2/18/25

VOICES!

blue jay

yellow rumped warbler

carolina chickadee

cricket frog

cardinal

tufted titmouse

mockingbird
- if we get cricket frog on the quiz, just put cricket frog

midterm is just lecture stuff (No ID)

Biology and Diversity of Mammals

Characteristics of mammals

• uniquely modified skull (jaw, ear, zygomatic arch)

• heterodont dentition

• Specialized skeleton, especially feet

• hair (another time of keratinized epidermis)

• dermal muscles (also in birds)

  • like hair going up on a dogs back (the dermal muscle be doing that)

• mammary glands (and other skin glands)

• endothermy

Origin and diversity of mammals, class Mammalia

• Mammal-like reptiles diverged from the stem reptiles about 300 mya

  • Theraspsida, a clade that includes mammals

    • reptilian vertebral column and ribs

    • mammalian limb orientation - under the trunk

    • mammalian and reptilian skull characteristics

Mammalian skull characteristics

• zygomatic arch

• coronoid process of dentary

• heterodont dentition (teeth with different shapes)

Reptilian Skull characteristic

• jaw articulation at the rear of the jaw on the articular

Evolution of the mammalian jaw

• appearance of heterodont teeth, some with multiple roots

• loss of jaw bones (articular moves to the middle ear, only dentary remains)

• enlargement of coronoid process

Molecular phylogeny of the mammals

• 3 old clades

  • monotremes (platypus (egg-laying mammals))

  • marsupials

  • eutherians (true placentals)

• Major eutherian clades

  • present by late cretaceous

• Eutherian diversification

  • after K-Pg extinctions (65 mya)

Dentition and dental formulas

• I = incisor

• C = canine

• P = premolar

• M = molar

• the amount of I, C, P, and M in the upper and lower jaws can be used to find out which animal, or what type (like carnivores, or bats)

Opossum - relatively primitive, lots of teeth (few in carnivores (eutherians))

Typical carnivore skull - specialized for tearing

• carnassial tooth (long tooth for tearing) in canids is a premolar on the maxillia and a molar on the manible

White-tailed Deer - ungulate skull

• highly specialized for plant diet

• often lose upper incisors

• usually lose canines

• long, flat molars and premolars with irregular surfaces

More dentition

• rodents have unique teeth

Armadillo skull - bizarre

• peg-like, single-rooted teeth are often not classified as incisors

Hispid Cotton Rat skull - typical rodent

• highly derived - loss of lots of teeth

• elongated incisors (do keep growing)

• no canines or premolars

• few broad molars

Mammal feet

Plantigrade (primate) - primitive

Digitigrade (carnivores) - derived

Unguligrade (ungulates) - most derived

Skin glands unique to mammals

• mammary glands - provide nourishment for young during postnatal growth (milk stimulated by endocrine system)

• sweat glands - promotes evaporative cooling and eliminates waste - typically restricted in location

• sebaceous glands - secretions lubricate hair and skin

Hair (also called pelage)

• keratin-based product of epidermis

• critical for endothermy

• pelage patterns important for communication or crypsis

• hair oriented by dermal muscles

Endothermy - circulatory system

• complete separation of systemic and pulmonary circulation (4 chambered heart, 2 chambers receive blood and 2 pump blood)

• many mammals can alter heart rate

  • hibernation

  • carnivore lethargy, alarm bradycardia (‘freezing’)

  • bats - resting and active heart rates differ by 500 beats per minute, and change within 1 second

Only in endotherms, with high oxygen demand, is it critical always to separate oxygenated blood (coming from the lung) from deoxygenated blood (coming from the body’s capillary beds)

Fat and energy storage

• not unique to mammals, but important for energy storage, source of heat and water, and insulation

• temperate mammals typically have localized fat storage

• boreal and aquatic species store fat subcutaneously over the body

Respiratory system

• disphragm - unique to mammals[

• heart and particularly lungs are large relative to body surface - required for endothermy

• exchange of gases occurs via alveoli, where oxygen enters bloodstream

• lung surface - humans have 70 m² of lung surface, about 40x the surface area of the body

Worldwide terrestrial mammal diversity (~5400 species terrestrial + aquatic)

Marine mammal diversity

Diversity of Louisiana Mammals

• 10 orders, 69 species excluding domestic species

  • Didelphimorphia (opossums) - 1

  • Cingulata (armadillos) - 1

  • Sirenia (manatees, dugongs) - 1

  • Cetacea (whales, dolphins) - 1 (+8 possible offshore)

  • Artiodactyla (even-toed ungulates) - 1 (+1 introduced)

  • Chiroptera (bats) - 12

  • Eulipotyphla (shrews, moles, hedgehogs) - 5

  • Carnivora (carnivores)

    • Canidae (dogs) - 3 (+extirpated Red Wolf)

    • Felidae (cats) - 2

    • Mephitidae (skunks) - 2

    • Mustelidae (weasels, otters) - 3

    • Procyonidae (raccoons, coatis) - 2

    • Ursidae (bears) - 1

  • Rodentia (rodents)

    • Castoridae (beaver) - 1

    • Geomyidae (pocket gophers) - 1

    • Heteromyidae (pocket mice) - 1

    • Cricetidae (New World rats and mice) - 10

    • Muridae (Old World rodents) - 3 (introduced)

    • Echimyidae (nutria and spiny rats) - 1 (introduced)

    • Sciuridae (squirrels, chipmunks) - 4

  • Lagomorpha (rabbits) - 2

  • Primates - 1

Who is absent from LA - why?

• orders absent from LA (of ~26 total)

  • Monotremata (monotremes - platypus and echidnas)

  • 5-6 orders of marsupials

  • 5 ‘afrotherian’ orders (hyrax, elephants, aardvarks, etc. plus manatees)

  • Pilosa - anteaters and sloths

  • Primates (+ 2 related orders - treeshrews and flying lemurs)

  • Philodota - Pangolins

• Compare to -

  • birds - 30-40 orders total, 1/3 absent from LA

  • Amphibians - only 1 orders (of 3 total), caecilians is absent

  • Reptiles - 1 order (of 4 total) tuataras, is absent

• terrestrial mammals couldn’t move from their land for a long time

Ecology of selected LA mammals

• Virginia Opossum

  • common, habitat generalist

  • omnivorous

  • only representative of S. American marsupial radiation in N. America

  • short life span (1-4 years)

  • mating in Jan, 2 week gestation, young extremely dependent at birth

• White-tailed Deer

  • Cervidae - deer

  • most common cervid in N. America

  • highly adaptable, habitat generalist

  • browser

  • considerable maternal investment, complicated social system

  • mate sept-march, gestation ~200 days

• Red Bat

  • order Chiroptera - bats

  • Solitary

  • insectivorous

  • common in LA, particularly along riparian area

  • LA bats probably include migrants

  • our LA bats are part of an Old World radiation

  • delayed fertilization

  • parturition in May-June

• Coyote

  • Family Canidae

  • generalist

  • distribution expanding

  • Keystone species in some systems - top carnivore in most of US

  • complicated and flexible social system with extended parental care

• River Otter

  • Mustelidae - weasels

  • riparian areas throughout NA- mostly aquatic

  • primarily carnivorous

  • high social

  • delay implantation + long gestation = 11-13 months

• Northern Raccoon

  • Procyonidae

  • omnivorous

  • dexterous

  • habitat generalist but often near water

  • family originated in northern New World

  • distributed from tropics to boreal forest

  • complex social structure

  • part of mesocarnivore release

• Louisiana Black Bear

  • Ursidae

  • omnivorous, habitat generalists

  • geographically isolated to 3 pops in LA

  • listen under ESA in 1992

  • Historically most abundant in MAV

  • Considerable maternal investment

• Beaver

  • Castoridae

  • manipulate aquatic systems - ecosystem engineers

  • generalist herbivores

  • established social/family groups

  • broad historical distribution in NA and Eurasia

• Hispid Cotton Rat

  • Cricetidae - most New World Rats

  • Herbivorous, granivorous

  • early successional habitats

  • good swimmers

  • litters may range to 15 and have 2 pulses per year, multiple litters in each pulse

  • pops fluctuate within years, greatest density during fall

• Nutria

  • Myiocastoridae

  • Nonnative wetland nuisance

  • severe effects on aquatic systems

  • generalist herbivores

  • nonseasonal breeders, first estrus can be at 6 months age (8 young/female/year)

• Eastern Cottontail

  • Leporidae - rabbits

  • herbivore/granivore

  • widest distribution of any rabbit, occupies nearly every habitat

  • sympatric with other rabbits

  • may produce 3-6 litters annually, over entire year

  • may reach very high densities (lowery reprots >6 mil killed in Missouri in 1958)

Current marsupial distribution - Oldest fossils are 125 mybp from China, but Australian marsupials are descended from a S. American ancestor. maybe across Antarctica?

Ungulate diversity worldwide - East Africa

Wallace’s Line

• New Guinea and Australia are distinct from neighboring Java, Sumatra, etc. because of a deep channel separating them. Java, Sumatra and Borneo are connected to Asia at times of low sea level