Written and published by : Ocean Classrooms, LLC. (dba Ocean First Education) 3015 Bluff St. Boulder, CO

Written and published by : Ocean Classrooms, LLC. (dba Ocean First Education) 3015 Bluff St. Boulder, CO 80301 303.996-7575 ISBN-10: 099049103X ISBN-13: 978-0-9904910-3-3 For inquiries and bundle prices, or for information about becoming an affiliate partner, please contact us at info@oceanclassrooms.com. 2015 Ocean Classrooms (Ocean First Education) All rights reserved. Ocean Classrooms inspires new depths of awareness and respect for our ocean. Through innovative education, research, and technologies, we connect people with the magic and beauty of the underwater world and create knowledgeable, passionate ocean stewards. Ocean Classrooms is dedicated to ocean education. To learn more, visit us at oceanclassrooms.com Acknowledgments Content Expert Caine Delacy, Ph.D., Ocean Classrooms, LLC. Photography and Videography Graham Casden Caine Delacy Klara Fejer Ocean First Education Team Graham Casden, Founder and Chief Visionary Officer Cathy Christopher, Curriculum and Content Specialist Caine Delacy, Science and Research Klara Fejer, Digital Media Marlee Glasgow, Graphic Artist Deb Hannigan, Curriculum Developer and Editor Paul Hilbink, elearning Cyndi Long, Chief Operating Officer and Director of Education Michael Rice, Information Technology

Chapter 1: Sea Turtle Species What 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 a shell. Unlike other turtles, a sea turtle cannot retract its head inside of its shell. There is a long history of marine turtles extending more than 125 million years. Evolutionary evidence shows many different species have swam in our oceans. Some had flippers, others had paddles, some had webbed feet, yet most marine lineages went extinct. There were several very large species that grew to more than 4 meters (12 ft). Most of the sea turtle species were evolutionary "experiments" that did not persist through 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's look at which species persist today and start by considering the one with the oldest lineage-the Leatherback. 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 its flippers and hind feet have no claws. The remaining six species of sea turtles all are members of the same family, the Cheloniidae (Keylone-ee-uh-dee). This lineage is relatively modern, dating back only about 60 million years. These turtles 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 to compare major characteristics that allow you to separate species into groups. Think of the many characteristics of sea turtles. The shell is an obvious one that help us identify turtles in general. One major difference between shells is whether the shell is hard and covered with plates or leathery with ridges. As the name suggests, the Leatherback has a leathery shell. All other species have hard shells with 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. These characteristics may seem like an odd characteristic to start with, but we use what is diagnostic for the group. The cheloniid sea turtles all have one or two pairs of scales on the snout. These are the prefrontal scales. Green turtles and Flatback turtles have just one large pair of prefrontal scales. All the remaining species (Loggerheads, Hawksbills, and both species of Ridley) have two pairs of prefrontal 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 and skin 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. So why are they called Green turtles? Their body fat is a greenish color probably because of their plantbased diet. Fishermen who hunted this turtle as food named it the Green turtle.

Chapter 2: Nests, Eggs and Hatchlings How 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 ashore to lay their eggs. Females store sperm from one or more males and that sperm supply fertilizes their multiple clutches of eggs throughout the season. A clutch is the total number of eggs laid by a turtle at one time. Sea turtles nest on oceanic beaches. Most species nest during the warmer months and their eggs incubate during the wet season. A nesting turtle will lay several clutches in a season, then take a year 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 species nested? Yes! The characteristics of the track left on the sand indicate which species nested in the area. When a sea turtle comes ashore to nest, it leaves a track called a crawl that looks like a tractor has moved up and down the beach. The size and shape of the track as well as the "foot print" pattern tells us what species came ashore. Leatherbacks have huge tracks that are often more than 3 meters wide and the track curves back and forth up the beach. Leatherback, Green turtles and Flatbacks use their flippers together like wide flat crutches to pull themselves up the beach while their hind limbs push. Loggerhead turtles crawl using their limbs in left-right pairs so that the right flipper moves with the left hind foot. The flipper prints are offset from one another because of this pattern. Both Ridley species and the Hawksbill also use this pattern, but their tracks are much smaller than those of a Loggerhead.

2.2 Nesting The nesting process is quite a sight. Only the females come ashore to dig a nest. Most nesting occurs at night when the sand tends to be cooler. The gravid turtles move into shallow water and then crawl up the beach where they select a nest site. In general, sea turtles select nest sites backed by tall, dark silhouettes from the dune face and dune plants. In some urban areas, buildings that remain dark create adequate silhouettes. The landward silhouette also is an important visual cue used by hatchlings to guide them away from land toward the ocean. As the turtle crawls up the beach, she leaves a distinctive trail, termed a "crawl. The nesting turtle throws sand out of her way with her front flippers to form a trough, called a "body-pit, then settles in and digs a nest with her rear feet. Turtles have a stereotypic pattern of movements that they use to dig nests. All turtles reach down with one hind foot and gather up sand to remove. Once they bring that first foot out of the nest cavity, the turtle kicks forward with the opposite hind limb. That foot is then extended into the nest to scoop out sand then brought out, and the first foot kicks forward again. This digging pattern is repeated until the nest cavity is complete. The turtle seems to stop digging when its foot can no longer reach the bottom of the nest.

Nesting sea turtles tend to come ashore alone. However, two species, Olive Ridleys and Kemp's Ridleys, have mass nesting aggregations termed "arribadas" in which all the turtles nesting that season come ashore over a short few days and deposit their eggs. Their nests are so concentrated that they often dig up the nests of turtles that nested earlier. In some areas where turtle eggs are eaten, the local community is allowed to harvest and sell the first clutches because they are likely to be destroyed by other nesting turtles. If the beach is full of many broken eggs, only few of the intact eggs will hatch because 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 some microbes 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 than a week prior to laying, eggs are fertilized by stored sperm and develop shells within the turtle's uterus. 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 more than 100 eggs in a clutch. However, the Leatherback and the Flatback lay smaller clutches of bigger eggs. Once the clutch is laid, the turtle scoops sand back on top of the eggs and packs it tight with her flippers, knees, and sometimes her plastron (the ventral, or belly part of the shell). She then disguises its location by throwing sand as she moves off the clutch site and returns to the water, leaving the nest to incubate unattended. When the eggs hatch, the hatchlings are on their own to figure out which way is 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 can incubate quickly and produce hatchlings in as few as six and a half weeks. Nests that incubate in warmer 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, like many 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 more females than males. In many sites, sea turtle nests produce many more females than males because the 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 upper jaw that it uses to slit the shell in a process called "pipping. The flexible egg shell weakens as the embryo develops because the embryo extracts calcium from it as its skeleton forms. When the turtle escapes its egg, it is not ready to move far. Hatchlings hatch with leftover yolk still outside the plastron. Over several days their bodies draw the yolk inside so that the plastron becomes flat and the hatchling is able to move up and out of the nest. That leftover yolk is its energy source for the offshore migration 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 the top of the group knock down sand from the sides and top of the nest. Those underneath squirm and flap, sifting the sand down so it buries the discarded egg shells and the floor of the nest rises from the bottom. Hatchlings show a kind of "safety behavior " called thermal inhibition. If hatchlings near the surface reach sand that is too warm, they stop moving. Those beneath them also stop. This behavior prevents emergence onto lethally hot surfaces. Hatchlings emerge from the nest in response to cooling sand temperatures. This change in temperature is usually at night, but can also occur during heavy rainfall. Some beaches have sand types that do not heat greatly and so daytime hatching can occur.

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

Chapter 3: Swimming and Migration Are 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 of animal movement. Sea turtles are migratory specialists. They migrate from nests to the sea from the shore to the ocean and, for nesting females, back again. What is migration? Animal migration is defined as travel from one place to another such as from nesting to foraging grounds. Scientists have mapped migration patterns of many animals across the seas. Why migrate? For sea turtles, there are ontogenetic migrations: these are movements between habitats that are linked to age or life stage. They move among feeding grounds as juveniles and between feeding and breeding grounds throughout the rest of their adult lives. Seasonal migrations by coastal juvenile and adult sea turtles are often associated with movements between distinct feeding grounds. Reproductive turtles migrate between feeding grounds and breeding grounds. What sets migration apart from other types of movements is that migration involves travel related to shifts from one habitat type to another. The body shape and physical adaptations of sea turtles indicate that even ancient forms of sea turtles were migratory. Sea turtle bodies are streamlined; their forelimbs are lift-producing flippers and their hindlimbs are steering rudders. Flippers allow organisms to move over great distances in water. They have 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 plesiosaurs had 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 feeding grounds. Nesting sea turtles are accessible to scientists. While laying eggs they enter into a temporary behavioral state in which they are not responsive to external stimuli. Consequently, scientists have learned much from tagging nesting turtles with flipper tags or other more costly tags such as passive integrated transponders (PIT) tags or transmitter tags. Because flipper tags have been used for more than 50 years, much of what we have learned comes from flipper tag data. This low-tech approach to studying migration gives start and end points but tells us little about the routes in between.

3.1 Loggerhead Turtles For sea turtles, the migration starts with hatchlings. The Loggerhead hatchling migrations are probably the best understood. Hatchlings enter the ocean and begin an amazing feat they swim for 24 to 36 hours without stopping to distance themselves from predator-rich near-shore waters. They continue swimming until they reach offshore currents that are parts of gyres (circular systems of currents). 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 to a few years before entering other productive areas around seamounts, along current boundaries, or coastal upwellings. Hatchling Loggerheads from Florida migrate all the way across the Atlantic where they reach the richly productive waters, Azores, Madeira, and the Canary Islands. They stay in these productive waters 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 often migrate 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. In addition to greater food availability, sea turtles (ectotherms) have a faster metabolic rate in warm waters which leads to faster growth. This is especially important for turtles who are particularly vulnerable 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 the nesting beaches of Trinidad migrate all the way to the productive waters off Nova Scotia, Canada to feed following their spring and summer breeding season. They leave those waters in the fall and migrate through the middle of the Atlantic eastward and southward. Turtles not returning to the Caribbean to breed return to Nova Scotia waters again in the summer and leave in the fall when the days shorten and the waters become cold. Leatherbacks usually nest every other year, swimming several 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 nesting at a famous rookery at Tortuguero, Costa Rica. For many years, Green turtles were tagged while nesting 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. Because Green turtles are primarily herbivorous (plant eaters) as adults, they travel to rich feeding grounds throughout the Caribbean. Evidence that highlights their ability to navigate is that they return to nesting beaches from so many different places. Green turtles are also important in maintaining healthy reefs and seagrass meadows. Because Green turtles crop the younger ends of seagrass, the plants tend to stay healthy. There is little opportunity for other organisms to attach to the plants, shade them, or for diseases to establish when the blades of sea grass are constantly regrowing. Further, because the turtles produce waste that is high in nitrogen and phosphorous compounds, they fertilize their feeding grounds. By feeding in one place, then moving to another, Green turtles often move nutrients to the reefs or other ecological communities as they move about.

Chapter 4: Living in the Sea Characteristics of the Sea Turtle What'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 salt levels. 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 requires some 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, water everywhere nor any drop to drink." Sea turtles, often called "ancient mariners" have solved the challenges captured in this phrase. In this chapter, explore how sea turtles can live in salt water and even 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 challenge of getting enough freshwater. Salt intake, if not controlled, can lead to dehydration. So how do turtles regulate salt and get the freshwater they need? When salt dissolves in water, it forms sodium (Na + ) and chlorine (Cl-) ions. If two different concentrations of salt water are separated by a semipermeable membrane, such as a blood vessel wall or the lining of the gut, water from the lower concentration side moves to the higher concentration to establish equilibrium. This process is called osmosis. The higher concentration is considered to be hypertonic relative to the lower concentration, which is termed hypotonic. Think about 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 sea turtles because they have adaptations to rid themselves of excess salt. Sea turtles are osmotic regulators, meaning they control osmosis in several ways. First, their bodies tend to be hypotonic relative to seawater. To keep the body from dehydrating and shriveling up, turtles have a tough barrier of scales that block the osmotic effects of seawater. Yet, sea turtles still drink a lot of salt water, either intentionally or accidentally. Whenever they eat, they ingest seawater. To prevent dehydration they must get rid of excess salt. Sea turtles have at least two ways of getting rid of excess salt. The first is a very muscular esophagus that squeezes saltwater out when they swallow their prey. It is common for turtles to "blow water out of their nostrils as they swallow. The second way sea turtles get rid of excess salt is through turtle tears.

Sea turtles have huge tear glands! These tear glands, the lacrimal glands, are larger than their brain and eyes. They constantly produce viscous salty tears that contain those salt ions. The tears are clear and are washed away in the water. However, when sea turtles come out of the water to nest or at the few places where they bask, they soon appear to be crying. While on land, nothing washes away the salty tears so the large viscous drops cling to their eyes and face. Turtle tears are not a reflection of emotion, 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 and semi-permeable, allowing water to be absorbed or released and oxygen and carbon dioxide also pass through the shell. The developing embryos need limited quantities of fresh water as they develop. If the nest sand is soaked in salt water the eggs can dehydrate by osmosis as water leaves the egg. Eggs that soak in fresh or salt water will soon suffocate because water does not hold enough oxygen to support 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 to answer. When hatchlings leave shore they are small and difficult to mark. It is only recently that Loggerhead turtles in Queensland Australia, marked as hatchlings by distinct patterns of notches in the shell, were documented to return to nest 23 to 24 years later. Scientists rarely use this method of aging turtles and it is even more rare for the scientists studying the turtles to be on the right beach at the right time to see their turtles return. In a separate study, scientists raised Kemp's Ridley turtles for a year or more in the lab then marked them internally with coded wire tags. They were identified by their wire tags when they stranded (washed ashore, weakened or dead). Others were documented nesting at specific beaches. However, these kinds of studies document age of return from the pelagic or 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. For some 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 about the same age when humans reach puberty. Sea turtles, humans, and some fish species including sharks and rockfish, are termed late-maturing. Late-maturing animals devote a lot of resources to growing big before they can reproduce. As a comparison, many animals reach maturity in a year or two. For example, Mahi-mahi, an oceanic fish that is harvested sustainably, undergoes puberty just 3 to 5 months after hatching.

The long-lived and late-maturing life cycle of sea turtles make them vulnerable to continued population declines. For example, threats such as prolonged harvest of eggs over many years can lead to population declines that may take a generation or two to recognize. It isn't until the adults that have been nesting die out and there are no juveniles replacing them that we recognize the population is in trouble. Similarly, if eggs and hatchlings are protected but juveniles are killed, as happens when they are 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 to document why juveniles are lost. Consequentially, it is this delay in recognition of problems combined with the life cycle characteristics, that together make sea turtle conservation very challenging.

4.3 Long-lived and Late Maturing Turtles are often thought to grow very old. For example, some common box turtles have been documented 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 seldom in captivity for long periods and in part because their age is often inferred rather than measured. The rare 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 any indicator, it is likely that sea turtle lifespans are similar to those of humans, assuming they outgrow the risk of their predators. Animals that live decades or centuries are considered to be long-lived.

Chapter 5: Threats and Conservation How 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, persisted for a period of time, and then went extinct. The seven remaining species are a remnant of the diversity of marine turtles that once swam the seas. Remember that the Leatherback is an extant species. At least 7 to 9 species of Dermochelys existed in the distant past. Many lineages of marine turtles have disappeared completely, extinctions occur naturally as environments change and natural but catastrophic events occur. Natural extinctions typically take place over thousands of years. Current declines in marine turtles have taken place over just a few centuries, and the rate of declines can be traced to many human-based causes, termed anthropogenic effects. Extinctions of marine turtles happen when they do not produce enough offspring to survive and replace themselves, so populations decline to such small numbers that reproduction eventually ceases and the species is lost. Declining numbers of turtles and losses of populations combine to make turtles vulnerable 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 to wash out or suffocate eggs and hatchlings. Tidal inundation is common because beaches are typically dynamic, growing and eroding, often in cycles. Predators on nests range from mammals that include raccoons, foxes, coyotes, armadillos, to invertebrates like ghost crabs and ants. Even some plants invade nests with roots that surround eggs dehydrating and eventually killing many eggs. Outside of the United States, monitor lizards are a major nest predator. Microbes, particularly some fungi, also attack eggs. The eggs that do hatch produce vulnerable hatchlings that may be lost to the same predators 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 a variety of fish; snappers, grouper, tarpon, and jacks, as well as invertebrates including crabs and squid. 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 (floating debris including Sargassum, a type of algal mat) through crypsis. Crypsis is hiding through shape and coloration. For sea turtles, this is important so the animals can outgrow their predators. Juvenile sea turtles 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 accidental capture and death associated with a variety of marine industries. Much of what we know about sea turtles in the water, where they spend the vast majority of their lives, comes from fisheries. Sea turtles are accidentally caught on fishing lines and in nets. They often drown when the fishing gear prevents them from surfacing to breathe. Types of detrimental practices used in fishing that lead to sea turtle 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 and killed 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 had already outgrown most of their predators. Large juveniles and adults have the greatest value in maintaining a population because they are reproducing or will reproduce soon. Their loss makes it particularly challenging to recover populations.

Today, fishing for sea turtles is illegal in many parts of the world and most fishers are more than happy to not catch sea turtles. Sea turtles are large, often dangerous to handle, and can reduce the target catch. Consequently, a number of US fishing industries have been active in developing methods to prevent the capture of turtles. Examples include Turtle Exclusion Devices (TEDs) for shrimp and flounder 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 a dredge. 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 sleep and feed on shallow sea floors, they are vulnerable to these dredging activities. The US Army Corp of Engineers has designed modified dredge heads to reduce the capture of sea turtles and implemented short tow trawling to relocate turtles away from dredge areas.

Loss or degradation of nesting beaches is another common cause of sea turtle declines. Degraded beaches are poor nest sites. In many places, property owners fail to account for the natural tendency for sand to migrate up or down the beach so homes and other structures can become at risk of collapsing into the ocean as sands shift with time. The addition of sea walls, sand bags (sometimes termed geotextile tubes), and rock walls (termed rock revetments) provide some protection for property 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. The National 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 is recorded 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. Many seagrass beds have been lost as waters become polluted and channels have been dredged for boat traffic. These near-shore habitat changes are relatively easy to document. The offshore habitats are important as juvenile nursery areas. Increasingly of concern are "garbage patches which have many hundreds of kilometers of floating plastics found within gyres of all oceans. Plastics that are eaten by turtles take up space in their digestive tracts without providing nutrition. They cause "dietary dilution 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 cannot produce enough offspring to replace their existing populations. "Imperiled" reflects both the risk of declines in numbers and the risk of going extinct. In the United States sea turtles are protected because they are among the species listed under the Endangered Species Act. All sea turtles are either endangered or threatened. Threatened species are those that are at 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 Fisheries Service 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 sea turtles to supply food and leather markets has been illegal for several decades. Yet the numbers of animals 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. In addition to pollution of the oceans by chemicals, plastics, and wastewater, the nesting beaches also are affected. If the turtles don't nest or their hatchlings don't reach the ocean, the species will not recover. Simple, seemingly innocent actions like putting lights on the beach or directing lights from homes and business to shine on the beach interfere with sea turtle nesting by causing many females to avoid those beaches or disrupting the ways hatchlings find the ocean. The lighting-up of the coastal skies is called photopollution. It affects sea turtles as well as many other creatures that depend on normal day-night light cycles and light levels. Many municipalities (counties or cities) protect sea turtles from photopollution by having lighting control 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 for humans to live, the control of light from more landward sources is becoming a major problem that is hard to control because it is due to many sources. "Sky-glow, a form of photopollution that is the reflection of lights from clouds, water vapor and dust particles in the air, also affects nesting sea turtles and hatchlings. It confuses the cues mothers use to select good nesting sites and both mothers and hatchlings to find the ocean.

5.4 Natural Mortality What about natural mortality? Sea turtles produce many more hatchlings than ever grow up. For example, the State of Florida is a major nesting ground for Loggerhead and Green turtles. More than 4.5 million hatchlings enter the ocean and swim offshore each year. Yet, the numbers of adult turtles nesting are minute compared to historic numbers. While numbers of Loggerheads and Green turtles are slowly increasing, this slow recovery means that many of the offspring are food for other organisms 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 and ethical. 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 and abundant species. For example, in areas where raccoons or feral pig populations have grown out of control, the racoons and pigs may be managed so that sea turtle nests can incubate and hatch undisturbed. Sea turtles, like any animals, are susceptible to diseases. Perhaps the most well-known disease is fibropapillomatosis (FP). This disease affects hard-shelled species of sea turtles and seems more common in green turtles. FP produces small and large tumors of the skin, eyelids, and even the seams of the scutes. In some areas, the disease produces internal tumors. This enigmatic disease sometimes leads 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 that strikes 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 gastrointestinal tract. Diseases also impact sea turtle survival. It is often challenging to know if a disease event is part of 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 imperiled species world wide, they are protected by laws and agreements among countries. The reasons for protecting 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 they have value as part of their ecosystems. Individual sea turtles produce thousands of hatchlings in their lifetime, yet sea turtle population sizes are not increasing dramatically. That fact reminds us that most sea turtle hatchlings never reach maturity; instead they are food for a suite of other organisms, from bacteria to birds. Those that do survive to adulthood are both lucky and smart enough to live in an environment that we could not survive without technology and tools.