Marine Mammals
Anyone who has ever
witnessed the early morning feeding at sea on a calm day has also seen the
superiority of the warm-blooded physiology over the cold-blooded way of life.
While the sardines, anchovies and other schooling fry are chased around by
faster fish, sea birds, like dive bombers take their share of the feast.
Marine Mammals
But even the predators,
bonitos and bass, are easy prey for the second circle of divers, the dolphins.
Sharks roam farther away to scoop up remains but don't venture in too close
because of the dolphins...from the air and from below, the fish are no match
for the warm-blooded birds and mammals
Marine Mammals
The warmer the blood the
higher the efficiency of the living thermodynamic machine. Birds and sea
mammals have acquired their power while evolving out of the oceans; their
physiology has coped with such problems as keeping their central temperature
constant or holding their breath during deep, prolonged dives.
Marine Mammals
The heat exchanging
system present in their flukes, fins, wings, or webbed feet is ingenious. Some
powerful fish, tuna, have also developed this system but this is only to keep
their muscles a few degrees warmer than the surrounding water while the marine
mammal and bird must keep their temperature constant whatever outside polar or
tropic temperatures may be.
Marine Mammals
The warm blooded animals
have no feeding problem. They have to eat a lot more compared to the same size
fish. Colonies of millions of seabirds pile up on islands, feeding twice a day
in less than half an hour and gorging themselves to a point of hardly being
able to fly.
Marine Mammals
In the sea, whales fill
up on crustaceans in a few daily dives, pilot whales dive deep and fill up on
squid or cuttlefish, and porpoises and dolphins and sea lions spend less than
an hour a day to quench their appetite.
Marine Mammals
Having no difficulty in
finding food, these warm blooded animals have lots of leisure time, explaining
why they play, travel for no apparent reason and some, like the sea elephant,
are so fat that they can afford to fast for several months when they come
ashore to breed.
Marine Mammals
Leisure time has been
used by the sea mammals that have a large brain to develop wit, intelligence,
communication, and even some unnecessary feelings such as faithfulness,
tenderness, and friendship
Marine Mammals
This warm-blooded
superiority has some severe limitations. Because of the high combustion of the
excess food, excess oxygen is also needed (from the air) and this limits the
duration of their dives. Some birds and cetaceans have modified their organs to
perform dives of extended duration.
Marine mammals
ancestral ties of mammals
terrestrial reptiles
diverged about 200 mya
(225-190 mya) Formation of present
Atlantic Ocean
Common mammalian characteristics
hair - mammary glands
few young, lots of care given
large brain - internal fertilization
Some on land, some in sea
viviparous birth- some
on land, some in sea
Endothermic - homeothermy
breathe air
derived from terrestrial tetrapod
ancestors who drank freshwater
Three separate groups independently gave
rise to aquatic descendents during
Eocene (65-50 mya)
Order Carnivora polar
bear, sea otters
Order Pinnipedia seals,
sea lions
Order Sirenia manatees,
dugong
Order Cetacea whales, porpoises, dolphins present
Species diverged about 15 mya
convergences
streamlining of body shape
limb modifications flippers,
disappearance of hind pair in some groups
thermal regulation
large size, thick skin, blubber, fur,
reduced peripheral circulation,
higher metabolic rate
modified respiratory system
diving adaptations
osmotic adaptations
impervious skin,
efficient kidney,
dont drink much seawater
echolocation in some
distribution more
significant ecologic role in polar seas
More species Polar
and cold temperate 66 sp.
Tropics and warm temperate 36-41
sp.
All seas 9
sp.
Fewer competitors
More individuals
Some species are circumglobal
Baleen whales, some toothed whales
Many species are confined to regions of one ocean seals and sea lions, manatees and dugong,
otters, polar bear, walrus
Marine Mammals
The largest group of
marine mammals are the Cetaceans. There are over 90 species. These have the
most complex transition to marine life
Marine Mammals
Cetaceans are shaped like
fish but are not fish. There are 90 different species . They are all marine
except a few freshwater dolphins. They are all totally dependent on support
afforded by the water and can't survive on land. The whales, dolphins and porpoises
are born live, suckle their young, and breath air.
Order
Cetacea Suborder Archaeoceti (Zeuglodontia) All now extinct
intermediate between terrestrial
ancestors and present day whales and porpoises
earliest fossils found in freshwater and
estuarine environments of the eastern Tethys Sea
Ancestral origins may have been from the
Ungulates, either from Artiodactyls
(cows, pigs, camels, hippos), Perissodactyls (horses, tapirs, rhinos) ,
and later, the Mesonychians (freshwater alligator-like mammals)
Appeared
in late Eocene (51.4 mya, 54-38 mya) and persisted to Miocene (26-7 mya) Transition from freshwater drinking to
seawater drinking in about 2 my Gave birth in tropics, but adults had
world-wide distribution heterodont teeth
Suborder Odontoceti Late
Oligocene (35 mya 38-26 mya)
Some teeth present during life, single
nostril (blowhole)
Asymmetric skull in most sp.
Good vision and hearing produce variety of sounds, clicks and whistles
swallow food whole (mostly fishes and
squids)
Usually produce single calves after a
9-15 month gestation
usually nurse for 6 or more months
most species are very social
Ziphiidae beaked whales 18 sp. Delphinidae dolphins
34 sp. Phocaenidae porpoises 6 sp. Platanistidae river dolphins 4 sp. Monodontidae beluga and narwhal Physeteridae sperm
whales 3 sp. A 1993 study of mitochondrial
DNA places this family with the suborder Mysticeti
Physeter feed
on squid at depths down to 1134 m
Remain submerged for up to an hour,
though the average is 30 min.
Source of spermaceti (sperm oil)
Source of ambergris
Grow to 38,000 kg (42 tons)
Males maintain harems of 15-20 females
Females remain in tropics, but males
migrate to high latitudes in summer
tuna fishing with purse nets
inadvertently trap and may kill dolphins and porpoises
Dolphin and porpoise pods are followed by
tuna schools because the mammals are better able to locate schools of the
fishes they both prey upon
Pods of 50 to several thousand in number
(mean is several hundred)
Fishermen use mammal pods to locate tuna
Most commonly caught species are Pacific
spotted porpoise (Stenella attenuata)
And spinner porpoise (Stenella
longirostris) And occasionally the common dolphin (Delphinus delphis)
Mammal pod is corralled by small fast
boats launched from the mother ship
Main vessel then surrounds pod and school
of tuna with a purse net ( up to 2000 m long and 200 m deep) which is deep
enough to reach into the thermocline
The net is then
pursed
at the bottom and slowly hauled in to concentrate the catch
In 1971, the estimated kill was 310,000
porpoises (3.8/ ton of tuna) ..Since
mid 1970s, U.S. fishermen are required to use Medina panel to allow mammals to
escape
Suborder
Mysticeti late
Oligocene (35 mya 38-26 mya)
Baleen or whalebone whales vestigial teeth
adult has baleen in mouth
Horny, elastic, nail-like material
derived from skin tissue
filters small sized food from water
two nostrils (blowholes)
skull is symmetrical
Mostly feed on zooplankton (one sp. feeds
on benthic amphipods)
Generally mate and give birth in tropics
or subtropics during winter and then move to high latitudes to feed during the
summer. The northern and southern hemisphere populations are separate.
one
(rarely two) calf every 2 years per female after a gestation of 11-12 months
Balaenidae right whales
Very fine filter
consume even copepods
Feed mostly by
skimming,
often in echelon
Prized
by whalers
Balaenopteridae
rorquals and humback
Moderately coarse filter, eat mostly euphausiids (krill)
Feed mostly by
gulping,
may use bubble ring to corral prey first
Include largest animal that ever lived,
the blue whale ---Up
to 30.5 m long, 150 tons [25 ft. long and 2 tons at birth ] Estimated to need 3 million
calorie intake/day in summer
3
tons of krill/day
Eschrichtiidae gray whale Coarse filter,
Eat mostly benthic amphipods Extinct in North Atlantic since late
1600s or early 1700s
Now
only along Pacific coast of North America
Senses in marine mammals receive information about the environment
Vision varies from poor in river dolphins
and manatees to very good in most odontocetes
Small odontocetes with a short snout or
pointed beak have binocular vison ..so
do right whales
Asymmetric eyeball allows clear vision in
both water and air
Taste
little
known, but taste buds are present on the tongue of some cetaceans
Touch area
of back around blowhole is very sensitive to touch
Touching is common in courting cetacean
adults and mothering of young
Rudimentary hairs on chin or rostrum
Sound well
developed and common in most
(Humans hear 16 to 20000 hz)
Sound velocity in water is some 4.5 times
faster than it is in air
purposes: communication, echolocation,
stun prey?
Sounds produced and detected
Walrus bell-like sound
Otariid seals clicks
(northern fur seal), trains of pulses (Weddell seal) Phocid seals musical chirrups and trills (Antarctic phocids), warbles
(bearded seal)
Manatees
generally silent, but do emit squeaks and chirps
Cows and calves maintain vocal contact
Dugong
Baleen whales generally produce low frequency sounds and their function
is not well known
more sounds when more active, often
appear to be contact calls
Rorqual whales 20-200 hz
Usually travel some 80 km, but can travel
up to 800 km in the SOFAR or deep ocean channel
Minke
and gray whales produce clicks
Humpback whale..40-5000 hz
Songs produced in tropics in winter,
usually sung by a single isolated male resting in 20-40 m of water over a
smooth bottom
May last 6-35 minutes and be heard 30 km
away
Comparable to bird songs (and if speeded
up, sound like them)
About 20 syllables or notes grouped in
phrases
Groups of similar phrases are called
themes
About 6 basic themes in population each
year
All males in an ocean basin sing roughly
the same song in each year, but all modify the song during the year
Bowhead whales also produce songs, in the
Arctic during the spring
Odontocetes generally produce a
variety of high frequency sounds
Tonal whistles usually used for social
messages
Distinctly pulsed clicks used for
echolocation50-200 microsec pulse, followed by 50-150 millisec gap, adjusted
for particular situation
Also used for communication in sperm and
killer whales
Less distinctly pulsed cries, grunts and
barks
Signature calls individually unique calls, most are
whistles
Delphinidae whistles and squeals 1000-20000 hz
Monodontidae whistles and pulses
Ziphiidae whistles
and clicks
Phocaenidae,
Platanistidae, and Physteridae produce only clicks
Sound production No
vocal cords in cetaceans, so use blowhole area or perhaps muscular pharynx
Small odontocetes usually bounce the
sound waves off the front of the scooped out skull behind the bulbous melon
Sound focused by fatty lens shaped melon
at boundary of the skin and water
Sperm
whale may produce clicks at museau du singe inside skin of front of head (hard,
taut internal lips)
Sound reception Seals external
auditory meatus and ear drum Cetaceans Inner
ear is more isolated from skull by fat and connective tissue
Allows greater limitation of sound
reception to a single direction
Sound
appears to travel to inner ear along the lower jaw bone, though some say the
outer ear passage may be involved in low frequency (But others say this is doubtful)
Echolocation Terrestrial animals bats, shrews, flying lemurs, fat dormouse,
golden hamster, oil bird
Marine mammals only
definite in odontocetes
A series of clicks Low frequency distant objects--High frequency-close objects
Narrow range of frequencies give more
precise image
Duration 40
clicks/sec., 9 pulses/click
Detect squid 400 m away
Feeding
For most marine mammals - whales,
dolphins and Dugongs - their entire life is in the water. Life in a marine
environment has shaped the biology of these mammals, especially feeding
mechanisms. The prey taken ranges from microscopic krill to marine mammals such
as seals and even whales.
The large whales - Blue, Sei and Right -
filtered feed from the water using baleen plates hanging from the roof of their
mouths. They feed on schooling fish and krill, the smallest prey.
Jaw and skull modifications, especially
within the whales, dolphins and Dugongs are the most extreme examples of this
adaptation to life in the water.
Adaptations include:
·
elongated jaws;
·
nostril moved to the top of the head; and
·
very few or no teeth.
Where teeth are present, they are a
conical shaped, designed to grab prey, not chew it. Some groups such as the
beaked whales that feed on squid and octopus have, over time lost all
functional teeth and now only the males retain a pair of front teeth, for
display.
Feeding strategies of the seals resemble
those of terrestrial carnivores. They largely feed on fish and possess the full
set of teeth needed by a carnivore to catch and kill other vertebrates.
Dugongs
are the only true vegetarian marine mammals. Their skull shape and teeth
reflect the needs of an animal that only eats seagrasses. The mouth is angled
so it is horizontal to the seabed when feeding. The functional teeth remaining
are used to grind up the plants.
Reproduction
Reproductive strategies are the most
difficult for the animals that are totally marine such as whales, dolphins and
the Dugong. For very social animals that live in groups such as dolphins, and
the Dugong, finding a mate is no problem. For others, such as loners of the
marine mammal world - the large baleen whales - success depends on making sure you
are in a certain part of the ocean at the same time each year.
Giving birth to a mammal while underwater
presents difficulties. Newborn whales come out tail first to prevent drowning.
When the whole body is free, they are gently raised to the surface for their
first breath. Most baleen whales wean their young after 6 - 12 months. Some
toothed whales continue to feed the offspring for years.
This prolonged nursing means a lower fat
content to the milk, around 10 - 30 percent. In whale and dolphin society there
is a strong bond between mother and young and amongst some species there is a
group responsibility for the care of the young.
Seals
return to land on a regular basis to mate and give birth. They congregate in
colonies, sometimes in the thousands, and all the pregnant females give birth
within days of each other. This situation does have its disadvantages.
Like
all crowded areas, the very young are vulnerable. Adult male seals have only
one reason for being there, to mate with as many females as possible. Like many
mammal species, there is no duty of care by the male of the species for the
young.
Migration
In Australian waters true migration - the
process of moving by a set route between one habitat and another - is only
really carried out by two species, the Humpback Whale Megaptera novaeangliae
and the Southern Right Whale Eubalaena australis. Each year populations
of both these species make a return journey from the colder feeding grounds of
Antarctica to the warmer calving grounds.
The Humpback migrates to the tropics and
the Southern Right Whale to the temperate waters of southern Australia.
Humpbacks travel thousands of kilometres
each way, rivalling the journeys of other animals, such as some bird species,
to giving birth and mate. This two to three month migration is even more
remarkable when you consider that the whales do not eat until they return to
the cooler temperate waters of southern Australia.
The
northern journey begins in June. The whales travel, usually in groups of three
or four, in some cases within a kilometre or two of the coast, up the east and
west side of Australia to the warmer tropical waters off north Queensland and
northern Western Australia
Births
The birth of a Humpback at sea has never
been observed but we know it occurs during the migration as new born calves are
seen returning with adults in September/October (spring). The interval between
births is generally two to three years so not every whale makes the journey
each year.
Southern Right Whales' winter migration
to warmer waters is a much shorter journey. The reasons however are the same.
Calves need to be born into the warmer waters of southern Australia. These
whales, often solitary, used this opportunity to socialise and mate.
Thermoregulation
Marine
mammals are well adapted to life in the water. Pinnipeds, sea otters and polar
bears are amphibious (able to operate on land and in the water).
Sirenians and cetaceans spend all their time in the water.
Keeping
a constant body temperature is the most serious challenge facing warm-blooded
mammals in an aquatic (watery) environment.
Most
marine mammals have an insulating layer of fat called blubber that keeps
their bodies warm and buoyant. Blubber is rich in lipids (fats or fatty
material that cannot dissolve in water) and stores large amounts of energy. Sea
otters keep their body temperature constant with a dense (thick) layer of fur
that traps a layer of air next to the skin so that their skin never gets wet.
Polar
bears and some pinnipeds have a thick layer of fur and a blubber layer.
Another way marine mammals control their
body temperature is by controlling their blood flow in a process called vasodilation.
During vasodilation, blood flow increases to and from peripheral vessels near
the surface of the flippers, flukes, and fins.
Countercurrent heat exchange
allows cold blood returning to the body core to be warmed up by exhanging heat
with arteries going to the periphery (flukes and flippers).
Diving
All marine mammals have special traits
that allow them to dive deep and stay underwater for a long time. At some
point, all must return to the surface to breathe. Whales and dolphins breathe
through single or paired blowholes on the dorsal (back) surface of their
head.
At the surface, they quickly inhale and
relax the muscular flap to close it so they can dive
is
directed away from tissues that can handle low oxygen levels and toward the
heart and brain where oxygen is needed most. During diving, the heartbeat slows
down. Some champion divers are the sperm whales. They can dive more than 1600
meters (over a mile) and may remain submerged for an hour or more!
Another
champion diver, the elephant seal can dive more than 1500 meters (4920 feet)
and stay under for two hours. Bottlenose dolphins can dive to depths of 540
meters (1770 feet) and remain underwater for 8-10 minutes.
Camouflage
To
blend into their environment, some marine mammals have countershading (their
top side is darker that their underneath surfaces). This coloration, typical of
many marine mammals, provides camouflage. The result is that predators
or prey do not see a contrast between the animal and the environment because
the top blends in with dark depths when viewed from above and
the
light belly blends in with the sunlit surface when seen from below. To the
right is a picture of an hourglass dolphin illustrating the general pattern of
dark upper dorsal coloration and light ventral (belly) coloration seen in many
marine animals
Another
example of camouflage is the coloring of the polar bear. The polar bear is
white to blend in with its snowy environment. When sneaking up on prey, the
polar bear will cover its black nose with its paw to blend in perfectly with
its surroundings.
Sensory
Systems
Pinnipeds
have large eyes for seeing in the low light conditions often found underwater.
In cetaceans, the eyes are located on the sides of the head, but focus forward.
Both the pinniped's and cetacean's eyes are adapted to see well underwater. As
a result, their in-air vision suffers.
Manatees
have small eyes and fair to poor eyesight. They seem to be farsighted and rely
on touch to identify objects close up.
Pinnipeds
have small olfactory (sense of smell) lobes, and evidence shows that
smell is important when interacting with other pinnipeds. Toothed whales do not
have a sense of smell, but baleen whales do have some olfactory nerves.
Cetaceans have taste buds at the base of their tongue, and the common dolphin
and the bottlenose dolphin are able to distinguish (tell apart) certain smells.
Manatees
have a good sense of smell and are often selective in their food choices.
Sirenians have many more taste buds than their cetacean cousins, and this may
contribute to their choices of food. Polar bears have an acute sense of smell,
and it is the most important sense for detecting prey on land. A polar bear can
smell a seal more than 20 miles away!
Mammals -Migration
& Distribution
Marine
mammals are widely distributed throughout the ocean. Some migrate and inhabit
many different waters while others confine themselves to one small area.
Migration is a regular journey between one region and another, usually
associated with seasonal changes or breeding and feeding cycles.
Polar
bears are found throughout the Arctic and the majority of them are found near
land masses at the edge of the polar basin. Polar bears travel over the whole
year within individual home ranges. Home range size depends on access to food,
mates and dens. They also prefer to travel on sea ice; therefore, their ranges
are limited by the amount of sea ice that forms in the winter.
Sea
otters are found along the Pacific Coast of the United States, Canada and
Alaska.
Pinnipeds
and cetaceans make long-distance seasonal migrations to rookeries (breeding
grounds) or warm-water birthing grounds. Reproduction and migration are often
timed with seasonal changes in the availability of food for the adults and
young. Many arctic pinnipeds migrate with the movement of food, but also with
the seasonal movement of the ice pack.
All
living sirenians are found in warm tropical and subtropical waters. They
migrate into warmer waters during the colder months of the year when the water
temperature drops below about 68 degrees F (20 degrees C). Manatees are found
in the warm waters of the West Indies, Florida peninsula and the Amazon Basin.
Dugongs are found in the Indian and western Pacific Oceans, northern Australia
and the Persian Gulf
Gray
Whales are baleen (filter-feeding) whales which are seen regularly along the
California Coast each year during their migration. Like most of the larger baleen whales, they
migrate each summer to cold, productive, Arctic waters to feed, returning to
protected Mexican lagoons each winter for breeding and calving. Pregnant
females lead the way on the South-bound journey, anxious to get to the
protected lagoon and give birth.
The
calf must be born in warm water as it is missing a thick layer of blubber to
protect it from the cold. Females with calves lag behind on the northward
migration, following the shoreline closely to avoid predators. Whales travel
southbound from December through February, northbound March through May. The
whales are recognized by having a low, heart-shaped blow, their mottled grey
color, and lack of a dorsal fin. A dorsal ridge with several bumps goes down
the center of the back
Marine Mammals
From the 4 ft. harbour
porpoise to the 110ft blue whale these mammals have no need to come on to land.
They have a pair of front flippers, but the rear limbs have disappeared and
though there are rear limbs present in the embryo, they are small useless bones
in the adult.
Marine Mammals
There is a dorsal fin and
the tail ends in a pair of fin like horizontal flukes. Blubber provides
insulation and buoyancy and body hair is almost absent. The nostrils form a
single or double opening called a blow hole on the head
Marine Mammals
There are two
sub-orders...Odontoceti (toothed whales) equipped with peg shaped, spade like
teeth for grasping food, using biosonar or echolocation to locate prey at great
depths (sperm whale) and include toothed whales, dolphins, porpoises and killer
whales.
Marine Mammals
The second sub-order is
Mysticeti (mustache G) or toothless baleen whales which scoop up minute
plankton and small drifting fish with overlapping flaps of baleen (made of
similar material as your hair and nails. They feed by taking in a big mouthful
of water, squeezing it through the bristles and licking the food left behind.
Marine Mammals
Included are the blue
whale and divide into three families; rorqual whales...blue, humpback, fin,
sei, Byrds and minke which feed on dense swarms of krill, 2. Right whales inc.
black, Greenland, pygmy which feed on swarms of Copepods and the 3. gray whale
which feed on worms, small crustaceans and other bottom organisms by sucking up
sediments and filtering its food from the mud.
Marine Mammals
Pinnipeds, seals, sea
lions and walruses while they need to come ashore to breed, they go to sea only
to feed. They evolved from early forms of terrestrial
carnivores/cats,dogs,bears and they are all predators. They also have blubber
which acts as insulation, food reserve, and buoyancy.
Marine Mammals
There are 19 species of seals, distinguished by having rear
flippers that cannot move forward. On the land they pull themselves forward
with their front flippers. Elephant seals are the largest with males reaching
up to 20' in length. Monk seals live in warm regions, the exception to the
relatively cooler regions where seals inhabit.
Marine Mammals
Sea lions or eared seals
are similar to seals except they have external ears and can move their rear
flippers forward so they can use all 4 limbs to walk or run on land. The head
of the sea lions look doglike while the seals look more like a cat. There are 5
species of sea lions and 9 related fur seals.
Marine Mammals
Walrus is a large
pinniped with a pair of distinctive tusks protruding down from the mouth. It
feeds mostly on invertebrates, clams but there is no evidence that the tusks
are used to dig up the clams and they travel along the bottom sucking up their
food, with their stiff whiskers acting as feelers.
Marine Mammals
Sea otters, the member of
Carnivora, the smallest of the marine mammals. They lack blubber and their fur
traps air there to act as a layer of insulation.
Marine Mammals
Sirenia- dugongs and
manatees, descendants from elephants, sluggish, with forearms modified as
flippers and no hind limbs, may have been the source of the mermaid legend,
thus the name Sirenia ( sailors probably had been at sea too long)
Order
Sirenia related to ancestral
Proboscidea (elephants)
Separate
since early Eocene sluggish, inshore marine and freshwater
dwellers
no
hind limbs
herbivores
on vascular aquatic grasses and seaweeds
Family
Dugongidae Dugong dugon Indo-West Pacific Ocean-Mozambique and Red
Sea to Fiji-Fossil evidence from Atlantic
Marine
bays and estuaries
Rare
everywhere except northern Australia
Up
to 3 m long 420 kg (930 lbs.)
Feed
on grass tops and roots and rhizomes
Tusk-like
pair of teeth in lower jaw
Hydrodamalis
gigas --Stellers
sea cow
Known
only from the Kommander Islands of the Bering Sea
First
described in 1741 by Georg Steller on the Bering Expedition
Probably
less than 1500 in whole population then
7.5
m (25 ft) long, some 7 tons
Fed
on seaweeds, especially around creek mouths
Very
docile and unafraid of humans
Monogamous
family groups with the young herded and protected by the parents
No
teeth, but horny tuberculated plates in mouth
External
bristled lips and internal lips also
Small
lidless eyes
No
external ears
Forelimbs
about 2 ft. long, with horse-like hooves set with brush-like bristles
no
hind limbs
1
inch thick hide with 4-9 inch blubber layer
Intestine
was 20 x body length
Eaten
by marine mammal hunter from Russia for beef-like meat and almond-tasting oil
Last
one was reported seen in 1768 (27 years after first one was seen)
Family
Trichechidae mainly confined to
freshwater in geologic past
now
found in freshwater and coastal areas
up
to 4.5 m long, 600 kg. (1320 lbs.)
Feed
on green parts of a variety of vascular aquatic plants alternately
feed and rest for short periods throughout the 24 hr day with no apparent
activity cycle
average
submergence time is 4-5 minutes
blunt
peg-like teeth formed at rear of jaw and move forward throughout life and are
lost from the front
mildly
social
three
sp. (all in Atlantic Ocean basin)
Trichechus
inunguis
Amazon manatee Most derived, most riverine
Trichechus
manatus
Caribbean manatee
Florida
to Brazil, coastal and estuarine
Trichechus
senegalensis West African manatee Tropical west Africa, coastal and estuarine
Marine Mammals
Adaptations;
Streamlining..in the
evolutionary process of streamlining the shape, cetaceans have undergone a
distortion of their skulls so the nostrils are pushed back atop the head. This
enables the animal to breathe at the surface without lunging out of the water.
Marine Mammals
It only needs to break
the seas surface with the top of its head, open the blow hole quickly and
exhale, then inhale quickly, close its blow hole, and submerge. It takes only
two to three seconds and may be repeated several times before a deep dive.
Marine Mammals
In large whales the
moisture of their warm breath condenses when it hits the air and together with
a little mucus and seawater a characteristic spout or blow which sometimes can
be used to identify the whale. Cetaceans have all but lost their necks as the
cervical vertebra are compressed and blubber fills in the natural constriction
behind the head.
Marine Mammals
Adaptation of bones
that make up the flippers
Bones in cetaceans are
also lighter as a result of being buoyed up by water and blubber. Beached
cetaceans can suffer serious injuries because of the lack of support
Order Pinnipedia
Family Odobenidae
Pacific walrus Odobenus
divergens
Arctic
Ocean from Cape Chalagaski, Siberia (170o E) to Banks Land, Canada --south to
Kamchatka , Bering Sea
Atlantic walrus Odobenus rosmarus
Atlantic
Ocean from eastern Canada to Spitsbergen and Franz Josef Land--south to Sable
Island, Nova Scotia
no
external ears, hind feet (flippers) can be turned forward, both sexes with long
tusks, male larger than female, 18-24 teeth
Eat
benthic invertebrates, mostly clams flat
peg-like teeth
Long
muzzle bristles
young
born on beaches or on ice floes
tusks
used as a defense or for hauling out on ice ?
Preyed on by killer whales, polar bears,
and man
Family Otariidae 14 sp. eared
fur seals and sealions
external
ears, hind feet (flippers) can be turned forward,
male
larger than female,
34-38 teeth,
swim
with fore limbs fur
seals
pointed
snouts and smaller bodies
sealions blunter snouts and larger bodies
most
feed on fishes, but some on squid and some on benthic invertebrates
air
retained in under fur, but do possess a blubber layer, too
some
offshore and some only coastal
9
in Southern Hemisphere, 5 in Northern
all
breed and give birth on shore in rookeries
territorial
males are polygamous and maintain harems
One
young per female per year
Sexually
mature at about 10 years and live 30-50 years
shed
fur once per year
most
sp. heavily hunted in 1700s and 1800s for fur and oil
Family Phocidae 19 sp. hair
seals
no
external ear,
hind
feet (flippers) cannot be turned forward,
no
great differences in sizes of male and female,
swim
with hind limbs most
feed on fishes, but some on squid and some on benthic invertebrates and some on
zooplankton
air
retained in underfur, but do possess a blubber layer, too
Some
are very deep divers
some
offshore and some only coastal
5
in Southern Hemisphere, 14 in Northern Hemisphere
2
sp. found only in large lakes
some
breed on shore in rookeries with polygamous males others breed on ice floes
others
breed in shallow water
some
phocids shed their skin!
Marine Mammals
Seals: Eared seals
(Otariidae) including fur seals and sea lions use front flippers for swimming
and can turn their hind flippers forward to walk on land, have visible ear
flaps and usually found in warmer waters. True seals (Phocidae) are propelled
through the water by their hind flippers and these can't support their weight
on land and get drug helplessly behind.
Marine Mammals
Walruses (Odobenidae) use
both front and hind flippers for swimming. The upper canine teeth in both males
and females develop into large tusks used to hoist them onto the ice and dig
clams and mussels in 300'water.
Order Carnivora
Suborder Fissipedia
Family Mustelidae
sea otter Enhydra lutris
smallest marine
mammal
Along margins
of kelp beds along coasts of North Pacific -Southern Kamchatka peninsula
to Kurile Island -Bering Sea islands Alaska
south to Southern California and Channel Islands
eat sea urchins, mollusks, crabs, fishes, and seaweeds
15-20
lbs/day/otter
Collect from bottom
down to 100 ft or so, crack and eat at surface
layer of air
trapped in thick fur provides most insulation No blubber
sleep at surface of water
rarely go ashore
give birth in
water
Preyed upon only by killer whales and man
Commercial taking began in 1742 at the Kommander Is by the
Vitus Bering expedition
Collected by spear or club or coarse mesh nets from
boats Commercial catch continued until 1910, when they became the first
species to receive international protection
Strong resurgence since 1970s
Conflict with abalone fishermen
Possible increase in killer whale predation
chungungo, sea cat
Lontra (Lutra) felina
kelp beds along coast of southern Chile
sea mink
Mustela macrodon
known only from bones in Indian middens and hearsay of
unusually large mink furs
coast of Maine
could be just unusually large individuals of freshwater
minks
if
real, then extinct since about 1700
Marine Mammals
Sea Otters (Mustelidae)
uses stone tools when it feeds cradling them on their abdomens and smashing
open shells of clams or sea urchins. They also have no blubber and with dense
fur and oil secreted from numerous glands, a layer of air is trapped under the
fur to prevent excessive loss of heat.
Marine Mammals
Also otters eat urchins
which feed on holdfasts (supporting structures of kelp) and have helped kelp
forests survive. With the decreased population of otters, the kelp forests
showed marked destruction.
Marine Mammals
Sea
Otter
Enhydra
lutris
STATUS:
Threatened off California. DESCRIPTION:
The sea otter has the thickest fur
in the animal kingdom. Unlike other marine mammals, the sea otter does not have
a layer of blubber (fat) to help keep it warm. If an otters fur gets coated with
oil or any other substance, it can easily die from cold and exposure.
Marine Mammals
SIZE:
The sea otter is the largest
member of the weasel family. Southern sea otters typically reach about four
feet in length. Females average 45 pounds, while males average 65 pounds.
Northern sea otters can reach up to 100 pounds.
Marine Mammals
POPULATION:
Today there are about 2,000
southern sea otters off the coast of California. There are between 27,500 and
52,500 northern sea otters residing in Alaska, Canada and Washington. There are
approximately 15,000 in Russia. Two hundred years ago, demand for the otters pelt nearly led to
its extinction.
Marine Mammals
LIFESPAN:
Male
sea otters live an average of ten to 15 years, while female sea otters live an
average of 15 to 20 years.
RANGE:
The sea otters historic range
stretched from Japan, along the coast of Siberia and the Aleutian Chain and
down the Alaska, British Columbia, Washington, Oregon and California coast to
Baja California.
Marine Mammals
HABITAT:Shallow
coastal waters of the northern Pacific.
FOOD:Sea
urchins, abalone, mussels, clams, crabs, snails and about 40 other marine
species.
BEHAVIOR:
Sea otters are the only mammals
other than primates known to use tools. Otters use small rocks or other objects
to pry prey from rocks and to hammer or pry open their food.
Marine Mammals
They can dive up to 330 feet when
foraging for food. Otters rest in coastal kelp forests, often draping the kelp
over their bodies to keep from drifting away.
OFFSPRING:
Sea otters breed throughout the
year. Females give birth to one pup after a gestation period of six to eight
months.
Marine Mammals
THREATS:
Oil spills, habitat loss, gill net
entanglement and conflict with shellfish fisheries.
PROTECTION:
*CITES, Appendix I, Marine Mammal
Protection Act, Endangered Species Act
*Convention on International Trade
in Endangered Species of Wild Fauna and Flora, an international treaty with
more than 144 member countries.
Marine Mammals
Appendix I listed species cannot
be traded commercially. Appendix II listed species can be traded commercially
only if it does not harm their survival.
Family
Ursidae polar bear
Ursus (Thalarctos) maritimus
circumpolar
Arctic Ocean
eat
seals, fishes
may
be found 100s of miles from land on ice floes, but generally near coast
give
birth on land
arent
visible to infra-red sensors
excellent
insulation
are
black to UV sensors
.reflect all UV?
Marine Mammals
Polar bears (Ursidae)
Have white fur to help them blend into the snow/ice around them, possesses
thick fur a layer of insulating hair on their paws, and a thick layer of
blubber and are streamlined more than other bears to help them swim better.
Marine Mammals
Fur, except in otters
which trap air bubbles under their fur, is generally used for insulation in the
air . Most marine mammals have to depend on blubber for insulation. Blubber is
a thick layer of fatty tissue between the skin and muscles.
Marine Mammals
The amount depends on the
species and the season. Species living in ice latitudes have thicker blubber
than those in warmer latitudes. Its buoyant and helps keep whales and dolphins
afloat. Right whales have blubber 28" thick and float when killed. Besides
insulation, its a food reserve.
Marine Mammals
Whales feed on fatty shrimp-like krill in colder waters and as
they move to warmer waters where food is less abundant, they draw on their
blubber as food reserves, thinning their layer out.
Marine Mammals
Pinnipeds have a fat
layer usually thinner than cetaceans (3"). Male fur seals when they come
ashore to breed, have flaps of fat hanging from them but after the season, are
relatively thin. During nursing, females draw from these reserves for milk
production.
Marine Mammals
Birds also have fatty
tissue within them that serve as a food reserve when they are migrating. With
little time to eat when heading towards their feeding grounds, they get their
energy from their reserves. (duck hunters know there are fat deposits on the
ducks in the early season but not late in the season)
Marine Mammals
Teeth -- Dolphins and
porpoises and sperm whales are well equipped with teeth 42-300) They use them
to hold their quarry not to chew.
Marine Mammals
Rorquals have bony plates
with hairy edges inside their mouths instead of teeth. The plates are called
baleen and are made of the same substance as our hair and fingernails. They
feed by straining the food out of the water, swimming with their mouths open.
Marine Mammals
Seals and sea lions also use their teeth to hold their prey rather
than chew while manatees use lips to gather plants that make up their diet.
Bird bills range from the
huge bill and pouch of the pelican to tiny bills of the sandpipers to the broad
bill prion which has strainers on the edges of the bill like baleen.
Marine Mammals
Ears Most Marine mammals
have no external ears but fur seals and sea lions do but they lay back while
swimming. Small openings mark the ears in birds and true seals. In cetaceans
and sirenians, a crease shows where the ear is
Marine Mammals
Nostrils Cetaceans have
nostrils (blow hole) on the top of their heads. Toothed cetaceans have had both
nostrils merge as one blow hole which remains sealed during its dive. The sperm
whale the nostril has its blow hole located on the left side of the head.
Pinnipeds have nostrils that close when relaxed so they, like cetaceans must
make a conscious effort to breathe
Marine Mammals
Water Fish eating
dolphins get their water from the fish they eat, Orcas, feeding on birds and
mammals, get water from them but both groups take in some seawater with their
food. Seals and sea lions take no seawater in with their food but whales walrus
and sea otters eat invertebrates whose body fluids are close to the salinity of
sea water. One reserve is the fat because when it is burned up, water is a
by-product.
Marine Mammals
Water conservation. Cetaceans have no sweat glands and lose
little water to the atmosphere when breathing because of the humid air near the
surface of the sea. Kidneys also dispose of excess salt.
Marine Mammals
Birds have a pair of
glands near the nasal passages in the head which help secrete excess salt.
These are found in all birds but not always functional and usually only work
when excess salt is present (after feeding).
Marine Mammals
Temperature control:
Body temp. regulation in
most marine mammals occurs through the flippers/forelimbs, and flukes or hind
limbs. These flattened hands/feet are thin sheets of flesh with no blubber but
are abundantly irrigated and allow cooling of the blood.
Marine Mammals
Each artery that feeds
these limbs is surrounded by veins that join to form a sheath through which the
blood returns to the heart. The blood in the veins, cooled by having circulated
in the cold limb, is warmed by the transfer of heat from the arteriole blood,
which is cooled in the process.
Marine Mammals
As the venous blood
returns to the heart it is progressively warmed and there is little heat loss
to the outside of the body, as the flipper/fin is irrigated by blood that is
already cold. To the other extent, the venous blood can bypass the heat exchanger
and return through another network of veins close to the skin that have no
insulation.
Marine Mammals
The rest of the body is insulated by a layer of blubber and
the peripheral blood circulation can slow /reduce during each dive.
Seals use their skin as a
heat exchanger opening or closing tiny blood vessels in the skin capable of
exchanging heat with the air.
Marine Mammals
Sea otters are the least
adapted but has developed a way to use the properties of its coat to trap small
air bubbles which engulf the otter when it dives.
Marine Mammals
Birds with their greased
feathers can control individual feathers in positions that allow precise
degrees of ruffling to imprison air either before or after a dive. The feet can
cool the animal off easily if needed or to retain heat, be retracted within the
belly feathers.
Marine Mammals
Digestion The marine
birds and mammals swallow their food whole, none is equipped for chewing.These
whole shrimp, fish etc. are dissolved by gastric juices and possibly ground up
by gravel and stones in the stomach or crop.
Marine Mammals
Cetaceans have a three
part stomach (cattle etc.) with the 1st part a great widening of the esophagus.
In whales this part has stones to grind up food. the second section of the stomach
is like the human stomach, secreting HCl and pepsin. The third stomach is
smoothed-walled but has a few glands that secrete digestive juices.
Marine Mammals
Rorquals can hold up to a ton of krill in the 1st two stomach
sections. After the stomachs, the food then passes to the small and large
intestines.
Pinnipeds also have
stones in their stomachs but one mystery is the huge length of their intestines
which is usually short in carnivores/ its 3x longer than a cow
Marine Mammals
Breathing: Cetaceans
exhale up to 80-95% of the air in their lungs (man 15-25%) and pinnipeds about
35%, sirenians, 50%. Exceptional development of the diaphragm muscles (compared
to man) in cetaceans and more floating ribs, may give them a more flexible and
powerful breathing pump.
Marine Mammals
It takes a rorqual two
seconds to exhale and inhale 1500 gallons of air and man 4 seconds to exhale
and inhale a pint.
Marine Mammals
Diving: When mammals
dive, the heart beats slower (bradycardia) 15-50% slower, and blood supply to
less essential areas of the body is shut off by sphincter muscles in some
arteries ( goes to heart, brain, lungs, muscles not stomach and kidneys).
Marine Mammals
By shutting down, less O2
is needed for the dive. Oxygen is also not stored as a gas but is either
accumulated as chemical combinations as oxides in blood or muscles or dissolved
in organic liquids and tissues.
Marine Mammals
Special adaptations
include substantial amounts of myoglobin and large volumes of blood. Myoglobin
in the muscle tissues binds a large amount of oxygen. The large pool of blood
allows for a storage place for Oxygen.
Marine Mammals
the blood is also a
storage site for glucose (more because more blood). Small twisted blood vessels
forming spongy masses in fatty tissue (retia mirabilia) seem to regulate blood
pressure during the dive so brain, heart and lungs are supplied with constant
blood pressure. The pressure on the blood stored in the RM forces blood into
the vital organs.
Marine Mammals
During deep dives, the
outside pressure squeezes their ribs as the volume of air in the lungs
decrease. The ribs of many diving mammals are designed to collapse inwardly.
Human divers as they dive deeper, take air in under the pressure which
dissolves in their blood.
Marine Mammals
As they ascend, this gas must get out of the solution in the
blood or air bubbles will form , embolism or the bends. cetaceans take very
little air down in their lungs, rather it is in solution as above and it can't
expand beyond its original volume when ascending because the original volume
was taken in at the surface rather than at the bottom under pressure.
Marine Mammals
Using Oxygen, glucose is
broken to CO2, water and energy but once the O2 is used up, glucose is broken
down anaerobically to lactate releasing a little energy, so they can use
glucose in a mixed anaerobic/aerobic metabolism..one of the most important
modifications ...oxidize lactate!
The
calf must be born in warm water as it is missing a thick layer of blubber to
protect it from the cold. Females with calves lag behind on the northward
migration, following the shoreline closely to avoid predators. Whales travel
southbound from December through February, northbound March through May. The
whales are recognized by having a low, heart-shaped blow, their mottled grey
color, and lack of a dorsal fin. A dorsal ridge with several bumps goes down
the center of the back
Oxygen Storage Capacity
Diving mammals do not have larger lung
volume to body size ratios than terrestrial mammals, yet they can dive for
extended periods of time without breathing (Schmidt-Nielson, 1997).
They have evolved alternative mechanisms for increasing the amount of oxygen
they carry.
The lungs, blood, muscle, and spleen are where the most noticible differences
between terrestrial and diving mammals oxygen storage capacities occur.
Seals do not use the lungs to store
oxygen. As seen in the graph below, when diving,
there is significantly less oxygen in the lungs of a seal in than the lungs of
a human. The lungs can not store air as a seal
dives because of the increased risk of decompression
sickness it would impose on the seal.
A seal's blood has a higher
oxygen-carrying capacity than a human's because a seal has a greater blood
volume than a human.
Because there is
more
blood in seals, there are more red blood cells (RBCs) (Schmidt-Nielson, 1997).
The increased number of RBCs increases the amount of hemoglobin, a blood
pigment found in RBCs that carries oxygen, in seals.
A seal's RBCs are composed of less water than a terrestrial mammal's, so even
at the cellular lever, a seal is designed to carry more oxygen (Castellini and Castellini,
1989).
The amount of RBCs that the blood can
carry is limited.
If there are too many cells, then the blood gets too viscous for the heart to
pump effectively, so marine mammals have accessory methods to store oxygen.
An additional place for marine mammals to store oxygen is in myoglobin, an
oxygen binding pigment found in the muscle tissue (Schmit-Nielson, 1997).
Myoglobin is highly concentrated in seal
muscle tissue, making it very dark, and allowing the seal muscle tissue to hole
more oxygen that human muscle is capable of holding.
Finally, marine mammals store more oxygen
in other tissues of the body than humans do, thus giving them the ability to
store more oxygen than humans.
The spleen is a very vascular organ which
stores large amounts of blood and red blood cells.
These characteristics make it an ideal source of oxygenated red blood cells
during a seal's dive. Zapol et al. (1989) estimate that 60% of the red blood
cell mass is stored in the spleen.
The seal capitalizes on the vasoconstriction
that occurs during diving and constricts the spleen as well as peripheral blood
vessels. The plasma volume (PV) remains constant
while the circulating red blood cell volume increases.
The increase in hematocrit (Hct.), or
proportion of RBCs to plasma, correlates with the blood volume (BV) composing a
larger percent of body weight (BW).
View the diagram below for a graphical representation of what occurs to the
spleen during diving.
The release of red blood cells helps reduce carbon dioxide and lactate
buildup as well as high
nitrogen tenions while increasing the oxygen content of the blood for the
first 10-12 minutes of a dive (Zapol et al., 1989).
Seals can dive for much longer than would
be predicted by evaluation of oxygen stores only.
The oxygen storage capacity is only one of may adaptations that seals have to
help them dive for extended periods of time. Click on the following buttons to
find out about the other responses marine mammals have that help them dive
efficiently.
1. times and depths for various species
figure 12.2 p. 5
2. problems: depletion of O2, buildup of CO2 and lactic acid by-products, need
for high amount of energy during dive.
3. apneustic breathing pattern - short breath, hold for long periods
·
large
whales can empty their lungs of 1500 liters of air and refill in 2 seconds!
·
see
fig. 12.23, p. 5
4. ability to remove 90% of O2 from air
(compare to 20% for humans
5. avoid nitrogen poisoning (the bends)
a. lungs contract and collapse under
pressure up to 250 atm
b. with no air in lungs, there is no risk of bubbles forming in blood during
descent. This would be dangerous because it can cause paralysis
6. have lots of blood for extra O2
storage
·
21%
of body weight is blood in sperm whale
7.
extremely lowered heart rate as low as 20% of normal
Aftermath
of whaling (Table from Carwardine, 1999)
Whales and other marine mammals have
special adaptations that allow them to hold their breath longer than a person.
Believe or it not, though, breath holding isnt
the key -- oxygen conservation and storage is. Seals have so much oxygen in
their body, you might be surprised to learn they actually exhale before they
dive!
Some of the ways marine mammals conserve
or store oxygen include:
Reduced heart rate: When a marine mammal
dives its heart rate slows down to conserve oxygen. Some drop from 120 beats per
minute to 4 to 6 beats.
Carrying oxygen: Marine mammals have a
high concentration of oxygen-carrying cells in their muscles and blood.
More blood equals more oxygen: Marine
mammals have two to three times more blood than a human. Other adaptations also
include a network of spiral blood vessels that act as reservoirs for oxygen
rich blood.
And, seals and sea lions store oxygenated
blood in their extra-large spleen (which can be 45% of their body weight).
Recirculating the blood: For extended
dives the blood is shunted or recirculated to only the most essential organs,
like the heart, lungs, and brain. How long a marine mammal stays underwater
depends on the species, where it lives, and what it eats.
Here are some examples of average diving
times:
A male
Northern elephant seals
dive is about 20 to 35 minutes, a harbor seal -- 3 to 7 minutes, and a walrus -- 10 minutes. A
bottlenose dolphin may stay under 8 minutes, a killer whale
10 minutes, an Amazon river dolphin can stay under only 2 minutes.
Tidbit:
Seals diving capabilities are often
underestimated. The breath holding ability of most seals is greater than most
whales
Marine Mammals
Echo-location and vocalization
Because their sense of
smell is so limited, any marine mammals have developed echolocation, natures
version of sonar. The animal emits sound waves which travel 5x faster in water
and listens for echoes reflected back from the surrounding objects.
Marine Mammals
The echoes are analyzed by the brain. Most toothed whales ,
some pinnipeds and some baleen whales may also echolocate. (Bats Too)!
The sounds of
echolocation consists of short bursts of sharp clicks repeated at different
frequencies. Low frequency clicks have high penetrating power and can travel
long distances.
Marine Mammals
The clicks, squeaks and
whistles of cetaceans are produced and air is forced through air passages and
air sacs while the blow hole is closed..no vocal cords so the frequencies are
changed by contracting and relaxing muscles along the air passages and sacs. A
fatty substance on the forehead, the melon appears to focus and direct sound
waves..this gives them the rounded forehead.
Marine Mammals
In toothed whales incoming sound waves are received primarily
by the lower jaw. Ear canals are reduced or blocked in most cetaceans. The
jawbone is filled with fat and oil and transmits sound to the two very
sensitive inner ears...each independently.
Marine Mammals
Behavior..the brain has evolved into complex behaviors like
learning..not instinct dominates...they rely on past experiences.
Most live in groups at
least part of the time.
Marine Mammals
Vocalizations play a
prominent role in communications loud barks, whimpers, sedate grunts, whistles,
chirps, moos, barks...there have been over 70 calls identified of the killer
whales. and there are different dialects. Cetaceans show play behavior and the
great whale breaches, some stick their heads out of the water to spy.
Marine Mammals
Migration
Most migrate from cold
polar waters to warmer areas in response to amount of food. In the fall, the
food in the polar waters becomes scarce and most cetaceans migrate to warmer
waters. The pacific gray whale migrates 11,000 miles from the Aleutian to the Baja
Peninsula.
Marine Mammals
Reproduction
Migration and
reproduction are closely interrelated: and adaptations are...birth of seal pup
must be exactly timed to coincide with the mothers return to the breeding area
11 months later because the pup would drown if born at sea. Whales must reach
war water prior to giving birth. Therefore, gestation must be timed exactly
Marine Mammals
In certain fur seals, the
period is lengthened by stopping development of the embryo for several months.
The embryo does not attach to the wall of the uterus after descending from the
fallopian tube. the delayed implantation of the embryo lasts 4 months. It then
attaches to the wall and begins to develop.
Marine Mammals
The delayed implantation
enables the mother to complete nursing her pup, and gives her body a chance to
build up the necessary food reserves to ensure the developing fetus will be
supplied nutrients during gestation.
Marine Mammals
In streamlining the body
the sex organs became internal. The penis is inside the body held by retractor
muscles attached to the pelvis. Connective tissue and a penis bone or baculum
keep the penis rigid. Copulation in cetaceans is belly to belly and is brief
being difficult to maintain contact in the sea.
Marine Mammals
Baby whales are born tail
first and guided to the surface for its first breath by its mother. Gray whales
weigh 907 kg at birth and 19 ft. long. Baby blue whales gain 90 kg each day.
The high fat and protein content of the milk (10x fat of cow milk) milk is
pumped into the young 9.5l/2-3 sec. 50x /day makes 490 l of milk daily.
Marine Mammals
Birth rate is low one / 3
years and offspring are looked after for some time.
Marine Mammals
Eared seals use their front
flippers for swimming and hind for walking on land.
Marine mammals are warm-blooded
and nourish their young on mothers milk.
Blubber, a thick layer of fat
insulates the body as well as providing buoyancy, padding and a source of
energy when food is scarce
The horzonital tails of the whales
are adaptations that enable them to dive and surface easily.
Marine Mammals
Eared seals use their front
flippers for swimming and hind flippers for walking on land.
True seals are usually found in
cold water and eared seals in warmer water.
Cetaceans can't survive on land
because of their lightweight skeleton which can not support the body out of the
water.
Sperm whales can dive
to depths of 3000 feet and stay down for 90 minutes.
Marine Mammals
Baleen whales feed on plankton
Cetaceans have good eyesight but
poor senses of smell and taste.
The tusk of the walrus is not used
to catch seals.
Sea otters have no blubber and
that is why they have thick fur.
Baleen whales have no teeth and
feed on plankton.
Marine Mammals
Porpoises have a stubby-nose form
and Dolphins have a long-beak form.
The decrease of kelp beds is
related to the increase of sea urchins and decrease of sea otters.
The retia mirabilia only functions
when the marine mammal is diving
Baleen whales are an example of
____ nekton
Marine Mammals
The statement that best describes
the adaptation of the Cetaceans skull concerning its nostrilsis that the
nostrils have migrated to the top of the skull and form a blowhole