Hello marine biology students.
In this video we're going to discuss marine
birds and non cetacean marine mammals.
[Intro Music]
So seabirds are birds that nest on land, but
feed exclusively or in part on marine organisms.
Like mammals, seabirds are able to maintain
a constant body temperature.
They are homeotherms.
And they do this through metabolic means,
making them endotherms.
They have feathers coated with oil from glandular
secretions to help waterproof their body.
As opposed to marine reptiles, they have hard-shelled
eggs that provide more protection than the
leathery shells for reptiles.
Many seabirds nest in large colonies on cliffs,
isolated islands, low shrubs or trees, or
even on the ground.
Some species are monogamous 
and mate for life.
Complex behaviors include rituals such as
selecting a mate, protection of young, and
long migrations.
Penguins are the most radically adapted of
all sea birds.
They are flightless and have flipper like
wings.
They spend a great deal of time searching
for prey at sea.
Most species live in Antarctica or sub Antarctic
regions, and in this case by sub-antarctic
we mean closer to the equator, but only a
bit.
They are adapted to cold water, with a layer
of fat and trapping of air within their feathers.
In penguins, males and females to share parenting
responsibilities.
Other types of seabirds include tube noses,
such as albatrosses and petrels, pelicans,
cormorants, frigate birds, gulls, terns, and
many species of shorebirds.
There's wide variety in the feeding habits
of these seabirds, with the beak shape often
giving clues as to what the feeding habit
would be.
We see some birds feed on surface organisms,
others can dive and pursue organisms under
water, and some seabirds actually even target
other seabirds, trying to make them regurgitate
their last meal and eating the fish that they
had already eaten.
Let's talk a bit about marine mammals.
Mammals are homeotherms and endotherms, so
they keep a constant body temperature.
They get their body heat from their metabolism.
Other mammalian features include hair, although
this is reduced in some species, such as the
cetaceans, which we'll see in a moment, and
layers of blubber for insulation.
Storing excess energy in the form of adipose
tissue in the skin is a uniquely mammalian
trait.
Mammals are viviparous, with the placenta
to provide nutrients to the embryo.
A uniquely mammalian trait is that the placenta
is derived of embryonic tissue as opposed
to maternal tissue, although it is the mother's
system that provides all the nutrients necessary
for the embryo to grow and develop.
Another unique characteristic of mammals are
mammary glands, which produced milk for the
young.
Mammals have a large brain in relation to
their body size and they also have complex
behaviors.
There are four orders within the mammals which
are considered to be marine mammals and not
all of them are exclusively marine, although
many of them are.
The first are the pinnipeds, order Pinnipedia.
These are seals, sea lions, and walruses.
Next, the carnivores, in order Carnivora.
These include sea otters, the marine otter,
and polar bears.
Next, we have the sirenians, order Sirenia.
These are the dugongs and manatees and are
named after “the Sirens” in Greek legend
that would tempt sailors to the sea.
It's believed that sightings of these manatees
and dugongs inspired the original tales of
mermaids, creatures who had the body of a
woman with the tail of a fish.
And then lastly, we have the cetaceans, order
Cetacea, which include whales dolphins and
porpoises.
So, we'll start by discussing the pinnipeds.
They are predators, feeding mostly on fish,
squid, and shellfish.
Most breed on land and return to sea after
giving birth.
They prefer breeding 
near shallow water and abundant food.
They typically live in cool or cold water
due to the presence of blubber.
The exception are the monk seals, of which
there are Hawaiian and Mediterranean monk
seals, although they are endangered.
And Caribbean monk seals have not been seen
since the 1950s.
In pinnipeds, their forelimbs and hindlimbs
are adapted as flippers for swimming and there
are 35 distinct species.
Here we see sea lions and seals.
They are similar and yet distinct from each
other in that sea lions have external ears,
whereas seals do not.
Sea lions are able to rotate their legs so
that they can move somewhat on land, whereas
seals are not able to use their hind limbs
on land.
Walruses are also in this order, Pinnipedia.
Odobenus rosmarus is their binomial nomenclature.
They have an absence of external ears, both
males and females possess large tusks, but
in general adult males are slightly larger
than the females with longer and stouter tusks.
On land, walruses are capable of rotating
their hind flippers to walk on all fours as
in sea lions, although they spend most of
their time in water.
Their diet consists mainly of bivalve molluscs,
although they may occasionally feed on other
benthic invertebrates like worms, snails,
sea cucumbers, squids, and crabs.
Some will occasionally prey on fish, such
as polar cod, and they might even scavenge
on seal carcasses.
Walruses are found in the Arctic sea on both
the Pacific and Atlantic sides, but they are
entirely northern hemisphere, so a walrus
is never going to be encountering a penguin.
They typically stay in relatively shallow
water and they migrate with the pack ice.
They will sometimes aggregate in small rocky
islands and coasts during the summer, when
the pack ice is mostly melted.
The females can delay implantation of a fertilized
embryo until a time where the gestation period
will result in a desirable time to give birth.
A mature female gives birth approximately
every two years, with copulation or intercourse
and nursing of the young occurring in water.
Our next group of mammals are the carnivores,
the otters and polar bear.
Sea otters, Enhydra lutris, have very fine
dense fur coats.
This fur coat ends up trapping air within
it for insulation, which is essential because
sea otters have no blubber.
They are the smallest truly marine mammal,
with anterior feet with small retractable
claws and posterior feet which are broad and
webbed.
They have a metabolic rate higher than most
mammals of similar size, so they must consume
large quantities of food.
Adult sea otters may eat as much as 9 kilograms
or 20 pounds of food each day.
This food includes sea urchins, crabs, abalone,
clams, mussels, octopuses, and fishes.
There are three species or races of Enhydra
lutris and small differences between them.
There are the Asian sea otter, which is found
in northern Japan and Siberia, the Alaskan
sea otter and the California sea otter.
Sea otters are typically found in waters close
to shore, although the Alaskan sea otters
have a greater tendency to come to shore than
the California sea otter does.
Sea otters are important predators 
in giant kelp beds, regulating the number
of sea urchins that graze on the kelp.
They can play a similar role in seagrass meadows
as well.
They are an endangered species, brought almost
to extinction by hunters for their valuable
pelts.
Now, a much lesser known otter is the marine
otter, Lontra felina.
They spend most of their time on rocky shores,
but feed on small marine invertebrates.
They live on the Pacific coast of temperate
South America.
They are also endangered 
due to hunting and habitat loss.
The last of our marine carnivores is the polar
bear Ursus maritimus.
Polar bears are the largest land carnivore,
although technically they're marine because
they can spend the entirety of life either
at sea or on ice over the sea.
Polar bears are threatened by decreasing ice
pack in the Arctic sea.
They have a thick fur coat that appears white
in coloration, but the hair on it is actually
translucent.
Polar bears have smaller ears and longer necks
than other bears.
These are adaptations to low arctic temperatures.
In polar bears, there is sexual dimorphism
and adult males are larger than adult females.
Adult polar bears need an average of two kilograms
of fat per day in order to maintain their
body weight.
Their diet includes mostly ringed and bearded
seals, but they are also known to feed on
other seal species, walrus, narwhals, beluga
whales, whale carcasses, fishes, birds, eggs,
berries, and kelp.
They have a gestation period of about eight
months including about a four month delayed
implantation in order for the cubs to be born
in the oncoming spring.
Mother polar bears provide milk for their
cubs for about two years.
Our next group of marine mammals are the Sirenians,
the dugongs and manatees.
Of manatees, there are three species, Trichechus
manatus, which is the West Indian manatee,
often found entering fresh waters along the
coasts of Florida and the West Indies.
Trichechus senegalensis which is the West
African manatee, and Trichechus inunguis,
the Amazonian manatee, which stays primarily
in freshwater.
Related to the manatees are dugongs, which
are found in East Asia to western Pacific
Islands.
Here we see an illustration of an adult manatee.
As we saw in that illustration, manatees have
front flippers but no rear limbs and they
have a wide paddle like horizontal tail.
They're primarily herbivores, consuming seagrasses
and freshwater vegetation.
In fact, manatees consume from four to nine
percent of their body weight in wet vegetation
daily.
That can be in the order of tens to even hundreds
of pounds for an average adult manatee.
Manatees may reach around four and a half
meters in length and 600 kilograms in weight.
All four species mentioned are endangered
or threatened, especially the dugong.
One of the threats to manatees is that they
have a very slow reproduction rate, which
it takes about five years to mature, and they
give birth to a single calf every two to five
years after a gestation period of about a
year.
And that concludes our discussion on marine
birds and non-cetacean marine mammals.
Now, before our next video I'd like you to
think about “Is there anyone who doesn't
think about dolphins and whales when they
hear about marine biology?”
Probably not, and we'll talk about that in
our next video.
