Marine Reptile Characteristics
 Land vertebrates are called tetrapods because they
have four limbs designed for locomotion on land. They
have lungs and breathe air, and, except for amphibians,
they have reproductive systems that are not tied to
water.
 Marine reptiles have scales to minimize water loss,
their eggs have a leathery shell to prevent them from
drying out, and they are poikilotherms and
ectotherms. There are about 7000 species of reptiles.
Marine Reptile Characteristics
 Poikilotherms are organisms that have a body
temperature that varies with that of the environment.
Ectotherms are organisms that lose metabolic heat to
the environment without it affecting their body
temperatures. Organisms that are poikilotherms and
ectotherms commonly are called “cold-blooded.”
Sea Turtles
 Sea turtles have an armor-like shell or carapace that is
fused to their backbone. Unlike land turtles, sea
turtles cannot retract their legs into their shells. Their
legs are modified into flippers for swimming. There
are only seven species of sea turtles in the world: the
green turtles, the hawksbill turtle, the leatherback, the
Ridleys, and the loggerhead.
Sea Turtle Reproduction
 All female sea turtles return to land to lay their eggs.
Many migrate very long distances (up to 1360 miles) to
return to the beach where they were born. They
probably do not breed every year. They lay 100 to 200
eggs in a nest that they excavate in soft sand. The eggs
hatch after 2 or so months and the baby sea turtles
immediately crawl to the water and swim away. Not
much is known about what happens to the babies as
they mature into adults. Mortality is very high.
Sea Turtle Endangerment
 Sea turtle beaches have been developed as beaches,
condos, and hotels, and the artificial lights that come
with people are detrimental to both the females and
the babies. Dogs, ghost crabs, raccoons, wild pigs, and
people eat sea turtle eggs. The babies are easy prey for
predators, both on land and in the water. Adult sea
turtles are accidentally caught in fishing nets and
drown. Ocean predators, including people, also eat
them.
Marine Snakes
 There are about 55 species of sea snakes and they are
found in the tropical Indian and Pacific oceans. Their
tails are paddle-shaped for swimming. They are
completely marine; they mate in the ocean and give
birth to live young. They are carnivores that are closely
related to cobras, and they are venomous.
Marine Iguanas
 Marine iguanas only occur on the Galapagos Islands, in
the equatorial Pacific just off the coast of South
America. These unique reptiles spend part of their
time on land, resting, mating, and sunbathing. They
live on rocky coastlines and feed in the coastal ocean,
eating sea weeds.
 BBC Video
Salt Water Crocs
 Salt-water crocodiles live in mangrove swamps and
estuaries in the eastern Indian Ocean, Australia, and
some of the western Pacific islands. They are mostly
coastal. They are very aggressive and will attack
people.
 BBC Video
 Saltwater Croc vs. Great White
Marine Birds
 Birds are homeotherms and endotherms, which allows
them to live in a wide variety of habitats. Birds can fly,
and their bodies are covered with waterproof feathers
that also help insulate them. Birds have hollow, light
bones that help them fly. The shells that cover bird
eggs are harder and more resistant to water loss than
are reptile eggs.
 Homeotherms are organisms able to keep their body
temperature more or less constant regardless of the
temperature of the environment. Endotherms are
organisms that retain some metabolic heat, which
raises their body temperature.
Sea Bird Characteristics
 Seabirds are birds that spend a significant part of their
lives at sea and feed on marine organisms. Seabirds
nest on land. Most breed in large colonies, mate as
lifelong pairs, and take care of their young.
Seabirds are related to several different groups of land
birds, and they differ from each other with respect to
their flying skills, feeding mechanisms, and ability to
live away from land. Most are predators on fish, squid,
and bottom invertebrates. They are found from pole to
pole.
Types of Sea Birds
 The five types of seabirds are the penguins, the
tubenoses, the pelicans (and related birds), the gulls
(and related birds), and the shore birds.
PENGUINS!
 Penguins are flightless and their wings are modified to
be flippers that help them “fly” underwater. They have
dense bones, which reduce buoyancy and help them
remain underwater. Penguins are very good swimmers,
but are very clumsy on land. They generally are
adapted for cold weather (both on land and in the
water) and prey on fishes. Penguins are found only in
the Southern Hemisphere or at the equator.
A penguin Dilemma
 2 volunteers are needed to voice the two penguins in
the following video
 A Penguin Dilemma
 Serious BBC Video
Tubenose Birds
 The tubenoses are a group of seabirds with tube-like
nostrils and heavy beaks that usually curve at the beak.
They have salt glands that help them get rid of excess
salt. The salt glands empty into the nostrils, and as a
result these birds often look like they have runny
noses. Tubenoses include the albatross, the
shearwaters, and the petrels. They are skillful and
strong flyers and fishers that spend months at sea
without landing. Their flights may take them
thousands of miles at a stretch. They only return to
land for reproduction.
Examples of Tubenoses
 Albatross Mating Dance
 Shearwater Behavior
Mammal Characteristics
 Marine mammals are in the Class Mammalia, and, like
birds, are endotherms and homeotherms. They have
hair, give birth to live young, and nurse their young.
Pregnant females nourish their unborn babies through
a placenta, a membrane that connects the embryo to
the womb. Like other mammals, marine mammals
have large brains relative to their body sizes.
Additionally, like other mammals but unlike fishes,
they breathe air.
Groups of Marine Mammals
 The four groups of marine mammals are the 1) seals, sea
lions, and walruses; 2) sea otters and polar bears; 3)
manatees and dugongs, and 4) whales, dolphins, and
porpoises. Seals, sea lions, and walruses are in the Order
Pinnipedia, which are closely related to the Order
Carnivora, with its cats, dogs, bears, and their kin. Sea
otters and polar bears are in the Order Carnivora. Manatees
and dugongs are in the Order Sirenia and are closely
related to elephants and their relatives. Whales, dolphins,
and porpoises are in the Order Cetacea and are distantly
related to animals such as cattle, sheep, pigs, and hippos.
Pinnipedia
 The Order Pinnipedia includes the seals, sea lions, and
walruses. They are streamlined and have paddleshaped flippers for swimming. They rest and breed on
land. Pinnipeds are predators that eat mostly fishes
and squid and mostly live in cold water. They have a
thick layer of fat called blubber just under their skin
that helps keep them warm, serves as a food reserve,
and aids in buoyancy. Pinnipeds also have bristly, thick
hair to help keep them warm.
Seals
 Seals are pinnipeds with rear flippers that do not move
forward well and which do not rotate backwards—this
limits their mobility while on land. In the sea, they
swim with powerful strokes of their rear flippers. On
land, they pull themselves forward using their front
flippers. There are 19 species of seals.
Conservation
 Seals have been hunted for their blubber, skin, and
meat for centuries and longer. Overhunting in the
20th century led to precipitous declines in some seal
populations—many species are endangered or
threatened. The Marine Mammal Protection Act of
1972 protects all marine mammals, including seals,
and restricts the sale of all products in the United
States.
Sea Lions
 Sea lions are pinnipeds that are similar to seals in
terms of their distribution and life styles. Sea lions
include the fur seals (which aren’t really seals!), and
there are 14 species. They have the following
characteristics: they have external ears, they can rotate
their rear flippers forward and backwards (which
means they can move around on all four limbs on
land), and their front flippers can rotate forward and
backwards (allowing them to prop themselves up on
land). Sea lions exhibit sexual dimorphism—the males
are much larger than the females.
Sea Lion Conservation
 Sea lions have been hunted for their
blubber, skin, and meat for centuries
and longer. Overhunting in the 20th
century led to precipitous declines in
some sea lion populations—many
species are endangered or
threatened. The Marine Mammal
Protection Act of 1972 protects all
marine mammals, including sea
lions, and restricts the sale of all
products in the United States.
Walruses
 The walrus is a large pinniped with a pair of large tusks
that protrude downwards from the mouth and that are
used for defense. Unlike the other Pinnipeds, it feeds
mostly on bottom-dwelling marine invertebrates.
Sea Otters
 Sea otters are the smallest marine mammals and,
unlike other marine mammals, lack a layer of blubber.
Instead, sea otters have dense fur that traps air as
insulation. Sea otters spend all of their time in the
water; they live, breed, feed, etc. there. They feed on
many different types of invertebrates, including sea
urchins, abalone, mussels, and crabs.
Sea Otter Conservation
 Sea otters were hunted to near extinction because of
their thick, soft fur. International protection in 1911
helped re-establish the severely decimated
populations. However, recently, populations are again
in decline, due most likely to changes in their
ecosystem due to pollution and overfishing. Sea otters
are a threatened species.
Polar Bears
 Polar bears are semi-aquatic marine mammals that
spend a lot of time on drifting ice in the Arctic. They
are carnivores, feeding mostly on seals. Their
populations have been declining due to habitat loss—
warmer climates near the poles is melting the ice upon
which they depend.
Sirenia
 The Order Sirenia includes the manatees and the
dugong. They are the only vegetarians among the
marine mammals and feed on sea grasses and
submerged vegetation. They have a pair of front
flippers but instead of rear flippers, they have a
paddle-shaped horizontal tail.
Manatees live in the Atlantic Ocean in tropical and
subtropical waters. The dugong lives on the east coast
of Africa to some of the Pacific islands
Sirenia
 People hunted sirenians for food, skin, and their oil-
rich blubber. Because they reproduce slowly and
because their habitat (the coastal ocean) has been
altered and destroyed by human development,
sirenians are in danger of extinction. Several species
are already extinct; the four remaining species are all
endangered.
Cetaceans (whales)
 The largest group of marine mammals is the Order
Cetacea, which includes the whales, dolphins, and
porpoise. Of all the marine mammals, the cetaceans
are most fully adapted to an aquatic life style. They
spend their entire lives in the water, have very streamlined bodies, and superficially resemble fish.
Why do these mammals
look like fish?
 Convergent evolution describes different, usually
“very” un-related species that have similar structures
because they have similar life styles. Cetaceans are
mammals; fish are fish—definitely not closely related.
They superficially resemble one another—streamlined bodies, pectoral fins/flippers, dorsal fins, etc.—
because their bodies are well adapted to swimming
and life in the ocean.
Cetacean Anatomy
 Cetaceans have a pair of front flippers. The muscular
tail ends in a pair of fin-like, horizontal flukes. There
is a dorsal fin, towards the end of the body. The
nostrils are on top of the head and form a single or
double holed opening called the blowhole. The
blowhole is using for both inhaling and exhaling when
the animal is at the surface.
Groups of Cetaceans
 The two groups are the toothless, filter-feeding whales
and the toothed, carnivorous whales (which includes
the dolphins and porpoises).
Baleen Whales
 The toothless whales are also known as the baleen
whales. There are 13 species of baleen whales, and
they are among the largest animals that have ever lived
on earth. They were once common in the oceans, but
hunting for their meat and blubber has decimated
many of their populations. Baleen whales have two
blowholes (compared to the toothed whales, which
only have one blowhole).
Baleen Whales
 The baleen whales have rows of flexible, fibrous plates
called baleen that hang from their upper jaws. The
inner edge of each baleen plate is made up of hair-like
bristles that form a dense mat on the roof of the
mouth. The baleen plates are made up of keratin, the
same material that makes up our fingernails and hair.
The baleen whales filter feed by gulping mouthfuls of
water and then squeezing the water out through the
bristles. Any food that is left behind sticks to the
bristles and the whale licks it off with is tongue and
then swallows it.
Toothed Whales
 There are approximately 80 species of toothed whales.
Their teeth are adapted to catch fish, squid, and other
prey—they don’t chew their prey; they swallow it
whole. The toothed whales have a single blowhole
opening, unlike the baleen whales, which have two
blowholes. The toothed whales include the dolphins,
porpoises, and the non-baleen whales.
Adaptations for diving
 A feature that helps the cetaceans swim and dive more effectively
is having the blowhole on top of the head, which helps them to
inhale and exhale very efficiently and quickly at the surface.
To help them remain underwater for long periods of time
without running out of oxygen for respiration, marine mammals
breathe very efficiently and are able to put large amounts of
oxygen into their bloodstreams. They have more blood cells that
carry oxygen and have more muscle cells that store oxygen.
Marine mammals are able to reduce their oxygen consumption
while diving. They typically reduce their metabolism and heart
rates and reduce blood flow to their extremities (while
maintaining blood flow to essential organs like the brain).
Echolocation
 Echolocation is a sensory system based on hearing
that most toothed whales (dolphins and porpoises)
and some pinnipeds and baleen whales use to find
prey and to orient to their surrounding.
Echolocation
 Cetaceans echolocate by emitting a series of clicks,
squeaks, and whistles as air is forced through passages in
the head while the blowhole is closed. These noises are
focused and directed outward by the melon, a fatty
structure on the forehead (the melon gives toothed whales
their characteristic rounded foreheads). The echo of the
noises (which bounce off objects around the cetacean) is
received primarily by the lower jaw, which transmits the
echoes to the two very sensitive inner ears. The echoes are
interpreted by the brain, which forms a mental “picture” of
the surroundings.
Communication
 Vocalizations are the sounds that animals make to
communicate with each other (echolocation is NOT a
type of vocalization). Sea lions and fur seals bark and
whimper; seals grunt, whistle, and chirp. Cetaceans
use low-frequency sounds such as grunts, barks,
squeaks, chirps, and even “moos” to communicate
with each other. Perhaps the most well known
cetacean vocalization is the song of the humpback
whale, which may last for 1/2 hour or longer.
Communication
 Marine mammals vocalize for many reasons.
Pinnipeds vocalizations are especially important in
maintaining territories and in recognition between
mother and pup. Cetaceans vocalize during social and
sexual encounters. Vocalization allows individuals to
identify one another and communicate information
about food sources, predators, and alarm. Male
humpback whales “sing” to attract females and to
advertise their readiness to mate.