I. Marine Mammals

B. Pinnipedia (suborder)• Many nest in rookeries

• Males establish territories and harems (polygynous)

• Females may have seasonal delayed implantation

• Fertilization and early development to blastocyst followed by delayed implantation

• Lactation period varies from days to months

Northern Fur Seals video

I. Marine Mammals

B. Pinnipedia1. Sea Lions (6 species)

• Extremely common in E Pacific• Highly social; usually congregate on shore• Males can be large (up to 3+ m, 1100+ kg)• Harems of up to 12 females

2. Fur Seals (10 species)• Related to sea lions• Thick, dense fur

Steller’s Sea Lion

Antarctic Fur Seal

California Sea Lion

I. Marine Mammals

B. Pinnipedia3. True Seals (19 species)

• Highest diversity in polar regions (esp. Antarctic)• Better adapted for aquatic existence vs. eared seals• Include largest pinniped

• Southern elephant seals (males) can reach 6.5+ m (22 feet) long and 4000+ kg

• Tend not to have harems (pair for breeding season)

Weddell

Leopard Crabeater

Harbor

S. Elephant

video

video

video

I. Marine Mammals

B. Pinnipedia4. Walrus (1 species)

• No external ears; distinct neck; hind limbs for walking• Feed on fishes and benthic invertebrates, esp. clams• Tusks used for defense or as anchors in ice• Males can reach 5+ m, 1500+ kg

• Males defend harems (up to three females + calves)video

I. Marine Mammals

C. Sirenia (4 species)• Manatees (marine and freshwater), dugongs

(exclusively marine), sea cows (extinct)• Restricted to tropics (modern)• Manatees reach 3.5 m, 550 kg• Dugongs reach 4 m, 1000 kg• Front flippers, vestigial pelvis, no hind limbs

(similar to cetaceans), tail flukes• Swim mainly with tail video

• Thick blubber layer• Strictly vegetarian video

• Eat seagrasses and other vegetation

West Indian Manatee

West African Manatee

Amazonian Manatee

Dugong

I. Marine Mammals

D. Cetacea• Whales, dolphins, porpoises

• ~90 species: ~85 marine• Front flippers, tail, no rear limbs

• Many have dorsal fin (stability, along with flippers)• Muscular tail ends in horizontal flukes

• Streamlined for efficient swimming• Reduced/fused cervical vertebrae, no external ears/nostrils• Limited hair• Example of convergent evolution

• Blubber layer – Varies by species and season• Insulation, energy, buoyancy

• Breathe through blowhole on dorsal surface• Single – toothed whales• Double – baleen whales

• Evolved from terrestrial ancestors

Fig. 12-10

I. Marine Mammals

D. Cetacea• Thermoregulation

• Eliminate heat: Shunt blood into blubber layer• Retain heat: Countercurrent exchangers

Fig. 12-11

I. Marine Mammals

D. Cetacea• Diving adaptations

• Mammalian diving reflex• Bradycardia (as low as 10 beats per minute)• Peripheral vasoconstriction

• Most oxygen in tissues• Nitrogen forced out of alveoli: prevents bends

• Collapsible ribcage• Up to 2x more blood per unit body weight vs. humans• 10-30x more myoglobin in muscles vs. land mammals• Muscles less sensitive to lactic acid• Medulla oblongata (controls breathing) less sensitive

to CO2

Fig. 12-12