Transcript Chapter 12 - marine mammals

Who, What, When, Where, Why, and How of
Marine Mammals
• Who studies mammals?
• What are the characteristics of mammals?
• Where are most marine mammals found?
Think diversity.
• When do whales migrate?
• Why do whales migrate?
• How are dolphins and whales related?
Chapter 12
Marine Mammals
Karleskint
Turner
Small
Characteristics of Marine Mammals
• Class Mammalia
• Most have an insulating body covering of
hair
• Homeothermic (warm body temperature)
– allows activity day and night, and adaptation
to a wide range of habitats
• Mothers feed their young with milk
– mammary glands: special glands in the
female that secrete milk
Characteristics of Marine Mammals
• Marine mammals are placental
mammals—animals that retain their young
inside their body until they are ready to be
born
– placenta: an organ present only during
pregnancy that sustains the young
• Feed at various trophic levels
Sea Otters
• Sea Otters (Enhydra lutris; order Carnivora)
• Found along California coast as far north as the
Aleutian Islands
• Short, erect ears
• Dexterous 5-fingered forelimbs
• Well-defined hind limbs with fin-like feet
• Have thick fur with an underlying air layer for
insulation (instead of blubber)
• Usually stay within a mile of shore, near coastal
reefs and kelp beds
Sea Otters
• Females normally give birth to 1 pup on
shoreline rocks, and it soon follows its
mother into the sea
• Consume nearly 25% of their body weight
in food each day
– eat sea urchins, molluscs, crustaceans, some
species of fish
• Diurnal, gregarious, vocal and playful
• Nearly hunted to extinction for fur
Polar Bears
• Polar Bears (Ursus maritimus; order Carnivora)
• Top predators in Arctic food chains
• Large, adult male may grow to ~3 meters (9.9 ft)
and weigh 725 kilograms (1,595 lbs)
• Live on shifting ice sheets and floes
• Well adapted to cold environment
– large body (small surface area to volume)
– black skin absorbs radiant energy
– dense layer of underfur
Polar Bears
• Diet consists primarily of seals
• Mate in spring, males compete aggressively with
other males for available females
• Females give birth usually to 2 cubs each weighing
1 lbs
• Global warming causing shrinkage of ice sheets on
which polar bears hunt
• Although population is now estimated at 40,000
(was 10,000 in the 1960’s) polar bears are
considered endangered
Pinnipeds: Seals, Sea Lions, and Walruses
• Order carnivora; Suborder Pinnipedia
– include seals, elephant seals, sea lions and
walruses
– pinniped—”feather-footed”
• Have 4 limbs like terrestrial animals, but
are more at home in the water
• Come shore to give birth and molt
– most also mate on shore, and some sleep on
land or ice floes to avoid entirely aquatic
predators
Pinnipeds: Seals, Sea Lions, and Walruses
• Eat fish, larger invertebrates; some eat
other homeothermic animals
• Natural predators include sharks, killer
whales and humans
Pinniped Characteristics
• 3 families:
– eared seals (Otariidae)
– true seals (Phocidae)
– walruses (Odobenidae)
• Eared seals have small external ears and
swim using their forelimbs
• Phocids (true seals) lack external ears and
swim with a sculling movement of their
hind flippers
Pinniped Characteristics
• Walruses swim with a combination of the 2
methods
• Pinnipeds have spindle-shaped bodies
• Many have several thick layers of
subcutaneous fat
• Round head is carried on a distinct neck
• Large brains, well-developed senses
• 2 pairs of limbs are modified into flippers
Swimming and Diving
• Fast swimmers and expert divers
• Adaptations for diving
– exhale before diving to decrease buoyancy
– metabolism slows by 20% and heart rate
decreases while under water to conserve
oxygen
– during dive, blood is redistributed to direct
oxygen to vital organs such as the brain and
heart
• Have 10 to 30 times more oxygen in their
muscles than humans
Eared Seals
• Sea lions
– coarse coat of nothing but hair
– e.g., California sea lion, the intelligent trained seal
seen in zoos and circuses
– highly social; congregate when on shore
• Fur seals
– distinguished from sea lions by thick, wooly
undercoats
– coats are prized in the fur market, so hunting is
limited to avoid decimating the population of fur seals
Phocids, or True Seals
• Forelimbs are set closer to the head and
smaller than the hind limbs
– less adapted to life on land, can’t move
around very well
– move on land by dragging their bodies
• Most congregate during breeding season;
males establish territories but mate with
only 1 female
• Most abundant: crabeater seal, which
actually eats plankton such as krill
Phocids, or True Seals
• Harbor seals are a familiar type
• Harp seal pups have a white coat, and are
thus prized in the fur market
• Leopard seal is only phocid that eats
homeothermic prey, penguins, sea birds
and other seals make up bulk of diet
Phocids, or True Seals
• Elephant seals are the largest, and bulls
have a unique proboscis that amplifies
their roar and attracts mates
Walruses
• Lack external ears but have a distinct neck and
hind limbs that can be used for walking on land
• Can grow to 3 to 5 meters (10 to 16 ft) in length
and weigh up to 1,364 kilograms (3,000 lbs)
• Canine teeth of the upper jaws of males have
developed into tusks
– used to fight with other males or hoist the animal onto
ice floes
• Typical family group = 1 dominant bull with a
harem of up to 3 females and 6 calves of various
ages
Walruses
• Reproduction
– 11-month gestation period
– 1 or 2 calves stay with the mother until they are
4 or 5 years old
– old bulls sometimes kill young
• Found in the Arctic region
• Eat fishes, crustaceans, molluscs and
echinoderms
• Native people are allowed to hunt them for
meat, but not for their tusks
Sirens: Manatees and Dugongs
• Order Sirenia (sirenians)
• Now confined to coastal areas and
estuaries of tropical seas
• Similarities to whales
– streamlined, practically hairless bodies
– forelimbs that form flippers, tail flukes
– vestigial pelvis without hind limbs
• Completely aquatic, helpless on land
Sirens: Manatees and Dugongs
• Gentle and often trusting of humans
• Two families: one represented by the
manatees (family Trichechidae) in Atlantic
Ocean and Caribbean Sea; the other by
the dugongs (family Dugongidae) of the
Indian Ocean.
Dugongs
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•
•
•
Strictly marine
Live in coastal areas of Indian Ocean
Feed on shallow-water grasses
Dugongs are distinguished anatomically
from manatees by:
– larger heads
– shorter flippers
– notched tail
• Only one species
Manatees
• Three species
• Inhabit both the sea and inland rivers and lakes
• Mate and give birth under water
– male remains with female after breeding
– female gives birth to single calf after 11 months
gestation period
• Strict vegetarians that consume large amounts
of shallow-water plants
• Motorboat propellers are the greatest danger to
northern manatees
Steller’s Sea Cow
• This Arctic sirenian is now extinct
• Species was first observed and recorded by
Georg Wilhelm Steller
• After his expedition brought furs from the
Commander Islands, this area developed a
reputation for furs which attracted hunters
• The hunters used Steller’s sea cow as a food
source, and hunted the species to extinction
Cetaceans: Whales and Their Relatives
• Include whales, dolphins, porpoises
• Mammals most adapted to life at sea
• Cetaceans have fascinated humans for
centuries
• Cetaceans have frequently appeared in art
and literature
General Characteristics of Cetaceans
• Thought to have evolved from terrestrial
carnivores (now extinct)
• Bodies closely resemble those of fishes
and are very streamlined
– blowhole: nostril at the top of the head
– uniformly thick layer of subcutaneous blubber
– streamlining of body results in lack of neck,
inability to move head separately
– internal ears with wax plugs
General Characteristics of Cetaceans
• Bodies closely resemble those of fishes and are
very streamlined (continued)
–
–
–
–
essentially hairless, except for a few hairs on the head
lack of sweat glands conserves water
forelimbs modified into stabilizing flippers
tail composed of flat flukes composed of dense
connective tissue is the main organ of propulsion and
regulates vertical movement
– countercurrent circulatory system with cold blood
directed to un-insulated flippers conserves heat
Flipper
Artery
Vein
Artery
Vein
Tail fluke
Artery
Warm arterial blood from the animal's body core
transfers heat to the cooler venous blood
Heat flow
Blood
flow
Heat flow
Blood
flow
Vein
Stepped Art
Fig. 12-10, p. 338
Adaptations for Diving
• Lungs are smaller in proportion to their body size
(compared to humans) and can exchange 80 to
90% of oxygen with their blood
• Lungs and rib cage structured to collapse easily
upon descent
– contain little air during a dive
– animal avoids problems of compression and
decompression while diving/surfacing
• During a dive:
– metabolism and heart rate decrease
– blood is preferentially shunted to vital organs and tissues
(e.g., brain, spinal cord)
Adaptations for Diving
• Medulla oblongata (portion of brain that
controls breathing) is less sensitive to CO2
levels in blood
– can hold breath without urge to breathe
• Large amounts of hemoglobin and
myoglobin
– hemoglobin: molecule in red blood cells
responsible for carrying oxygen
– myoglobin: molecule in muscle tissue that is a
reservoir of oxygen for muscle activity
Adaptations for Diving
• Muscles less sensitive to lactic acid
– lactic acid: a waste produced during vigorous or
extended muscle activity in the presence of
insufficient oxygen
• Exhalation of mucus from blowhole upon
surfacing helps eliminate nitrogen from
inhaled air, preventing the bends
– the bends: condition in which nitrogen gas
dissolved in blood comes out of solution and
forms gas bubbles
Adaptations for Diving
• Water is prevented from entering
respiratory passages
– larynx opens into the nasal chambers instead
of the back of the throat
– cetaceans can open their mouths under water
without food or water entering respiratory
passages
Cetacean Behaviors
• Spy hopping: sticking the head straight up out of
the water and surveying the surroundings
– uses strong fluke to push itself partially out of water,
position maintained with buoyancy control and
positioning of pectoral fins, tail flukes
– occurs when cetacean is interested in a passing boat
or other object
– may help whale to establish bearings in coastal
waters
Cetacean Behaviors
• Breaching: completely or almost
completely leaving the water
– whale accelerates under water and then hits
the surface, exiting the water
– may be used to establish dominance or
communicate arrival/leaving
– serial breaching: breaching several times in a
row
– head lunge: breaking the surface and falling
forward instead of backward
Cetacean Behaviors
• Slapping
– tail slapping or lobbing: lifting the tail and
slapping it forcefully on the surface of the water,
creating huge splash and loud noise, associated
with marking position, interpreted as an
aggressive behavior
– tail cocking: cocking the tail in the air and
bringing it down upon an opponent, also
considered aggressive behavior
– peduncle slap: swinging the rear portion of the
body out of the water, and then dropping it
down sideways on the water or another whale
Cetacean Behaviors
• Slapping (continued)
– peduncle slap: swinging the rear portion of the
body out of the water, and then dropping it
down sideways on the water or another whale
– tail slashing and tail swishing: moving the tail
from side to side across the surface of the water
to create turbulence
– whale may arch its body and then bring the
flukes above the surface
• straight up so ventral surface is visible = fluke up
• fluke clears the water but remains turned down =
fluke down
Cetacean Behaviors
• Slapping (continued)
– flipper flapping: rolling over onto the back and
flapping the flippers in the air
– pectoral stroking: stroking the body of another
whale with the pectoral fins
• occurs between mother and calf or during
courtship and mating
– both flipper flapping and pectoral stroking are
thought to be forms of communication
Types of Whales
• 2 suborders
– Mysticeti – baleen whales
– Odontoceti – toothed whales
• Baleen whales lack teeth, and filter food
from the water using baleen
– largest whales are of this type
• Toothed whales feed on larger prey
– e.g., dolphins, killer whales
Baleen Whales
• Enormous mouths with plates of baleen
– each plate has an elongated triangular shape
and is anchored at its base to the gum of the
upper jaw
– composed of keratin—a tough protein—in
fibers fused except at the inner edge, where
they form a fringe
– hundreds of plates form a tight mesh
– used to capture plankton, especially krill, and
fish
Baleen Whales
• Whale feeds by swimming open-mouthed
through the water into dense groups of krill
and fish, then strains out water through
baleen
– bubble net: a ring of bubbles blown by a
humpback whale to trap krill near the surface
for collection
• Baleen is protected by the underlip when
the whale is not feeding
Krill
Bubbles
Whale ascends in a spiral
pattern blowing bubbles
from its blowhole
Stepped Art
Fig. 12-15, p. 344
Baleen Whales
• Right Whales and Bowhead Whales
(family Balaenidae)
– distinguished by lack of dorsal fins and
grooves on throat and chest
– name derived from identification of these
whales as the “right whales” for hunting
– the bowhead whale is the rarest of all whales
Baleen Whales
• Rorquals (family Balenopteridae)
– have dorsal fin and ventral grooves lacking in
balaenids
• ventral grooves allow the throat to expand while the
animal is feeding
– slender, streamlined, fast swimmers
– blue whale is the largest whale, maybe the
largest animal that has ever lived, 24-30 meters
(80 – 100 ft) long, weighing more than 100 tons
– fin whale is second largest
– humpback whale has hump on its back, bosses
(bumps) on its snout, and very long pectoral fins,
inhabits coastal waters frequently enters harbors
and ventures up river mouths
Baleen Whales
• Rorquals (family Balenopteridae) (continued)
– modern whaling techniques allowed for effective
hunting of large rorquals
– blue whale given worldwide protection in 1966
by the International Whaling Commission
Baleen Whales
• Gray whale (Eschrictius gibbosus)
– only eastern Pacific population survives today
after western Pacific and Atlantic populations
were hunted to extinction
– migrate from summer feeding grounds in
Bering Sea to waters off Baja California to
mate and give birth
– referred to as mossback whales owing to
large accumulations of barnacles on their skin
Toothed Whales
• Include sperm whales, dolphins, porpoises, killer
whales and narwhals
• Sperm whales (Physeter macrocephalus; family
Physeteridae)
– 3rd largest animal with massive blunt snout
– have a series of humps on the rear third of the body,
no real dorsal fin
– aggressive attackers of squid and fish, occasionally
whalers in small boats
– polygynous – males accompanied by several females
– named for spermaceti—an oily, wax-like substance in
the animal’s head
Toothed Whales
• Sperm whales (continued)
– ambergris: a digestive product; a secretion
thought to function in protecting the enormous
digestive system from undigested squid beaks
and cuttlefish cuttlebone
– spermaceti was sought as a high-grade wax;
ambergris, as a base for perfumes
Toothed Whales
• White whales (family Monodontidae)
– Beluga whales
• are unique for their white color and ability to bend
neck, are found in northern polar seas
• main predators are killer whales and polar bears
– Narwhals
• close relatives of beluga whales
• male have tusk developed from 1 of 2 tooth buds
• narwhals also inhabit Arctic waters, eskimos only
remaining predators
Toothed Whales
• Porpoises (family Phocaenidae)
– Related to dolphins, both in same
superfamily, Delphinoidea
– porpoises have a rounded head with no beak
(dolphins have a beak)
– harbor porpoises are small cetaceans known
for great intelligence, and have a wide
distribution in the North Atlantic
– Dall’s porpoise is perhaps the first animal to
be protected by law – Europeans once
considered it a rare delicacy
Toothed Whales
• Dolphins (family Delphinidae)
– collectively referred to as delphinids
– common dolphin has a definite beak
separated from the snout by a groove; known
for encircling and following ships
– bottlenose dolphins are used in research on
cetacean intelligence, and as performing
animals at aquariums
– orca (killer whale) is the largest dolphin; only
cetacean that eats homeothermic prey (e.g.
seals, sea lions, penguins)
Toothed Whales
• Dolphins (continued)
– pilot whales have a globular head, projecting
forehead, and muzzle that forms a small beak
• known for beaching themselves in large numbers
Echolocation
• Ears are modified to receive a wide range of
underwater vibrations
• Echolocation allows cetaceans to distinguish
and hone in on objects from distances of several
hundred meters
• Dolphins emit clicking sounds
– orientation clicks: low-frequency clicks that give the
animal a general idea of its surroundings
– discrimination clicks: high-frequency clicks that give
the animal a precise picture of a particular object
Echolocation
• No vocal cords; sounds are produced by a
ring of muscles in the larynx, which allows
control of air flow
• Sounds are directed by being focused in
the melon
– melon: an oval mass of fatty, waxy material
located between the blowhole and the end of
the head
• Clicking sounds bounce off objects;
echoes picked up by sensitive areas on
the lower jaw
Echolocation
• Echoes provide 4 types of information:
– direction from which echo is coming
– change in frequency
– amplitude
– time elapsed before the sound returns
• With this information, dolphin determines
object’s range, bearing, size, shape, texture
and density
• Traveling dolphins move their heads side to
side and up and down, scanning for objects
Chapter 12 Concepts
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•
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Mammal characteristics
Cetacean characteristics
Adaptations of diving
Behaviors
Echolocation
Table 12