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Who, What, When, Where, Why, and How of
Reptiles and Birds
• Who studies reptiles? Birds?
• What is an adaptation that allowed for
reptiles to be successful as a group?
• Where are shore birds found?
• Why are birds adapted to flight?
• How do birds and reptiles compare?
Chapter 11
Marine Reptiles and Birds
Marine Reptiles
• Ancestors of modern reptiles appeared about 100
million years ago.
• 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:
• All are represented in the marine environment
Amniotic Egg
• An amniotic egg is covered by a protective shell
and contains:
amnion: a liquid-filled sac in which the embryo develops
yolk sac: sac where yolk (food) is stored
allantois: an additional sac for disposal of waste
chorion: membrane lining inside of the shell providing a
surface for gas exchange during development
• Evolution of amniotic egg allowed longer
development (within egg) eliminating predator
prone larval stage and because eggs are laid in dry
places, aquatic predators are avoided
• Copulatory organs allow efficient internal
Physiological Adaptations
• Other adaptations helping reptiles survive on
land and in the ocean include:
• Advanced circulatory system in which circulation
through the lungs is nearly completely separate
from circulation through the rest of the body
– more efficient method of supplying oxygen to animal’s
• 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
• 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
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
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
– 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
– 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
• pharynx is lined with sharp spines to hold slippery
• digestive system adapted to withstand stings
– 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
– 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
– green sea turtles feed on grasses in warm, shallow
continental waters, but breed on remote islands
thousands of kilometers away
• 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 af 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
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
– 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
• Descendants of lizards that have lost their limbs as
an adaptation to a burrowing lifestyle
• 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
– can lower metabolic rate to use less O2
• Feeding and nutrition
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
• Sea Snakes and Humans
– toxin can be highly toxic to humans
– sea snakes timid by nature, rarely bite
humans, no accounts of attacking swimmers
– in Japan, sea snake consumption supports a
major fishery
• 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:
gulls and their relatives
pelicans and their relatives
Adaptations for Flight
• Homeothermic—maintaining a constant body
• 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
• Waders that feed on an
abundance of intertidal marine life
• Include oyster catchers, plovers
and turnstones, sandpipers and
curlews, avocets and stilts and
• Oystercatchers (Family
– oystercatchers use long, blunt,
vertically-flattened orange bills
to slice through adductor
muscles of bivalve molluscs
– use bills to pry limpets off rocks,
crush crabs and probe mud
• Plovers and Turnstones (Family
• Plovers
– have short, plump bodies with
bills resembling a pigeon’s,
and are shorter than other
– have nests characteristic of
waders, built in depressions
or hollows on the ground
• Turnstones
– heavyset birds, use slightly
upturned bills as crowbars to
turn over stones, sticks and
beach debris in search of food
• Sandpipers and Curlews (Family
• Sandpipers
– are relatives of plovers and
– feed on small crustaceans and
molluscs in sand as tide
• Curlews
– long-billed curlew uses bill like
a forceps to extract shellfish
from their burrows
• Avocets and Stilts (Family
– avocets and stilts have very long
legs, elongated necks, and slender
– avocets wade through shallow water,
moving a partially opened beak from
side to side through the water, to feed
– stilts probe the mud for small animals
(e.g. insects, crustaceans) with their
• 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, skuas, jaeger
birds, skimmers and alcids
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
– small, graceful birds with
brightly-colored and delicatelysculpted bills, forked tails
– hunt by plunging into the water
for fish and invertebrates; will
steal food
– usually gregarious nesters
Skuas and Jaegers
– very aggressive omnivores and
– “hawks” or “vultures” of the sea
– jaegers will pursue other birds
to steal their prey
Gulls and Their Relatives
• Skimmers (scissorbills)
– small birds with pupils that are
vertical slits and a flexible lower
jaw protruding much farther than
the upper bill
– fly over water and use the lower
bill to create ripples at the water’s
surface that attract fish
– fish are then collected by flying
along the same path over the
water a second time
Gulls and Their Relatives
• Alcids (Family Alcidae)
• Include auks, puffins and murres
– look like penguins but are related to
• convergent evolution: similar
selective pressures brought
about similar adaptations in
unrelated groups of animals
• ecological equivalents: different
groups of animal that have
evolved independently along the
same lines in similar habitats,
and therefore display similar
– major difference is that alcids can fly
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
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 gular
(throat) pouches as nets
• gular pouch: a sac of skin that hangs between the
flexible bones of the bird’s lower mandible
Pelicans and Their Relatives
– 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
– 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
– 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
• Tubenoses (Order Procellariiformes) include
petrels, albatrosses and shearwaters
• Have obvious tubular nostrils on their beaks
which join with large nasal cavities within
the head
• Nasal glands secrete concentrated salt
• Stomachs contain a large gland that
produces a yellow oil composed of liquefied
fat and vitamin A, used for feeding
hatchlings and defense
• 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
• Petrels (Family Hydrobatidae)
– storm petrels are small birds with long legs with
a characteristic, fluttering flight
• feed with legs extended and feet paddling rapidly just
below the surface
• form long-term pair bonds for breeding
– diving petrels resemble auks
• live only in the Southern Hemisphere in year-round
cold water
• spot prey from the air, perform a headlong dive, and
pursue prey by “flying” underwater
• 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
• 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
– 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
Chapter 11 Concepts
• What is the amniotic egg? What did the
step in evolution do?
• What are the physiological adaptations of
reptiles to marine life?
• What are the adaptations necessary for
bird flight?
• Table 11