- Horizontal flukes.
- Hind limbs vestigial.
- No external ears.
- Very little hair in adults.
- No external genitalia, withdrawn into slits.
- Thick layer of blubber.
- No sweat or oil glands.
Life History of Cetaceans
- Open mouth wide, take in large quantity of water, strain out food. e.g. Humpback Whale,
corrals krill in a bubble net.
- Swimming through water, mouth partly open. Water comes in through gap at front of mouth,
strained through baleen, and out the sides of the mouth. e.g. Right Whales, Sei Whales.
- Using suction of tongue against palate to draw water in and opposite movement to force
water out. e.g. Gray Whales.
- How much food? Blue Whale needs 1.5 million Cal/day for Basal metabolic rate (during
fattening for winter 3 million). 1 lb. of krill = 400 Cal, so 4 tons per day are needed.
Fastest of the large whales is the Fin Whale, bursts up to 32 mph.
- Gestation is as little as 10 months for some of the dolphins, up to 15 months for
- Much larger compared to mother than in other mammals, 40% in Harbor Porpoises.
- Born tail first, able to swim immediately.
- Pair of teats concealed in slits, milk very rich in fat.
- Weight gain very rapid, dolphin may double length and 7X its weight in first year.
- Most whales calve only every 2-3 years, dolphins 1-2 (usually 2) years.
- Blubber with few blood vessels.
- Countercurrent system in blood circulation.
- Low surface to volume ratio.
- Decreased respiration rates.
- Most larger whales migrate poleward in the summer and toward the equator in winter,
calving often in wintering grounds.
- Some migrate to stay in warmer waters with abundant food year around. e.g. right whale.
- Small whales, dolphins and porpoises do not migrate.
- Gray whale is a common migrant past the California coast, Humpback is less common.
Breaching & Beaching
- Some breach some do not.
- No good answer as to why they beach.
- Historically hunted for baleen and oil.
- IWC banned factory ship whaling in 1979, some nations are not members though and still
capture some whales.
- Some species have been drastically reduced in numbers. e.g. Gray Whale now extinct in
- Many dolphins and porpoises are drowned after becoming entangled in nets.
- Great Blue Whale is the largest. Spend summers from Central Cal to AK.
- Humpback Whale: Rarely sighted off Cal coast in Summer.
- Gray Whale: Dec-Jan is best time to sight them off Cal.
- Sperm Whales: pelagic, deep waters off CA during winter.
- Killer Whales: Worldwide, can be seen in CA, Prey upon other whales.
- Pacific White-sided Dolphin: All along CA, commonly used in shows.
- Harbor Porpoise: Commonly found in bays, river mouths and shallow inshore waters. Small
Order Carnivora (The Pinnipeds)
- Pinnipeds used to be recognized as an order, now not used.
- All limbs form flippers.
- Body covered with hair.
- Feed on fish and other marine animals.
- Come to land to rest and give birth to young.
- 3 Families: Odobenidae (Walrus), Otariidae (Eared Seals), Phocidae (True Seals).
Comparison of seal families:
||long, hairless or
partially haired, claws away from flipper edge
||shorts, hairy, claws on
||large, can be rotated
||intermediate, cannot be
rotated under body.
||external in a scrotum.
||separate outside body
cavity in the hypodermal layer of skin.
||Splashing back and
forth figure eight motion with back of body, fore limbs for control
||extend head and neck
for steering and use a sort of breast stroke
Life History of Pinnipeds
- Varied diets among all the different species.
- Little is known about how they capture prey.
- Many eat stones or pebbles.
- Twinning is rare.
- Pupping interval 1 or more years.
- Mating occurs during a very short breeding season.
- Gestation is 10-12 months.
- Milk very rich in fat, little liquid.
- Lungs collapse from 25-70 m and force air into poorly vascularized cartilaginous
- tissue (keeps nitrogen from getting into blood too much).
- More blood volume than most other mammals.
- High concentration of RBCs in blood and muscle.
- Heart rate drops from 120 down to 4-6!
- Northern Elephant Seals have been recorded diving to 1600 m for ca. 80 min.
- Have been extensively exploited in the past.
- Not currently hunted.
- Many species making a comeback.
Order Carnivora Family Mustelidae (Otters)
- Only marine mammal without blubber.
- Very thick and fine fur.
- Historically they were hunted, southern form almost wiped out.
- Eat shellfish and sea urchins.
- Also eat fish.
- Prevent urchin barrens in kelp beds and thus encourage greater fish production.
- Compete with humans for shellfish, demise of Abalone fisheries in some parts of CA might
be partly due to otters.
- Male mates with female in water by grasping her head and jaws (including nose) in
- his mouth while she is floating on her back.
- Gestation is 8 months.
- Single pup, born on land or water.
- Swims on stomach from 4-5 up to 10 months, swim on back at that point.
- Pupping every 1-almost 2 years.
- Pups fully independent at 6 months.
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