© 2006 thomson-brooks cole chapter 11 reptiles and birds

© 2006 Thomson-Brooks Cole

Chapter 11

Reptiles and Birds


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.


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.


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.


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.


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


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


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


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


Sea Turtles


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


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


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


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


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


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


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


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


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


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


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– eat mainly fish and eels, sometimes eggs– most ambush prey and strike with

venomous fangs– can swallow prey more than twice their

diameter


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


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


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 4-

chambered heart• Keen senses


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 with long legs and thin, sharp bills used to feed on intertidal organisms

• Oystercatchers, curlews & turnstones– oystercatchers use long, blunt, vertically-

flattened orange bills to slice through adductor muscles of bivalve molluscs

– long-billed curlew uses its bill like a forceps to extract shellfish from burrows


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


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


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


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



• 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



• 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



• 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



• 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



• 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



– 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


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



• 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



• 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



• 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


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


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


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 year-

round cold water• spot prey from the air, perform a headlong

dive, and pursue prey by “flying” underwater


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


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


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 chapter 11 reptiles and birds

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