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Chapter 11
Marine Reptiles and Birds
Karleskint
Turner
Small
Marine Reptiles
• Reptiles adapted for success on land, then
used the same characteristics to return to
the sea and gain success there as well
• Modern-day reptiles include:
– crocodilians
– turtles
– lizards
– snakes
• All are represented in the marine
environment
Physiological Adaptations
• Advanced circulatory system in which
circulation through the lungs is nearly
completely separate from circulation
through the rest of the body
• Kidneys are efficient in eliminating wastes
while conserving water, allowing reptiles to
inhabit both dry regions and the salty
ocean
• Skin covered with scales and lacking
glands decreases water loss
Marine Crocodiles
• Best adapted to the marine environment is
the Asian saltwater crocodile (Crocodylus
porosus)
• Largest living reptiles (males can grow up to
6 to 7 m long)
• Feed mainly on fishes
• Drink salt water and eliminate excess salt
through salt glands on their tongues
• Lives along the shore, where it nests
Marine Crocodiles
• Females reach sexual maturity at 10 – 12
years of age, males mature at ~ 16 years.
• Elevated nests contain 40 – 60 eggs,
incubation period is ~ 90 days
• Communicate with calls or barks
• Good navigational skills, can return to home
estuary after being displaced long distances,
using clues from sun and earth’s magnetic
field
Sea Turtles
• Seven species inhabit world’s oceans
• Adaptations to life at sea
– protective shells that are fused to the skeleton
and fill in the spaces between the vertebrae and
the ribs
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•
•
•
outer layer of shell composed of keratin
inner layer composed of bone
carapace: dorsal surface of the shell
plastron: ventral surface of the shell
– leatherback turtle lacks shell and has a thick
hide containing small bony plates
Sea Turtles
• Adaptations to life at sea (continued)
– shell is flattened, streamlined, reduced in size
and weight, for buoyancy/swimming
– large fatty deposits beneath the skin and light,
spongy bones add buoyancy
– large fatty deposits beneath skin and spongy
body also aid in buoyancy
– front limbs are modified into large flippers
– back limbs are paddle shaped and used for
steering and digging nests
Sea Turtles
• Behavior
– generally solitary, interact for courtship and
mating
– remain submerged while at sea; breathe air but
can stay under water for as long as 3 hours
– alternate between feeding and resting during the
day
– sleep on the bottom under rocks or coral, in
deep water, sea turtles can sleep on surface
Sea Turtles
• Feeding and nutrition
– have a beak-like structure instead of teeth
– green sea turtle is the only herbivore, others
are carnivorous
– leatherback sea turtles eat jellyfish
– large amounts of salt consumed with food and
water are eliminated as concentrated tears
through salt glands above the eyes
Sea Turtles
• Reproduction
– courtship – males court females before mating; males
may compete for a female, or 1 female may mate with
several males and lay eggs fertilized by several different
males thereby increasing genetic diversity of population
– nesting – females dig shallow pits on the beach, usually
at night, and bury eggs, clutch size is between 80 – 150
eggs
– Single female can lay several clutches of eggs at 2 to 3
week intervals
– development and hatching
• average incubation time is 60 days
• temperature determines development time and sex ratio
• hatchlings rush for the safety of the sea after hatching
Sea Turtles
• Turtle migrations
– migrate hundreds to thousands of kilometers from
feeding grounds to nesting beaches
– females return repeatedly to beaches where they were
born to nest
• some breed on a 2- or 3-year cycle
– many hypotheses explaining method for sea turtle
navigation over long distances:
• utilize smell and taste as well as auditory cues
• sense angle intensity of earth’s magnetic field
• use sun
Sea Turtles
• Sea turtles in danger
– beach erosion/alteration
– artificial lighting near nesting beaches
– sea turtles are killed when trapped in fishing nests,
especially those used for shrimpers
• turtle exclusion devices can reduce turtle mortality by as
much as 95% when used for shrimp nets
– turtles are hunted by humans for meat, eggs, leather
and shells
– Dogs, cats and raccoons dig up nests and prey on
eggs
Marine Iguana
• The marine iguana of the Galápagos Islands
off Ecuador is the only marine lizard
• Most are black, but some are mottled red
and black
– dark coloration is thought to allow more
absorption of heat energy
– raising body temperature allows them to swim
and feed in cold Pacific waters
– few natural predators but vulnerable to feral
predators such as rats, dogs and cats
Marine Iguana
• Feeding and nutrition
– herbivores with a short, heavy snout for grazing
on dense mats of seaweed
– larger animals dive at high tide to feed on deep
water algae, smaller animals feed in the
intertidal
– excess salt from consumed seawater is
extracted and excreted by specialized tear and
nasal glands
Marine Iguana
• Behaviors
– good swimmers, using lateral undulations of
the body and tail
– each male occupies a small territory on the
rocks, usually with 1 or 2 females
– intruders or challengers are attacked when
they enter the male’s territory
• fights between male iguanas rarely result in
serious injury and population remains unaffected
Sea Snakes
• Adaptations to life in the sea
– scales are absent or greatly reduced for
streamlining
– tail is laterally compressed into a paddle
– nostrils are higher on the head
• valves in the nostrils prevent water from entering
when the snake is submerged
– single lung reaches to the tail, and trachea is
modified to act as an accessory lung by
absorbing oxygen
Sea Snakes
• Adaptations to life in the sea (cont.)
– can exchange gases through the skin while under
water
– can lower metabolic rate to use less O2
• Feeding and nutrition
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–
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eat mainly fish, fish eggs and eels
most ambush prey and strike with venomous fangs
can swallow prey more than twice their diameter
eliminate excess salt by way of a salt excreting gland
located posteriorly under the tongue
Sea Snakes
• Reproduction
– congregate in enormous numbers to mate
• Sea snakes and humans
– sea snake venom is toxic to humans
– being timid, sea snakes rarely bite humans;
people eat them in Japan
Seabirds
• 250 of 8,500 bird species are adapted to live
near or in the sea
• Seabirds feed in the sea
• Some spend months away from land, but all
must return to land to breed
• Types of seabirds:
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–
–
–
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shorebirds
gulls and their relatives
pelicans and their relatives
tubenoses
penguins
Adaptations for Flight
• Feathers aid in flight and insulate
• High rate of metabolism to supply energy for active
flight/nervous system
• Strong muscles, quick responses and great deal of
coordination aid birds in flight
• Advanced respiratory system with 4-chambered
heart provides more oxygen to active muscles
• Keen senses (especially sight and hearing) and
relatively large brain to process sensory
information effectively
Adapting to Life in the Sea
• Large amounts of salt are consumed with
food and salt water
– salt glands above the eyes produce tears to
remove excess salt
– these tears have twice the salt concentration
of seawater
Shorebirds
• Waders feed on an abundance of intertidal
marine life
Shorebirds
• Herons (Family Ardeidae)
– include egrets and bitterns
– widespread, represented on every continent
– skinny legs and long necks aid in hunting
– most stand still and wait for prey to come in
range to feed
– some stalk prey or stir up the bottom to frighten
prey into motion so it can be caught
Gulls and Their Relatives
• Family Laridae
• Gulls have webbed feet and oil glands to
waterproof their feathers
• They are not true ocean-going birds, and do
not stray far from land
• Have enormous appetites but are not
selective feeders
• Relatives of gulls include terns
Gulls and Their Relatives
• Gulls
– herring gulls are the most widespread, and are
vocal, gray and white, and travel in large groups
– feeding
• noisy, aggressive, efficient predators and scavengers
• may drop prey with hard shells on rocks or parking
lots to break the shell open
• highly successful at finding food and surviving, in
some areas have reached nuisance proportions
Gulls and Their Relatives
• Gulls (continued)
– nesting
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•
•
•
gather in large colonies
not picky about nesting sites or materials
both sexes assist in incubating 2-3 eggs
chicks hatch in 3-4 weeks, and remain in the nest
until almost fully grown, camouflaged by speckled
down
• female can lay another clutch of eggs immediately if
first one is lost
• chicks are vulnerable to predation by other animals
and by other gulls, not uncommon for only 1 out of
every 5 hatchlings to survive
Gulls and Their Relatives
• Terns
– small, graceful birds with brightly-colored and
delicately-sculpted bills, forked tails
– hunt by plunging into the water for fish and
invertebrates; will steal food
– usually gregarious nesters
Gulls and Their Relatives
• Alcids (Family Alcidae)
• Includes puffins
• look like penguins but are related to gulls
– major difference is that alcids can fly
Gulls and Their Relatives
• Alcids (continued)
– parental care of the young
• young plunge into the water to be joined by the
parents, and swim out to sea
• parents spend most of their time gathering food for
hungry chicks
• adult puffins abruptly leave chicks to learn to swim
and survive by themselves after 6 weeks of constant
care
Pelicans and Their Relatives
• Pelicans (Order Pelecaniformes) include
gannets, boobies, cormorants, darters,
frigatebirds, tropicbirds
• Have webs between all 4 toes
• Upper mandible is hooked in pelicans,
cormorants and frigatebirds
• Many are brightly colored, or have head
adornments
Pelicans and Their Relatives
• Pelicans (Family Pelecanidae)
– large birds preferring warm latitudes and
estuary, coastal and inland waters
– require a large fish population to support
colonies of large birds
– feed just under the water’s surface using
pouches as nets
• a sac of skin that hangs between the flexible bones
of the bird’s lower mandible
Pelicans and Their Relatives
• Boobies
– dive into the sea from 18-30 m up to fish
– species lay differing numbers of eggs; this is
thought to reflect the reliability of the food supply
around where they nest
• Cormorants
– swim along the surface scanning for fish, then
plunge deep to pursue them
– lacking oil glands, they must periodically dry
their wings in order to fly
Pelicans and Their Relatives
• Cormorants (continued)
– most are strong fliers, but the Galápagos Island species
is flightless
– guano cormorant of the coast of Peru valued for its
guano (bird manure)
• Frigatebirds (Family Frigatidae)
– lightweight body and near 2 m wingspan
– lacking oil glands and cannot waterproof their feathers –
if forced to settle on ocean surface most likely will drown
– hence they feed by skimming surface with their bills
– pursue/attack other birds to steal prey
Tubenoses
• Albatrosses (Family Diomedeidae)
– gliders with wings nearly 3.5 m long
– most live in the Southern Hemisphere where
winds circle the earth without encountering land
– usually come to land only to breed
– elaborate courtship displays precede mating
– 1 egg is incubated by both parents on a
volcano-shaped nest, and the young are fed on
stomach oil, then regurgitated fish
Penguins
• Penguins (Family Sphenisciformes)
• Bird most adapted to marine lifestyle
• Awkward on land, but swift swimmers
– flap their wings to swim
– torpedo-shaped bodies are streamlined
– flat, webbed feet are used for steering
– leap from the water to breathe
• Eat fishes, squid and krill
• Eaten by leopard seals and killer whales
Penguins
• Adelie penguins lay eggs in summer;
emperor penguins in mid-winter
• Female emperor penguin lays 1 egg, which
the male incubates for 2 months while she
visits her feeding grounds
– egg sits on his feet, covered by a fold of skin
– male can feed the chick a secretion from his
crop if it hatches before female’s return
– crop—a digestive organ that stores food before
it is processed
Penguins
– female returns with food in her crop for the
chick, and male can feed
– both parents help to feed the chick once it
reaches 6 weeks
– by summer, the chick can feed itself, and is
ready to enter the sea