Chapter 9: Marine Reptiles, Birds, and Mammals

Vertebrates

350 m.y.a. vertebrates invaded land

Decendents of bony fish

Land vertebrates had to adapt to harsher conditions on shore

Tetrapods had to develop lungs that allowed for absorption of oxygen directly from air.

Tetrapods had to evolve in ways to keep from drying out.

Amphibians, early tetrapods, have eggs that are vulnerable. They need to stay moist and lay them in water.

Reptiles on the other hand solved the problem of waterloss, resulting in the evolution of birds and mammals.

One they were equipped with adaptations for land they reentered the ocean.

Classification

Marine Reptiles

•7000 species

•Dry skin with scales

•Eggs leathery shell

•Poilkilotherms (body temp varies w/environment) and ectotherms (lose metabolic heat to environment)

Sea Turtles

•Shell, carapace, is fused with their backbone.

•Cannot retract their heads into the shell

•Legs are modified into flippers for swimming

•Warmer waters

Feed on seagrass, seaweed, sponges, sea squirts, barnacles, jellyfish

Must return to land to reproduce

Migrate to original beach, possible use of magnetic fields

Return every 2-4 years, copulate offshore, females come on shore at night, dig a hole lay between 100 – 160 eggs, hatch approx. 60 days

7 (8) species of Sea Turtles (all classified as threatened);

Green (Chelonia mydas)

Hawksbill (Eretmochelys imbricata)

Leatherback (Dermochelys coriacea) D.o.d,largest turtle

Kemp’s Ridley (Lepidochelys kempii)

Loggerhead (Caretta caretta)

Flatback (Natator depressa)

Black (Chelonia agassizii)

Olive Ridley (Lepidochetys olivacea)

Green Sea Turtle

Hawksbill Sea Turtle

Black Sea TurtleFlatback Sea Turtle

Kemps Sea TurtleLeatherback Sea Turtle

Loggerhead Sea Turtle Olive Ridley

Sea Snakes

Approx. 55 species found in tropical waters

Laterally flattened and tail paddle-shaped for swimming, 3-4ft long

Mate in the ocean, ovoviviparous

Closely related to cobras, rarely aggressive

Marine Iguana (Amblyrhynchus cristatus)

Galapagos Islands

Eats seaweed and can dive 33ft to graze

Saltwater Crocodiles (Crocodylus porosus)

Mangroove swamps and estuaries

20-33ft long, very aggressive

Seabirds

Endothermic

Waterproof feathers

Hollow bones

Hard-shelled egg

Spend significant amount of time in marine environment and eat marine organisms

Penguins

Flightless, wings modified into stubby flippers

Bones are denser to reduce buoyancy

Layer of fat and dense waterproof feathers

Feed on fish, squid, and krill

Lay eggs during cold times of year to ensure food availability when egg hatches

Emperor penguin (Aptenodytes forsteri) mate for life

Tubernoses

Large group with distinctive tube-like nostrils and heavy beaks usually curved at tip

Spend months and sometimes years at sea

Salt glands are used to get rid of excess salt

Albatrosses (Diomedea) glides almost never flap, wing span 11ft

Shearwaters (Puffinus) and Petrels (Pterodroma)

Skillful, catch fish at sea

Faithful mates, elaborate mating rituals

Nest in remote islands and cliffs

Incubation and care for single chicks can take up to 8 months

Fig. 9.7

Pelicans and Related Birds

Webbing between all four toes

Large fish eaters, widely distributed

Pelicans (Pelecanus) unique pouch below their beaks, plunge into water to catch fish in its pouch

Cormorants (Phalacrocorax) black long-necked, dive to pursue their prey, float low in water with only neck seen

Fig. 9.8

Frigate Bird

Narrow wings, long forked talk

Pirates, very seldom enter water feathers are not very waterproof

Nest in large colonies called rookeries, creating large deposits of guano (fertilizers)

Gulls and Related Birds

Gulls (Larus) the largest variety of seabirds, common and widespread

Predator and scavengers

Terns (Sterna) graceful flyers, hover over their prey, slender beaks

Puffins, Razorbill, Great Auk cold water species 

Shorebirds

Wading, do not have webbed feet

Live inland as well as sea

Plovers, sandpipers, rails, coots, herons, egrets, and even ducks 

Marine Mammals

• 200 m.y.a

• Class Mammalia evolved from extinct reptiles

• 4600 species of mammals

• Endotherms and homeotherms

• Hair, mostly viviparous (embryo receives nutrients and oxygen through the placenta, mammary gland

• Larger brain, live anywhere air to breathe and food to eat

Pinnipeds – Order Pinnipedia

• Paddle-shaped flippers for swimming

• Predators, fish and squid

• Streamlined bodies

• Coldwater, thick layer of fat (blubber)

• Breed on land

Seals

• Largest group, rear flippers that cannot be moved forward

• They move on land with front flippers

• Harbor Seals (Phoca vitulina)

• Elephant Seals (Mirounga)

Sea Lions and Fur Seals

• Eared seals

• Move their rear flippers forward

• Use all fair limbs to walk/run on land

• Graceful swimmers

• Males much larger than females, massive head and hairy mane

• California sea lion (Zalophus californianus)

Walrus (Odobenus rosmarus)

• Tusks are used for defense

• Feeds on invertebrates that it sucks up from the sea bottom

• Dependent on sea ice

Odobenus rosmarus

Sea Otter and Polar Bear

• Order Carnivora

• Sea Otter (Enhydra lutris)

• Smallest marine mammal averages between 60 – 80 pounds

• Lacks layer of blubber instead uses air trapped in its dense fur

• Breed and give birth in water, eats up to 30% of its body weight/day (invertebrates and fish)

• Lives in kelp beds

Polar Bear (Ursus maritimus)

• Semi aquatic animals that live in the Arctic and feeds primarily on seals

• Depends on sea ice for survival

Manatees and Dugong (sea cows)

• Order Sirenia, relatives of elephants

• Pair of front flippers, no rear limbs

• Paddle – shaped horizontal tail

• Blubber, live in shallow coastal waters

• Strict vegetarians, large in size Dugongs (10ft) and Manatees (15ft)

• Manatee (Trichechus)

Whales, Dolphins, and Porpoises• Order Cetacea, largest group• Many legends, art, and literature come from these animals• Bodies are streamlined, breath air, warm-blooded, have hair,

and produce milk for their young• Front flippers, no rear limbs (present in embryonic stage

only)• Many have dorsal fin, muscular tail fin-like (fluke)• Blubber, provides insulation and buoyancy• Single or double opening on the top of their head –

blowhole• 90 species, all marine except 5 freshwater dolphin species• Divided into two groups; toothless and toothed

Fig. 9.15

Baleen (toothless) whales, Mysticeti

• Rows of flexible, fibrous plates (baleen) hang from upper jaws made up of keratin and bristles overlap

• Largest whales, 13 species

• Blowhole has two openings

• Blue Whale (Balaenoptera musculus)

• Largest, males up to 80ft and females up to 110ft

• Weigh up to 90 – 140 tons

• Feed by gulping up schools of fish and swarms of krill, Grey Whales are bottom feeders

Toothed Whales, Odonticeti

• 80 species, teeth are adapted for diet of fish, squid, and other prey that they can catch and hold

• Food is swallowed whole not chewed

• Blowhole has one opening

• Largest toothed whale is the sperm whale (Physeter catadon) at 42 tons

• Killer Whale (Orcinus orca)

Fig. 9.18(Contd.)

• Small toothed whales are called dolphins or porpoises. Dolphins tend to be classified by their distinctive beaks and porpoises have more blunt shorter “noses”. They are very social and move in pods.

• Bottlenose (Tursiops truncatus)

WhalingEarly as 6000 B.C.Blubber used to make soap and lamp oilBaleen used for corsetsMeat

•1800s harpoons and steamships made whaling easier•The problem with whaling was that whales are long-lived mammals, had low reproductive rate, and were slow swimmers •Factory ships made whaling more efficient•Whaling reached it peak in 1930s

• Right Whales were named so because they would float after being harpooned

• 1946, from the decline in whale populations, 20 whaling nations established International Whaling Commission (IWC) in attempt to regulate whale hunting

• IWC collected data and set annual quotas

• Marine Mammal Protection Act of 1972, US Congress banned the hunting of all marine mammals in the US waters and importation of marine mammal products (except in traditional fisheries of AK natives)

Pacific white-sided dolphin drowned after getting caught in a drift net in the North Pacific, today MMPA has enforced the use of dolphin – safe methods

Tab. 9.2

Biology of Marine Mammals

Swimming• Streamline

• Use their flippers, tails and flukes up and down

• Cetaceans have blowhole on the top of their head that allows them to breathe even though most of their body is underwater

• Also means that cetaceans can eat without worrying about drowning, to avoid inhaling water cetaceans take very quick breaths

• Cetacean spout or blow can be seen at great distances. The spout is filled with mucus and warm seawater. The height and angle of the spout can help identify whales.

• To keep warm in the cold water, whales have a thick layer of blubber

Fig. 9.25

Diving

• Marine mammals can make the most prolonged dives and go to considerable depths for their food.

• Adaptations for these deep prolonged dives include the efficient exchange of air on the surface, the storage of more oxygen in the blood and muscles, a reduction of the blood supply to the extremities, and collapsible lungs to help prevent the bends.

• Marine mammals have higher concentrations of hemoglobin and myoglobin, which help them store more oxygen.

Fig. 9.26

• They also slow their heart rate down conserving oxygen and ensuring the flow to vital organs, like the brain and heart.

• In the absence of oxygen, marine mammal muscles begin anaerobic respiration, which results in the build of lactic acid in their muscles that they have evolved to be tolerance to.

• Marine mammals have adapted methods to prevent from getting the bends.

• The bends or decompression sickness is a painful condition caused when nitrogen dissolves in blood.

• The bubbles caused as a result of ascending can become lodged in the joints or blood vessels preventing the circulation of blood.

• Mammals have evolved so that their lungs actually collapse as they dive.

• They have a flexible rib cage that gets pushed in by the pressure of the water, as the lungs are compressed air is pushed into a central location where nitrogen is not readily absorbed.

Echolocation

• Marine mammals have excellent vision, but they really rely on their echolocation. Echolocation is based on hearing. Nature’s Sonar

• Marine mammals echolocate by emitting sound waves and listen for the echoes to reflect back from surrounding objects. Their brain then analyzes the echoes.

• Echolocation is used to find prey and orient to their surroundings.

• Short bursts of sharp clicks

Fig. 9.27

• Cetaceans produce these sounds as air is forced through the air passages and several associated air sacs while the blowhole is closed.

• A fatty structure on the forehead of toothed whales, the melon, may be used to focus and direct outgoing sound waves.

• In the sperm whale, the huge forehead is filled with a massive melon called the spermaceti organ. It produces a waxy oil, called spermaceti.

• There are many theories for the actual function of this organ; regulate buoyancy, absorb excess nitrogen during deep dives.

Behavior

• Marine mammals, particularly cetaceans, use a rich variety of vocalizations and tactile and visual signals to communicate with each other.

• Play behavior and mutual assistance are additional evidence of the complexity of their behavior.

Fig. 9.28

Fig. 9.30

Stranding or beaching

Migration

Most great whales migrate from winter breeding areas in the tropics to summer feeding areas in colder waters.

Reproduction

The reproductive system of marine mammals is similar to land mammals.

Delayed implantation allows pinnipeds to time the birth of pups with the arrival of pregnant females in breeding areas.

Reproduction cont’d

• Little is known about cetacean reproduction.

• Gestation lasts for 11 to 12 months in most cetaceans.

• Calves are born tail first which allows for the placenta to stay attached as long as possible, so that the calf will have oxygen until it is fully born and can reach the surface of the water.

• They can live more than 40yrs.

Tab. 9.3

Green Turtle