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Marine Mammals
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Introduction• Insulating body covering of
hair• Maintain a constant warm
body temperature (homeothermic)
• Mothers produce milk with mammary glands
• Placental animals– Retain young inside their
body until ready to be born• Provide parental care• High metabolic rate
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Sea Otters
• Found along coast of California and Alaska
• Skin covered by thick fur with underlying air layer– Protects from cold
• Short, erect ears
• 5-fingered forelimbs
• Well-defined hind limbs with finlike feet
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• Hunted by sharks and killer whales
• Stay close to shore
• Consume 25% of their body weight in food per day
– Ex: sea urchins, mollusks, crustaceans, and fish
• Diurnal
• Playful and vocal
• Population of 130,000
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Pinnipeds• Name means
“featherfooted”• Come ashore to give birth,
molt, mate, and sleep• Found in all oceans–Most prefer colder water
• Feed on fish, penguins, and some seals
• Hunted by sharks, killer whales, and humans
• 30 million today
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• Characteristics:
–Body is spindle-shaped
–Several thick layers of subcutaneous fat
–Round head carried on a distinct neck
•Can move independently of body
–Large brains with well-developed senses
–2 sets of limbs modified into flippers
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• Swimming and diving:
–Fast swimmers (25-30 km/hr)
–Can remain underwater for 45 minutes
•Decrease metabolism to conserve oxygen
• Some can dive deep
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• Reproduction:– Leave water and go to
breeding beaches– Bulls (males) arrive first
to establish territories– Some are polygynous 1
male with up to 15 females
–Most mate annually• Gestation between 9-12
months• 1-2 pups born
– The shorter the lactation period (nursing) the faster a pup develops insulation
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• 3 families of Pinnipeds:
1. Eared Seals (Otariidae)• Visible but small external ears• Forelimbs main propulsive force for swimming– Look like flying underwater
• Hind limbs remain motionless during swimming–Used for steering
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• Examples of Eared Seals: Sea Lions
–Course coat of hair
–Naturally playful
–Highly social congregate in groups
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• Examples of Eared Seals: Fur Seals–Thick, dense underfur beneath stiff,
outer guard hairs–Smaller than sea lions–9 species with 1.5 million population
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2. Phocids or True Seals (Phocidae)– Lack external ears–More streamlined for swimming underwater– Propel themselves with a sculling movement of
hind flippers– Forelimbs closer to the head and smaller than
hind limbs
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• Less adapted to life on land– Drag bodies or slide/roll
• Male mates with single female for entire breeding season
• Ex: crabeater seal, harbor seal, harp seal, leopard seal, and elephant seal
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3. Walruses (Odobenidae)
–Lack external ears
–Streamlined for swimming underwater
–Rely on forelimbs to move bulky body
–Distinct neck
–Hind limbs used for walking on land
–3-5 m in length
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• Can weigh up to 1364 kg (3000 lbs)
• Canine teeth of upper jaw developed into tusks in males
–Used for fighting with other males
–Can help lift body onto ice like a pick ax
–Appear at 5 years old
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• 1 large male with a harem of females
• 11 month gestation with 1-2 calves
–Stay with mom until 4-5 years old
• Found in the Arctic
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Sirens
• Confined to coastal areas and estuaries of tropical seas
• Similar to whales–Streamlined, hairless bodies–Forelimbs that form flippers–Vestigial pelvis with no hind limbs
• Tail flukes
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• Completely aquatic
• Gentle animals who are trusting in captivity but shy and elusive in India
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2 families:
1. Dugongs (Dugongidae)
–Found in Indian Ocean
–Strictly marine
–Feed on shallow-water grasses
–Larger head and shorter flippers than a manatee
–Notched tail
–1 species (Dugong dugon)
–Endangered
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2. Manatees (Trichechidae)
–Found in Atlantic Ocean and Caribbean Sea
•Can also be in inland rivers and lakes
–Rounded tail
–3 species:
•Northern manatee
•Brazilian manatee (freshwater species)
•African manatee
•All hunted
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• Mate and give birth underwater
–Male remains with mate
–11 month gestation 1 calf
• Strict vegetarians (eat 60 lb/day)
Stellar’s Sea Cow
–Extinct 27 years after discovery
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Cetaceans• General characteristics:
–Body resembles fish (streamlined)
–Probably evolved from ancient land-dwelling carnivorous mammals
–Flippers with bone structure of a 5-fingered hand that only move up and down
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• Nostrils form a blowhole
–Allows them to surface and breathe
• Thick layer of blubber under the skin
–Provides insulation
–Energy reserve
• Source of water when fat is metabolized
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• No neck head is continuous with body and cannot be moved separately
• No external ears– Small opening on side of head• Plugged with wax to prevent water from damaging
eardrum
• Body has no hair except a few on the head• Skin lacks sweat glands• Tails consist of flat flukes
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• Adaptations for diving:– Large lungs that collapse easily when diving
contain little air–Metabolism and heart rate decrease• Blood moves to vital organs
– Blood contains huge amounts of hemoglobin• Absorb and transport more oxygen
–Muscles can tolerate more lactic acid with no ill effects
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• Behavior:– Intelligent and inquisitive– Spy hopping stick head
straight up out of water to survey surroundings
– Breaching completely or almost completely leaves the water• Can go as high as 45 feet• Horizontal position as it falls
back to the water
– Slapping lift huge tails above water and slap them to make splash and noise• Aggressive behavior
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• Reproduction and development:
–Travel in groups called pods (adults and young)
–Bear 1 offspring at a time
• Fed rich milk to grow fast
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• Types of whales:
1. Baleen whales (Mysticeti)
• Lack teeth (plates of baleen)
• Filter food from water
• Largest whales
• Feed on plankton, krill, or fish
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2. Right whales
–Lack dorsal fin
–Absence of grooves on throat and chest
–Rare
–Slow and easily hunted
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3. Rorquals
–Have dorsal fin and ventral grooves
–Slender and streamlined
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• Examples of Rorquals: Blue whale
–Largest of whales (24-30m)
–Over 100 tons
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• Examples of Rorquals: Fin whale
–2nd largest whale (19-22m)
–45-75 tons
–Large dorsal fin that slopes backward
–Dark gray to brownish black
–White ventral surface
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• Examples of Rorquals: Humpback whales
–Low hump on back
–Large bumps (bosses) on its snout
–Long pectoral fins
–Slow-moving and heavyset
–Still endangered
–Coastal species
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• Examples of Rorquals: Gray whales
–Eastern Pacific only living population (15,000)
–Female aggressively defend young
–Carry barnacles on skin
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4. Toothed whales (Odontoceti)
–Teeth simplified
–Feed on larger prey
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• Examples of toothed whales: Sperm whale
–Massive blunt snout
–No real dorsal fin
• Series of humps
–Aggressive
–Polygynous
–Still rare and endangered
–Oily, wax-like substance in animal’s head
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• Examples of toothed whales: White whales
–Beluga whale
–Narwhal
•Males develop tusks
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• Examples of toothed whales:Porpoises
–Stocky body
–Rounded head with no beak
–100-200 identical teeth fused to jaw
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• Examples of toothed whales: Dolphins–Most numerous group– Definite beak separated from snout by a groove– Ex: bottlenose dolphins• Used for scientific studies of intelligence
– Playful– Very intelligent– Socialize with other species
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• Examples of toothed whales: Killer whale (orca)
–Largest of dolphins
–Only cetacean that feeds on homeothermic animals
–High dorsal fin
–Broad, rounded flippers
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• Echolocation
–Allows animal to distinguish and home in on objects from distances of several hundred meters
–Dolphins use series of clicking sounds
–Acts like sonar