Marine Vertebrates: Lecture 9
February 11, 2008
Marine Mammal Diversity (continued)
I.
Overview: Order Cetacea
A.
Origins (briefly)
1.
Appear most related to the Mesonychidae, a extinct group of hoofed mammals
2.
Archaeocetes (~50 mya)
a.
Pakicetus

Long, slender jaws with simple teeth, dorsal blowhole

Some with robust pelvis and hindlimbs, yet whale-like head structure
b.
Basilosaurus (34-40 mya)

Still with small hindlimbs
B.
Split into two Suborders began ~34 mya
1.
Embryos of the Mysticeti have tiny, vestigial teeth, evidence of toothed origin
II. Focus: Suborder Mysteceti, the baleen whales
A.
Overview
1.
Baleen
a.
Upper jaw only
b.
Baleen is composed of keratin
c.
Distinct baleen plates are stacked together

Portion facing inside of mouth is frayed to form fine bristles

Bristles are coarse or silky depending upon prey
2.
Head: Roughly symetrical, with a double blowhole (not so in Odontoceti)
3.
Eleven recognized species
4.
Found in more shallow water
B.
Family Balaenidae: bowhead and right whales (3 species total)
1.
Overview:
a.
Large heads
b.
Bowed (highly curved) mouth to accommodate very long baleen plates

Balaenidae have the longest and finest (silkiest) baleen of all the Mysticeti
c.
No dorsal fin
d.
Relatively small pectoral fins
e.
Primarily known to feed on copepods

Feed by skimming—plough through water with mouth open
2.
Bowhead whales
a.
Arctic (4 populations, circumpolar)

Follows advance and retreat of pack ice

Most northerly of any baleen whale
b.
Hunting began ~1600, near extinction by 1900

Appear to be making a slow recovery

Special exemptions to the IWC moratorium allow the Inuits to take 60-70
bowheads/year
c.
Head may be up to 40% of body length
d.
Baleen is the most valuable due to its size and silkiness
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3.
C.
D.
E.
Right whales
a.
Recognized by their distinct callosities

What are collosities? Which organisms are associated with
callosities? Are these organisms parasitic or commensal?
b.
Called right whales because???
c.
Two species

Northern right whales: Northern hemisphere, higher latitudes ( not polar)

First whale to be commercially hunted beginning in the 12th century

Driven to near extinction in the North Atlantic

~300 left, mostly in Western N. Atlantic
▪
This population breeds off the coasts of Georgia & FL

Southern right whales: Southern hemisphere, primarily South Africa,
Australia, New Zealand for breeding,

Feed near Antarctica (but north of the Antarctic convergence)

Also hunted to near-extinction, recovering at key breeding grounds
Family Neobalaenidae: pygmy right whales (briefly, no photo
1.
Southern hemisphere
2.
Somewhat similar features as right whales, but do have a small dorsal fin...
Family Eschrictiidae: grey whale (one species)
1.
From Baja, California (breeding) to Alaska (feeding)
a.
Also a very small Asian population (subspecies?)
2.
Features
a.
Long, slender head and relatively slender body compared to other whales
b.
Notable patches of whale lice and barnacles (highest infestation of any whale.)
c.
Two-seven throat grooves (the Balaenidae have no throat grooves)
3.
Feeding
a.
Mud bottom; Amphipods (and mysids); suction; roll on one side to feed

Only whale known to feed in this way.
4.
Life-history/migration pattern (briefly)
5.
Whaled to near-extinction, but have made a remarkable recovery
a.
Removed from U.S. endangered species list in 1994.
Family Balaenopteridae: rorquals = minke, humpback, blue, fin, Sei and Bryde’s
1.
Features
a.
Distinctive throat grooves allowing for enormous throat expansion during feeding
b.
Distinctively depressed frontal bone above eyes
c.
Small, posteriorly-positioned dorsal fin
d.
Flipper sizes vary…
e.
Relatively fast swimmers: gotta be fast to catch those krill and schooling fish!
2.
Minke whales
a.
Worldwide distribution, especially abundant in temperate and polar regions
b.
Whaling is controversial
c.
Antarctic populations feed on…krill!
d.
Northern populations feed on krill, but also on schooling fish.
3.
Humpback whales
a.
Found in all oceans; migrate between breeding (tropical) and feeding grounds
(temperate to polar)

Heavily exploited, but have made some great progress

Considered “vulnerable” by IUCN.
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4.

~20,000 worldwide (probably 10x that at one time…)

Natives of Bequia in Caribbean take 1-2/year
b.
Largest pectoral fins of any whale, ~ 1/3 of body length, serrated on leading edge.
c.
Distinctive white patches on neck, throat, flukes and pectoral fins
d.
Scars, barnacles and cookie-cutter shark bites are common.
e.
Migration: cold waters to tropics

Apparently feed only in cool/cold waters (KRILL and fish)
f.
Distinctive behaviors

Bubble-netting: up to 20 animals

Breaching

Flipper-slapping (can they really stun krill?)

Lob-tailing
g.
Whale songs

Song probably produced in the larynx, but not known for sure.

Which gender sings?

Always the same song?

A single song lasts from minutes to near an hour.
Blue whale
a.
Distribution: Once worldwide; largest populations now found where?

Migrate to tropical waters for calving

In some areas of the tropics, blue whales are seen year round

Why might this be?

Appear to avoid coastlines, so they are difficult to track
b.
Largest animal ever

Can be up to 24.5 meters (female)

Mouth alone of 6 meters

Max weight: 190 tons

Heart the size of a VW bug

Spray from blow is about 6 meters high.

Larger prior to mechanized whaling

Only hunted after the development of the grenade harpoon in the 19th
century.

In one year, 30,000 were killed (not sure which year)
c.
Loudest and deepest voice of any animal (180 dB, 10 Hz)
d.
Diet is almost exclusively…???? (What else could it be?)
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