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Acknowledgments

Content ExpertCaine Delacy , Ph.D., Ocean Classrooms, LLC.

Photography and VideographyGraham CasdenCaine DelacyKlara Fejer

Ocean First Education TeamGraham Casden, Founder and Chief Visionary OfficerCathy Christopher, Curriculum and Content SpecialistCaine Delacy , Science and ResearchKlara Fejer, Digital MediaMarlee Glasgow, Graphic ArtistDeb Hannigan, Curriculum Developer and EditorPaul Hilbink, eLearningCyndi Long, Chief Operating Officer and Director of EducationMichael Rice, Information Technology

Chapter 1: Sea Turtle SpeciesWhat are sea turtles and where did they come from?

Describe the characteristics of a sea turtle.Compare and contrast sea turtle species.

Sea turtles are reptiles that live in oceans and estuaries. All living sea turtles have flippers and ashell. Unlike other turtles, a sea turtle cannot retract its head inside of its shell. There is a long historyof marine turtles extending more than 125 million years. Evolutionary evidence shows many differentspecies have swam in our oceans. Some had flippers, others had paddles, some had webbed feet, yetmost marine lineages went extinct. There were several very large species that grew to more than 4meters (12 ft). Most of the sea turtle species were evolutionary "experiments" that did not persistthrough time.

How many species of sea turtles currently exist?

There are seven living species of sea turtles currently swimming in our oceans and estuaries. Let'slook at which species persist today and start by considering the one with the oldest lineage-theLeatherback. It is approximately 100 million years old. The Leatherback, Dermochelys coriacea(pronounced derm-o-kellys core-ee-A-key-uh), is the lone survivor of the family, Dermochelyidae,which once was represented by 7 to 12 species. It has a thick shell of blubber, notched jaws and itsflippers and hind feet have no claws.

The remaining six species of sea turtles all are members of the same family, the Cheloniidae (Key-lone-ee-uh-dee). This lineage is relatively modern, dating back only about 60 million years. Theseturtles all have shells covered by patterns of plates or shields and the flippers have claws.

1.1 How do we identify the species?

Scientists use a dichotomous key to identify species. The idea behind a dichotomous key is tocompare major characteristics that allow you to separate species into groups. Think of the manycharacteristics of sea turtles. The shell is an obvious one that help us identify turtles in general. Onemajor difference between shells is whether the shell is hard and covered with plates or leathery withridges. As the name suggests, the Leatherback has a leathery shell. All other species have hard shellswith plates. Let's continue by comparing the rest of the species of sea turtles--those with hard shells.

The next set of characteristics we can compare will be the scales on top of the snout. Thesecharacteristics may seem like an odd characteristic to start with, but we use what is diagnostic for thegroup. The cheloniid sea turtles all have one or two pairs of scales on the snout. These are theprefrontal scales. Green turtles and Flatback turtles have just one large pair of prefrontal scales. Allthe remaining species (Loggerheads, Hawksbills, and both species of Ridley) have two pairs ofprefrontal scales. We can separate the Flatback from the Green turtle by location, color, and the

presence of a triangular scale between the eyes and nose. The Flatback has blue eyes and its shell andskin are colored various shades of gray.

Green turtles are black and white as hatchlings but turn shades of brown and white or tan with age. Sowhy are they called Green turtles? Their body fat is a greenish color probably because of their plant-based diet. Fishermen who hunted this turtle as food named it the Green turtle.

Chapter 2: Nests, Eggs and HatchlingsHow do sea turtles make more sea turtles?

Distinguish the mating patterns of sea turtles from other animals.Compare the crawls of sea turtle species.Describe key events in sea turtle nesting.Explain characteristics that help sea turtles hatch and return to the sea.

Sea turtle mating occurs at sea at the beginning of the nesting season, before the females come ashoreto lay their eggs. Females store sperm from one or more males and that sperm supply fertilizes theirmultiple clutches of eggs throughout the season. A clutch is the total number of eggs laid by a turtle atone time. Sea turtles nest on oceanic beaches. Most species nest during the warmer months and theireggs incubate during the wet season. A nesting turtle will lay several clutches in a season, then take ayear or two off before returning to nest again.

2.1 The Crawl

Many sea turtles nest unseen because they come ashore at night. Is it possible to tell what speciesnested? Yes! The characteristics of the track left on the sand indicate which species nested in thearea. When a sea turtle comes ashore to nest, it leaves a track called a crawl that looks like a tractorhas moved up and down the beach. The size and shape of the track as well as the "foot print" patterntells us what species came ashore. Leatherbacks have huge tracks that are often more than 3 meterswide and the track curves back and forth up the beach. Leatherback, Green turtles and Flatbacks usetheir flippers together like wide flat crutches to pull themselves up the beach while their hind limbspush. Loggerhead turtles crawl using their limbs in left-right pairs so that the right flipper moves withthe left hind foot. The flipper prints are offset from one another because of this pattern. Both Ridleyspecies and the Hawksbill also use this pattern, but their tracks are much smaller than those of aLoggerhead.

2.2 Nesting

The nesting process is quite a sight. Only the females come ashore to dig a nest. Most nesting occursat night when the sand tends to be cooler. The gravid turtles move into shallow water and then crawlup the beach where they select a nest site. In general, sea turtles select nest sites backed by tall, darksilhouettes from the dune face and dune plants. In some urban areas, buildings that remain dark createadequate silhouettes. The landward silhouette also is an important visual cue used by hatchlings toguide them away from land toward the ocean.

As the turtle crawls up the beach, she leaves a distinctive trail, termed a "crawl”. The nesting turtlethrows sand out of her way with her front flippers to form a trough, called a "body-pit”, then settles inand digs a nest with her rear feet. Turtles have a stereotypic pattern of movements that they use to dignests. All turtles reach down with one hind foot and gather up sand to remove. Once they bring thatfirst foot out of the nest cavity, the turtle kicks forward with the opposite hind limb. That foot is thenextended into the nest to scoop out sand then brought out, and the first foot kicks forward again. Thisdigging pattern is repeated until the nest cavity is complete. The turtle seems to stop digging when itsfoot can no longer reach the bottom of the nest.

Nesting sea turtles tend to come ashore alone. However, two species, Olive Ridleys and Kemp'sRidleys, have mass nesting aggregations termed "arribadas" in which all the turtles nesting that seasoncome ashore over a short few days and deposit their eggs. Their nests are so concentrated that theyoften dig up the nests of turtles that nested earlier. In some areas where turtle eggs are eaten, the localcommunity is allowed to harvest and sell the first clutches because they are likely to be destroyed byother nesting turtles. If the beach is full of many broken eggs, only few of the intact eggs will hatchbecause the egg debris attracts predators and is a fertile culture for growing fungi and bacteria.Scientists researching the effects of fungus and bacteria on developing sea turtles find that somemicrobes invade the egg causing the embryo to die.

2.3 Egg Deposition and Incubation

Just as abruptly as the nesting turtle begins digging, the nest is ready and she lays her eggs. More thana week prior to laying, eggs are fertilized by stored sperm and develop shells within the turtle'suterus. Flexible egg shells, called parchment shells, provide cushioning as the eggs drop into the nest.The average clutch size, or number of eggs produced, varies with species. Most species lay morethan 100 eggs in a clutch. However, the Leatherback and the Flatback lay smaller clutches of biggereggs. Once the clutch is laid, the turtle scoops sand back on top of the eggs and packs it tight with herflippers, knees, and sometimes her plastron (the ventral, or belly part of the shell). She then disguisesits location by throwing sand as she moves off the clutch site and returns to the water, leaving the nestto incubate unattended. When the eggs hatch, the hatchlings are on their own to figure out which wayis up, to find the ocean, and to embark on their first migration offshore to their nursery areas.

2.4 Temperature and Incubation

Eggs incubate for 45 to 80 days depending upon temperatures. When temperatures are cooler,embryos are slower to grow and eggs take longer to hatch. At the warmest temperatures, eggs canincubate quickly and produce hatchlings in as few as six and a half weeks. Nests that incubate inwarmer temperatures tend to produce smaller hatchlings that have a large internal yolk reserves. Cooler nests tend to produce large hatchlings with less yolk reserve.

The temperature of a sea turtle's nest is also key in determining the sex of hatchlings. Sea turtles, likemany other turtle species, lack sex chromosomes. Instead, they have environmentally determined sex. Our current understanding is that warmer temperatures, usually above 29º C, tend to produce morefemales than males. In many sites, sea turtle nests produce many more females than males becausethe nests incubate in the warmest part of the season.

2.5 Hatching

Eggs in a clutch tend to hatch almost synchronously. The embryo has a sharp "egg-tooth" on its upperjaw that it uses to slit the shell in a process called "pipping.” The flexible egg shell weakens as theembryo develops because the embryo extracts calcium from it as its skeleton forms. When the turtleescapes its egg, it is not ready to move far. Hatchlings hatch with leftover yolk still outside theplastron. Over several days their bodies draw the yolk inside so that the plastron becomes flat and thehatchling is able to move up and out of the nest. That leftover yolk is its energy source for the offshoremigration it will undergo—sort of a "brown bag lunch" to go!

Hatchlings in a clutch show pretty remarkable behavior as they dig out of the nests. The turtles on thetop of the group knock down sand from the sides and top of the nest. Those underneath squirm andflap, sifting the sand down so it buries the discarded egg shells and the floor of the nest rises from thebottom. Hatchlings show a kind of "safety behavior " called thermal inhibition. If hatchlings near thesurface reach sand that is too warm, they stop moving. Those beneath them also stop. This behaviorprevents emergence onto lethally hot surfaces. Hatchlings emerge from the nest in response tocooling sand temperatures. This change in temperature is usually at night, but can also occur duringheavy rainfall. Some beaches have sand types that do not heat greatly and so daytime hatching canoccur.

2.6 Finding the Sea

Once hatchlings reach the surface, they often sit with their heads out of the sand until the sand fallsaway from their eyes. Then abruptly, one or more sticks its flippers out and the majority of the turtlescome out and head for the ocean. Seafinding is the process by which hatchlings locate the water. Thehatchlings seem to use the same cues their mothers used to select a nesting site, which are tall, darksilhouettes. However, they flee from these cues rather than approach them. This system works toguide them to the water under most natural circumstances. Newspapers and popular sources oftenreport that sea turtle hatchlings are attracted to the moon or the stars. Such celestial cues are notreliable and these romanticized views are not supported by scientific evidence. The turtles emergeand find the water on cloudy nights, new moon nights, and even nights when the moon is landward!

Chapter 3: Swimming and MigrationAre sea turtles able to travel the globe?

Identify sea turtle body characteristics that indicate their migratory lifestyle.Analyze the different types of sea turtle migrations and distinguish from other types ofanimal movement.

Sea turtles are migratory specialists. They migrate from nests to the sea—from the shore to the oceanand, for nesting females, back again.

What is migration? Animal migration is defined as travel from one place to another such as fromnesting to foraging grounds. Scientists have mapped migration patterns of many animals across theseas.

Why migrate? For sea turtles, there are ontogenetic migrations: these are movements between habitatsthat are linked to age or life stage. They move among feeding grounds as juveniles and betweenfeeding and breeding grounds throughout the rest of their adult lives.

Seasonal migrations by coastal juvenile and adult sea turtles are often associated with movementsbetween distinct feeding grounds. Reproductive turtles migrate between feeding grounds and breedinggrounds. What sets migration apart from other types of movements is that migration involves travelrelated to shifts from one habitat type to another.

The body shape and physical adaptations of sea turtles indicate that even ancient forms of sea turtleswere migratory. Sea turtle bodies are streamlined; their forelimbs are lift-producing flippers and theirhindlimbs are steering rudders. Flippers allow organisms to move over great distances in water. Theyhave evolved in a number of migratory organisms. Species such as penguins and seals also have

forelimbs modified as flippers. Other ancient and extinct reptiles such as pliosaurs and plesiosaurshad all four limbs as flippers, which suggests they too were migratory.

Some of the best documented migrations are those of sea turtles between nesting grounds and feedinggrounds. Nesting sea turtles are accessible to scientists. While laying eggs they enter into a temporarybehavioral state in which they are not responsive to external stimuli. Consequently, scientists havelearned much from tagging nesting turtles with flipper tags or other more costly tags such as passiveintegrated transponders (PIT) tags or transmitter tags.

Because flipper tags have been used for more than 50 years, much of what we have learned comesfrom flipper tag data. This low-tech approach to studying migration gives start and end points but tellsus little about the routes in between.

3.1 Loggerhead Turtles

For sea turtles, the migration starts with hatchlings. The Loggerhead hatchling migrations areprobably the best understood. Hatchlings enter the ocean and begin an amazing feat—they swim for24 to 36 hours without stopping to distance themselves from predator-rich near-shore waters. Theycontinue swimming until they reach offshore currents that are parts of gyres (circular systems ofcurrents). The hatchlings migrate to ocean's offshore productive regions known as nursery areas,where they feed, seek shelter, and grow. Many Loggerheads may reside on the high seas for months toa few years before entering other productive areas around seamounts, along current boundaries, orcoastal upwellings.

Hatchling Loggerheads from Florida migrate all the way across the Atlantic where they reach therichly productive waters, Azores, Madeira, and the Canary Islands. They stay in these productivewaters for about 5 to 7 years before returning to coastal zones back on the other side of the Atlantic.Young Loggerheads return to the US Atlantic coast to feed in the neritic and benthic zones. They oftenmigrate to temperate waters during the spring and summer and to subtropical waters in the winter.Such migrations optimize the use of different foraging areas and ensure growth in warm waters. Inaddition to greater food availability, sea turtles (ectotherms) have a faster metabolic rate in warmwaters which leads to faster growth. This is especially important for turtles who are particularlyvulnerable to predation at a small size. The faster they can get big, the safer they are.

3.2 Leatherback Turtles

Leatherback turtles undergo the longest migrations of any marine turtles. Adult females tagged on thenesting beaches of Trinidad migrate all the way to the productive waters off Nova Scotia, Canada tofeed following their spring and summer breeding season. They leave those waters in the fall andmigrate through the middle of the Atlantic eastward and southward. Turtles not returning to theCaribbean to breed return to Nova Scotia waters again in the summer and leave in the fall when thedays shorten and the waters become cold. Leatherbacks usually nest every other year, swimmingseveral thousand miles between feeding grounds and breeding grounds.

3.3 Green Turtles

Flipper tagging was used to understand the diversity of migratory routes used by Green turtles nestingat a famous rookery at Tortuguero, Costa Rica. For many years, Green turtles were tagged whilenesting at Tortuguero. At the end of the nesting season, they migrated to their feeding grounds.

One of the surprises was the discovery of diversity of feeding grounds for these sea turtles. BecauseGreen turtles are primarily herbivorous (plant eaters) as adults, they travel to rich feeding groundsthroughout the Caribbean. Evidence that highlights their ability to navigate is that they return to nestingbeaches from so many different places.

Green turtles are also important in maintaining healthy reefs and seagrass meadows. Because Greenturtles crop the younger ends of seagrass, the plants tend to stay healthy. There is little opportunity forother organisms to attach to the plants, shade them, or for diseases to establish when the blades of seagrass are constantly regrowing. Further, because the turtles produce waste that is high in nitrogen andphosphorous compounds, they fertilize their feeding grounds. By feeding in one place, then moving toanother, Green turtles often move nutrients to the reefs or other ecological communities as they moveabout.

Chapter 4: Living in the Sea—Characteristics of the SeaTurtleWhat's life like as a sea turtle?

Explain why salt presents a physiological problem for marine organisms.Recognize and describe adaptations sea turtles possess to help them regulate their saltlevels.Interpret why it is difficult to determine accurately how long sea turtles live.Describe the concept "late maturing” and associated risks.

Living at sea poses ecological opportunities, like niche expansion for sea turtles, but also requiressome rather impressive anatomical and physiological adaptations to survive in the salty environment.Most of us have heard the old seaman's woe from The Rime of the Ancient Mariner, "Water, watereverywhere nor any drop to drink." Sea turtles, often called "ancient mariners" have solved thechallenges captured in this phrase. In this chapter, explore how sea turtles can live in salt water andeven drink it, yet still thrive. You will also learn how they grow and age and why that matters.

4.1 Physiology and Salt Water

Marine turtles live in oceans, but they need freshwater too. Many marine animals face the challengeof getting enough freshwater. Salt intake, if not controlled, can lead to dehydration. So how do turtlesregulate salt and get the freshwater they need?

When salt dissolves in water, it forms sodium (Na ) and chlorine (Cl ) ions. If two differentconcentrations of salt water are separated by a semipermeable membrane, such as a blood vesselwall or the lining of the gut, water from the lower concentration side moves to the higherconcentration to establish equilibrium. This process is called osmosis. The higher concentration isconsidered to be hypertonic relative to the lower concentration, which is termed hypotonic. Thinkabout this relationship and salt ion regulating process as we look more closely at marine organisms,like the sea turtle, that must regulate the effects of saltwater on its system.

The expression "water, water everywhere but not a drop to drink” does not exactly apply to seaturtles because they have adaptations to rid themselves of excess salt. Sea turtles are osmoticregulators, meaning they control osmosis in several ways. First, their bodies tend to be hypotonicrelative to seawater. To keep the body from dehydrating and shriveling up, turtles have a toughbarrier of scales that block the osmotic effects of seawater. Yet, sea turtles still drink a lot of saltwater, either intentionally or accidentally. Whenever they eat, they ingest seawater. To preventdehydration they must get rid of excess salt. Sea turtles have at least two ways of getting rid of excesssalt. The first is a very muscular esophagus that squeezes saltwater out when they swallow theirprey. It is common for turtles to "blow” water out of their nostrils as they swallow. The second waysea turtles get rid of excess salt is through turtle tears.

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Sea turtles have huge tear glands! These tear glands, the lacrimal glands, are larger than their brainand eyes. They constantly produce viscous salty tears that contain those salt ions. The tears are clearand are washed away in the water. However, when sea turtles come out of the water to nest or at thefew places where they bask, they soon appear to be crying. While on land, nothing washes away thesalty tears so the large viscous drops cling to their eyes and face. Turtle tears are not a reflection ofemotion, or even eye irritation. Instead, they are the result of the body ridding itself of excess salt.

Remember the flexible eggs that sea turtles lay in sandy nests? The shells of the eggs are flexible andsemi-permeable, allowing water to be absorbed or released and oxygen and carbon dioxide also passthrough the shell. The developing embryos need limited quantities of fresh water as they develop. Ifthe nest sand is soaked in salt water the eggs can dehydrate by osmosis as water leaves the egg. Eggsthat soak in fresh or salt water will soon suffocate because water does not hold enough oxygen tosupport the needs of the embryo.

4.2 Growing Up

How long does it take a turtle to become an adult? This is an extraordinarily difficult question toanswer. When hatchlings leave shore they are small and difficult to mark. It is only recently thatLoggerhead turtles in Queensland Australia, marked as hatchlings by distinct patterns of notches in theshell, were documented to return to nest 23 to 24 years later. Scientists rarely use this method ofaging turtles and it is even more rare for the scientists studying the turtles to be on the right beach atthe right time to see their turtles return. In a separate study, scientists raised Kemp's Ridley turtles fora year or more in the lab then marked them internally with coded wire tags. They were identified bytheir wire tags when they stranded (washed ashore, weakened or dead). Others were documentednesting at specific beaches. However, these kinds of studies document age of return from the pelagicor age to maturity—not lifespan.

Age to maturity is a measure of the age of a sea turtle when it goes through puberty and breeds. Forsome turtles, such as Loggerheads from Australia and the Atlantic, this age is about 20 to 25 years.Other sea turtles, like the Leatherback and the Kemp's Ridley, mature in about half the time or at aboutthe same age when humans reach puberty. Sea turtles, humans, and some fish species including sharksand rockfish, are termed late-maturing. Late-maturing animals devote a lot of resources to growingbig before they can reproduce. As a comparison, many animals reach maturity in a year or two. Forexample, Mahi-mahi, an oceanic fish that is harvested sustainably, undergoes puberty just 3 to 5months after hatching.

The long-lived and late-maturing life cycle of sea turtles make them vulnerable to continuedpopulation declines. For example, threats such as prolonged harvest of eggs over many years can leadto population declines that may take a generation or two to recognize. It isn't until the adults that havebeen nesting die out and there are no juveniles replacing them that we recognize the population is introuble. Similarly, if eggs and hatchlings are protected but juveniles are killed, as happens when theyare accidentally killed by some fisheries, the loss of those juveniles is still harmful to the population.It may take decades to see the overall impact of this loss of new nesting turtles and longer todocument why juveniles are lost. Consequentially, it is this delay in recognition of problemscombined with the life cycle characteristics, that together make sea turtle conservation verychallenging.

4.3 Long-lived and Late Maturing

Turtles are often thought to grow very old. For example, some common box turtles have beendocumented to live in excess of 130 years. The Galapagos tortoises also can live a very long life,well over a century. Extreme ages of sea turtles are less well known, in part because they are seldomin captivity for long periods and in part because their age is often inferred rather than measured. Therare exception is Myrtle, a Green turtle that resides in the New England Aquarium in Boston,Massachusetts. Myrtle's captive records estimate her age at about 80 years. If Myrtle's age is anyindicator, it is likely that sea turtle lifespans are similar to those of humans, assuming they outgrowthe risk of their predators. Animals that live decades or centuries are considered to be long-lived.

Chapter 5: Threats and ConservationHow can we help sea turtles survive?

List several causes of the decline in sea turtle populations.Recognize natural and anthropogenic threats to sea turtles.Construct an understanding of several ways to reduce anthropogenic impacts on sea turtles.Compare and contrast "threatened" and "endangered" species.

Sea turtles are ancient animals. Throughout their history, many lineages of sea turtle arose, persistedfor a period of time, and then went extinct. The seven remaining species are a remnant of the diversityof marine turtles that once swam the seas. Remember that the Leatherback is an extant species. Atleast 7 to 9 species of Dermochelys existed in the distant past. Many lineages of marine turtles havedisappeared completely, extinctions occur naturally as environments change and natural butcatastrophic events occur. Natural extinctions typically take place over thousands of years. Currentdeclines in marine turtles have taken place over just a few centuries, and the rate of declines can betraced to many human-based causes, termed anthropogenic effects.

Extinctions of marine turtles happen when they do not produce enough offspring to survive andreplace themselves, so populations decline to such small numbers that reproduction eventually ceasesand the species is lost. Declining numbers of turtles and losses of populations combine to make turtlesvulnerable to both natural threats and humans causes.

5.1 Natural Threats

Natural threats to eggs and hatchlings are high. Nests are lost to weather events that cause tides towash out or suffocate eggs and hatchlings. Tidal inundation is common because beaches are typicallydynamic, growing and eroding, often in cycles. Predators on nests range from mammals that includeraccoons, foxes, coyotes, armadillos, to invertebrates like ghost crabs and ants. Even some plantsinvade nests with roots that surround eggs dehydrating and eventually killing many eggs. Outside ofthe United States, monitor lizards are a major nest predator. Microbes, particularly some fungi, alsoattack eggs. The eggs that do hatch produce vulnerable hatchlings that may be lost to the samepredators that attack eggs, as well as birds, such as herons and crows, and insects.

Once in the water, hatchling predators await near shore. These hungry marine animals include avariety of fish; snappers, grouper, tarpon, and jacks, as well as invertebrates including crabs andsquid. Farther offshore, dolphinfish (mahimahi) and sharks prey upon neonate sea turtles.

The strategies that most sea turtle hatchlings use to avoid predators is hiding in flotsam (floatingdebris including Sargassum, a type of algal mat) through crypsis. Crypsis is hiding through shape andcoloration. For sea turtles, this is important so the animals can outgrow their predators. Juvenile seaturtles grow rapidly and so effectively outgrow the mouths that can eat them.

5.2 Anthropogenic Threats

Other threats in the water are due to anthropogenic effects (human activity). These include accidentalcapture and death associated with a variety of marine industries. Much of what we know about seaturtles in the water, where they spend the vast majority of their lives, comes from fisheries. Seaturtles are accidentally caught on fishing lines and in nets. They often drown when the fishing gearprevents them from surfacing to breathe. Types of detrimental practices used in fishing that lead to seaturtle deaths world wide are gill netting that entangles turtles, trawling that catches or crushes turtles,and long lining that catches turtles on their thousands of bated hooks. Sea turtles have been caught andkilled by indiscriminant fishing practices that catch many species in addition to their target species.Additionally, there was once a fishery targeting sea turtles, particularly Green turtles for their meat,oil and leather and Hawksbills for their shell. Such fisheries harvested the larger turtles that hadalready outgrown most of their predators. Large juveniles and adults have the greatest value inmaintaining a population because they are reproducing or will reproduce soon. Their loss makes itparticularly challenging to recover populations.

Today, fishing for sea turtles is illegal in many parts of the world and most fishers are more thanhappy to not catch sea turtles. Sea turtles are large, often dangerous to handle, and can reduce thetarget catch. Consequently, a number of US fishing industries have been active in developing methodsto prevent the capture of turtles. Examples include Turtle Exclusion Devices (TEDs) for shrimp andflounder trawl nets and the switch by longline fishers from J-hooks to using large circle hooks.

Dredging (sand removal or sand pumping) operations are usually lethal to any turtle picked up by adredge. The dredge head is similar to a giant metal vacuum cleaner that sucks up sand and rock,breaking it up as it is transported from the sea floor to its intended site. Because marine turtles sleepand feed on shallow sea floors, they are vulnerable to these dredging activities. The US Army Corpof Engineers has designed modified dredge heads to reduce the capture of sea turtles andimplemented short tow trawling to relocate turtles away from dredge areas.

Loss or degradation of nesting beaches is another common cause of sea turtle declines. Degradedbeaches are poor nest sites. In many places, property owners fail to account for the natural tendencyfor sand to migrate up or down the beach so homes and other structures can become at risk ofcollapsing into the ocean as sands shift with time. The addition of sea walls, sand bags (sometimestermed geotextile tubes), and rock walls (termed rock revetments) provide some protection forproperty but change the shape of the beach. Sand no longer piles up so the beach has no slope.Turtles either reject such modified beaches and lay their nests elsewhere, often in substandard areas,or they lay eggs in nests on these flat beaches that are doomed to become flooded by rising tides.

Collisions with boats are one of the most clearly documented threats to sea turtles in the US. TheNational Marine Fisheries Service maintains a continuous database of sea turtle strandings.Strandings occur when turtles wash ashore dead, injured, or sick. The cause of the stranding isrecorded when the animal is reported and seen. The most frequently recorded cause of stranding is"unknown” cause of death. The second most frequent category of strandings is interactions with boats.Boats can injure or kill turtles by impact (even small boats can be heavy) or by propeller cuts.

Recently, scientists are beginning to understand the importance of degraded feeding habitats. Manyseagrass beds have been lost as waters become polluted and channels have been dredged for boattraffic. These near-shore habitat changes are relatively easy to document. The offshore habitats areimportant as juvenile nursery areas. Increasingly of concern are "garbage patches” which have manyhundreds of kilometers of floating plastics found within gyres of all oceans. Plastics that are eaten byturtles take up space in their digestive tracts without providing nutrition. They cause "dietarydilution” so that small turtles do not get enough food and eventually weaken and die.

5.3 Conservation

Sea turtles are imperiled because their numbers have dropped to such low levels that they cannotproduce enough offspring to replace their existing populations.

"Imperiled" reflects both the risk of declines in numbers and the risk of going extinct. In the UnitedStates sea turtles are protected because they are among the species listed under the EndangeredSpecies Act. All sea turtles are either endangered or threatened. Threatened species are those that areat risk of becoming endangered. Endangered species are those that are at risk of going extinct.Government agencies including the US Fish and Wildlife Service and the National Marine FisheriesService have the responsibility of preventing the species from going extinct by identifying the causes,reducing the risks, and establishing plans to allow the species to recover.

Many of the causes for the decline in sea turtles are historic. For example, hunting and fishing for seaturtles to supply food and leather markets has been illegal for several decades. Yet the numbers ofanimals that were killed for the centuries preceding added up to create a tipping point so the

populations could not easily recover.

Habitat destruction in the form of urbanization of nesting beaches is another cause for decline. Inaddition to pollution of the oceans by chemicals, plastics, and wastewater, the nesting beaches alsoare affected. If the turtles don't nest or their hatchlings don't reach the ocean, the species will notrecover. Simple, seemingly innocent actions like putting lights on the beach or directing lights fromhomes and business to shine on the beach interfere with sea turtle nesting by causing many females toavoid those beaches or disrupting the ways hatchlings find the ocean. The lighting-up of the coastalskies is called photopollution. It affects sea turtles as well as many other creatures that depend onnormal day-night light cycles and light levels.

Many municipalities (counties or cities) protect sea turtles from photopollution by having lightingcontrol ordinances that are in effect during sea turtle nesting season. Control of lighting adjacent to or

on the beach is critical. However, because so many nesting beaches are adjacent to favorite areas forhumans to live, the control of light from more landward sources is becoming a major problem that ishard to control because it is due to many sources. "Sky-glow”, a form of photopollution that is thereflection of lights from clouds, water vapor and dust particles in the air, also affects nesting seaturtles and hatchlings. It confuses the cues mothers use to select good nesting sites and both mothersand hatchlings to find the ocean.

5.4 Natural Mortality

What about natural mortality? Sea turtles produce many more hatchlings than ever grow up. Forexample, the State of Florida is a major nesting ground for Loggerhead and Green turtles. More than4.5 million hatchlings enter the ocean and swim offshore each year. Yet, the numbers of adult turtlesnesting are minute compared to historic numbers. While numbers of Loggerheads and Green turtlesare slowly increasing, this slow recovery means that many of the offspring are food for otherorganisms from bacteria to squid and crabs to fish such as tarpon and sharks.

Should we protect turtles from natural sources of mortality? This question is both philosophical andethical. When a species is imperiled, it is managed for recovery. When numbers are particularly low,every turtle counts. Sometimes it is necessary to protect rare species from the effects of common andabundant species. For example, in areas where raccoons or feral pig populations have grown out ofcontrol, the racoons and pigs may be managed so that sea turtle nests can incubate and hatchundisturbed.

Sea turtles, like any animals, are susceptible to diseases. Perhaps the most well-known disease isfibropapillomatosis (FP). This disease affects hard-shelled species of sea turtles and seems morecommon in green turtles. FP produces small and large tumors of the skin, eyelids, and even the seamsof the scutes. In some areas, the disease produces internal tumors. This enigmatic disease sometimesleads to debilitation and likely death. In other cases, the tumors regress and the turtles recover. Other significant diseases include lethargic loggerhead syndrome, a disease of unknown cause thatstrikes loggerheads regionally. The turtles strand with flaccid paralysis, very slow heart rates, and

often with pneumonia. Parasites produce a variety of diseases in sea turtles. Nematodes(roundworms and flatworms) can cause diseases of the nervous system, liver, and gastrointestinaltract. Diseases also impact sea turtle survival. It is often challenging to know if a disease event is partof natural cycles or shows up because the animals are physiologically and ecologically stressed.

Sea turtles are ancient, unique among vertebrates and fascinating for many. Like many imperiledspecies world wide, they are protected by laws and agreements among countries. The reasons forprotecting imperiled species are many and can range from esthetic (people like sea turtles) to cultural(they are significant in the traditions of many non-western cultures). As scientists, we recognize theyhave value as part of their ecosystems. Individual sea turtles produce thousands of hatchlings in theirlifetime, yet sea turtle population sizes are not increasing dramatically. That fact reminds us that mostsea turtle hatchlings never reach maturity; instead they are food for a suite of other organisms, frombacteria to birds. Those that do survive to adulthood are both lucky and smart enough to live in anenvironment that we could not survive without technology and tools.