Transcript Subphylum Vertebrata – Early Vertebrates and

Marine Mammals – Diversity
 General Characteristics of Mammals
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Nurse young with mammary glands
Insulation to maintain endothermy (hair, blubber)
All marine forms with internal development (via placenta)
All marine forms evolved from terrestrial ancestors
 Diversity of Marine Mammals
 Order Cetacea: whales, dolphins, and porpoises
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Suborder Odontoceti (toothed whales): echolocation and teeth
Suborder Mysticeti (baleen whales): strain food with baleen
 Order Pinnipedia: true seals, eared seals, and walrus
 Order Sirenia (sea cows): manatees and dugong
 Order Carnivora: sea otter (insulation with dense fur) and polar
bear
Marine Mammals – Cetaceans
 Baleen Whales (Mysticeti): baleen (whalebone) composed
of keratin, filters plankton and small fishes
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Rorquals: with pleated, expandable throats; include Blue, Finback,
Humpback, Sei, Bryde’s, and Minke Whales
 Blue Whale: largest animal, with low-frequency calls
 Humpback Whale: long, white pectoral flippers; males sing
 Minke Whale: currently hunted (ex., Japanese “scientific whaling”)
Right Whales: first to be hunted (slow, float when dead)
 Southern Right Whale: males with oversized testes (sperm
competition; females with multiple partners)
 Northern Right Whale: critically endangered (migratory routes in
shipping lanes)
 Bowhead: Arctic; over-hunting led to calls for protection in 1800s
Gray Whale: migration from Bering Sea (feeding) to Baja (mating
and calving in lagoons); western population extinct (?)
Figure 5-105
Marine Mammals – Cetaceans
 Toothed Whales (Odontoceti): lack baleen; teeth present
 Sperm Whales (incl. pygmy and dwarf sperm whales)
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Males with larger head, filled with spermaceti wax (clean burning and fine
lubricant); dives to 4000 meters (90 min) to hunt giant squid;
ambergris (digestive fluid)  perfumes; “Moby Dick” whale
Beaked Whales: oceanic, deep divers, uncommon to rare (several
species); males often with tusks (used aggressively)
Arctic Whales – Narwal: male with long single tusk, and Beluga: white
whale, found in large pods; sing
Dolphins - include killer whale (note resident orcas of Pacific Northwest), bottlenose (coastal), common (offshore), spinner and
spotted (tropical), pilot whales (mass strandings), and river
dolphins: boutu (Amazon), susu (India), beiji (China, likely
extinct due to habitat loss re. Three Gorges Dam)
Porpoises: spade-like teeth, lack snout; include harbor porpoise, Dall’s
porpoise, and vaquita (smallest cetacean; Gulf of California;
endangered)
Figure 5-108
Marine Mammals - Cetaceans
 Fully aquatic: horizontal tail fluke, blowhole, vestigial hind limbs
 Extensive fossil record with intermediate forms (re. loss of hind limbs and
evolution of blowhole)
 Large-scale migrations common between feeding and calving grounds
 Endothermic: blubber (thick layer of subcutaneous fat); counter-
current heat exchange and rete mirabile (“beautiful net”)
 Diving: lungs collapse before dive (reduces nitrogen/bends); dive
reflex (blood shunted to core) and bradycardia (heart rate
slows); blowhole under voluntary control; efficient gas
exchange (muscles with myoglobin)
 Intelligence and Communication: easily trained (entertainment and
research); cooperative hunting and birthing documented in the
wild; social groups with shifting relationships; communication
via signature whistles (dolphins), songs of humpbacks and lowfrequency moans of other baleen whales; echolocation for
detection and tracking of prey, sensing surroundings
Figures 7-30 and 7-31
Marine Mammals - Pinnipeds
 Most with polygynous mating systems (harems with rookeries)
 True Seals (Family Phocidae): no external ears, swim with rear
flippers, crawl on bellies
 Northern Elephant Seal: dives to 1250 m; males with proboscis and
large canine teeth; population bottleneck in recent past
 Hawaiian Monk Seal: critically endangered; preyed on by sharks
 Others: harbor seals; ringed and harp seals (Arctic); Weddell, crabeater, leopard seals (Antarctic)
 Eared Seals (Family Otaridae): external ears, swim with front
flippers, walk with hind flippers
 California Sea Lion: protected by Marine Mammal Act; overpopulated?
 Stellar Sea Lion: North Pacific; population declines due to fish loss
 Fur Seals: Northern, Galapagos fur seals
 Walrus: lack external ears, but walk on hind flippers; males with
twin tusks; Arctic habitat
Figures 5-104b and 15-18
Marine Mammals - Others
 Order Sirenia (sea cows): large, flat tails; eat surfgrasses; all
endangered due to over-hunting; mermaid legends
 Manatee: Florida and Caribbean; swim up rivers; often hit by boats
 Dugongs: Indo-Pacific; marine (coastal wetlands and mangroves)
 Stellar Sea Cow: extinct by 1768; fed on kelps; over-hunted by whalers
 Order Carnivora: defined by carnassial tooth (shears flesh)
 Sea Otter: Alaska south to Central California; use rock tools to open
shellfish; insulated by coat of fine hairs (lack blubber); must eat 25%
of body weight per day; very social
 Polar Bear: truly marine due to adaptations (webbed feet, transparent
eyelids); Arctic habitat; declared threatened (re. declining time
periods between seal pup births and ice breakup)
 The Aquatic Ape Theory (Hardy, 1960): humans adapted for aquatic
life and possessed an aquatic ancestor; supported by anecdotal
evidence (hairlessness, breath control, oil glands)
Figure 5-109
Marine Mammals – Modern Whaling
 International Whaling Commission (IWC): formed in 1946 in
response to the near extinction of large whales (to manage
the fishery; voluntary membership, no enforcement)
 Banned whaling in 1982 (took effect in 1986); Japan signed with
allowance to kill 500-600 Minke whales a year; Norway once a
member but later withdrew, continued hunting Minke whales
 Established Southern Ocean Whale Sanctuary in 1994
 Island nations in Caribbean receiving millions of dollars in aid from
Japan and joining IWC as pro-whaling nations
 Marine Mammal Protection Act (U.S., 1972): protects all marine
mammals from direct hunting in U.S. waters; preceded U.S.
Endangered Species Act (1973)
 Explosive harpoons replaced with electrocution and thermal
harpoons (5000⁰ instant combustion snaps spine)