Download Crocodylus porosus

Chapter 11
Reptiles and Birds
© 2006 Thomson-Brooks Cole
Key Concepts
• The evolution of the amniotic egg gave
reptiles a great reproductive
advantage.
• The Asian saltwater crocodile lives in
estuaries and is adapted to life in the
marine environment.
• Sea turtles have streamlined bodies
and appendages modified into flippers.
© 2006 Thomson-Brooks Cole
Key Concepts
• Sea turtles mate at sea and lay eggs
on the same beaches where the
females hatched.
• Sea turtles may migrate long distances
between their breeding grounds and
their nesting beaches.
• Sea turtle populations are endangered
by a number of human endeavors.
© 2006 Thomson-Brooks Cole
Key Concepts
• The marine iguana of the Galápagos
Islands is the only marine lizard.
• Several species of venomous sea
snake live in the marine environment.
• Shorebirds have long legs for wading
and thin, sharp bills for finding food in
shallow water and sand.
© 2006 Thomson-Brooks Cole
Key Concepts
• A variety of bird species, including
gulls, pelicans, and tubenoses, are
adapted to feeding on marine
organisms.
• Penguins are the birds most adapted to
life in the sea.
© 2006 Thomson-Brooks Cole
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
© 2006 Thomson-Brooks Cole
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—sac for disposal of waste
– chorion—a membrane lining the inside of
the shell which provides a surface for gas
exchange during development
• Copulatory organs allow efficient
internal fertilization
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Physiological Adaptations
• 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
• Kidneys are efficient in eliminating
wastes while conserving water
• Skin covered with scales and lacking
glands decreases water loss
© 2006 Thomson-Brooks Cole
Marine Crocodiles
• Best adapted to the marine
environment is the Asian saltwater
crocodile (Crocodylus porosus)
• Large animals (up to 6 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
© 2006 Thomson-Brooks Cole
Sea Turtles
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Sea Turtles
• Adaptations to life at sea
– protective shells that are fused to the
skeleton and fill in the spaces between the
vertebrae and ribs protect their bodies
• outer layer of shell composed of keratin
• inner layer composed of bone
• carapace—dorsal surface of the shell
• pastron—ventral surface of the shell
– leatherback turtle lacks shell and has a
thick hide containing small bony plates
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Sea Turtles
• Adaptations to life at sea (continued)
– shell is flattened, streamlined,d reduced in
size and weight, for buoyancy/swimming
– large fatty deposits beneath the skin and
light, spongy bones add buoyancy
– front limbs are modified into large flippers
– back limbs are paddle shaped and used
for steering and digging nests
© 2006 Thomson-Brooks Cole
Sea Turtles
• Behavior
– generally solitary, don’t interact
– 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
© 2006 Thomson-Brooks Cole
Sea Turtles
• Feeding and nutrition
– have a beak-like structure instead of teeth
– green sea turtle is the only herbivore
– leatherback sea turtles eat jellyfish
• pharynx is lined with sharp spines to hold
slippery prey
• 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
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Sea Turtles
• Reproduction
– courtship – males court females before
mating; males may compete for a female,
or 1 female may mate with several males
– nesting – females dig shallow pits on the
beach, usually at night, and bury eggs
– development and hatching
• temperature determines development time and
sex ratio
• hatchlings rush for the safety of the sea after
hatching
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Sea Turtles
• Turtle migrations
– females migrate from feeding grounds to
the beaches where they were born to nest
– green sea turtles feed on grasses in warm,
shallow continental waters, but breed on
remote islands
• some breed on a 2- or 3-year cycle
– method for navigation over long distances
is unknown
© 2006 Thomson-Brooks Cole
Sea Turtles
• Sea turtles in danger
– beach erosion
– 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
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
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
© 2006 Thomson-Brooks Cole
Marine Iguana
• Feeding and nutrition
– herbivores with a short, heavy snout for
grazing on dense mats of seaweed
– swallow small stones to reduce buoyancy
for feeding under water
– excess salt from consumed seawater is
extracted and excreted by specialized tear
and nasal glands
© 2006 Thomson-Brooks Cole
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
© 2006 Thomson-Brooks Cole
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
© 2006 Thomson-Brooks Cole
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
– eat mainly fish and eels, sometimes eggs
– most ambush prey and strike with
venomous fangs
– can swallow prey more than twice their
diameter
© 2006 Thomson-Brooks Cole
Sea Snakes
• Reproduction
– 3 oviparous species lay eggs on land
– others are viviparous, with females
retaining the eggs within their bodies until
they hatch; young can swim at birth
• Sea snakes and humans
– sea snake venom is toxic to humans
– being timid, sea snakes rarely bite
humans; people eat them in Japan
© 2006 Thomson-Brooks Cole
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:
– shorebirds
– gulls and their relatives
– pelicans and their relatives
– tubenoses
– penguins
© 2006 Thomson-Brooks Cole
Adaptations for Flight
• Homeothermic—maintaining a constant
body temperature
• Feathers aid in flight and insulate
• High rate of metabolism to supply
energy for active flight/nervous system
• Strong muscles, quick responses, great
deal of coordination
• Advanced respiratory system with 4chambered heart
• Keen senses
© 2006 Thomson-Brooks Cole
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
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Shorebirds
• Waders with long legs and thin, sharp
bills used to feed on intertidal
organisms
• Oystercatchers, curlews & turnstones
– oystercatchers use long, blunt, verticallyflattened orange bills to slice through
adductor muscles of bivalve molluscs
– long-billed curlew uses its bill like a
forceps to extract shellfish from burrows
© 2006 Thomson-Brooks Cole
Shorebirds
– heavyset turnstones use slightly upturned
bills as crowbars to turn over stones,
sticks and beach debris in search of food
• Plovers
– have short, plump bodies with bills
resembling a pigeon’s, and are shorter
than other waders
– have nests characteristic of waders, built
in depressions or hollows on the ground
© 2006 Thomson-Brooks Cole
Shorebirds
• Avocets, stilts, and sandpipers
– avocets and stilts have very long legs,
elongated necks, and slender bodies
– 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 bills
– sociable sandpipers feed on small
crustaceans and molluscs as the surf
retreats
© 2006 Thomson-Brooks Cole
Shorebirds
• Herons (e.g. egrets and bitterns)
– 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
© 2006 Thomson-Brooks Cole
Gulls and their Relatives
• 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
• Are not very selective feeders
• Relatives of gulls include terns, skuas,
jaeger birds, skimmers and alcids
© 2006 Thomson-Brooks Cole
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
© 2006 Thomson-Brooks Cole
Gulls and their Relatives
• Gulls (continued)
– nesting
• highly gregarious; 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
• chicks are vulnerable to predation by other
animals and by other gulls
© 2006 Thomson-Brooks Cole
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
• Skuas and jaegers
– very aggressive omnivores and predators
– “hawks” or “vultures” of the sea
– jaegers will pursue other birds to steal their prey
© 2006 Thomson-Brooks Cole
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
© 2006 Thomson-Brooks Cole
Gulls and their Relatives
• Alcids (e.g. auks, puffins, murres)
– look like penguins but are related to gulls
• 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 adaptations
– major difference is that alcids can fly
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Gulls and their Relatives
– nesting and reproduction
• alcids gather in dense, noisy colonies in the
cliffs along the northern Atlantic and Pacific
oceans in early spring
• both parents care for 1 pear-shaped egg
– parental care of the young
• young murres plunge into the water to be
joined by the parents, and swim out to sea
• alcid 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
© 2006 Thomson-Brooks Cole
Pelicans and their Relatives
• E.g., 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
© 2006 Thomson-Brooks Cole
Pelicans and their Relatives
• Pelicans
– 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 pouches as nets
• gular pouch—a sac of skin that hangs between
the flexible bones of the bird’s lower mandible
© 2006 Thomson-Brooks Cole
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
© 2006 Thomson-Brooks Cole
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
– lightweight body and near 2 m wingspan
– lacking oil glands, they feed by skimming
with their bills
– pursue/attack©other
birds to steal prey
2006 Thomson-Brooks Cole
© 2006 Thomson-Brooks Cole
Tubenoses
• E.g. petrels, albatrosses, shearwaters
• Have obvious tubular nostrils on their
beaks which join with large nasal
cavities within the head
• Nasal glands secrete concentrated salt
solution
• Stomachs contain a large gland that
produces a yellow oil composed of
liquefied fat and vitamin A, used for
feeding hatchlings and defense
© 2006 Thomson-Brooks Cole
Tubenoses
• Albatrosses
– 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
– 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
© 2006 Thomson-Brooks Cole
Tubenoses
• Petrels
– 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 yearround cold water
• spot prey from the air, perform a headlong
dive, and pursue prey by “flying” underwater
© 2006 Thomson-Brooks Cole
Penguins
• 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
© 2006 Thomson-Brooks Cole
Penguins
• Reproduction in Antarctic species
– 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
© 2006 Thomson-Brooks Cole
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
© 2006 Thomson-Brooks Cole