Ch. 9: Marine Reptiles, Birds, and Mammals - Mr. Hoyle's Science ...

Mr. Hoyle 

Marine Biology Lecture Notes 

Ch. 9: Marine Reptiles, Birds, and Mammals 

Vertebrates originated in ocean 350 million years ago 

Descended from bony fish had to adapt to 

harsher conditions on land 

Lost structural support for swimming had to 

develop crawling & walking (tetrapods-“fourfooted”) 

Tetrapods evolved from fishes that had lungs 

& ways to keep from drying out 

Amphibians never really solved this problem 

that is why they lay eggs in moist 

environments & none are strictly marine 

A specimen of the Jurassic ichthyosaur Ichthyosaurus 

intermedius, found in Somerset County, England. Photo 

by Sara Rieboldt, © UC Museum of Paleontology. 

Reptiles solved the problem of water loss, truly adapted to living on land, 

and evolved from now-extinct amphibians 

Birds and mammals both evolved from different groups of now-extinct 

reptiles 

Some reptiles, birds & mammals have reinvaded the ocean 

9.1 Marine Reptiles 

7,000 living species including lizards, snakes, turtles, and crocodiles 

Dry skin covered w/scales to prevent water loss 

Have leathery shells prevent desiccation, so can lay eggs on land 

Poikilotherms and ectotherms – “cold-blooded” 

Activity & metabolic rate depends on temperature of environment 

Sluggish in cold & stay away from cold regions 

Stay away from land where temperatures fluctuate & stay in ocean 

where temperatures are constant 

Appeared more than 300 million years ago 

Many are rare & endangered & others are common 

A. Sea Turtles 

Ancient group of reptiles, body enclosed in shell (carapace) fused 

w/backbone 

Cannot retract head into shell 

Large forelimbs are modified into flippers 

9 species that live in warm waters

Green turtles 

Found in coastal waters in tropics 



Shell grow to 1 meter & mostly eat seagrasses and seaweeds 

Lack teeth but have strong biting jaws 

Hawksbill 

Reddish-brown with yellow streaks 

Beak-like mouth & eats encrusting animals 

(sponges, sea squirts, & barnacles) & seaweeds 

Leatherback 

Largest at 2 m (7 ft) and weighs 540kg (1,200 lbs) 

No solid shell instead have series of small bones 

buried in dark skin forming longitudinal ridges 

Live in open water rarely seen except laying eggs 

on beaches 

Deep divers-2100 ft down 

Eat jellyfish 

Endangered! 

All return to land to reproduce & migrate long distance to lay eggs on 

remote sandy beaches 

Green turtles gather to nest on east coasts of Central America, Northern 

Australia, Southeast Asia, Ascension Island & other locations 

Marine biologist have tagged green turtles to map migration to feeding 

grounds 

2 month journey & 1360 miles along the coast of Brazil 

Not sure how they find their way, but evidence of sensing earth’s 

magnetic field 

Most studied of all turtles 

Return to nesting area every 2-4 years against currents 

Females return to same beach where they were born 

♦ How do we know? 

Analyzing DNA of breeding populations 

DNA of populations differ from population from other beaches 

Copulating pairs seen offshore, but only females venture on shore 

usually at night 

Biologist tag mostly females because easier to tag organisms on land



When laying eggs, females excavate a hole using 

their flippers, lay 100-160 eggs, and cover eggs 

w/sand 

♦ May make several trips to lay eggs each time 

Eggs hatch after 60 days 

Babies dig out of the sand crawl to the water protected by the dark, if 

lucky 

Eggs eaten by dogs, ghost crabs, wild pigs, & other 

animals 

Hatchlings easy prey for crabs & birds during the day 

While in the water taken by variety of fish & seabirds 

Sea snakes 

Tropical Indian & Pacific oceans 

Laterally flattened, tail paddle-shaped & 1-1.3 m long 

Total marine existence & ovoviviparous (birth live young) 

Few come on shore to lay eggs 

Carnivores-feed on bottom fish & few on fish eggs 

Closely related to cobras 

Venomous & can be fatal to humans (swimmers who step on 

them & fishers removing them from nets) 

Rarely aggressive & mouth too small to get good bite 

Hunted for skins & some have become rare 

B. Other Marine Reptiles 

Marine iguana (Galapagos Islands) spend most of time 

basking in sun 

Eats seaweeds & dive 33 ft to graze 

Salt-water crocodile inhabits mangrove swamps & estuaries along the 

coast 

Known to venture into open sea 

Largest ever recorded is 33 ft, but rarely over 20 ft 

Most aggressive & known to attack & eat people 

More feared than sharks 

9.2 Seabirds 

Homeotherms- “warm-blooded” & endotherms 

Live in variety of environments



Waterproof feathers provided by oil glands above the base of their tail 

help conserve body heat 

Preening helps apply the oil to their feathers 

Light hollow bones help for flight 

Eggs covered by hard shell more resistance to water loss 

Seabirds significant portion of life at sea & feed on marine organisms 

Most nest on land in large colonies w/mate as life long pairs & take 

care of young 

Webbed feet for swimming 

Predators of fish, squid, bottom invertebrates, other small marine 

organisms 

Voracious appetites to supply energy needed for flying 

A. Penguins 

Flightless, w/wings modified into stubby flippers for 

swimming 

Denser bones reduces buoyancy making diving easier 

Streamlined bodies w/powerful strokes of wings makes 

excellent swimmers 

Can jump out of water & cover long distances by alternating 

swimming & jumping 

Galapagos penguin 

Clumsy on land & nearsighted (eyes adapted for 

underwater vision) 

Protected from cold by layer of fat under skin 

Dense, water-proof feathers trap air warmed by body heat 

All but 1 of 18 species live in Antarctica and other colder 

temperate regions of S. Hemisphere 

The Galapagos penguin which lives at Equator but 

confined to region with cold currents 

Emperor penguin hunts fish & squid while most small 

Adelie 

penguin (Adelie) eat krill 

Strong beaks like seabirds 

Some migrate seasonally between feeding grounds at sea and nesting 

areas on land or ice 

Establish breeding colonies 

Emperor penguins mate for life 

Male incubates one large egg on ice during the Antarctic winter while 

female leaves to feed as soon as she lays egg



Male hold egg on top of feet for 64 days while huddling 

close together protecting themselves form the cold & 

storms 

Lay eggs at the coldest time so that hatching occurs 

during the productive summer when food is most 

plentiful 

When egg hatches female returns and regurgitates 

food for chick 

Then both parent take turns feeding 

When parents feeding chick herded into groups guarded by few adults 

(babysitters) 

Returning parent identify chick by voice & appearance 

Feeding takes place for 5 ½ months 

B. Tubenoses 

Have tube-like nostrils & heavy beaks that usually curve 

at tip 

Months –years on open ocean 

Have salt glands (like turtles & other sea birds) get rid of 

excess salt emptying into nostrils 

Albatrosses (wing span up to 11 ft), shearwaters, petrels 

Skillful flyers catching fish at the surface & some feed on dead birds or 

whales 

Mate for life & perform elaborate courtships and greeting 

behaviors 

Nest on remote islands, on cliffs that are inaccessible to 

predators 

Incubation & care of single chick takes 8 months or longer 

Breed on islands around Antarctica then migrate to Arctic to feed 

C. Pelicans and Related Birds 

Webbing between all four toes 

Relatively large fish eating w/large distribution 

1. Pelicans 

Pouch below large beak 

Brown pelican plunge into water & catch fish in pouch 

Diminishing population along coast of United States 

because of pesticide pollution 

♦ Has made come back because of restrictions on

manufacture & use of pesticides 

2. Cormorants 

Black, long-necked seabirds dive & pursue prey 



Low flights over water & float low in water (only neck above surface) 

3. Frigate Birds 

Narrow wings w/long forked tail 

Force other seabirds to regurgitate fish in midair or catch 

prey from surface 

Agile pirates seldom enter water, not even to rest because 

feathers are not water proof 

Nest in large colonies 

Build messy nest w/twigs & anything else they can find 

the feces of boobies, cormorants, pelicans, other seabirds accumulates 

as guano 

mined for fertilizer 

D. Gulls and Related Birds 

1. Gulls 

Largest variety of seabirds 

Predictors and scavenger will eat just about anything 

Successful in company of humans & congregate near 

piers, garbage dumps 

Jaegers & skuas are gull-like predators that steal fish 

from other birds 

Nest near rookies of penguins & other seabirds & eat their eggs & 

young 

2. Terns 

Graceful flyers that hover over prey before plunging 

for it 

Slender beaks specialized to catch small fish which 

swallowed whole 

Arctic tern breeds in Arctic during northern summer 

travels 10,000 miles to Antarctica for southern summer 

3. Cold water diving birds 

Puffins, razorbill 

♦ Fill the role of penguins in northern hemisphere 

♦ Use wings to swim underwater



♦ Extinct great auk acted like penguin but slaughtered for their eggs, 

meat, & feathers, last died in 1844 

E. Shorebirds 

Wading & do not have webbed feet 

Live inland as well as sea 

Common in estuaries & coastal marshes 

Plovers, sandpipers, rails, coots, herons, egrets, ducks 

9.3 Marine Mammals 

Crabeater Seal 

Monk Seal 

Great Auk 

200 million years ago mammals evolved from extinct reptiles 

65 million years ago dinosaurs died & mammals began to thrive 

Endotherm & homeotherm 

Skin has hair to retain body heat 

Viviparous w/few exceptions 

Embryo receives nutrients through placenta 

New born fed by milk from mother therefore mother has mammary glands 

Few, well-cared offspring 

Larger brain in relation to body size- storage & process more information 

A. Types of Marine Mammals 

1. Seals, Sea Lions, and Walruses 

Seals (order Pinnipedia) 

Paddle-shaped flippers need to rest and breed on land 

Evolved from early form of carnivore (order Carnivora) 

Predators, feeding on fish and squid 

Live in cold water 

Thick layer of fat under skin-blubber & bristly hair 

Large body helps conserve body heat because less surface area 

Rear flippers cannot move forward 

On land use front flipper to pull forward & swim w/rear 

flippers 

Harbor seal common in N. Atlantic & N. Pacific 

Elephant seals largest-bulls reach 20 ft & weigh 4 tons 

Crabeater seal strain krill w/cusped, sieve-like teeth 

Endangered monk seal live in warm water 

(Mediterranean & Hawaii) 

Carribbean monk seal was last seen in 1952 

Hunted for skin, meat, & oil extracted from blubber 

Marine Mammal Protection Act of 1972 extends protection to all



marine mammals & restricts sale of Products in US 

Sea lions 

External ears, use all four flippers to swim and run on 

land 

Front flippers rotate backward to support permitting it to 

sit on land w/neck & head raised 

Adult males much larger than cows & have massive 

head w/hairy mane 

California sea lion lives Pacific coast of N. America & 

Galapagos Islands 

♦ Do trick for fish in shows 

Northern Fur seals almost exterminated for thick fur 

♦ Now mostly protected around world, though some 

are still hunted 

Some drowned in nets or shot while stealing fish from 

fisherman 

Walrus 

Large w/tusks eats mostly on bottom invertebrates 

(clams) 

Once thought tusk use to dig up food, no evidence 

to prove this 

Suck up food while moving along bottom 

Sea lion 

Northern fur seal 

Stiff whiskers act as feelers & tusks used for defense & hold anchor on 

ice 

2. Sea Otters and Polar Bears (order Carnivora) 

Sea otters 

Smallest marine mammal 

Lack layer of blubber & insulation from trapped air in 

dense fur 

Slaughtered to almost extinction & became protected 

in 1911 

Population declining in Aleutian Islands & in CA because of pollution 

from sewage 

Spend most of time in water feeding & giving birth 

Pup groomed and nursed constantly by mother 

Need to eat 25-30% of body weight per day & spend most of day 

looking for food 

Eat sea urchins, abalone, mussel, crabs, & fishes 

Live around kelp beds from Pacific coast of Siberia to 

central CA & protect kelp beds from sea urchins 

Polar Bears



Semiaquatic spend part of life on drifting ice in Arctic 

Eat seals by stalking & capturing as seals surface to take breath 

3. Manatees and Dugongs (order Sirenia) – sea cow 

Relative to elephant 

Pair of front flippers but no rear limbs 

Swim with up down stroke of paddle-shape tail 

Body padded w/blubber, wrinkled skin & scattered hair 

Manatee 

Named after mermaids whose songs drove sailors crazy 

Gentle creatures who are vegetarians eating seagrasses 

Dugongs 10 ft long & weigh 930 lbs & Manatee 15 ft long & 

weigh 1320 lbs. 

Exploited for meat , skin, & oil-rich blubber 

Dugong 

Reproduce slowly 1 calf every three years 

Seagrasses being destroyed at alarming rates by anchors & 

excess slit from deforestation and farming on land 

Only 4 species remain & all are in danger of extinction 

4. Whales, Dolphins, and Porpoises (order Cetacea) 

Largest group 

Inspired countless stories & art 

Rescuing whales, performing in shows, or watching birth 

bring out strong emotions in all of us 

Most complete transition to aquatic life, most other marine 

mammals return to land this group spend entire life in ocean 

Streamlined bodies show evidence of convergent evolution 

Breath air & will drown if trapped under water 

Blue whale 

Warm-blooded, with hair (scanty) & produce milk for young 

Have front flippers, but rear pair of limbs has disappeared although 

present in embryo, only useless bones left 

Dorsal fin (convergent evolution) w/muscular tail ends in pair-like fins 

called flukes 

Blubber provide insulation & single blowhole 

90 species all marine except 5 species of fresh water dolphins 

Two groups toothless filter feeders whales & toothed whales including 

porpoises & dolphins 

Toothless whales (baleen whales) 

Have rows of flexible, fibrous plates made of keratin (same material as 

hair & nails) form dense matt on roof of mouth 

Take in huge amount of water & squeezes it out through bristles



Whale licks off food left on baleen 

Largest animals that ever lived on earth 

Overhunting has brought many species to brink of 

extinction 

Average blue whale male 80 ft & female 110 ft 

Blue, fin, & minke whale are rorquals & humpback- feed 

by gulping up schools of fish & krill 

♦ Low neck expands giving accordion-like grooves 

♦ Humpback herd fishes (mackerel & herring) by blowing bubbles 

Right whale & bowhead feed by swimming with mouth 

open at surface 

♦ Largest baleen plates w/finest bristles allowing filter 

copepods & krill 

Gray whales bottom feeders eating amphipods 

Minke 

♦ Stir up bottom w/pointed snouts & filter sediment leaving Fin 

characteristic pits on bottom 

♦ Feed on right side because right side more worn 

♦ Some are left handed 

Toothed whales 

Feed on fish, squid, & other prey 

Use teeth to catch & hold prey not to chew, food swallowed whole 

3 compartment stomach & one blow whole instead of two like baleen 

whales 

Largest is sperm whale-grouped w/baleen know as great whales 

♦ Eat giant squid, fishes, lobsters, & other marine animals 

♦ Undigested squid beaks and other debris accumulate in gut forming 

sticky ambergris (ingredient in fine perfumes) 

Killer whale (orca) 

♦ Black & white eat seals, sea lions, penguins, fishes, sea otters, & 

other whales 

♦ Flash white bellies to frighten schools of herring & use flukes to stun 

prey 

♦ Most common in cold water, but found around world 

♦ Few confirmed cases of attacking humans 

Dolphins & porpoises 

♦ Are toothed whales



♦ Dolphins have beaks & porpoises blunt noses 

♦ Some places dolphins called porpoises 

♦ Travel in pods (herds, schools) 

♦ Catch rides along bows of boats 

♦ Bottlenosed seen in theme parks & spinner know for 

twisting jump 

♦ Dolphins not only cetaceans to be threatened 

♦ Whaling old tradition in many different groups of 

people 

Native Americans, Eskimos (still hunt them), 

Basques 

In 1600s Europeans & Americans started exploiting in N. Atlantic 

& New England 

Blubber provided train oil, soap, & lamp oil 

Baleen used for corsets & other goods & meat 

Increased w/ steam ships & explosive harpoons 

Low reproductive rate 

One calf carried by mother for year or more 

Females do not become pregnant for 2-3 years after giving birth 

Because of low reproductive rate, they could not keep up w/ whaling 

Almost all of great whales are classified as endangered 

Right whale was the first to deplete because slow moving & float after 

being harpooned 

Whaling nations developed factory ships to invade 

the rich waters of Antarctic 

Blue whale (largest) especially sought 

80% of whales caught in 1963 were immature 

Fin whales (second largest) 1950-1960s 

Sei Whale in mid 1960s were hunted 

1946 20 countries established IWC International Whaling Commission to 

regulate whaling to stop over fishing 

Collected data on number of whales & set annual 

quotas but could not be enforced 

Blue whale hunted until 1971 

Under pressure from conservationist banned 

hunting of other whales & demand for whale



product reduced because of substituted ingredients 

US Congress passed Marine Mammal Protection Act of 

1972 bans hunting of all marine mammals in US waters 

(except traditional hunting by native Alaskans) 

Soviet Union halted whaling in 1987 However Japan, 

Iceland, & Norway continued hunting minke, fin, & sei 

1994 IWC vast sanctuary for all whale in waters in 

Antarctica (main feeding grounds) but Japan decided to 

continue 

Japan has set its quota in 2005-06 at 850 minkes, 50 

humpbacks, and 50 fin 

Iceland was allowed to take 38 minkes in 2005-06 

Norway in defiance of IWC set quota of 796 minkes for 2005-06 

Small-scale whaling remains as part of tradition of native inhabitants of 

Arctic region (Greenland-Siberia), Lesser Antilles 

Killer whale, narwhal, and beluga are also hunted 

No one knows if the whales will ever recover 

California gray has made a comeback & removed form endangered list in 

1997 

IWC allowed 600 gray whales to be hunted by native hinters in Siberia 

& 20 by Makah Indian tribe in Washington state but tribe has only 

taken 1 

They are returning to southern reaches of Arctic Ocean north of 

Norway 

IWC has shifted to conservation of also dolphins & porpoises 

Because of over fishing of squid & fish dolphins are threatened 

Dolphins are also hunted for human food 

Rarest dolphin Yangtze River dolphin found in only 

China is an verge of extinction numbering less than 

100 

Large fishing nets trap and drown 200,000 dolphins a 

year during 1970s 

Public outrage demanded that dolphins be protected 

against large fleet 

Special nets was enforces & observers were placed on 

board and in 1990 no dolphins were killed by the tuna 

fleets 

1990 3 of the largest tuna packers vowed not to buy or



sell tuna that was caught using methods that injured or 

killed dolphins & “ dolphin safe” was put on labels 

Dolphins, sea turtles, seals, seabirds, and other marine 

life are still dying in drift nets as long as 37 miles & 50 

feet deep 

Drift nets used to catch squid & fish will catch anything that comes by 

Wasteful because large percentage of catch drops out of net during 

hauling 

International pressure persuaded Japan (largest drift net fleet) & Taiwan 

to end drift-net fishing 1993 

B. Biology of Marine Mammals 

1. Swimming and Diving 

Move by tails & flukes going up & down 

Group of dolphins recoded bowriding speeds of 40 mph 

Dolphins jump out of the water to take a breath when swimming fast 

Can eat and swallow w/out drowning 

To avoid inhaling water take very quick breaths 

Fin whale empty and fill lungs in 2 seconds, ½ the time we take even 

though breathes 3,000 times more air 

Warm breath condenses in cold air, little mucus, and seawater this forms 

the spout or blow (20-40ft high) seen long distances 

When great whales open mouth exposed to low temperatures 

Recently discovered network of blood vessels in the tongue reduce 

heat loss by transferring heat form warm blood into vessels that carry it 

back of body core 

Sea otters dive 4-5 minutes to 180 ft, most pinnipeds dive for up to 30 

minutes to 150-250 ft but some capable of 1300 ft -5000 ft 

Baleen whale seldom go below 300ft 

Toothed whales great divers 

Dolphins dive to 990 ft 

Sperm whale under at least hour to 7380 ft 

Deep dives required critical adaptations 

Pinnipeds & cetaceans hold breath 15-20 seconds then rapidly take in 

new breath 

♦ 90% of oxygen contained in lungs is exchanged unlike humans 

20% 

♦ Better at absorbing oxygen from air & storing in blood



♦ Have more blood than nondiving mammals 

♦ Have higher concentration of erythrocytes carrying more 

hemoglobin 

♦ Muscles rich w/ myoglobin (can store oxygen in blood) 

When diving heart rate slows & blood flow to nonessential parts 

(extremities & intestine) but maintained in vital organs 

To prevent the bends lungs collapse & rib cage gets pushed in by 

pressure of water 

Air moved into central space where nitrogen is not absorbed 

Some pinnipeds exhale before they dive reducing nitrogen in air 

Recent evidence shows some diving whales do suffer from the bends 

2. Echolocation 

Nature version of sonar 

All toothed whales, some pinnipeds, and baleen whales 

Not exclusive to marine (bats) 

Emit sound waves, which travels 5 times faster in water, & listen for 

echoes that are reflected off object 

Time it take for echoes tells distance of object 

Used to find prey & orient to surroundings 

Use short burst of low frequency clicks to stun prey 

To see more detail, high-frequency clicks are inaudible to humans 

Experiments have shown blinded bottlenose can discriminate slightly 

different sized objects made of different material 

Not sure how it operates 

Cretaceans produce clicks, squeaks, & 

whistles as air forced though air passages & 

several associated air sacs while blowhole is 

closed 

Frequency of clicks change by contracting & 

relaxing muscles along air passages & sacs 

Fatty structure-melon appears to focus & direct 

outgoing sound waves 

Because of shape of melon, skull is modified to 

form a pointed, dish-shape face & asymmetrical 

Right side slightly different from left 

Belugas bulging forehead moved by muscles to 

focus sound



The sperm whale melon called spermaceti organ filled w/waxy-oil 

spermaceti 

Spermaceti use for making candles & still used for lubricants for 

precision instruments 

Help to regulate buoyancy or absorption of excess nitrogen, keeping 

out of blood stream 

Toothed whale receiving sound by lower jaw 

The jaw bones filled w/fat or oil transmit 

sound two very sensitive inner ears 

Each ear receives information 

independently 

Inner ear encased by bone & embedded 

in oil insulates ear but allows sound 

waves to pass from jaw 

Captive dolphins can recognize by 

echolocation objects they have seen & 

recognize by sight they have previously 

echolocate 

3. Behavior 

Rely on past experiences, stored & 

processed by brain, to respond to changes 

in environment 

Social living in groups part of time 

Pinnipeds live in huge colonies during breeding season 

Cetaceans spend entire life in small to large pods 

Vocalizations play role in communication 

Maintain territories during reproduction 

Females and pups/calves recognize each other by sound 

Cetaceans can sound of echolocation & communication at same time 

Social are low frequency sounds (humans cannot hear) 

Different sounds for different moods and sexual signals 

70 calls in killer whales be identified & used by all orcas other calls are 

dialects that can identify certain pods 

Sound used to maintain distances in pods 

Male humpback whales sing to attract females consisting of phrases & 

themes repeated over ½ hour to hour over days 

Cetaceans known for playful behavior



Play w/food or floating objects by throwing them up in the air or holding 

on snout 

Swim head down 

Dolphins play w/ring bubbles they make 

♦ Surf 

Sexual play by touching genital openings 

Breaching is for play, getting rid of external 

parasites, warning signal, scanning surface or 

shoreline 

After deep dive sperm whales may breach & 

fall on backs making splash that can be heard 

2.5 mil and seen 17.4 miles 

Assist in injured members of the group 

Whalers know the harpooned whale lures other whales 

Dolphins carry individual to surface to breath 

Females will carry stillborn calf until it rots 

Many toothed whales work together to hunt- taking turns eating while 

others herd schools of fish 

In dolphins complex society w/long term partnership important in sexual 

behavior, parental care, and other aspects 

Cetaceans show many parallels w/social behavior of apes & humans 

Relationship between dolphins & humans controversial 

Swimming among dolphins offered some resort hotel amazing 

experience 

Trained for military purposes by the former soviet navy being used for 

treatment of children w/ behavior disorders 

Some believe it is the exploitation of captive animals 

Stress of captive dolphins decrease life span 

Authentic cases of dolphins approaching human swimmers in trouble 

Fishers have interpret cues given by dolphins about location and 

abundance of fish 

Generations of dolphins exploited the rows of fishers holding 

nets 

Beaching or stranding occurs w/one to a dozen 

Even if pulled back to sea many will beach again 

Die from collapse of organs without support of water



Follow one or more individuals that have become disoriented by a 

storm, illness, or injury indicating strong cohesiveness & herd instinct 

Stranding whale linked to high-intensity sonar 

After exercises where sonar was used showed hemorrhage in brain & 

inner ears causing disorientation & death 

2002 court decision temporary banned the US Navy from world wide 

sonar 

Noise from ship propellers, depth sounders, & sonar used for scientific 

purposes disturbing whales 

Dolphins spend most time on surface & rest less 

Killer whale calls last longer when whale-watching boats are close 

4. Migrations 

Pinnipeds & cetaceans make seasonal migrations, 

traveling thousands of miles from feeding to breeding 

grounds 

Male southern elephant seals known to travel 5,000 

miles to mate 

Most toothed whales do not migrate but move about to 

feed 

Great whales congregate to feed during summer in 

productive waters of polar regions in both hemispheres 

during winter migrate to warmer waters to breed 

Migratory of gray whale is best known 

End of May to late Sept. feed in shallow waters in 

northern Bering, Beaufort, & East Siberian seas 

Move south lat Sept. by Nov. crossing Aleutian 

Islands 

Lose quarter of body weight traveling 115 miles a day 

Travel alone or small groups along coast of Alaska down to Baja 

California Peninsula in Mexico 

Show spying behavior, pushing head out of water possibly looking for 

landmarks 

Reach Oregon lat Nov. or early Dec. & San Francisco by mid- 

December 

Female migrate earlier 

Late Feb. pregnant females first to appear in Baja California and 

southern mainland of Gulf of California & give birth & males mate 

w/non-pregnant females



North bound migration begins by March after birth of 1500-3000lb calf 

Females mate every 2 years & first to migrate are newly pregnant 

females & return 12 months later to give birth 

North takes longer because of unfavorable currents & newborn calves 

Reach feeding grounds in late May-8 month trip 11200 miles longest 

migration of any mammal 

Suggested navigate by magnetic field implying an internal compass 

Investigation of migration using small transmitters & tracking by satellite 

Some isolated groups of gray whales do not migrate and call the islands 

of the coast of British Columbia home 

Gray whales know to avoid cities by moving away form coast 

Female w/calves known to tack shelter from orcas in kelp forests 

DNA analysis of humpback whale populations in Hawaiian Islands 

suggest that individuals always return to the feeding grounds of their 

mothers 

5. Reproduction 

Reproductive systems similar to land mammals 

Male cetaceans have internal penis and testes 

Penis of blue whale is 10 ft long is kept rigid by 

backbone 

Extrudes just before copulation through genital 

slit (anterior of anus) 

Pinnipeds breed on land & ice migrating long 

distances to isolated islands 

Most species of seals each adult male breeds w/only one female 

Male harbor seals make rumbling noises, quiver necks, & release air 

bubbles to attract mates 

Sea lions, fur seals, & elephant seals a male 

breeds w/many females 

Males, bigger & heavier than females, come 

ashore & establish breeding colonies 

Stop eating to defend territories by constant, 

violent fighting 

Harems may include up to 50 females 

Only strongest male can hold territories & breed 

Others gather into bachelor groups & send much of their time sneaking 

into harems for quick copulation

Male controls harem for 1-2 years 

Pays off w/ huge number of offspring but short life 

span 

Female pinnipeds give birth to pups on shore 

Females go to sea to feed must be able to 

recognize pup by sound and smell 



Pups generally cannot swim at birth & nursed for periods of 4 day to 2 

years depending on species 

Most have two pairs of mammary glands producing 

fat-rich milk for rapid developing pup 

Can only become pregnant after ovulation (when egg 

is released) occurring just days or weeks after the 

birth of pup 

Return to breeding grounds only once a year 

Gestation is less than a year 

♦ This difference would cause pup to be born too early , before 

mother returns to breeding ground 

♦ To prevent this embryo stops development & remains dormant in 

uterus 

♦ Delayed as long as 4 months the embryo attaches to uterus & 

continues w/normal development-delayed implantation 

Cetaceans perform sex play is important component for behavior of 

captive dolphins 

Sex for procreation & pleasure 

Sexually maturity 5-10 years of age in great whales 

Sexual behavior role in establishing & maintaining bonds among all 

individuals, not just mates 

Sexes segregated in pods & males perform elaborate displays 

Fights among rivals are common 

Gray whales are known to copulate w/help of another male supporting the 

female 

Group mating observed in humpback & beluga 

Touching & rubbing after copulation 

Actually copulation less than a minute but repeated 

frequently 

Gestation 11-12 months in most cetaceans 

Sperm whale gestation of 16 months

Birth timed w/migration 



Cetacean calves born tail-first allowing to remain attached to placenta, 

supply of oxygenated blood from mother, preventing oxygen deprivation 

Calf swims immediately to surface 

Captive dolphins mother or attending female many 

help calf to surface 

Fat-rich milk helps calf gain weight before migration 

Blue whale calf gains 200 lbs & 1.5 in every day for 7 

months 

Nipples located on both sides of genital slit & milk squirts into calf’s mouth 

allowing to drink underwater 

Calves not weaned until reach feeding grounds-some species nurse loner 

than a year 

Mother defends calf from danger 

Report of gray females lifting calf on flipper to save from orcas 

Bond may last several years 

Captive young dolphins known to return to mother in times of danger 

or stress 

Great whales live at least 30-40 years on average 

Humpbacks 50 years & bowheads 150 years

Ch. 9: Marine Reptiles, Birds, and Mammals - Mr. Hoyle's Science ...

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