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Marine Mammals
- about 50 million years ago some mammals started evolving to a life from land to sea
- their body evolved to make them more suitable for swimming and diving than walking
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class Mammalia
The distinguishing characteristics of all mammals are:
- four chambered heart
- have hair (or fur)
- give birth to live young
- feed offspring milk from mammary glands
- breathe air
- warm-blooded or endothermic
- well developed brain, so therefore are considered intelligent
Marine Mammals can be divided up into different Orders:
1. Order Cetacea
a. Mysticeti- Baleen Whales- mustached whales
b. Odontoceti- Toothed Whales
2. Order Carnivora
a. Bear Family- polar bear
b. Mustelidae (Weasel) Family- Sea Otter
3. Order Pinnipeda- Seals & Sea Lions & Walruses
4. Order Sirenia- Manatees & Dugongs
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Whales & Dolphins
General Characteristics
1. have a streamlined body with a blubber layer underneath the skin that contributes to
the smooth shape the blubber is a thick layer of fat with fibrous network that acts as
insulation for the whale or dolphin
2. have no hair except for the facial hair which they can lose as they mature
3. they have no external ear (pinna) but a small opening is present
4. the bones of the arm are shortened while the bones of the fingers are longer
5. the blubber layer has a lot of blood vessels but the circulation (blood flow) can be
restricted during diving to conserve body temperature
6. the muscle layers of the body hold a larger amount of oxygen due to myoglobin and will
Undergo anaerobic respiration during diving the lactic acid that is produced
from that will help maintain the body temperature when diving
7. the lungs have cartilage throughout the tissue to prevent
the lungs from being compressed when diving
8. the heart is broader and flatter than ones in land mammals which helps during diving
9. there are special areas that are part of the vascular
system in these animals called retes that act to hold
extra blood (and therefore oxygen) which can be used during diving
10. the liver has extra spaces in it to also hold extra blood
to be used by the organs during diving
11. whales and dolphins have no gall bladder
12. the kidneys are completely lobulated meaning that
each small lobe can act independently as a kidney (the
kidney looks like a bunch of grapes compared to land mammals)
13. the stomach has three parts:
- forestomach- which acts to mechanically breakdown food
- main stomach- which has digestive glands
- pyloric stomach- which has a minor amount of enzyme secretion
14. in some whales and dolphins there is no obvious
distinction between the small and large intestine
15. the testes may alter in size during breeding season
16. body temperature 95.9° F- 99° F
17. Heart Rate of 50 – 150 beats per minute- heart rate slows down during diving (the
slowing of the heart rate is called bradycardia)
18. whales & dolphins travel in groups called pods; the size of the pod will depend on the
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species
19.communicate through a series of clicks & whistles, they have a signature whistle
Which is a unique voice pattern for each individual animal
20. Toothed whales only Have large fatty mass in the forehead is called the melon this
allows sounds produced in
the airways to be focused in a specific direction sound waves can be
used to communicate with other animals or sense objects sound waves are
reflected and then detected back by the marine mammal through special
fatty tissue in the lower jaw the detection of the
sound waves is called echolocation
21. Groups of whales or dolphins are called pods
22. Marine mammals breed in the water fertilization and development is internal
the gestation period (which is the length of time a female carries the developing fetus
until birth) can range from 11 months to 18 months they breed about every three years
and give birth to one calf calves are usually born tail first calves are nursed for 6-
10 months and the milk is rich in fat and protein to help them grow fast and put on
layers of insulating fat quickly
Husbandry in Whales & Dolphins
-Whereas, it is difficult to keep baleen whales in a tank it has been done but never
for a long period of time
-The salinity or amount of dissolved salts in water is best is between 25-35 ppt,
similar to that in marine fish
-pH is best is at 7.5 – 8.2
-dolphins and whales that are in captivity are usually in chlorinated tanks to reduce
the growth of algae and kill bacteria from feces (body wastes);
chlorine levels have been kept from 0.3 – 3 ppm ( a swimming pool level is about 1.5
– 3 ppm)
- diets consist of fish, squid, krill with added vitamins
Behavior
Spyhopping- whales stick their head out of the water and take a look around, just to see
what is going around on the surface of the water
Breaching- whales jump totally out of the water which could be for communication,
show dominance or just for play, it could also knock off parasites
Slapping (Lobbing)- slap their tail fluke or flipper on the water to mark their position,
show aggression, or to communicate with others
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Whales and dolphins can get similar illnesses as those found in other mammals such as colds,
cuts with minor infections, dolphin pox, sunburn, intestinal parasites, external parasites, heart
problems, liver problems, kidney problems and other illnesses
Sub-order Mysticeti (Mustached Whales)
- Baleen whales – baleen is a fibrous protein material (keratin) that forms
overlapping plates in the mouth of these whales baleen is derived from hair like tissue
the baleen looks like a giant comb that hangs from the roof of the mouth
they act as a filter to trap small organisms in the fringe edge of the baleen plate which can
then be swallowed
- some of the baleen whales have an expandable throat that extend when the whale
takes in a mouthful of water and then contracts to expel the water (as seen
with throat grooves)
- baleen whales have two blowholes (nostrils) through which the whale breathes
which is located on the top of the head when the whale breathes the air
exchange is quick and efficient baleen whales can be distinguished by the
blow which is water vapor seen when the whale exhales
Groups of Baleen Whales
1. Right Whales-no dorsal fin, no throat grooves, the right whale to hunt in the past
because when killed the whale floats
2. Rorquals- Blue Whale, Humpback Whale- have a dorsal fin, have throat grooves, so they
eat by taking in water and the throat area expands and water is pushed out through the
baleen plates
3. Gray Whales- “mossback” whales due to the growths on their back, the only type of whale
which has been taken off the endangered species list due to population recovery.
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Toothed Whales- Suborder Odontoceti (65 different species)
Whales or dolphins are streamlined, only have one blowhole opening, and have teeth
They use their teeth to catch food and swallow it whole.
They are intelligent, they can imitate and solve problems
Porpoises are smaller toothed whales, have a shorter snout and teeth that are flattened
like incisors
Narwhal is found in the arctic region, the horn coming out of their head is actually a
tooth
Sperm Whale- the largest of the toothed whales, they have a massive head filled with an
oil substance called spermaceti – the oil becomes thicker in deep,
cold water which may help them dive (become less buoyant)
- they produce ambergris a substance that is formed in the intestines, it
has been used by the perfume industry
Bottlenosed Dolphin (Tursiops truncatus) is the most common toothed whale especially in
Florida- teeth are cone shaped (round and pointed)
Order Sirenia _ Manatees Dugongs and Steller Sea Cow
1. Manatee- herbivores
- are euryhaline can live in both marine or fresh water
- slow moving, docile animals
- tail is paddle shaped which they move up and down to move them through
the water
- spends the winter in the freshwater springs 72 degrees and then can
travel anywhere during the summer
- grow to be 12 feet long and weigh 3500 pounds
- they have rough skin with sparse hair
- they have grinding molars with flexible lips to help grab food
- the closest living relative is the elephant
2. Dugong – herbivore
-they are only marine animals
- their tail is shaped like a whales fluke
- they are found in the Pacific
3. Stellar Sea Cow is extinct
Threats to the Sirenia come from boats, flood gates, pollution, hunting and loss of
habitat as well as natural causes
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Order Carnivore
Sea Otter belongs to the Family Mustelidae (Weasels)
Sea Otter is closely related to river otters, minks and badgers
- is the only member of this family that is marine
- poorly adapted to a large number of habitats so their range (where they can be
found) is limited to a small area
- they usually don’t wander past one mile off shore
- smallest of all the marine mammals (1 meter in length)
- found in the Northern Pacific
- commonly found in kelp beds
- sea otters wrap kelp around their body to anchor themselves when water gets
rough or when resting at night
- they have webbed hind feet for swimming
- eat mussels, crabs, abalone, sea urchins
- eat by floating on their back and using a stone to crack open mollusks
- only marine mammal to use a tool
- they have the thickest (densest) fur of any animal which is necessary to keep
them warm since they have no blubber underneath their skin, air gets
trapped in the lower layers of the fur to help in insulating the otter
- they constantly groom their fur to keep it clean
Polar Bears belongs to the Bear Family
Polar Bears are considered to be a large predator
- males weigh an average 1000 pounds
- females weigh an average 500 pounds
- they are graceful and athletic, very good swimmers
- the only marine mammal that is most adapted to land
- live on ice flows and along the shore in the Northern Polar region
- they have dense fur though the hair shafts are hollow
- their skin is black which will trap heat from the sun so it helps them maintain
their body temperature
- they have a thick blubber layer beneath the skin
- they have large rough pads on their feet which keeps the bear from slipping on
the ice
- they have an excellent sense of smell, so they can detect they prey from 2-3
miles away or hidden in an ice den below the snow
- they usually give birth to 2 cubs in the middle of winter and the cubs weigh about
1 pound at birth
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- the cubs will grow 4 times their original size at 1 month of age and at 3 months
will leave the den with their mother who they will stay with for 3 tears
- the polar bears diet is fish, birds, plants, seals (preference) and whales
Order Pinnipeda
Pinnipeds are feather-footed animals, they come onto land to sleep and give birth
- they are intelligent social animals
- they have a thick blubber layer under their skin which is covered with a
dense fur
- they use sound (barks) to communicate
- they have whiskers on their snout
1. Eared Seal – Sea Lions and Fur Seals (California Sea Lion)
- they have an external ear flap called a pinna
- they are capable of walking on land because they have long fore flippers (front
legs) that can lift up their body plus their hind flippers can rotate forward and
push up the back end of their body
- they swim by using their fore flippers to push them through the water
- the sea lion is the most common pinniped found in zoos and aquatic attractions
2. True Seals (includes the elephant seal, harp seal, leopard seal) called Phocids
- this is the group of pinnipeds with the greatest variety of species
- they have no external ear flap
- they use their hind flippers to propel them through the water
- they cannot use their flippers to lift up their body so they end up dragging their
body on land (do not walk on land)
- the elephant seal is the largest pinniped getting to 20 feet in length and 4 tons in
weight; it can also dive the deepest of the pinnipeds
- the leopard seal is the only pinniped that eats warm blooded animals
3. Walruses
-they are the only group of pinnipeds that have tusks.
- they have small eyes and no external ear flap
- they can swim using either their front or hind flippers
- they can walk on land because they can rotate they hind flippers forward