Presentation developed by John Rohm, VDGIF Wildlife Biologist.

Modified by Ron Hughes

Mammalogy- simply the study of animals in the Class Mammalia Kingdom – Animalia Phylum – Chordata

o Subphylum – Vertebrata Class – Mammalia Order – Rodentia, Carnivora, etc. Family – Canidae, felidae, etc. Genus – Procyon Species – lotor

What are the diagnostic characters of mammals?

Skin glands – mammary, sweat, sebaceous, scent.

Hair/fur Single dentary (lower jaw bone) that is

hinged to skull 3 bones of the middle ear (incus, maleus,

stapes) Muscular diaphragm Red blood cells are enucleate (without a

nucleus) Two occipital condyles Epiphyses on long bones

4,600+ known species (not many when compared to other vertebrates)

Largest mammal – Blue whale (Balaenoptera musculus) 160,000 kg, 100 feet (30.5 M)

One of smallest – pygmy shrew (Sorex hoyi) 3 g > 7 orders of magnitude difference

Rodentia is largest order (2,016 species) Meadow vole (Microtus pennsylvanicus)

can produce 72 offspring/yr

Evolution of Mammals Structure and function

o Skin, hair, claws o Skeletal features & locomotiono Reproduction

Important Diseases Conservation and Management in VA.

Mammals evolved from reptiles sometime during late Paleozoic to early Mesozoic Era (280 mya)

Arose from the subclass of reptiles known as Synapsidao Within synapsids the Order of Therapsida;

often referred to as “mammal-like reptiles”

Relatively rare and small (mouse-sized) Were nocturnal (most reptiles during Mesozoic

were diurnal)o Avoided predation by shifting activity to the

night Contributing adaptations:

o Endothermyo Skull modifications that allowed for improved

hearing ability, more complex nervous system, & feeding efficiency .

During the Cenozoic Era the mammalian radiation started (diversification)

130 million years elapses then an explosion in the mammalian species in the Cenozoic Era. Why then?

Two main reasons1. Dinosaurs become extinct 2. Large continental land mass known as

Pangaea breaks up

The skin is the largest organ of the body. Functions: o Protectiono Sensoryo Insulationo …

Consists of three layerso Epidermis (outer most layer, nonvascular)o Dermis (vascularized and contains hair

follicles, sweat glands, etc). Provides support to epidermis.

o Hypodermis (inner most layer, consists of

Hair – one of the diagnostic characters of mammals.o Provides insulation; helps maintain body

temperatureo First layer of protection from elements o Three well defined structural layers Cuticle – outer layer; forms a scale like

patterns used to identify species Cortex – middle layer Medulla – center of hair (absent in deer)

Shaft of dead keratinized cells Zone of growth in the root Two functional types:

o Underfur – short and fine. Provides most of insulation

o Guard Hairs – outermost hair that contains pigments. Protects the underfur.

Vibrissae – long, stiff hairs with extensive nerve network at base. Tactile function.

Spines – greatly enlarged, stiff with definitive growth (i.e., Porcupine quills)

Bristles-long, firm with continual growth (i.e., Horse or lion’s mane)

Awns- have a firm, expanded distal portion and a smaller, weaker base (most common). Considered a guard hair.

Wool – long, soft, and usually crimped (sheep)

Underfur – common on many mammals; consists of closely spaced, fine, short hairs. Aquatic mammals contain thick underfur in winter.

Velli- very short and fine; referred to as “down or fuzz” (common on newborns)

Teeth are an important feature of mammalsoReflect a mammal’s trophic level

(feeding specialization) oCan be used for identification and aging

purposes Most mammals have heterodont teethoTeeth are differentiated in basic form

and function

Occlusalsurface

EnamelCrown RootDentinePulpCementum

Occlusal surface

Incisors – cut or gnawCanines – enlarged in carnivores

(piercing and tearing) Premolars – deciduous; for grinding Molars – not deciduous; also for

grinding

Sectorial teeth -modified molars and premolars used for shearing flesh

Enlarged and elongated canines

Dental formula is shorthand description of total # and position of teeth

Used specifically for identification purposes. Uses half of skull mandible teeth:

5/4,1/1,3/3, 4/4 = 25

o Above the line (numerator) are the upper jaw teetho Below the line (denominator) lower jaw teetho Order = incisors, canines, premolars, and molars o Know this formula because only one NA mammal

posses it

Mammary gland and mammae unique to mammals

Mammary glands – responsible for producing the milk inside the mothers body

Mammae – structures on the outside of the body that function to release/disseminate the milk to offspring.oNipplesoTeats

Epidermal structures made primarily of keratin.

Nails:o Found on top of the digitso Characteristic of mammals that grasp or hang onto

objects

Claws:o Found on end of the digitso Curved and sharp at tipso Serve a variety of functions – digging, climbing,

capturing/holding prey

Hoofs:o Weight-bearing structures found at end of

digitso Highly modified bone structures in hoofed

animals to enhance running ability.o Deer , elk, swine, goats, sheep, bovids

Cursorial – animals adapted to runningo Most canids, felids, ungulates

Ambulatory – animals that exclusively walk o Most rodents, shrews, elephants, rhinos

Saltitorial – animals that jump and hopo Lagamorphs (rabbits), some rodents, kangaroos

Scansorial – animals that climbo Some rodents, raccoon, opossum, most primate

Swimming – animals that swim almost exclusivelyo Whale, seal, sea lion, walrus

Gliding – not true flyerso Flying squirrels

Flying – animals that truly flyo Bats are only mammals that can fly

Fossorial – amimals that travel underground almost exclusivelyo Moles

Plantigrade – walk or run on the soles of hands and feet

Digitigrade – run on toes/digits (phalanges)

Unguligrade – run on only the tips of their digits on one or two hooves

Monotreme mammals lay eggs (but they do have mammary glands and suckle their young)

Marsupial mammals have an inefficient placenta resulting in short gestation and long nursing as fetus develops in the marsupium(pouch). One marsupial in Virginia!

Plecental mammals have an efficient, more developed plecenta. Make up the bulk of all mammals

Mammalian Reproduction: of monotremes, marsupials, and placentals…

Male system (we are all familiar with)o They make spermo some have a baculum or ospenis bone

Female system (we all understand the basic concept)o Ovulation: In ovary the egg matures and

follicle surrounding it bursts releasing the egg into oviduct, corpus luteum forms (important for research)

Copulation Fertilization Fertilized egg attaches to the placenta.

Function of the placenta:oAnchors fetus oTransports nutrients oGets rid of waste oProduces hormones

Gestation…

Gestation continues (fertilization -birth)

Parturition (birth) occurs Lactation – production of milk by

mammary glands nourishes offspringA lot of time and effort goes into

reproduction and maternal care in mammals vs. other organisms

Induced ovulationo Copulation induces estrus (cats & some

rodents)

Delayed fertilizationo Copulation – sperm is stored – mammal

hibernates – fertilization is initiated at end of hibernation. Nothern temperate bats

Delayed Developmento Copulation – fertilization – development is

delayed or occurs at a very slow rate. Jamaican fruit bat.

Delayed Implantationo Copulation – fertilization – some

development occurs but stops without blastocyst implanting

o Blastocyst floats freely until optimal conditions occur, then development continues to completion. Bears & weasels

Bears mate during summer Fertilization occurs but blastocyst does

not implant Sows enter dens and if she’s fit

development occurs (implantation delayed five months!)

Cubs are born in winter dens (February) while females are “hibernating”

Advantages:o Weight gain in fall is critical to femaleo Young are protected in dens o Bears emerge from dens with cubs under

better seasonal conditions

1 day 60 day

Habitat Generalists Can occupy a wide range of habitat types Deer, opossums, woodchucks, white-footed

mice, raccoons, etc. Habitat Specialists Linked closely to a specific habitat type Forests – tree squirrels, flying squirrels, gray

foxes Old fields – eastern cottontail rabbits,

meadow voles, red foxes, etc.

Brucellosiso caused by bacteria occurs in ungulates

(domestic and wild) and other mammals, including humans

o Causes abortion and fever Giardiasis (beaver fever)

o Caused by protistans commonly associated with beavers; causes severe intestinal disorders

Trichinosiso Caused by nematodes carried by wild

carnivores and rats and infects humans via ti f d k d t

Lyme diseaseo Caused by bacterium carried by ticks

(mainly black-legged tick) o White-footed mice are main reservoirs;

deer are secondary host

Tularemia – documented in >100 mammalian species o Caused by bacterium and maintained in

tick rabbit cycle (most often).

White Nose Syndromeo Caused by an introduced funguso Effects hibernating bats, primarily cave bats.o Most significant disease to hit NA mammals. Extensive

population delcines – Little brown bats and more importantly northern long-eared bat

Rabieso caused by RNA-viruses and transmitted by carnivores o Almost always Fatal

Spongifrom Encephalopathieso Mad Cow o Scrapie – sheep o Chronic Wasting Disease – Deer (Cervids)

Hemorrhagic FeversoHantavirus – carried in small

rodents Humans contract via inhaling dust

were rodents have left droppings or via bites

o Epizootic Hemorrahagic Disease(EHD)or blue tongueEffects white-tailed deer (Odocoileus

virginianus) throughout SE

Extirpation vs. Extinction o Extirpation- the extinction of a species from

a portion of its geographical rangeTimber and red wolves Eastern puma (mountain lion) Eastern elk Bison

o Extinction – a species gone forever…

Overexploitation by humans (market hunting; unregulated trapping)

Habitat degradation and loss

Increasing human population resulting in…

Habitat destruction (development, highly intensive agriculture, loss of wetlands)

Habitat alteration (fragmentation, shift in composition, reduced diversity)

Environmental changes Climate change Oak and hemlock decline Red spruce decline

Damage to caves Continual increase of generalists

o Thrive in human dominated landscapes (deer, foxes, and raccoons)

Poaching/selling animal parts on black market (e.g., black bears gall bladders)o Regulated hunting doesn’t adversely impact

populations Hybridization – coyotes vs. red wolf

recovery efforts

Nutria (Myocastor coypus)

Feral hog (Sus scrofa)

Feral cats (Felis catus)

Coyotes (Canis latrans) o immigrated and introduced

Red fox (Vulpes vulpes)