Mammalogy Exam 2

insectivore

insects, short intestine, no cecum

carnivore

animal matter (“meat”). short intestine and colon, small cecum

nonruminant herbivore

simple stomach, large cecum

ruminant herbivore

four chambered stomach with large rumen, long small and large intestine

herbivory

plant matter

Omnivory:

plant and animal matter

Mymecophagy:

ants and termites

Piscivory:

fish

Sanguinivory:

blood

Filter feeder:

krill

Granivory:

Two types of herbivore gut fermentation:

Hindgut, foregut

Hindgut fermentation

a digestive process that occurs in the hindgut (cecum and colon) of certain herbivorous animals, such as horses, rabbits, and rodents

Foregut fermentation

digestive process where microbes break down tough plant matter in a specialized stomach compartment before it reaches the true stomach.

ex. cervids and bovids

Coprophagy

the eating of feces or dung

to help them establish intestinal flora, and for the dams of young of some species, to keep the nest area clean

shrews, rodents, and lagomorphs

Monotremata

Family Tachyglossidae
Family Ornithorhynchidae

Family Tachyglossidae—

echidnas or spiny anteaters
Australia, Tasmania, and New Guinea

Family Ornithorhynchidae—

duck-billed platypus
Eastern Australia and Tasmania

Derived Characters of Monotremes

Rostrum covered with mechanoreceptors and/or
electroreceptors
• Reduced dentition
• Modified skull morphology

Monotreme reproduction

Combination of ancestral and derived traits:

Multiple sex chromosomes (5 X and 5 Y)
• Lay eggs (oviparous)
• Shell gland deposits thin leathery shell
• Egg tooth present at hatching

• monotremes have cloaca

Ornithorhynchidae characteristics

Single species (Ornithorhynchus anatinus) (platypus)

-Semi-aquatic lifestyle

-Eye and ear openings covered by skin folds when
submerged
- Males have medially directed spurs on ankles
connected to venom glands

-Has leathery bill

Tachyglossidae characteristics

Four species in two genera (echidna!)

-Thick bodies covered with short spines

-capable of daily torpor and seasonal
hibernation

-Rostrum slender and beak-like

Marsupials (Metatherians) and eutherians diverged:

diverged 100 million years ago

Derived Characters of Marsupials (Metatherians):

• Unusual pattern of tooth replacement

• Small narrow braincase

• Hindfeet may be specialized (e.g. for arboral or
  saltatorial locomotion)

kanagroos, koalas, etc.

Marsupials (Metatherians) reproduction:

Gestation is short (8–45 days)
Young born tiny and poorly developed
• Newborns crawl to marsupium and attach to nipple
• Lactation period is long

Order Didelphimorphia: Family Didelphidae

18 genera and 111 living species (opossums!)

Southeastern Canada to southern Argentina
Prominent sagittal crest
• Marsupium present or absent
• Tail usually prehensile

Order Paucituberculata characteristics

Called shrew-opossums

Disjunct distribution on Andes Mountains

No marsupium
• Lower incisors procumbent

Order Microbiotheria characteristics

One species (Dromiciops gliroides), Monito del monte

Southern Andes Mountains

Cloaca opens on ventral side of tail

May undergo hibernation

Order Dasyuromorphia families:

Family Dasyuridae (small carnivores)
• Family Myrmecobiidae (numbat)
• Family Thylacinidae (Tasmanian “wolf”—extinct)

Order Peramelemorphia

Family Peramelidae (bandicoots)
• Terrestrial omnivores
• Arid deserts to tropical forests
• Chorioallantoic placenta (similar to eutherians)

Chorioallantoic placenta

a structure found in placental mammals that facilitates gas and nutrient exchange between the mother and fetus during pregnancy. 

Order Peramelemorphia families: 

Family Thylacomyidae (bilbies)
• Family Chaeropodidae (pig-footed bandicoot—
extinct)

Order Notoryctemorphia

2 species of “marsupial moles”
• Fossorial adaptations
Cornified skin on nose

Eyes vestigial and lensless

Order Diprotodontia families:

Dominant herbivores of Australia (some omnivores)

11 families

Family Vombatidae

Wombats
• 2 genera and 3 species
• Stocky bodies up to 36 kg
• Limbs short and powerful
• Tail vestigial

Family Phascolarctidae

Single species – koala (Phascolarctos cinereus)
• Specialized arboreal herbivore
• 8–12 kilograms
• Fairly sedentary

Family Burramyidae

• Pygmy possums

Small, delicately built (up to 40 grams)
• Mountain pygmy possum capable of hibernation

Family Phalangeridae

cuscus and possums 

primarily arboreal

nocturnal, prehensile tails 

Family Tarsipedidae

Single species (Tarsipes rostratus)
• 7-12 grams in weight
• Long, prehensile tail
• Long, bristled tongue used to
extract nectar

Family Acrobatidae

Feather-like hairs on tail tip
• Feathertail glider has a gliding membrane between
elbows and knees (glissant)
• Feathertail gliders exhibit embryonic diapause

Family Pseudocheiridae

Ringtail possums and the greater glider

Tail prehensile
• Microbial fermentation in caecum
• Greater glider largest gliding metatherian

Family Petauridae

Tail long, bushy, and prehensile
• Dark dorsal stripe on head and back

Nocturnal and arboreal (except trioks)

Family Hypsiprymnodontidae

Single species of musky rat-kangaroo

Omnivorous
• Inhabits rain forest and riparian areas
• Retains all digits on hindfeet—quadrupedal

Family Potoroidae

Small kangaroo-like metatherians
• Retain slightly prehensile tail
• Well-developed upper canines

Family Macropodidae

900 grams to 90 kilograms
• Marsupium opens anteriorly
• Broad diastema
• Highly specialized for jumping

includes kangaroos

syndactylous

digits (fingers or toes) that are fused together by skin or bone

Order Chiroptera Characteristics:

Second-largest mammalian order

• only mammals capable of true flight

• Echolocation in most species

• temperate to tropical
  – Greatest diversity in tropical regions

bat uropatagium

The patagium that stretches between an animal's hind limbs

Bat Flight

Relatively slow, but highly maneuverable
Wings provide both thrust and lift
• Wing profile asymmetrical
• Unequal pressures above and below wing
generate lift

Angle of attack

the angle between the bat's wing and the oncoming air, crucial for controlling lift and preventing stalls

Camber

a curvature in an object,

Bat Flight cont; 

A few bats can hover
– Nectar-feeding bats

SuperFamily Pteropodoidea

Family Pteropodidae

Old World fruit bats (flying foxes)

Family Pteropodidae characteristics

Largest up to 1.5 kilograms (1.2 meter
wingspan)
• Some are small (13 grams)

• Non-echolocating bats
– except Rousettus use tongue-click echolocation

Ears lack tragus

SuperFamily Noctilionoidea

Phyllostomidae ** - NW leaf nose bats

Mormoopidae ** - ghost-faced bats

Family Mormoopidae characteristics

2 genera and 17 species
• “Ghost-faced” or “Mustached” bats

Conspicuous leaf-like flap of skin on chin
• Southwest United States, West Indies,
south to Brazil

Family Phyllostomidae

62 genera and ~214 species

Most diverse bat family
• Neotropical distribution

“Leaf-nosed” bats

Wide diversity in morphology and ecology

SuperFamily Vespertilionoidea

Vespertilionidae** – Vesper (evening) bats

Molossidae** – free-tailed bats

Family Molossidae

“Free-tailed” bats
Southern Europe, southern Asia, Australia,
most of New World

Shoulder and forearm adaptations for flight
• Wing long and narrow—high speed flight
• Tail extends well beyond uropatagium

Family Vespertilionidae

Nearly world-wide distribution
• “Vesper” bats
Small bats with simple faces
• Wing broad and uropatagium is large
• Mostly insectivorous

Male Anatomy

Testes—produce male gametes (sperm)
– Spermatogenesis
Spermatids undergo spermiogenesis

Testes remain abdominal in:

– Monotremes, elephants, sirenians, and
cetaceans

Testes descend into external pouch—
scrotum in most mammals

Scrotal position may be seasonal

Female Anatomy

Ova develop in paired ovaries
(oogenesis)
– Takes place only in female fetus
– Oogonia divide via mitosis forming oocytes
– Meiosis arrested until ovulation
– Many oocytes disintegrate before birth

Monotreme Reproduction

Combine reptilian and mammalian features

Reptilian traits: Yolky egg with shell
– Fetal egg tooth
– Urethra enters urogenital sinus dorsally
– Embryos at somite stage at laying
– Eggs incubated outside mother’s body
– Lack teats

Monotreme Reproduction cont.

Eggs laid into shallow depression (pouch) on
female abdomen
• Sticky coating adheres eggs to female
• Ten days later (in echidna) young emerges
• Young moves to mammary lobule to suckle milk
• Young evicted at roughly 55 days (echidna)

Estrous Cycle

Time from one entry into estrus (heat)
and the next

Monestrous—

single estrous cycle per year

Polyestrous—

multiple estrous cycles per year

Menstruation—

uterine lining shed if no
conception (some primates)

Four phases of estrous cycle:

– Proestrus, estrus, metestrus, and diestrus

Estrous Cycle

Ovulation typically occurs during estrus
• Surge in LH
• Follicle ruptures releasing ova (ovulation)
• Ruptured follicle becomes corpus luteum
• Corpus luteum secretes hormones to
prepare endometrium for implantation
• If no fertilization, corpus luteum regresses

corpus luteum

a temporary endocrine gland that forms in the ovary after ovulation. 

Placentas

Functional connection between fetus and
mother

Placenta Types

Discoid
Zonary

Cotyledonary

Parturition

Fetus and corpus luteum play roles in birth

Discoid

flat, circular shape, typical in humans and primates. 

Cotyledonary

Composed of numerous small lobes (cotyledons) connected by blood vessels, seen in ruminants. 

Zonary

A band-like shape that encircles the fetus, found in carnivores

Marsupial Parturition

Kangaroos adopt birth posture
• Tiny young appears and crawls toward pouch
• Newborn attaches to bud at tip of teat
• Newborn begins suckling
• Rudimentary lungs so uses cutaneous gas
exchange

Eutherian Parturition

Rising estrogen levels and declining
progesterone levels results in:
– Rhythmic, powerful contractions of uterus
– Increase sensitivity of uterus to oxytocin
– Softening of cervix
• At birth, fetal part of placenta is expelled
– Nondeciduous
– Deciduous

Mammary glands likely evolved from

apocrine- or eccrine-like glands

Proto-milk probably licked off fur

Lactation period longer in metatherians

Three stages of metatherian lactation

– Mammogenesis

– Early lactogenesis
– Late lactogenesis

Mammogenesis—

preparation of mammary
glands

Early lactogenesis—

period when young
attached to teat

Late lactogenesis—

after young detached from
teat

Metatherians—milk composition changes
during

lactation

– Metatherians may produce different milks at
each teat

Eutherians—milk composition remains

fairly constant

Postnatal Growth

Small mammals generally have higher
postnatal growth rates

Higher postnatal growth rates

– Stressful environments
– Short seasons
– Hibernation
– Some marine mammals

Lower growth rates

– Less seasonal environments
– Stable food supply

Delayed Fertilization

Females mate and store sperm in uterus, vespertiliontid bats do this. Adaptation to long dormant periods

Delayed Implantation

Ovulation, fertilization, and early cleavage
stages occur normally
• Development arrested at blastocyst stage

Some metatherians, carnivora, chiroptera,
pilosa, and artiodactyla

metatherian vs eutherian

Metatheria are marsupials, and Eutheria are placental mammals; the main difference is their reproductive strategies and the type of placenta they use

Delayed Development

Ovulation, fertilization, implantation occur
normally
• Embryonic development delayed after
implantation

Occurs in some bats

Life History Patterns

Altricial young

Precocial young

Altricial young

Helpless at birth
– Nearly naked
– Eyes and ears closed
– Unable to locomote or thermoregulate

Precocial young

Furred young
– Eyes and ears functional
– Capable of locomotion and thermoregulation

Unusual Life Patterns

• Elephant shrews
– Long gestation period
– Highly precocial young

Unusual Patterns pt. 2

Pilosa
– Low metabolic rates
– Myrmecophagous feeding habits, or
– Folivorous feeding habits

Choloepus hoffmanni—two-toed sloth