BIOL 331, Lecture 14, Marine Mammals

BIOL 331
Lecture 14
Marine Mammals

Order Cetacea

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.

Gestation is as little as 10 months for some of the dolphins, up to 15 months for whales.
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.

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.

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 North Atlantic.
Many dolphins and porpoises are drowned after becoming entangled in nets.

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 and chunky.

3 Families: Odobenidae (Walrus), Otariidae (Eared Seals), Phocidae (True Seals).

	Otariidae	Phocidae
ear flaps	yes	no
fore flippers	long, hairless or partially haired, claws away from flipper edge	shorts, hairy, claws on each digit.
hind flippers	large, can be rotated under body.	intermediate, cannot be rotated under body.
Testes	external in a scrotum.	separate outside body cavity in the hypodermal layer of skin.
Swimming	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

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.

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.