Marine Mammals Return to the Oceans Mammals have

Marine Mammals

Return to the Oceans Mammals have returned to the oceans multiple times Adaptations vivipary suckling young thermoregulation feeding diving osmoregulation

Marine mammals • Characteristics of marine mammals: – Warm-blooded – Breathe air – Have hair (or fur) – Bear live young – Females have mammary glands that produce milk for their young

Fusiform Shape and Streamlining Evolutionary Convergence

Adaptations for diving • Exchange a large amount of air on each breath • Up to 90% in each breath (humans exchange about 20%) • Blood with more oxygen carrying capacity • Heart rate slows • Blood flow shunted • Higher concentration of myoglobin in the muscles • Collapsing lungs • Dive with no air in contact with blood vessels to avoid problems of nitrogen being forced in

Two basic bioenergetic strategies used by animals : • Endothermy “warm blooded” • Ectothermy “cold blooded”

Countercurrent Exchange Concurrent exchange Countercurrent exchange

Osmoregulation (water balance) • Marine Mammals have highly efficient kidneys capable of producing very hypertonic urine. • These animals also rely on metabolic water and water from feeding on fishes and invertebrates. • Unlike most other aquatic mammals, sea otters commonly drink sea water and manatees frequently drink fresh water

Marine mammals: Order Sirenia • Sirenian characteristics: – Large body size – Sparse hair all over body – Vegetarians – Toenails (on manatees only) • Includes: – Manatees – Dugongs

Manatee & Dugong • Most complete transition to marine life along with whales and dolphins • Related to the elephant, but common ancestor didn’t look like either of them • Once many more species around • Large layer of blubber • Origin of the mermaid myth • Herbivores • Nostrils on top of snout have valves to keep water out • Both species have one calf at a time • Tend to have a single calf every 3 years

Dugong Location: coastal and inland waters of the western Indo-Pacific region • Dugongs are exclusively marine and have a dolphin-like tail • Dugongs tend to dig seagrass rhizomes • Predator includes tiger sharks

10, 000 Dugong Range

Family Dugongidae Dugong dugong 8. 9 ft, 551 -661 lbs Steller's Sea Cow t. Hydrodamalis gigas Discovered 1741. 30 ft, 4. 4 tons

Manatee Location: Florida, Central and South America • • Manatees have paddle-like tails and frequent freshwater Manatees tend to crop and grab with prehensile lips Manatees are larger than dugongs Few predators Threats: • Careless boaters • Habitat loss

Manatee 9. 8 ft, 800 -1200 lbs 3, 000 in U. S.

Relationship between Sirenians and elephants (mt. DNA) Asian elephant African elephant tmammoth tmastadon t. Stellar’s sea cow Dugong Ancestral mammals West Indian manatee Brazilian manatee West African manatee Other mammals 80 60 40 20 Million of years before present 0

Marine mammals: Order Carnivora • All members of order Carnivora have prominent canine teeth • Includes: – Sea otters – Polar bears – Pinnipeds (flipper-footed) • Walrus • Seals • Sea lions/fur seals Hawaiian Monk Seal

Sea Otter

Sea Otter • Enhydra lutris – Native to north Pacific – 394, 000 hairs/cm 2 – No blubber – Female 45 lbs; Male 65 lbs – Diet: Sea urchins, abalone, mussels, clams, crabs, snails and about 40 other marine species. – Uses tools – Dives to 330 ft – Rests in coastal kelp forests

Polar Bear Pop size: 22, 000 to 27, 000 Weight: 550 to 1, 700 pounds

Polar Bear • Ursa maritimus – United States, Canada, Russia, Greenland on the Arctic islands of Norway – Male: 10 feet tall and weigh over 1400 lbs – Female: seven feet and weigh 650 lbs – wild polar bears live up to age 25. – Good swimmers – Thick blubber – Thick fur

Polar bears • Polar bears are the least adapted to the marine lifestyle • Land animals that are adapted to the cold • Considered marine mammals because they feed almost exclusively on marine organisms • Very good swimmers, but can’t dive below surface well • Hunt seals and walruses, occasionally cetaceans

Range: • Circumpolar in Arctic • Range depends on sea ice • normal range occasional range over pack occasional range over permanent ice

Pinnipeds (Latin for winged-foot)

Pinnipeds Hawaiian Monk Seal Family Phocidae Walrus Sea Lion Family Otariidae Family Odobenidae

Biology and Natural History Order Pinniped (seals, sea lions, & walruses) Family Phocidae- true, earless seals Family Otariidae- eared seals and sea lions Family Odobenidae- walruses • • • 34 known species Evolved 20 mya from Order Carnivora (ancestors of dogs and bears) Differ in possession of external ears and mode of locomotion

Differences between seals and sea lions/fur seals

Hawaiian Monk Seal Family Phocidae • • Lack external ears Hind flippers propel them while swimming Front flippers act as rudders Travel on land is difficult (wiggle)

Sea Lion Family Otariidae • • Eared seals Front flippers propel animal when swimming Rear flippers act as rudders Fairly mobile on land

Walrus Family Odobenidae • • • Found in Arctic region Lack external ears Paddle with front flippers Rear flippers act as a rudder Fairly mobile on land

Walrus Range Map Pacific walrus is in lavender, Atlantic walrus is in rose.

Walrus Facts Location: • Bering sea, Pacific Ocean, Atlantic Ocean, Arctic Ocean Pop Size: • 250, 000 Size: • Weight: 2, 000 -3, 500 lb. Breeding: • Sexually mature late - females, usually 6 -7 years - males, 15 years. • Produce few offspring

Walrus Facts Lifestyle • Habit: Gregarious, living mainly in herds. • Diet: Benthic suction feeders. Feed mainly on bivalve mollusks, but also other invertebrate marine animals, fish, sometimes seals and whales. • Predators: polar bears, killer whales, and humans • Lifespan: Up to 40 years.

Walrus Facts • • • Swim speed: 7 -35 kph Tusks: - Both male & female - Used for dragging body across land or ice - Symbolize age, sex, and social status Pharyngeal pockets: - 2 found on either side of the esophagus that hold up to 50 liters of air ). - For buoyancy; these pockets facilitate sleep in the water in an upright position - May be used to amplify mating calls

Whales, Dolphins, & Porpoise

Pakicetus attocki Age: Early Eocene, 50 million years old Location: Pakistan

Whale Evolution

Ambulocetus natans in action. A reconstruction of an early close cousin of whales.

Marine mammals: Order Cetacea

Marine mammals: Order Cetacea • Cetacean characteristics: – Blowholes on top of skull – Skull telescoped (streamlined shape) – Very few hairs • Includes: – Whales, dolphins, and porpoises

Two suborders of order Cetacea (55 mya- entered sea) • Suborder Odontoceti (toothed whales) – Echolocate (send sound through water) – Includes killer whale, sperm whale, dolphins, porpoises, and many others • Suborder Mysticeti (baleen whales) – Have rows of baleen plates instead of teeth – Includes blue whale, finback whale, humpback whale, gray whale, and many others

Differences between Odontocetes and Mysticetes Anatomical Features Toothed whales Baleen whales • • • Symmetry of skull Feeding structures Stomach divisions External blow holes Digits in hand Asymmetrical Teeth Three to 13 One Five • • Wax ear plug Not present Hair Present in fetus Always Larger sex Males largest Food Squid, fish Symmetrical Baleen Always three Two Four (five in right whales) Present present on adults Females largest Plankton, small fish

Differences between dolphins and porpoises • Dolphins have: – An elongated snout (rostrum) – A sickle-shaped (falcate) dorsal fin – Conical-shaped teeth Killer whale jawbone

Differences between dolphins and porpoises • Porpoises have: – A blunt snout (rostrum) – A triangle-shaped dorsal fin – Spade-shaped teeth

Echolcation - the location of objects by their echos - is a highly specialized faculty that enables dolphins to explore their environment and search out their prey in a watery world where sight is often of little use. As sound travels four and a half times faster in water than in air, the dolphin's brain must be extremely well adapted in order to make a rapid analysis of the complicated information provided by the echoes. Although the ability to echolcate has only been proven experimentally for a few odontocete species, the anatomical evidence - the presence of the melon, nasal sacs and specialized skull structures - suggests that all dolphins have this ability. The dolphin is able to generate sound in the form of clicks, within its nasal sacs, situated behind the melon. The frequency of this click is higher than that of the sounds used for communication and differs between species. The melon acts as a lens which focuses the sound into a narrow beam that is projected in front of the animal.

Echolocation • Sensing environment • Produce clicks that travel out, hit objects and reflect back • Produced by a structure in the airway called the “monkey lips” • Sound received through the lower jaw • Low frequency clicks travel further but can only be used for big objects • High frequency clicks can discriminate small objects but don’t travel as far

Deepest Diver (3 km~1. 5 miles)

Mysticeti: The baleen whales • Mysticeti whales have baleen instead of teeth • Baleen plates: – Hang as parallel rows from the upper jaw – Are made of keratin – Are used as a strainer to capture zooplankton – Allows baleen whales to eat krill and small fish by the ton

Baleen

Types of baleen whales • Baleen whales include three families: – Gray whale (a bottom-feeder with short baleen) – Rorqual whales (medium-sized baleen) • • Balaenopterids (blue whales, finback whales, and other large whales ) Megapterids (humpback whales) – Right whales (surface skimmers with long baleen)

Whale Migration