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



•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,

•don’t 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



          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 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 



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.






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.






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





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.





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).


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.








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, 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       --Steller’s 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


• 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 otter’s 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 otter’s 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 otter’s 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 

•aren’t 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 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. 










. Diving ability - respiratory and circulatory adjustments.

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 isn’t 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 seal’s 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 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


•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


•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