Order Proboscidea: the Elephants

1
Order Proboscidea the Elephants

• One living Family, two living genera, 2 living
  species.
• For most of our species-existence, most people
  have lived with elephants. As we move through
  the 21st century, this co-existence is becoming
  increasingly difficult!

2
The plan for the day

• Ancestry and evolution
• Range and Status
• Anatomy
• Size
• Legs
• Trunk (including some weird speculation on
  evolutionary origins)
• Tusks skull
• Cheek teeth
• Basic ecology (eating even the worst plants)
• Metabolism (be big)
• Social organization (center on females)
• Specifics on Asian elephants (including
  conservation)
• Conservation of African elephants

3
Ancestry and Evolution

• Elephants should probably be considered part of
  the Afrotheria. Closest living relatives are
  seacows and hyraxes (see next slide).
• Earliest proboscideans were tapir-like.
• Evolutionary trends were deepening the teeth,
  shortening skull, lengthening trunk and legs.
• Elephas Mammuthus evolved in Africa they were
  most modern elephants, invading Eurasia, North
  America and finally South America.
• Loxodonta, more primitive, survived in Africa.

4
They may not look like elephants, but

• An ancient branch of the Afrotheria evolved to
  exploit low-quality vegetation.
• One twig of the branch became aquatic (seacows,
  upper left).
• Another twig invaded xeric habitats (hyraxes
  upper right once some types were much bigger).
• The third twig exploited intermediate habitats
  and became elephants.

5

• Note the complexity of the Proboscidean tree.
• Many taxonomists would show Mammuthus branching
  even later from Elephas.
• Note that Mammut, Mammuthus, and Stegodon
  survived until relatively recent times.

New dates 1 7.6MYBP 2 6.7MYBP
2
1
1
6
Range and status today

• Loxodonta Once pan-African, now intra-tropical.
• In plains and savannas, African elephants are now
  largely restricted to hunting preserves and
  national parks.
• In thick forest, status less well known (but may
  be common).
• Elephas Once widely distributed from India
  throughout continental S.E. Asia and into
  southern China. Now very rare.
• Working elephants in Myanmar tourist elephants
  elsewhere.
• Wild elephants in Indian national parks and a
  few are widely scattered in some other national
  parks.
• Almost everywhere they occur, elephants are often
  considered more valuable (or less trouble) dead
  than alive. Nowadays, people have the equipment
  to make em that way.

7
(No Transcript)
8
Dimensions of Elephants

• African elephant
• Shoulder height
• XX 2.4-3.4m
• XY 3.0-4.0m
• Mass
• XX 2400-3500kg
• XY 4000-6300kg
• Asian Elephant
• Shoulder ht 2.5-3.0m
• Mass 3500-5000kg

9
Elephant legs are graviportal.

• Bones are large and stacked.
• Elephant walks on 5 toes heel pad.
• Elephants move long distances for food, for
  water, for sex, maybe for fun.
• Elephants dont run
• Typical elephant walk is like brisk human walk.
• Fastest walk is like top human sprint.

10
Evolutionary elongation of the trunk

• Apparent paradox
• Short trunk is useless to tall grazer
• Evolving structure must be useful at all stages.
• Ancient elephants relatively short legs trunk
  that reached ground.
• Intermediate elephants longer legs, longer
  skull, longer jaws, longer trunk that reached
  ground.
• then trunk stays on the ground as skull and jaw
  shortened.
• But?

The conventional history of elephant evolution
Terrestrial ancestor of Afrotherian
megavertebrates gives rise to elephants, seacows,
and hyraxes. The trunk of elephant ancestor
lengthens in accompaniment with lengthening legs.
11
A Garrettian ( wild-ass, contrarian)
trunk-centered hypothesis on elephant evolution

• The structure of elephant lungs and thoracic
  cavity suggests adaptation for snorkeling.
• Anatomical adaptations are numerous and profound.
• These adaptations cannot easily be accounted for
  by use of the trunk for terrestrial drinking.
• Did snorkeling adaptations occur early?
• Identical structures exist in Asian and African
  elephants.
• Early snorkeling adaptations would suggest that
  elephants evolved from aquatic animals.
• The logical candidate would be some ancestor
  shared w/ seacows (conventional).
• The question is, was that ancestor aquatic?
• If so, the lengthening of the trunk might have
  preceded the lengthening of the legs, which would
  have occurred after an invasion of the land,
  contrary to the conventional wisdom.

12
The snorkeling-elephant conundrum
(Note Were talking about systemic circulation
to parietal pleura pulmonary circulation is
protected by Zone 2 Phenomenon.)
13
Anatomy suggests that snorkeling adaptations may
have been fundamental.

• The vulnerable pleural membranes are replaced by
  thick plates of dense connective tissue.
• The pleural cavity itself is filled with loose
  connective tissue.
• The diaphragm is much thicker than would be
  expected for an animal of elephant size.
• All these adaptations (and others) are observable
  early in embryonic development.
• But weve digressed long enough back to the
  trunk?

Remember The origin of these adaptations must be
more than 7.6MYBP.
14
Uses of the trunk

• As a tool
• Grazing browsing
• Manipulating objects
• Moving water
• As a sense organ
• Touch
• Smell
• As a social-signaling organ
• A trumpet that amplifies vocalizations
• A bearer of visual signals
• A touch-communicator

Tusks are next ?
15
Evolution of tusks skull
Remember The trunk helps maintain contact with
the ground as the legs lengthen.

• Tusks are second upper incisors. Tusks typically
  emerge in XY XX African but only in XY Asian
  adults.
• Tusks utility and social importance are
  enormous.
• Evolutionary tendency for skull to shorten
  tusks to lengthen.
• The conservation significance of tusks ivory.
• Now Other teeth?

16
Cheek teeth

• Shredding in living sps mammoths
  crush-grinding in mastodons.
• 6 molarform teeth per jaw-quadrant
• 1 functioning tooth per quadrant loss in front
  magazine replacement from rear (see next 2
  slides).

Elephant or mammoth
Mastodon
Not a member of the Elephantidae.
17
Elephant teeth their replacement
To know about elephant teeth is to know about
elephant demography.
18
Schedule of Tooth Replacement
Tooth M1 M2 M3 M4 M5 M6
Ages of use, African 0-1 years 1-2 years 2-6 years 6-15 years 15-28 years 28-47 years
Ages of use, Asian 0-1 years 1-6 years 6-8.5 years 8.5-22.5 years 22.5-40 years 40-70 years
Note African-elephant data are from wild
animals Asian-elephant data are from captive,
working animals.
Next, ecology?
19
Basic ecological strategy

• Elephants grow very large, thereby decreasing
  surface-to-volume ratio.
• This reduces per-kg thermoregulatory expenses and
  therefore the amount of calories needed per kg
  body mass. (See next slide for Kleiber Curve?)
• Vast variety of plants eaten (Kibale, Uganda 227
  of 255 known species) but most food is usually
  from few species.
• Absorptive efficiency is low, and elephants meet
  minimal nutritional needs by eating large
  quantities of OK food or vast quantities of
  wretched food.
• Elephants have the capacity to alter an
  environment and the mobility to move into a new
  area.

20
Elephant Metabolism(C is caloric expenses M
is Mass a M are fitted constants)

• Some general principles (Kleiber Curve)
• C aMß
• ß is always lt 1 (0.75/-)
• Now figure expense/size
• C/M (aM0.75)/M
• C/M a/M0.25
• That is, expenses per kg decline with increases
  in body size.
• That is, elephants main metabolic specialization
  is to be BIG.

• Some elephant specifics
• Small stomach, large caecum.
• Feeding per day
• 10-18 hours
• 150-250kg (c. 5 mass)
• Throughput time c. 11-26 hours.
• Defecation per day 150-250kg
• Assimilation efficiency
• Elephant 44
• Cow 66

21
Social organization(Most data are from African
elephants.)

• A baby elephant is born into a matriarchy after
  21-22mo. gestation. It receives much education,
  and interbirth interval is typically 4-6 years.
• For 1st 6months, baby is watched all the time.
• Baby is weaned at 6-18 months (occasionally
  later).
• Until its almost 10 years old, juvenile spends
  c. 50 of its time within 5m of its mother
  (closer in moments of danger).
• XXs stay in natal group, cementing relationships
  w/mothers, grandmas, sisters, aunts, XX cousins.
• Between ages 8-20yrs, XYs think increasingly of
  sex become such pests that XXs run them out of
  herd. Thereafter they join bachelor society
  (next slide).

22
The machismo of bachelor society

• Young males entering elephant bachelor society
  learn their places or else.
• Size is the major factor in establishing
  dominance.
• Mutsch temporarily over-rides other
  considerations.
• Temporal glands drain, penis drips, testosterone
  levels soar.
• Temper, temper.
• Skull structure cushions head-bashing (pneumatic
  skull).
• Use of tusks is dangerous.
• Biggest XY occasionally return to XX groups.
• Now, back to the more important considerations of
  XX groups!

23
Long-lasting female groups form the nucleus
around which all elephant society is organized!
24
Female groups elephant commo

• Oldest XX is matriarch
• She knows the area the elephants.
• She outlives repro years (only elephants and
  people) why?
• Interaction commo holds group together
• Lots of touching and signaling
• Trunk-in-mouth greeting ceremony
• Low-frequency sounds
• Play builds tightest bonds among young XX cousins
• Courtship can be dramatic
• XX receptive for only a day or two (but she
  courts longer)
• Many XYs may follow a receptive XX, but in a
  typical elephant population, only a few become
  fathers.

25
The sociology and physiology of (African)
elephant ears looking big and cooling off!

• Elephant social processes are mediated by size.
  Threat or dominance position has ears extended.
• Ears also serve as radiators.
• Each is right triangle, 1.5mX2m total surface is
  6m2, or about 20 of total.
• Mass of each ear is about 20kg, or lt 1 of total.
• Blood-flow through ears can be gt 1000 liters/hr.

Next A little on the sociality of Asian
elephants?
26
A few social specifics on Asian elephants

• Lots like Loxodonta, but havent shared common
  ancestor for about 7.6MY (people-chimps
  separation is about 5MY.).
• Are Asian XYs more connected w/XX groups?
• Its reported that Asian XXs may form communal
  nursery groups. (Is this true? If so, does this
  occur in African elephants too?).

27
Uh, how do you tell an Asian elephant from an
African elephant?

• Well, if youre in Africa.
• Otherwise,
• African has larger ears.
• Asian has convex spinal line African has concave
  spinal line.
• Two-lip trunk in African elephant Asian elephant
  has single trunk-lip.
• Asian elephant usually smaller.
• African XX usually have emergent tusks.

Even with these babies, cant you tell which is
which?
28
A general note on S.E. Asian conservation

• Although not particularly urban, S.E. Asia is the
  most crowded area in the world.
• Intensive agriculture covers almost every
  available hectare of reasonably flat land.
• Most vertebrate wildlife survives only in
  national parks, many of which are also under
  threat.
• In 1975, Vietnam was thought to have many
  hundreds, perhaps thousands, of elephants.
• Today population is probably lt 100, in widely
  separated small groups.
• Elephants interfere with local people.

29
Conservation of African elephants

• The subject is much more complex than most
  experts would like to admit!
• Elephant demography makes harvest potentially
  damaging to elephant populations.
• Prior to international ivory ban (enforced by
  1989), different countries had experienced
  different results with their management plans.
• Conservation decisions, which should have been
  made on a biological basis, were driven by
  largely political concerns.
• The arrogance of the developed world was
  demonstrated yet again.

30
Elephant conservation How does one act
responsibly in a world of limited resources,
inequitably distributed?
Conservation? In January 2008 the Philadelphia
Zoo announced that it would breed its African
elephants to help with species-conservation. The
zoo also announced the construction of a 27
million elephant exhibit. One baby might be
produced by 2010. Meanwhile, RSA will start
killing thousands of elephants in May 2008, and
the per-capita income in Zimbabwe is lt 1/day.
For 2010, cut by 50
31
The future of elephants

• Elephants are not an evolutionary dead-end, not a
  taxon that has outlived its ecological capacity.
• Elephants are smart, adaptable, modern and can
  live almost anywhere on almost any plant food.
• BUT more than any other large mammal, elephants
  are efficient competitors with people!