
• Cusped around the foramen magnum

Number of Vertebrae

• The majority of mammals have seven cervical vertebrae
  • Except manatees, two-toed sloths, and three-toed-sloths

Tetrapodality

• Phalanges → Metacarpals → Carpals → Ulna + Radius → Humerus

Biological Modifications

• Mammary glands produce milk for young
• Endothermic regulation: High and constant body temperature

Physiological Modifications

• Hair on bodies
• Four limbs

Reproductive Behaviors

Eutherians

• Viviparous with an extended pregnancy
• “Placental”: Embryo is connected via a placenta

Monotreme

• Oviparous
• Duck-billed platypus, echidnas

Marsupials

• Viviparous with a shorter pregnancy cycle
• “Pouched-mammals”: Young crawl into a pouch to suckle on teats through development
• Kangaroos, koala, opossums

Lifestyle Behaviors

Terrestrial

Aerial

Arboreal

Fossorial

Aquatic

Orders

Monotremata

Duck-billed Platypus

• Many diverging evolutions from placental mammals:
  • Soft bill
  • Electroreception
  • Partially webbed feet
  • Tail that stores fat
  • Painful venom via poison spikes/spurs
  • Ear slits
• Native to Australia

Marsupialia

• “Pouched-mammal” development
• Opossums: Only native marsupial in North America
• Kangaroos, koalas, wallabies

Opossum (Didelphis virginiana)

• Bumblebee size
• Nurses for 2 months
• Rat-like prehensile tail
• Large canines
• Entered CA in 1900s; agricultural and sub/urban areas
• Predates insects, eggs, nuts, berries

Insectivora

• Small mammals
  • Long, pointed snouts
  • Sharp-cusped teeth
  • Occluded molars that overlap with cusps
• Predate on insects
• Shrews, moles, hedgehogs

Moles

• Mostly undeerground
  • Low ridges on ground show tunnels
  • Mounds push up evacuated soil
  • No entrance hole visible
  • Elaborate tunnel systtems
• Broad, flat palms and long claws
• Tiny eyes hidden by thick fur
• Insectivores; also eat worms and invertebrates

Shrews (Sorex)

• destructive
• confused with mice and voles
• high metabolism
• eats insects, earthworms, snails, invertebrates, lizarrds, salamanders, mice, berries, nuts
• Small eyes, short tail, small ears, pointed snout
  • vs mice (large eyes, long tail, large ears, pointed snout)
  • vs vole (small eyes, short tail, small ears, round snout)
• Dark red teeth from iron in tooth enamel
• Venommous; Soricidin and Blarina toxin via grooves on lower incisor external

Chiroptera

• Only aerial mammals
  • Pectoral appendages modified into wings
  • Small hind legs that hang on roosts
• Most predate on insects (70%); others are frugivores, carnivores, nectivores, or rarely blood
• Bats; Over 1,400 species

Lagomorpha

• Teeth modifications
  • Four incisors on the upper jaw
  • Enamel on both sides of the incisors
• Herbivores
• Hares, rabbits, pikas

Desert Cottontail Rabbit (Sylvilagus audubonii)

• Strong hind limbs and emphasis on hopping
• Feeds on grasses and forbs (cellulose)
• Produce hard and soft pellets
  • Coprophagous soft pellets to redigeest
• Young are born blind and helpless, but can mature in 3 months earliest
• Second set of teeth behind front incisors

Black-tailed Jackrabbit/Hare (Lepus californicus)

• Larger than rabbits
• Long back legs and ears; thin and visible blood vessels
  • Ears used for thermoregulation/dilation
• Herbivorous; eats more shrubby vegetation
• Nests in shallow depressions in vegetation
• Precocial young

Pikas

• High elevations; Western North American mountains
• Adapted to cold; endangered by climate change

Rodentia

• Teeth modifications
  • Chisel-shaped, developing upper and lower front incisors
  • Hard enamel on the front surface of incisors
  • Soft dentine on the back surface of incisors
  • Unequal wear maintains sharpness of teeth
• Largest group of mammals; over 2,000 species

American Beaver (Castor canadensis)

• Semi-aquatic
• “Gnawing” incisors
  • Orange coating of iron enamel only on the front surface
  • Feeds on bark, roots, leaves, shoots, and soft plants; uses hard bark and mud to build dams and lodges
• Flat tails for swimming rudders and communicating danger (slapping surface of water)
• “Ecosystem-engineers”

North American porcupine (Erethizon dorsatum)

• Sharp barbed quills for defense
  • Erect; can be swung, but not thrown
• Found in forests high in trees
• Predates twigs, shoots, bark, leaves
• Self-sharpening incisors

Western Gray Squirrel (Sciurus griseus)

• Local native tree squirreel
• Predates conifer seeds, green cones, acorns, green foliage, fungi
• “Salt and pepper” tail with white underparts
• No red on head or tail; white belly, bushy tail
• Found in woodlands and low-middle elevation forests
• May be replaced by introduced eastern gray squirrels

Eastern Fox Squirrel

• Extensive red spots on head, body, and tail

Eastern Gray Squirrel

• Intermediate red on face and tail
• Narrower tail

Kangaroo Rat (Dipodomys ingens)

• “Gnawing mammals”
• Desert regions; adapted for arid environments
  • Highly concentrated urine and dry fecal pellets
  • Survives on water from food direct and metabolized; doesn’t need to drink liquid water
    • Stores seeds in deep areas of burrows
  • Strong back legs and balancing tail; small front feet
    • Fur-lined cheek pouches for storing seeds without dehydration
  • Camouflage
• Auditory bullae on rear of head: inflated middle ear that increases frequency reception
• Nocturnal
• Caches seeds

Carnivora

• Synapomorphic carnassial teeth for predation
  • Blade-like upper premolar and first lower molar
  • Used to shear meat
• Highly diverse group
• Dogs, cats, bears, weasels, skunks, raccoons

Striped Skunk (Mephitis mephitis)

• Black-and-white aposematic striping
• Sprays noxious chemicals up to 20 feet away
  • Stamping warning + Rear + Tail
• Non-desert habitats
• Omnivorous: Invertebrates like insects, eggs, small vertebrates, and seeds and fruit; beetle larvae, worms, mice, plant bulbs/fruits
• Lives in burrow/cavity nests in most of CA except deserts
• Litter of ~4 young
• 18-32’, 2-13 lbs.; males larger than females

Raccoon (Procyon lotor)

• Widespread to North America
• Omnivores: Crayfish, insects, eggs, acorns, fruit
• Raid trash cans and gardens
• Nest in tree cavities and dens

Ringtail (Bassariscus astutus)

• Related to raccoons; striped tail
• Smaller than racoons; 24-30’’, half of length is tail
• Omnivorous: rodents, rabbits, reptiles, invertebrates, eggs, acorns, fruits, seeds, carrion
• Lives in rocky shrubland/woodland, near streams
• Nocturnal
• Fully protected in CA/AZ

Black Bear (Ursus americanus)

• Hibernates in winter
• Intelligent; can invade human areas
• Large skull

Mountain Lion (Puma concolor)

• California’s largest cat
• Hunts with stealth
• Small number of molars
• 6-8’ long, 200 pounds max
• Large, tan cat: white belly and long, black-tipped tail
  • Static coloration, not seasonal
• Habitates in forests and chaparral, sometimes central valley
• Feeds on deer, hares, small mammals

Bobcat

• 3-4’ long; 15-30 lbs
• Spotted red-brown coat and black short tail
  • Static coloration
• Lives in open woodlands, chapparal, forests
• “Bobbed” tail
• Rests in vegetations in day and hunts in night
• Eats rabbits, rodents, birds, reptiles, amphibians

Long-tailed Weaseel

• 11-18’ in; males larger than females
• 3-9 oz.
• Long, slender
• Seasonal coloration
  • Summer: cinnamon brown, buffy coat on chest and belly; black-tip tail and masked face
  • Winter in North: Pure white except for tail
  • Winter in South: Year-round
• Predators try to attack tip vs. head/body
• Lives in brushy, grassy areas near water; found in croplands, fallow fields, suburban areas
• Eats rodents, small mammals, birds, bird eggs, lizards, insects

Kit Fox (Vulpes macrotis)

• Primarily nocturnal; spends day in underground dens
• Deserts and arid ecosystems
• Predated by Red-tailed hawks, golden eagles, coyotes, Great horned owls, bobcats
• Carnivorous: kangaroo rats, ground squirrels, rodents, black-tailed hares, desert cottontails, birds
• Searches clumps of vegetation and sneaks
• 2* / 3* consumer

Gray Fox (Urocyon cinereoargenteus)

• Climbs trees with forking
• Active year-round
• Crepuscular and nocturnal
• Large, but timid; can be driven from food
• Predated by Red-tailed hawks, golden eagles, coyotes, Great horned owls, bobcats
• Omnivorous: Ground squirrels, mice/wood rats, rodents, rabbits, birds, berries, fruit, grain
• Stalks and pounces, pursues
• 1* / 2* consumer

Perissodactyla

• Odd-toed ungulates: One or three toes
• Upper jaw with a long diastema
• Cellulose is digested in intestines, not stomach
• Horses, donkeys, zebras, rhinos, and tapirs

Cetartiodactyla

• An order of the classes Cetacea and Artiodactyla

Cetacea

• Streamlined body
  • No hair
  • Insulated by blubber
  • Flat, horizontal fluke tails
  • Forelimbs are flippers
  • Vestigial hind limbs
• Whales, dolphins, porpoises
  • Rarest marine mammal: Vaquita from Gulf of Califorrnia

Dolphins

• Aquatic
• Swims in pods
• High up nostrils

Artiodactyla

• Even-toed ungulates: two or four toes
• Ruminant digestion: Food is regurgitated and rechewed
• Stomach is divided into three or four chambers

Horns vs. Antlers

Horns

• Bone with a keratin sheath
• Single protrusions, no forking
• Grown across lifespan; never shed

Antlers

• Bone, no keratin
• Extensions of skull, forking
• Shed and regrown to be larger per year

Camouflage

Concealing Coloration

• Same color as the background makes sight difficult

Disruptive Coloration

• Patterning
• May conceal in an uneven background
• Breaks up outline of outline and makes recognition difficult, esp. in large groups

Warning/Aposematic Coloration

• Stands out
• Strong defense
• Amphibians, reptiles, insects; sometimes seen in mammals

Extirpated Mammals

Gray Wolf — 1924

• Re-established in ~2011
• Shasta and Lassen pack

Grizzly Bear — 1922

• Unique population
• Smaller and more social than other grizzlies

Jaguar — 1860

Bison — 19th century

Introduced Mammals

Burro

Wild Boar

Norway Rat

Black Rat

Nutria (Myocastor coypus)

• Rodentia
• South America
• US fur farms
• Eats large qty aquatic vegetation
• Affects wetlands
• Bank and levees cause erosion, water breaching, and integrity weakening
• Similar to Beaver and Muskrat
  • Nutria: White whiskers, white muzzle, round rat-like sparse tail stilled during swimming, 10-20 lbs and 2’ with 1’ tail in adulthood, hunched behavior
  • Beaver: Black whiskers, flat broad tail that slaps water, 40 lbs and 3’ including tail
  • Muskrat: Fine black whiskers, sometimes white muzzle, flattened sides of tails that helps rapid swimming via a serpentine motion, 2-5 lbs and 1’ body