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Chapter 11Chapter 11Marine Reptiles and BirdsMarine 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:– crocodilians– turtles– lizards– snakes

• 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 fertilization

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

tissues

• 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

• 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

• 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• 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 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• 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 water

– 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• Reproduction

– 3 oviparous species lay eggs on land– others are viviparous, with females retaining the eggs

within their bodies until they hatch– congregate in enormous numbers to mate– male sea snakes have two penises called hemipenes– gestation period ranges from 4 to 11 months, 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

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

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 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 that feed on an abundance of

intertidal marine life • Include oyster catchers, plovers and

turnstones, sandpipers and curlews, avocets and stilts and herons

• Oystercatchers (Family Haematopodidae)– 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

Shorebirds• Plovers and Turnstones (Family

Charadriidae)• 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

• Turnstones– heavyset birds, use slightly upturned bills as

crowbars to turn over stones, sticks and beach debris in search of food

Shorebirds• Sandpipers and Curlews (Family

Scolopacidae)• Sandpipers

– are relatives of plovers and oystercatchers– feed on small crustaceans and molluscs in sand

as tide recedes

• Curlews– long-billed curlew uses bill like a forceps to

extract shellfish from their burrows

Shorebirds

• Avocets and Stilts (Family Recurvirostridae)– 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

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, 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

• 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

• 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

• Skuas and Jaegers– very aggressive omnivores and predators– “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 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

Gulls and Their Relatives• Alcids (continued)

– 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

• 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 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

• 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• 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 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 (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

Tubenoses

• 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

• 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