The Weddell Seal

The Weddell Seal
and its amazing adaptations to a
very extreme environment
Photo by Steven Profaizer
Antarctica is a place of extremes
It is the…..
and Coldest
continent on Earth!
Animals in Antarctica have unique and
special adaptations for survival
Rebecca Shoop
Robyn Waserman
Steve Rupp
3 Types of Adaptations
Anatomical Adaptations (will be purple)
- have
to do with structure
Physiological Adaptations (green)
- have to do with function
Behavioral Adaptations (red)
- have to do with action or activity
A little about the Weddell Seal
• The most southerly dwelling mammal on
• Live on fast ice, floating ice that is attached to
land. Enter the water through cracks in the ice
• Spend most of the year in the water, coming
out in the summer (Nov-Jan) for pupping,
breeding and molting (and soaking up sun!)
• Can dive for over an hour, and up to 600
meters deep!
Weddell Seals (Leptonychotes weddellii)
Daniel Costa
Jennifer Burns
Michelle Shero
This map shows
the general
range of the
Weddell Seal,
and the seasonal
ice cover around
Image credit: Jennifer Burns
Now for the
Remember the colors!: Anatomical
How do Weddell seals stay warm
in such a cold environment?
•Blubber vs. Fur
•Basking in the sun
•Very rich milk
•Unique Nose structure
Obesity problem? Or perfect adaptation?
Blubber is warmer than fur!
How much
blubber are we
30-40% of body weight is blubber. That
means, up to 240 kg, or 528 lbs in the largest
seals, is pure blubber! Over 2 inches thick!
Image credit: Michelle Shero, 'Weddell Seal Body Composition'.
But what is the fur for?
Weddell seals, unlike fur
seals and sea lions, do not
have a thick layer of fur.
Blubber is warmer! Fur is
more for protection than
Pups, however, are born
with a soft, downy fur coat,
which keeps them warm
while they build up blubber
from Mama’s milk!
Remember this picture from the first slide?
A seal pup showing off his fuzzy fur coat.
Weddell seal milk – pure fat!
Weddell seal milk is 60% fat!
Human milk is 4%fat.
Grams of Fat Consumed
per Day
% Fat Content
Weddell seal babies consume 5400
grams of fat per day. That’s 48,600
Breastfed human babies consume 40
grams of fat per day. That’s only 360
Weddell seals gain 150 pounds in the first few weeks of life!
A very special nose!
Nasal turbinates are thin bones that divide the nasal passage. They are lined with
nasal epithelia which is loaded with capillaries. Their functions are to
•Warm and moisten incoming air
•Prevent heat and moisture loss in outgoing air
in a process called counter-current heat exchange
Notice how
form and
function work
Grey seal nasal cavity. Photo credit: Jennifer Burns
Seal vs. human nasal turbinates. The seal turbinates are far more numerous and convoluted!
How do Weddell seals get around in the
dark of winter under the ice?
Huge eyes
Special teeth
Daniel Costa
It’s dark down here!
Photo by Steve Rupp
A Focus on Eyes
•Very large iris – the part of the eye that
gathers light. Notice there is no visible white
on the seal’s eye.
•Large number of rods, photoreceptors that
allow vision in poor light
mucus covers the
eye surface
Chris Burns
The tapetum lucidum is a reflective layer behind
the retina that reflects light back to the retina for
a second go around and more light absorption!
Eye shine in nocturnal
animals is caused by the
More Focus on Eyes – the lens
The cornea loses 87% of its refractive power in water! The light is then focused
behind the retina, resulting in hyperopia (far-sightedness).
Seals make up for this with a very round
lens, which bends the light more than
the flat lens that humans have. This
gives the seal good vision under water.
On land, they are myopic (near-sighted).
Wild Whiskers!
Also called vibrissae, whiskers
have two functions:
•To help find food
•To help navigate
Special features of whiskers:
•Each vibrissa can move independently
•They have many sensitive nerve fibers
to detect water movement from
passing prey
•Whiskers are shed periodically, and
new ones grow
Whiskers can be relaxed (on land) or stiff
and erect when they sense movement.
This video shows some very alert whiskers!
Can you think of another animal that has large whiskers? Is this animal nocturnal?
Chew on this – special teeth!
•Weddell seals can open their mouth
very wide.
•There are large canines, typical of
•The incisors jut forward for a
special purpose – to keep the
breathing hole open
Daniel Costa
Photos by Jennifer Burns
This video shows how the Weddell seal uses its teeth to keep the breathing hole open
Noisy seals!
•Weddell seals make some of the most bizarre and
interesting sounds of all marine mammals.
•Sounds are used for social interaction, territorial
displays, and aggression
•They have a very wide frequency range of sound
•Males are more vocal, to attract females and display
territory to other males
•Sounds are made both above and below the ice
Click on any of these buttons to
listen to some of their sounds
Just for fun, listen to these
mothers and pups
How do Weddell seals dive so deep and
for so long?
Remember, Weddell seals can dive for over
an hour, and go as deep as 600 meters!
Their dives can range 5km from their
breathing hole!
•Blood stores a lot of oxygen
•Muscle stores a lot of oxygen
•Collapsible lungs for diving deep
It’s a bloody seal!
They have a very
high hematocrit of
50-70% – that is
the % volume of
blood that is red
blood cells. This is
caused by very
large blood cells.
Weddell seals have a high volume of blood
– 20% of body volume!
Hemoglobin range
The Weddell seal’s blood is all about
holding the most oxygen possible!
Hemoglobin, g/dl
Plus, they have 30-50% more hemoglobin
than human blood. Hemoglobin is the
oxygen carrying protein in blood.
Human Weddell
Mighty muscle myoglobin
What is the difference between hemoglobin and myoglobin?
--They are both similar molecules that carry oxygen-Heme = blood, myo = muscle, globin – the name of the protein
portion of the molecules. Myoglobin is the oxygen carrying
protein in muscles.
Michelle Shero
From left to right: white fish, chicken breast, cow muscle, Weddell seal
muscle. The darker the muscle, the more oxygen it can carry, which means
it can sustain more activity for a longer period of time. Enough said!
Remember the adaptation color code: anatomical, physiological, behavioral
A flexible chest and collapsible lungs
The oxygen storing capacity of the blood
and muscles are important in supporting
the seal during deep dives, because…..
the chest cavity of Weddell seals collapses
when diving, and the air within them
compresses. No oxygen exchange happens
in the lungs during a dive!
The alveolar
sac and lobule
collapse when
the seal dives.
A seal’s lung. Image credit: Kooyman GL
(1973) Respiratory adaptations in marine
animals. American Zoologist 13: 457–468
A seal depends entirely on oxygen stored in the muscles and blood to
carry it through the dive!
More amazing oxygen info
Weddell seal
Notice the remarkable
numbers in the
Weddell seal!
Image credit: Kooyman GL (1989) Diverse Divers:
Physiology and Behaviour. Berlin: Springer.
Oxygen stores of dolphins, sea lions and fur seals, true seals, humans and
penguins. The numbers in parentheses are the percent of oxygen stored in
the lung, blood and muscle.
Before diving, the Weddell seal takes several huge breaths of air, to saturate
the blood and muscles with oxygen. Then they exhale all the air, so the
lungs can collapse more easily.
More interesting adaptations to the
extreme climate
•Bask in the sun in summer, saving energy
for pupping, breeding, and molting
•Pups grow fast, are weaned at 6-7 weeks
(when the fast ice breaks up), and are on
their own
•Adapted to a habitat – the fast ice - that
is hard for any predators to reach
•Delayed implantation of up to 90 days
after breeding. Fertilized eggs don’t start
developing until January
Terrie Williams
•Have strong nostril muscles that snap
shut when diving
•Fusiform (torpedo) shape makes
for very efficient swimming
Steve Rupp
The End!
Alex Eiliers
Thanks to:
Alex Eilers, PolarTREC teacher
Dr. Jennifer Burns, University of Alaska, Anchorage
Sarah Crowley and Janet Warburton, Arctic Research Consortium of the U.S.
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