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Marine Vertebrates: Lecture 7
January 30, 2008
Class Mammalia
I.
Marine Mammal: Defined
II.
Evolutionary relationships and key mammalian features
III. Groups
A.
Order Carnivora
1.
Family Ursidae: Polar bears; the least adapted for a truly marine existence
2.
Family Mustelidae (badgers, otters, weasels, minks, ferrets): Sea otters
B.
Order Carnivora, Suborder Pinnipedia (sometimes considered its own order)
1.
Phocidae (true or “earless” seals)
2.
Otariidae (eared seals)
3.
Odobenidae (walruses)
C.
Order Sirenia: Dugongs (1 species) and manatees (3 species)
D.
Order Cetacea
1.
Suborder Odontoceti
2.
Suborder Mysticeti
IV. Adaptations for a marine existence
A.
Osmotic balance
1.
Acquiring water
a.
From Diet
b.
Drink
c.
Metabolically-produced water from the breakdown of food
2.
Water loss
3.
Excretion of water and ions
a.
Kidneys are key

What is their solute-concentrating ability?
B.
Thermoregulation
1.
Heat retention: Fur vs. blubber
a.
For its thickness and weight, dry fur is a much more efficient insulator than
blubber
b.
Marine mammal fur is different than that of most terrestrial mammals [Fig. 2-2]

How so?

How effective in keeping out water

Which marine mammals primarily use dry fur to stay warm when
submerged and how is this possible?

What about polar bears?

Why do otters have such high metabolic rates despite their fur?

In most marine mammals, this is still not sufficient to keep dry,
2.
Regulation of heat via blood flow changes
a.
Locations of key capillary beds
b.
How they work in heating and cooling
c.
Countercurrent exchange
3.
Large size
a.
Surface to volume low…
b.
Importance of buoyancy for attaining large size
Page 1 of 2
Marine Mammal Diversity (first of 2 lectures)
V. Focus: Carnivora (non-pinnipeds)
A.
Family Ursidae: Polar bears (Ursus maritimus)
1.
Differences from non-marine bears/adaptations to aquatic life
a.
Same genus as brown and black bears (Ursus)
b.
Streamlining
c.
Adaptations for swimming
d.
Thermoregulation
2.
Habitat/feeding ecology
a.
Circumpolar distribution
b.
Considered seal specialists, but…
c.
Male vs. female foraging
d.
Hunting ringed seals

Use their sense of smell
3.
Life-history (briefly)
a.
Young born in December/January while mother is still fasting.
b.
Break out of dens around March/April.
c.
Cubs with mother for 2.5 years, so that she can only give birth every 3 years.
4.
Conservation status: threatened (IUCN)
a.
Major threats?
B.
Family Mustelidae: sea otters
1.
Overview and adaptations to a marine existence
2.
Habitat/feeding ecology
a.
Live in kelp forests
b.
Feed on a wide variety of benthic invertebrates

May play important role in maintenance of kelp beds
c.
Tool users
d.
Kelp itself provides some protection from predation.
3.
Historical vs. current distribution
4.
Conservation status and threats
Page 2 of 2