Marine Mammals

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

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

• 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

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

• 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

• Swimming and diving:

–Fast swimmers (25-30 km/hr)

–Can remain underwater for 45 minutes

•Decrease metabolism to conserve oxygen

• Some can dive deep

• 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

• 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

• Examples of Eared Seals: Sea Lions

–Course coat of hair

–Naturally playful

–Highly social congregate in groups

• 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

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

• 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

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

• 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

• 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

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

• Completely aquatic

• Gentle animals who are trusting in captivity but shy and elusive in India

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

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

• 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

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

• 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

• 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

• 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

• 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

• Reproduction and development:

–Travel in groups called pods (adults and young)

–Bear 1 offspring at a time

• Fed rich milk to grow fast

• Types of whales:

1. Baleen whales (Mysticeti)

• Lack teeth (plates of baleen)

• Filter food from water

• Largest whales

• Feed on plankton, krill, or fish

2. Right whales

–Lack dorsal fin

–Absence of grooves on throat and chest

–Rare

–Slow and easily hunted

3. Rorquals

–Have dorsal fin and ventral grooves

–Slender and streamlined

• Examples of Rorquals: Blue whale

–Largest of whales (24-30m)

–Over 100 tons

• 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

• 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

• Examples of Rorquals: Gray whales

–Eastern Pacific only living population (15,000)

–Female aggressively defend young

–Carry barnacles on skin

4. Toothed whales (Odontoceti)

–Teeth simplified

–Feed on larger prey

• 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

• Examples of toothed whales: White whales

–Beluga whale

–Narwhal

•Males develop tusks

• Examples of toothed whales:Porpoises

–Stocky body

–Rounded head with no beak

–100-200 identical teeth fused to jaw

• 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

• Examples of toothed whales: Killer whale (orca)

–Largest of dolphins

–Only cetacean that feeds on homeothermic animals

–High dorsal fin

–Broad, rounded flippers

• 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