Marine MammalsMarine Mammals

Return to the Oceans Mammals have returned to the oceans

multiple times

Adaptationsviviparysuckling youngthermoregulation feedingdivingosmoregulation

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 StreamliningEvolutionary 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 & DugongManatee & 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

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

Dugong

Dugong Range

10,000

Family Dugongidae

Dugong dugong Steller's Sea CowtHydrodamalis gigasDiscovered 1741.8.9 ft, 551-661lbs

30ft, 4.4 tons

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

Manatee

9.8 ft, 800-1200lbs3,000 in U.S.

Million of years before present

80 60 40 20 0

Ancestral mammals

Asian elephant

African elephant

tmammoth

tmastadon

Dugong

tStellar’s sea cow

West Indian manatee

Brazilian manateeWest African manatee

Other mammals

Relationship between Sirenians and elephants (mtDNA)

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 OtterSea Otter

Sea Otter• Enhydra lutris

– Native to north Pacific– 394,000 hairs/cm2

– No blubber– Female 45 lbs; Male

65lbs – 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

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

Polar BearPolar Bear

Polar Bear• Ursa maritimus

– United States, Canada, Russia, Greenland and 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

PinnipedsPinnipeds

(Latin for winged-foot)

Sea LionWalrus

Family Phocidae

Family OtariidaeFamily Odobenidae

Hawaiian Monk Seal

Pinnipeds

Order Pinniped (seals, sea lions, & walruses)Family Phocidae- true, earless sealsFamily Otariidae- eared seals and sea lionsFamily 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

Biology and Natural History

Differences between seals and sea lions/fur seals

Family Phocidae

Hawaiian Monk Seal

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

Sea LionFamily 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

                               

                       Pacific walrus is in lavender, Atlantic walrus is in rose.

Walrus Range Map

Walrus FactsLocation: • 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 FactsLifestyle

• 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, Whales, Dolphins, & Porpoise& Porpoise

Age: Early Eocene, 50 million years oldLocation: Pakistan

Pakicetus attocki

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

• 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

(55 mya- entered sea)

Differences between Odontocetes and MysticetesAnatomical Toothed Baleen

Features whales whales

•Symmetry of skull Asymmetrical Symmetrical

•Feeding structures Teeth Baleen

•Stomach divisions Three to 13 Always three

•External blow holes One Two

•Digits in hand Five Four (five in right whales)

•Wax ear plug Not present Present

•Hair Present in fetus Always present on adults

•Larger sex Males largest Females largest

•Food Squid, fish 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

(3km~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