Orders Not Yet Discussed
Cetaceans. These aquatic mammals—whales, dolphins,
porpoises, etc.– include the largest animals ever known.
Rabbits. These small herbivores are built to move fast, and they
exploit cellulose by a double-cycling, hindgut-fermentation
strategy.
Hyraxes. These small African herbivores are distantly related to
elephants and to sea cows.
Sea cows. Manatees and dugongs are large, entirely aquatic
herbivores.
Elephant shrews. These are small African insect-eaters, typically
with monogamous mating systems.
Tree shrews. Once thought closely related to primates, these
Southeast Asian mammals are mostly insect-eaters.
Colugos, flying lemurs, or dermopterans. These arboreal
animals of the Southeast Asian rainforests are the best
gliders in the Class Mammalia.
Aardvark. This African mammal exploits colonial insects and is a
world-class digger.
Today we have a grab-bag of leftovers…
Whales
•
•
•
•
•
Large to very large, entirely aquatic mammals.
Two living Suborders (baleen & toothed); 1 extinct Suborder.
About 10 Families.
About 78 species.
Often inhabit higher latitudes (in summer), where long daylight
& concentrations of dissolved O2 produce abundant life.
Phylogenetic relationships of Whales
• Archaeocetes
are extinct.
• Baleen whales
are large & form
a coherent
group defined by
foraging
technique.
• Modern “toothed
whales” are a
diverse group,
ranging from
smallish to very
large.
Whales, etc.
Suborder
Family
Common
name
Mysticeta
Balaenidae
Right
whales
2
3
All oceans except
tropical & Antarctic
Gray
whales
1
1
N. Pacific, coastal
Rorquals
2
6
All oceans
Platanistidae
River
dolphins
4
5
Oriental & Neotropical
rivers
Delphinidae
Dolphins
16
31
Porpoises
3
6
All oceans except
Arctic & Antarctic
Monodontidae
Narwhal &
beluga
2
3
Arctic Ocean &
adjacent big water
Physeteridae
Sperm
whales
2
3
All oceans
Ziphiidae
Beaked
whales
6
18
All oceans
Eschrichtiidae
Balaenopteridae
Odontoceta
Phocoenidae
# of
genera
# of
distribution
species
All oceans & major seas
Thoughts on whale evolution
• The earliest whale fossils are from the Eocene,
perhaps about 50MYBP.
• Some primitive whales had external rear legs (no
modern whales do), and all early varieties had teeth.
• The relationship between whales and other mammals
is now well established:
– A few authorities once classified whales in a loose group
with elephants-hyraxes-sirenians, or even w/ perissodactyls.
– At one time some biologists thought that toothed whales had
their own separate ancestry, from carnivores.
– Now most mammalogists with any sense believe that all
cetaceans are distantly related to hippopotamid artiodactyls
(next slide).
Whale ancestry
• Of course whales are highly
derived, so affiliations are not
obvious from fossils.
• However, by 1880’s clever
mammalogists noticed foot
similarities between
atriodactyls and animals like
Ambulocetus.
• In 1950, Boyden & Gemeroy
compared serum proteins of
cetaceans against all other
mammal orders (except
rabbits). Artiodactyls were
closest.
Some anatomical properties of living whales
• Whales have streamlined bodies w/ tails flattened into
horizontal flukes.
• Limbs:
– Traces of femurs and pelvic girdles are present in some species.
– Arm bones (humerus, radius, & ulna) shortened; however, fingers 2 & 3
(& occasionally others) lengthened to support paddle-like swim-fins.
• Nostrils exit through “blowholes” on the top of the head.
– In almost all species these are displaced high & far back; resulting
alterations in the structure of the mammalian skull are impressive.
– Two blowsholes in baleen whales, one in toothed whales
• The skin of adults is hairless, but a thick layer of blubber
(subcutaneous fat) provides insulation.
• All whales exhibit an extensive suite of anatomical,
physiological, and behavioral specializations connected with
aquatic existence and deep diving.
• More whale anatomy:
– Rear legs are absent.
– Front legs are modified
as “flippers.”
– Cervical vertebrae are
fused.
– Backbone is modified
for vertical flexing.
Size & the physics of swimming
• Most cetaceans cruise at approximately “brisk
bicycle” speeds; orcas have been clocked at
55kph.
• Speeds are a function of power-input/drag ratio.
– Reducing drag (=minimize turbulence/laminar flow):
• Protrusions eliminated; shape sculpted…
• Skin evolved to minimize local pressure fluctuations…
– Increasing ratio:
• Drag is a function of X-sectional area (a “squared”
quantity).
• Power is a function of muscle-mass, which is a function of
body-volume (a “cubed” function).
• Therefore, get big (and get long)!
Baleen (“whale-bone”) whales
• The toothless whales take their name from the baleen with
which they strain out their food from the H2O. Basic feeding
strategy is to eat fairly low on the food chain!
• Structure of baleen:
– Formed in triangular, flat plates, which are composed from strands of
horny epithelium embedded in a less durable material.
– At the edges of a baleen plate, the less durable material erodes away
and leaves a comb-fringe of the epithelial material.
• Mouths of baleen whales:
– 130-400 baleen plates hang from each side of the whale’s upper jaw.
– The plates are arranged so that their fringes form a continuous strainer.
• Baleen whale feeding:
– Whale takes in a huge gulp of H2O.
– Then the animal closes its mouth (not tightly).
– As the whale then raises its huge tongue, H2O is forced out through the
baleen strainer—thereby retaining small food-organisms (see next slide).
– Some baleen whales skim the surface (slide after next).
– Gray whale scrapes the bottom & strains the muck (not illustrated).
• A: Open mouth of baleen whale, showing hanging sheets of baleen and
large tongue.
• B: A triangular sheet of baleen, frayed toward the bottom to form a strainer.
• C: Cross-section of baleen whale’s head. 2 sets of baleen sheets show as
dark triangles hanging from upper jaws. Tongue is drawn almost entirely
raised—& would be forcing water out of mouth, through the baleen “strainer.”
• D: Reduced skeleton of a whale within the outline of the animal’s body.
Tongue
Two (of 3) baleen-whale feeding methods:
straining (left) and skimming (right):
Biggest baleen whale
• Size: ave 27m; 150,000kg (XX somewhat larger than XY).
• The blue whale’s year:
– Spend 3-4 months/yr in higher latitudes.
– As weather cools, blues move equatorially, pregnant XX’s first.
– Young born near equator; nursed until they have enough blubber to
withstand polar summer.
– New mothers & young return ASAP to feeding waters (offspring must
grow, & XX’s must recover energetic expenses of repro).
– XX w/o calves mate in tropics; on return to feeding grounds they eat like
crazy to carry them through 11-mo gestation & subsequent lactation.
– XY’s—esp. adolescents—leave feeding grounds later than XX’s.
Toothed whales (Odontoceti)
• This Suborder includes 6 Families with about
35 genera and 67 Recent species. In contrast
to baleens, odontocetes eat high on food chain.
• Odontocetes occur in a bewildering array of
forms–medium, large, and very large.
• Some species are particularly adapted for fresh
water (in South America and Asia).
• The Suborder’s most interesting adaptations
include sounds:
– Narrow-band continuous tones (whistles & squeaks
used for intraspecific commo).
– Broad-band clicks used for echolocation.
Odontocete mysteries:
• Echolocation: How does it work? (Next slide.)
• “Death Rays”: Evidence from sperm whales
suggests that some odontocetes can focus
sounds very precisely, emitting waves of high
frequency and extraordinary intensity….
• Geomagnetic navigation. It appears that some
(many?) odontocetes (and some baleen
whales?) can orient with respect to the earth’s
geomagnetic field….
• Neither of these latter 2 suppositions has been
definitively demonstrated.
Echolocation
Ganges river
dolphin
• Sound is generated by
movement of air through
amplifying nostrils.
• Sound bounces off
dorsal surface of
cranium and is
“focused” by melon
(complex lipids, “slow”
center & “fast” shell).
• Reception is through
thin mandible and
associated fat running
from snout to ear.
• Some species can
pretty much substitute
echolocation for sight.
Sperm Whale (Physeter
macrocephalus)
• XY maybe to 30m, mass 45,000-70,000kg.
• XX much smaller (c. 10m & 17,000kg).
• Social organization:
– XX near-tropical, in groups of 10-40 (+ dependent young).
– XY worldwide, w/competition for harems.
• Preferred food probably giant squid; also eat fish, octopus,
crustaceans. Consume 3-4% body mass daily.
• Dolphins (Dephinidae, worldwide) are the most familiar & abundant
cetaceans. (B.N.D.’s are called “porpoises” in South Carolina!)
• Range in size from person-sized miniatures to killer whales (7m & 4,500kg).
• Evolved in late Miocene, c. 10MYBP).
• Food:
– Species w/long beaks & many cone-like teeth: fish-eaters.
– Species w/shorter beaks & larger teeth: squid-eaters (but orcas…).
• Bottlenose dolphins have huge brains.
– Evidence suggests this is associated w/ hearing & processing of echolocative
sounds.
– Individual animals have unique whistles.
• Bottlenoses associate in large groups that fracture into smaller groups of
definite composition.
Narwhale (above) 4.25m; 1250kg (XY
slightly larger than XX)
Some other
toothed
whales
Dall’s porpoise (below): 1.82.1m; 135-220kg
Beluga (above): XY 5m,
1600kg; XY: 3.75m, 350kg
B.N.D.
(right)
4m
635kg
Next Order: Lagomorpha
• Includes two living Families:
– Ochotonidae (pikas): 1 genus, c. 14 species.
– Leporidae (rabbits): 8 genera, > 50 species.
• Evolutionary history:
– Ancient group, probably Cretaceous in origin.
– Earliest fossils are Paleocene of Mongolia.
– By Eocene both Families in Eurasia & N. America.
• Basically, lagomorphs are small herbivores able
to exploit relatively wretched vegetation
because of unusual fermentation strategies.
Lagomorpha
“Lattice-work” rostrum and somewhat
mobile, almost “hinged” cranium
Incisors 2/1
Rodent-like diastoma
• 2 Families, c. 80
species.
• Most major
landmasses (not
Australia, southern
South America,
Madagascar, or
Antarctica).
• Known from
Paleocene.
• Possibly related to
rodents.
• Small herbivores.
Ochotonidae (pikas) 2 genera, 26 sps.
• Pikas are round animals,
c. 150-200g, resembling
fat squirrels w/o tails (or
resembling big-eared
voles).
• Mountains of western
North America, + steppes
& mountains of Asia.
• Live colonially in rock
jumbles.
• Dry vegetation for “silage”
& base territory around
defense of these hay
piles.
Rabbits
• Informally split into two subfamilies:
– Rabbits: altricial young (e.g., cottontails)
– Hares: precocial young (e.g., jack “rabbits”)
• Nutritional strategy:
– Eat coarse vegetation high in cellulose.
– Hindgut fermenters w/ high surface/volume ratios.
– Re-ingestion of caecotrophic feces (next slide).
• Reproductively an extreme r-species (next + 1)
• Social systems (2 basic types):
– Dispersed, somewhat like forest artiodactyls.
– Warrens w/ dominance hierarchies (especially
important among XX’s).
Rabbit digestion
• Rabbits eat a lot!
– Mass: 6%-8% body mass
– Calories: 54kcal/kg-day
• Cellulose:
1. Food input
2. Stomach; regular emulsification, etc.
3. Small intestine; absorption of proteins,
starches, sugars….
4. Large intestine; recovery of water, etc.
5. Caecum; Amino acids (?), water-soluble
vitamins, fatty acids, etc.
6. Hard feces (“rabbit pellets”).
7. Caecotrophic pellets; re-ingested.
– Mostly separated out.
– Even if fermented in
caecum, cellulose is
poorly digested (c. 14%).
– Very rapid throughput!
• Importance of caecum is
poorly understood….
• Problems w/calcium
metabolism….
Rabbit reproduction
• Gametogenesis:
– Winter quiescence; reactivation by photoperiod.
– Males more easily activated.
– Ova mature in response to FSH (if sufficient food); their
development is arrested in sub-mature stage.
• Courtship and copulation:
– Faint heart never won fair rabbit!
– Feedback through pituitary: LH surge in < 1hour; ovulation
within 10 hours.
• Pregnancy (28-day gestation):
– Corpora lutea are initial progesterone-secreting structures.
– Later, placenta; CL regress; FSH, ova to sub-mature stage
• Recycling:
– Post-partum copulation
– If insufficient milk, total resorption in days 8-15.
South Carolina rabbits
• The most common statewide is cottontail, left.
– Exploits successional
habitats.
– Populations vary from year to
year.
• The marsh rabbit is a
coastal-plain species.
– Eats mostly semi-aquatic
vegetation.
• Swamp rabbit is restricted
to Pickens, Anderson, &
Oconee Counties.
– This is a big rabbit of river
bottoms and canebrakes.
Other rabbits
Idaho pygmy rabbit
S.E. Asian forest rabbit
Jackrabbit
Snowshoe hair
• I.P.R. is an endangered,
small cottontail.
• Tropical rabbits of
Southeast Asia are poorly
known.
• Jackrabbits (hares) of
the American west
compete with domestic
livestock.
• The snowshoe hare
(left) is a large, northern
animal varying seasonally
in color. It makes huge
caloric demands.
Hyracoidea 3 genera, 6 species
• This Order includes a single living Family, the
Procaviidae, which has 3 genera and 11-12
species.
• Formerly widespread, hyraxes are now
restricted to Africa and a tiny segment of the
Middle East.
• Extinct varieties included rat-sized and rhinosized animals; living members are rabbit-size.
• Hyraxes are thought to be related to elephants
and sea cows, part of an Afrotherian radiation
(next slide) into drier, herbivorous niches….
Hypothesized components of the
Afrotherian Radiation:
•
•
•
•
•
Aardvarks (later in this presentation)
Elephant shrews (later in this presentation)
Golden moles (treated as “insectivores”)
Tenrecs (treated as “insectivores”)
A proto-ungulate radiation:
– Hyraxes (the Order of present consideration)
– Sea cows (later in this presentation)
– Elephants (considered as a separate topic)
• Hyraxes were most successful; why have
they declined so much?
Hyraxes
• Rock hyraxes are highly
social animals living in
groups of 5-50.
• Food is vegetation, often
heavy in cellulose,
fermented in the hindgut.
• Perhaps to conserve
energy, hyraxes have
labile body
temperatures.
• “Group huddles” on cold
mornings help hyraxes
thermoregulate.
Hyrax digestive system
• Hyraxes might have
been the first efficient
mammalian fermenters.
• 2-compartment stomach,
small intestine, two
different caeca, and
joining large intestine all
have different digestive
rolls.
• Uh, but different roles
are not well understood
by me!
Hyrax technical characters
• Skull and teeth:
– Convergence w/rodents:
• Ever-growing upper incisors
• Dental diastoma
– Note deep lower jaw
• Feet (rear illustrated):
– 3 syndactylus toes w/nails
instead of claws
– Sole evolved for superior
traction
– Foot structure is associated
with the Order’s survival
and its limits!
Sea cows
• Part of Afrotherian radiation, these big, aquatic herbivores have
oar-like arms, vestigial hindlimbs, & paddle-shaped tails.
• The nostrils are high on the skull, behind the anterior margin of
the small eyes. The lips are large & flexible. The upper lip has
numerous vibrissae-like whiskers, but the sea cow body is
otherwise hairless.
• All living sirenians lack canine teeth.
• Dugongs: XY dugongs have 1 blade-like incisor in each upper
jaw. Molarform teeth are un-enameled. A dugong’s jaws can
appear to be covered with horny plates—something like those
seen in many turtles.
• Manatees: Adult manatees lack incisors as well as canines.
Their molarform teeth are adapted for grinding massive
quantities of aquatic vegetation. These teeth are lost from the
front and replaced in the rear, as with their distant relatives, the
elephants (but manatees have more teeth).
Recent Sea-Cow Species
• Manatees:
– Amazonian manatee. A fresh-water animal
feeding in floating meadows of aquatic vegetation.
– West Indian manatee. Mostly salt water entering
fresh water in N. Am. mostly for warmth. (Slide.)
– West African manatee. Late Pleistocene reimmigrant from New World. Fresh & salt water.
• Dugongs:
– Dugong. Indian Ocean & South Pacific. (Slide.)
– Steller’s Sea Cow. Bearing Sea. To 10,000kg
(largest non-whale). Discovered 1741; extinct
1768.
Manatees
• These are large (c. 400kg) New
World & West African animals.
– Insulation is not good, so despite
small S/V ratio, manatees are
restricted to warm H2O.
• Feeding, & Nutritional physiology:
–
–
–
–
–
Diet low in nutrition
Teeth (6-7/quad, horiz. replace.)
Huge digest.-tract (40m long)
Very slow throughput
Very high extractive efficiency
• Groups ephemeral; multiple XY’s
chase receptive XX’s.
• Manatees make many sounds that
carry great distances & convey
social information
• Interbirth interval is c. 3 years;
social maturity for XY is at 9-10
years; XX mature more rapidly.
Lifespan is long.
More on manatees
T. senegalensis?
•
•
•
•
•
Bones are very heavy (no marrow cavities in longbones or ribs).
Shape and position of lungs; breathing efficiency….
Bone-weight, CH4, diaphragm, and buoyancy….
Brain is relatively small and relatively simple.
Low metabolic rate, K-selection, general life strategy.
Dugong
• Appearance:
– Dugong: indented tail.
– (Manatee: paddle-like tail.)
• Range:
– East coast of Africa, south
coast of Asia; South Pacific
to Australia & Caroline
Islands.
• Size: 250cm; 300kg.
• Feeding:
– Strong lips for eating sea
grasses.
• Other:
– Large incisors apparently
used in XY-XY combat.
Macroscelidia (elephant shrews)
Giant Short-eared
Checkered
Goldenrumped
Elephant shrews
• Once classified w/
Insectivora; now called
members of Afrotheria.
• Fossils known only from
Africa (as early as
Eocene of Tunisia).
• 4 genera and 15 living
species.
• Size:
– Large mouse (50g) to
large rat (450g)
• Food is primarily insects
(termites & ants in one
studied species).
More on
elephant shrews
• Elephant shrews are
monogamous, with XX & XY
scent-marking territories &
defending against same-sex
conspecifics.
• Gestation is long; twins are
produced, XY does a little
child-care, but….
• Pairs maintain trail systems
(important), with XY doing
most trail maintenance.
Tree Shrews (Scandentia)
• The Order has one Family, about 5 genera and
perhaps 19 living species.
• Range includes much of South & Southeast Asia.
• Classification:
– Once placed w/primates because of skull features.
– Now considered sister Order to primates, bats, and
dermopterans (and rabbits?????????????).
• Social system:
– Long-term bonds between XY & multiple XX’s.
– Territories defended against same-sex conspecifics.
– Mothers deal with their babies about 1 time/2 days, feeding
w/ large quantities (to 20% body-mass) of high-quality milk
(10% protein, 26% fat).
Two Treeshrews ( Tupaia tana & Dengrogale
minuta)
• Three shrews were
formerly thought to be
largely insectivorous
(because of teeth).
• Now they are known to
consume much fruit.
• Rapid pass-through rate
(13-29 min!) is like fruiteating bats– and makes
tree shrews important
seed dispersers.
Dermopterans
Protected orbits Multi-cusped canines
•
•
•
•
1 genus, 2sp. of S.E. Asian arboreal leaf eaters.
1-1.75kg; h-b 34-42cm; tail 25cm; 70cm wing-span (note tail).
Hindgut fermenters, so low-energy creatures.
Crepuscular or nocturnal gliders in forests with broken
canopies.
• 1 altricial young clings to mother’s underside.
•1-1.75kg; h-b 3442cm; tail 25cm;
70cm wing-span (note
uropatagium).
•Hindgut fermenters,
so low-energy
creatures.
Colugo
Dermopteran
“Flying lemur”
Cynocephalus
variegatus
The Noble Aardvark
• H-b 100-160cm; mass
50-100kg!
• Ancestor of artiodactyls?
Member of Afrotheria?
• Have regular foraging
routes & exploit termites
(wet season) and ants
(dry season) in ways
reminiscent of giant
anteaters.
• Dig enormous burrows
shared by many
vertebrates.