Marine Mammals Not Including Whales

I. What is a mammal? A. Characteristics 1. Pelage - hair or fur made of protein called keratin covering all or part of the body for insulation & camouflage. 2. Mammary glands in females are modified sweat glands that make milk containing sugars, proteins, & fats to nourish young. 3. Single lower jawbone.

B. Ancient Mammals 1. Fossil records show mammals arose from group of reptiles called cyanodonts at the end of the Paleozoic era. 2. Early mammals were small, shrew like, insect eaters that had large eye sockets making them probably nocturnal.

C. System Upgrades Circulatory a. Endothermy – hair helps insulate against heat loss. b. Four-Chambered Heart – keeps oxygenated blood away from O2 poor blood. 2. Digestive a. Ungulates (hoofed mammals) have four-chambered stomachs with bacteria living inside to help them digest cellulose from plants. b. Specialized mouth structures (teeth, baleen, etc.) help start the process of digestion.

3. Nervous a. Large cerebrum allows for higher-order thinking. b 3. Nervous a. Large cerebrum allows for higher-order thinking. b. Bats and some whales can echolocate.

3. Reproductive a. Monotremes 1) Females lay 1-2 leathery-shelled eggs containing yolk and incubates them with her body heat. 2) Young monotremes are small and partially developed at hatching so depend on mother for protection and milk from sweat glands on skin.

b. Marsupials 1) Have short development period inside of the mother b. Marsupials 1) Have short development period inside of the mother. 2) Newborns must crawl to the mother's pouch or marsupium after birth, attach to a nipple for milk, and finish developing.

c. Placentals 1) Gestation (period of development inside mother) is longer in placental mammals. 2) Nutrients, wastes, gases exchanged through membrane lining uterus called the placenta.

II. Marine Mammals A. Sea Otters (Family: Fissipedia) 1. Location: Kelp beds and coastal reefs along Pacific coast of N. America. Once found throughout Pacific but hunted to near extinction (100 in 1911 to 130,000 today). 2. Thick fur rather than fat, playful, vocal, consume 25% of body weight / day. 3. Leave water if threatened by predators or weather.

B. Polar Bears (F: Fissipedia) 1. Found only in Arctic (N. Hemisphere). 2. Considered a marine species because they feed on marine organisms. 3. Largest bear, swims and walks great distances for food. 4. Habitat is threatened by humans and global warming – may be extinct within 50 years.

C. Sirens: Manatees and Dugongs (F: Sirenia) 1. Once widespread, now only found on coastal areas. 2. Vegetarians – sea grasses and shallow water plants. 3. Dugongs: marine; Manatees: marine and fresh 4. Stellar Sea Cow: extinct Arctic species

D. Pinnipeds (F: Pinnipedia) 1. General C’ristics Retain 4 modified limbs, fast swimmers, expert divers. Come ashore to mate, molt, give birth, some to sleep. Found in colder waters, most species not endangered.

2. Eared Seals a. Visible ears, long necks, can rotate flippers. b. Sea lions: Highly social, vocal, playful - California Sea Lion c. Fur Seals: Thick woolly undercoats, 1 species in N. Hemisphere & 8 in Southern

3. Phocids – True Seals a. Not able to easily move on land – roll or slide, short necks, no external ears. b. Most species marine but a few live in rivers and estuaries. c. Harbor, harp, leopard, elephant.

4. Walruses a. Live only in the Arctic, feed on bivalve mollusks, echinoderms and crustaceans, fish. b. Once hunted to endangerment for large ivory tusks. See the best exercise video ever…