MAMMAL NOTES
There are 4600 species of mammals known and
300 of these are considered endangered, mainly
due to habitat destruction.
General characteristics:
1. Mammals are endothermic ( mostly
homeothermic)
2. Have hair or fur, if the coat of hair is thick, it is
called pelage and species with
sparse hair usually have very
thick skin or a layer of blubber
to insulate against
temperature extremes.
3. Nourish their young with milk secreted by the female’s
nipples.
4. All mammals are dioecious with
internal fertilization.
All mammals are heterogametic
which means that the sex of the
offspring is determined by the male.
Most mammalian embryos are
are nourished by a placenta.
5. All mammals breathe with lungs.
6. Have a four-chambered heart and a
closed circulatory system.
7. Most are terrestrial but a few are marine and one
Order has developed true flight.
8. Mammals have the most
advanced nervous system of any group.
9. All mammals have a lower jaw formed of a
mandible called the dentary which articulates with
the upper jaw called the squamate and an upper
palate which allows young to breathe while nursing.
10. All mammals have excellent hearing
and external ears called pinnae.
Living Representative Mammals
There are 21 orders of Mammals classified into two subclasses
1. Subclass Prototheria (egg-laying mammals)
ex. Duck-billed Platypus, echidna ( one order)
2. Subclass Theria-( Placental mammals)
a. infraclass Metatheria-marsupials
(one order)
ex. Kangaroo
b. infraclass Eutheria- true placental
mammals ( 19 orders)
I.
MAJOR ADAPTATIONS OF MAMMALS
Internal temperature regulation is the most important
adaptation in mammals!
A. Most mammals are both
endothermic and homeothermic.
B. Internal body heat results from
cellular metabolism.
1. a typical resting mammal has a metabolic rate 10 X
higher than a reptile
2. Mammals eat more calories and process them more
efficiently than reptiles in order to maintain a higher body
heat.
3. the smaller the mammal, the greater its body size to
surface ratio and the more it must eat to maintain life
ex. A 3 g. mouse eats 5X more than a 10Kg. Dog and
30X more than a 50,000 Kg. elephant.
*per gram of body weight
camel is example of non-
homeothermic animal
MAJOR ADAPTATIONS OF MAMMALS con’t
II. Sources of heating the body of a mammal
A. Shivering
B. brown fat
C. changing the pelage with the seasons
D. Arrector pilli muscles to erect hairs and trap
warm air.
E. Insulating blubber accounts for 45% of body weight of
seals and whales
III. Sources of cooling the body in mammals.
A. Panting
B. sweating
C. remaining inactive during the hottest part of
the day
D. spreading out and exposing skin where hair is
IV. Additional forms of temperature adaptation
A. hibernation- winter dormancy
B. aestivation-summer dormancy sparse
MAJOR ADAPTATIONS OF MAMMALS con’t
V. Mammalian integument ( outer covering of skin)
1. hair is formed of fine scales of the protein keratin.
a. Various types of mammalian hairs include: soft
undercoats, guard hairs, bristles and quills. Hair of
sheep and humans grow continuously, also the
manes and tails of horses, most other mammal hair
growth is determinate.
b. Molts are periodic sheds of hair in most mammals. Fox and
seals shed once a year in summer, most mammals shed twice a
year, in spring and fall. Some mammals change
color with the seasons, the white winter coat
of Artic mammals is called leukenism.
c. Whiskers or Vibrissae are sensory hairs,
they provide a tactile extra sense.
MAJOR ADAPTATIONS OF MAMMALS con’t
V. Mammalian integument
2. glands- sweat, scent, sebaceous, mammary
a. Eccrine sweat glands secrete a watery fluid that draws heat away
from the body surface…found in hairless regions of the body
b. Apocrine sweat glands are larger and open into a hair follicle.
They are unrelated to heat and tied to reproductive cycles. In
humans, they develop during puberty and are restricted to
armpits, ear canals, and pubic areas.
c. Scent glands used to communicate with members of same
species for breeding, territory marking, and defense
d. Sebaceous glands which serve as a dressing to keep skin
moist, fur glossy or waterproof.
e. Mammary glands occur on all female mammals. Some
mammals develop only during nursing, humans develop at
puberty with additional fat deposits.
Types of glands
Sweat glands
Mammary glands
Scent glands- marking territory!
Sebaceous glands
MAJOR ADAPTATIONS OF MAMMALS con’t
V.Mammalian integument
3. Horns and antlers
a. true horns-found in ruminants
(sheep and cattle family)
1. hollow sheaths of keratin over bone
2. they embrace a core of bone arising
from the skull
3. they are not normally shed and are not
usually branched.
4. are found on both sexes within a
species but are usually longer in males
TRUE HORNS
3. Horns and antlers continued
b. Antlers-found in the deer family
1. composed of solid bone when mature
2. grow under a covering of vascular skin called
velvet.
3. when growth is complete, the blood vessels
constrict and the stag removes the velvey by
rubbing it against trees.
4. antlers are shed after breeding season
5. each year the antlers are bigger than the year
before
6. only Caribou females have antlers
7. in Moose and Elk, males must acquire over 50
lbs. of calcium each year to grow their antlers
Types of Antlers
Rhino horn
• C. Rhinocerous Horn
1. hairlike keratinized filaments are cemented
together
2. Are not attached to the skull
VI. FOOD AND FEEDING
A. Teeth-structure of teeth reveal the lifestyle of an
animal
1. Incisors have sharp edges for biting
2. Canines are specialized for piercing
3. PreMolars have compressed
crowns for shearing
4. Molars have larger, flatter tops
for Grinding
5. Generally, mammals have one
deciduous set and
one Permanent set.
Feeding Specializations
1. Insectivores include shrews, moles, and most bats
2. Herbivores include 3 sub-groups
a. Gnawers include rodents, rabbits
b. Browers and grazers include horses, deer, cattle, sheepall hooved animals are called Ungulates, one sub
group of ungulates are called ruminants which have a
huge 3-4 chambered stomach. The chambers of the
stomach are called the rumen, the reticulum, the
omasum, and the abomasum
3. Omnivores include raccoons, bears, pigs, rats and
most primates
4. Carnivores include members of the dog, cat, and
seal family.
Teeth types
Carnivore teeth
Omnivore teeth
Insectivore
teeth
Herbivore
teeth
VII. Special Senses in mammals
A.
Many mammals have large moveable pinnae
(ear flaps) to aid in capturing sound and locating
the source.
B. Senses of smell, sight, and hearing are more or less intense in each species.
C. Echolocation is the ability to use sound waves to locate and identify objects.
Two orders, Cetacea
and Chiroptera
have this ability, but it is used in very different environments.
Reproduction in Mammals
A. Monotremes are egg-layers
and there is a cloaca for fertilization in
the female and the male’s testes are
housed inside the abdominal cavity
B. Marsupials have a
placenta that doesn’t allow
for many nutrients to pass
from mother to offspring, so
the embryo is expelled and crawls
to the marsupium which is a pouch
with a teat inside that the young
animal attaches and completes
development.B
primitive
C. Marsupial males have testes
housed outside the abdominal
cavity in a sac-like extension
called the scrotum. Most
placental males also have
a scrotum, except for the
aquatic mammals and elephants.
D. Placental mammals carry their
Young in the uterus for the entire fetal period and
The fetus is fed and cared for by the placenta.
E. Mammary glands are made up of clusters of milksecreting glands. Milk is made up of the sugar
lactose. Various proteins, fats, salts, vitamins and
antibodies from the mother’s immune system.
Immediately after birth, there is a special milk
produced called Colostrum which is made up
of large amounts of white cells
and antibodies to protect
the infant from infection
until its own immune
system develops.
Reproduction Timing
A. Estrus is the condition of a female mammal being
receptive to the male during certain intervals in an
ovarian hormonal cycle.
1. Polyestrus mammals mate and rear young several times a
year
ex. Mice and Rats
2. Monoestrus mammals mate only once a year (or longer)
sometimes called seasonal breeders
ex. Buffalo and Deer
Gestation periodsCats-56 days
mice-16 days guinea pigs-77 days
Dogs-63 days bats-154 days
humans-280 days
Elephant-670 days
ORDERS OF CLASS MAMMALIA
I. Subclass Prototheria
A. Monotremata-egg laying mammals with a cloaca
Duck-billed platypus
1.
2.
Lack teeth, but have a beak like a bird
Female platypuses lack nipples but secrete milk onto their
fur.
3. Stream dwellers who live on invertebrates
Spiny anteaters (echidna)
1. Eat ants and termites and earthworms
2. Female lays one egg at a time which she carries in a pouch
3. Infant anteaters live in the pouch for two months sucking
milk from two skin projections (primitive nipples)
Monotremata
Spiny anteater or
Echidna
Duck-billed
platypus
II. Subclass Theria-two subgroups called Metatheria and Eutheria
A. Infraclass Metatheria-one order Marsupialia
1. identified by the presence of a marsupium which acts as a brood pouch
for the developing embryo after it has left the womb.
2. only one marsupial species in North America, the opposum
3. 250 species of Marsupials, found mainly in Australia, and Central and
So. America
4. Australia has been marsupial heaven because of its remote locale
a. the dominate herbivore is the Kangaroo
b. the dominate carnivores were the Tasmanian
Wolf and the Tasmanian Tiger and the Tasmanian Devil
c. other Distinctive Australian marsupials include the
Wombat, Bandicoot, Koala, and Wallaby
Marsupiala
B. Infraclass Eutheria
True placental mammals made up of 18 orders
1. Order Insectivora
a. small, terrestrial or semi-aquatic mammals
with long tapered snouts, tiny eyes and short fur.
b. most are carnivorous, feeding on insects and
earthworms.
c. some have poisonous saliva
EX. Hedgehogs, shrews, moles
Order Insectivora
shrews
hedgehogs
voles
tenrecs
2. Order Chiroptera
About 1000 species of bats (second largest order)
a. most new-world bats are insectivores and
most old-world bats are fruit and flower
eaters.
b. there are also bird, fish, frog and bat eating
bats. Three species of new-world bats are
blood-drinkers
c. Bats are the only mammals to have evolved true flight.
The fore-limbs are modified with the 2nd to 5th digit
elongated to support thin membraneous wings, thumb
usually free.
d. Bats are mainly nocturnal in order to avoid direct
competiton with birds for food.
e. Bats that are carnivorous have developed Echolocation to
locate prey.
Order Chiroptera
BATS
“HAND WING”
Order Primates
175 species (including humans)
a. Found in Africa, S.E. Asia, and South America
b. Most species are aboreal or tree-dwellers
c. Examples include: Lemurs, Baboons, Apes,
Monkeys, and Chimps & Humans
d. All have forward facing eyes and opposable
thumbs
e. Family Hominidae includes four genera:
Gorilla, Pan (chimps), Pongo (orangutan) and
Homo (humans)
Order Primates
“FIRST”
Order Carnivora
About 240 species
A. terrestrial carnivores include the dog, cat,
weasel, hyenas, racoon, bear, badger, coyotes
B. aquatic carnivores include seals, otters,
walrus
C. not all carnivores are truly carnivores, bears
and racoons are omnivores and the Panda
eats only bamboo.
D. Most other carnivores have a well
developed sense of smell, and have limbs
adapted for running down prey.
Bear family
Order Carnivora
Weasel family
Dog family
Musk family
Marine family
Cat family
Order Perrisodactyla
Odd-toed animals (ex. Horses, rhinos, and tapirs)
And
Order Artiodactyla
Even-toed animals (ex. Swine, camel, deer, giraffes, cattle, sheep,
and hippos)
Collectively called the Ungulates
a.
b.
c.
All are hooved herbivores
Have limbs adapted for running in order to escape predators.
One sub group of Ungulates are called ruminants, these
animals hae a modified digestive system to aid in digesting
Cellulose. ( This group includes cattle, sheep, and antelope)
“ Eyes on the side, likes to hide
Eyes in the front, likes to hunt!”
Order Perrisodactyla
“odd-toed” hoofed
mammals
Order Artiodactyla
“Even-toed” hooved
mammals
7. Order Proboscidea (ex. Elephants)
Order Sirena ( ex. Manatees, dugongs)
Order hyracoidea ( ex. Hyraxes)
These three orders are referred to as the
Subungulates
Because they have a caecum and some have
vestigial hooves
a. All are herbivores
b. Thought to have come from a common
ancestor in Africa.
Order Proboscidea
African elephant
Indian elephant
Order Sirena
“Sea Nymph”
Order Hyracoidea
“Shrew”
Hyraxes-closest
living relative
to the elephant
7. Order Xenartha
a.
b.
c.
d.
e.
(ex. Anteaters, sloths, armadillos)
Only found in the new world tropics
Have extra cervical joint and lack canine
teeth and incisors
Anteaters lack all teeth but have a long,
sticky tongue that they capture ants with
Sloths are herbivores that sleep a lot and
spend their life hanging upside down. Their
body temperature is very low.
Armadillos are omnivores and have
distinctive bony plates covering their bodies.
Order Xenartha
“Intrusive
joint”
8. Order Cetacea
a.
b.
c.
d.
e.
f.
(Whales, dolphins and porpoises)
Highly intelligent
Form social groups
All excellent swimmers
Tail fins undulate up and down rather than side
to side as fish do
Nostrils are located on top of the head and is
called a “blow hole”
This order is divided into two suborders, the
Mysticeti which filter feed on small
invertebrates and the Odontoceti which use
Echolocation to locate prey in the ocean
Order Cetacea
9. Order Rodentia
a.
b.
c.
d.
(Ex. Beavers, rats and mice, squirrels)
Largest order with 1760 species
Have one pair of elongated incisors that grow
throughout life
Most rodents are herbivores but some, such
as rats are omnivores
Have the highest rate of reproduction and
many are considered pests
bottom of the food chain!
Order Rodentia
“To gnaw”
Largest order!!
10. Order Lagomorpha
(ex. Rabbits, hares and pikas)
a. Also have continuosly growing incisors but also
have a second pair of incisors in the upper jaw.
b. Are similar morphologically but different
physiologically
c. Hares have well-developed young, that find their
own homes in the grass and the mother visits
them to nurse several times a day. Usually have
three to four offspring
ex. Jackrabbits, snowshoe hares
d. Rabbits have hairless and blind young in a
burrow and have 6-9 offspring at a time.
ex. Cottontails-easter bunnies
Order Lagomorpha
“Hare form”
Order Scandentia
TREE SHREWS
“climbing”
Order Dermoptera
“Skin wing”
Flying
lemurs
Order Macroscelida
Elephant shrews
Order Pholidota
pangolins
“Horny scale”
Order Tubulidentata
“Earth pig”
Aardvark