Webpage created in November 2002

 

 

 

 

The Biogeography of Leatherback Turtles
 

(Dermochelys coriacea)

 

By Marc Carvajal, a student in Geography 316

 

Current Status:

Endangered

(Provided by NOAA)

Photo 1

Female leatherback laying her eggs in a nest on a Puerto Rican beach. (Photo provided by CRESLI).

 

Thank you for visiting our site. this web page was written by a student in Geography 316: Biogeography and edited by the instructor, Barbara Holzman, PhD. All photos and maps are poster with specific copyright permission for the express use of education on these web pages. The students have tried to be as accurate as possible with the information provided, and sources and references are cited at the end of each page.

 

 

Taxonomy

Description

Natural History

Evolution

Distribution

Conservation

Bibliography

 

This site is best viewed with 1024 x 768 resolution on a maximized Internet Explorer screen.

Approximate loading time: 3 min. (@ 28.8kbps). Please be patient while the graphics and photos load...

 

 

à Taxonomy

Kingdom: Animalia

Phylum: Chordata

Class: Reptilia

Order: Testudines

Family: Dermochelyidae

Genus: Dermochelys

Species: Dermochelys coriacea

 

<TOP>

 

 

 

 

 

 

 

Photo 2 and 3

Female leatherback turtles returns to sea after laying her eggs on a beach in Isla Culebra, Puerto Rico. (Photo provided by CRESLI)

à Description of Species

 

Physical Characteristics - Adults

The leatherback is the largest of living turtle species. Full-grown specimens reach average lengths of 7 feet, have a span of 8.9 feet from flipper to flipper, and can weigh as much as 650 to 1200 lbs (Eckert, 1997).

 

The common name “leatherback” comes from the physical characteristics unique to this species – an

exterior rubber-like layer of tough, oil-saturated connective tissue about 1.5 inches thick, which is black in color and scaleless. The leatherback’s shell is not made up of a few large bony plates. Rather, it is composed of hundreds of small, fused bones. This unique feature allows the leatherback to dive to depths of up to 3000 feet. Having a more rigid shell structure would result in the turtle being crushed at these depths.

 

Another unique characteristic of the leatherback is that there is no sharp boundary formed where the carapace and the plastron are fused. The carapace is the hard, bony outer covering, and the plastron is the underside of the shell. The carapace is covered with the layer of black skin, while the plastron is either pink, black, or white, to serve as a camouflage. Photo 2 shows the leatherback’s large, barrel-shaped body which is ideal for long-distance sea travel. There are seven longitudinal ridges on the carapace and five on the plastron to increase hydrodynamics; i.e. to be more streamlined to reduce drag from the friction with water.

 

The leatherback’s carapace is made up of thousands of tiny bone fragments that are fused together and wrapped with a layer of skin. This shell provides protection to the turtle’s soft internal organs. Its ribs and vertebrae are fused to the shell, adding more strength while keeping the shell somewhat flexible to allow for diving to depths of more than 3000 ft (Gaffney,2002).

 

Another function the layer of skin serves is to aid in breathing. Leatherbacks “can probably exchange gases through their skin as indicated by sphincter muscles in the pulmonary arteries that can divert blood from the lungs to the skin” (VA F&W, 2002).

 

Another feature that helps the leatherback glide through the water are limbs modified to long, narrow front flippers. These flippers act much like wings, similar to humpback whales and penguins. There are no claws on the flippers’ ends, as the leatherbacks don’t need to be mobile on land. At birth the leatherback hatchlings’ front flippers are as long as their carapace (Bilinski, 2001).

 

Having a large body gives the leatherback the benefit of “a small body-to-volume ratio, which means lots of thermal inertia” (Stanback, 2000). In other words, the leatherback has the ability to retain its body heat even while swimming through colder waters at the higher latitudes. This is done by countercurrent exchangers – close proximity of veins and arteries in the flippers “allows the core of the body to retain much of the heat generated by muscular activity because blood cooled by the surrounding water is warmed up before [reentering] back into the body core” (Stanback, 2000). The net effect is the leatherback’s body is kept warm, and its flippers are kept cool. This evolutionary advantage allows the leatherback to “take advantage of highly productive cooler parts of oceans, which result in a wider latitudinal distribution” (Stanback, 2000).

 

Many of the leatherback’s features are not shared among other living turtle species. Thus, the leatherback was put in its own taxonomic family, Dermochelyidae, because of its uniqueness.

 

Physical Characteristics – Hatchlings

 

A female leatherback can produce “several hundred eggs during a nesting season” (FL Travel Guide, 2002). Unlike poultry eggs, turtle eggs are leathery and thicker. Adults lay “large number clutches as soon as possible” (FL Travel Guide, 2002). This serves three purposes: 1) it minimizes the amount of time the turtles have to spend away from feeding grounds; 2) it minimizes the chance of predation toward the adults at the beach; and, 3) the hatchlings will emerge from the nests at the same time, reducing the number of mortalities due to predation by birds, crabs, small mammals, fish, etc. Perhaps this is an ideal example of the Darwinian Theory of Evolution, which states that “more offspring are produced than can survive”.

 

Leatherback hatchlings are no more than two-and-a-half inches in length and 1.6 oz in weight (Eckert, 1997). Female leatherbacks show no sign of parental care toward their young, so the hatchlings have to fend for themselves in their most vulnerable state. Hatchlings scurry toward the ocean in thousands, but only a few are successful. During the first 48 hours, the hatchlings must swim relentlessly at a speed of 1 mile per hour to the open sea where they encounter few predators, but also have an abundant supply of floating Sargassum weed. During their first journey, “leftover yolk retained in the abdomen provides food for the first few days (FL Travel Guide, 2002). Many hatchlings “in the Atlantic and Caribbean make their way into the Gulf stream currents” where food is abundant and predators are few. For the next several years, the turtle grows exponentially until it is large enough to feed in coastal waters (FL Travel Guide, 2002).

 

<TOP>

 

 

à Natural History

 

The leatherback’s behavioral traits have not been extensively documented because of their “poor survivability in captivity” (Eckert, 1997). Thus, many traits documented in scientific reports are derived from few isolated sightings and from direct observation of other sea turtle species. The leatherback is a very migratory turtle that cannot be successfully confined in marine parks or laboratories for careful observation.

 

Breeding and Nesting

 

Reproduction of leatherbacks is seasonal. Females “are believed to migrate long distances between foraging and breeding grounds…at intervals of typically two or three years” (Eckert, 1997). Mating usually occurs in shallower tropical waters before the females’ migration. Males have a concave plastron to aid in intercourse.

 

There is no data on the chronological order of mating habits for this species.

 

When the females reach their desired nesting location, they will crawl onto the beach at night. Their preferred beaches are usually gradually-sloped and without vegetation to avoid injury to their flippers. When the female locates her desired nesting spot, she will first dig a “body pit”. This body pit is dug in such a way that the end closer to land is deeper than the end closer to the ocean. This is where she will be positioned to deposit her eggs. When the body pit is completed, female leatherbacks will start to dig a “nest chamber”. This is a small, tube-shaped, sloped hole that will receive her eggs. The

sloped sides are an integral part of the nest – if it is too steep, i.e. closer to 90˚, her eggs will break when they hit the bottom or each other. The nest is oriented in such a way that when hatchlings emerge from it, they will be on the downward slope towards the ocean. Hatchlings use their eyesight to determine the location of the moon, and crawl towards it. Artificial lighting in the immediate vicinity causes some hatchlings to go the wrong direction, and eventually die of dehydration or predation.

 

After the clutch is laid, the female covers up the nest and the body pit with her hind flippers and returns to sea. The entire process generally takes about 2 to 3 hours (Eckert, 1997).

 

Nestings occur “1-11 [times] per season at 9-10 day intervals, and clutch sizes [for Pacific leatherbacks] averages 85-95 yolked eggs” (Eckert, 1997).

 

As with other reptiles, the gender of a leatherback hatchling is determined by the nest’s temperature (Eckert, 1997). Cool nests (82.5˚F) produce almost all males, and warm nests (85˚F) produce almost all females. Incubation takes an average of 65 days (FL Travel Guide, 2002).

 

Nesting beaches are also the prime vacation spots for many tourists, contributing to the decline of the leatherback population. This is most evident along the Pacific coast of Mexico where the population of leatherbacks “declined at an annual rate of 22% over the last 12 years” (Green Nature, 2002).

 

Migration

 

The method employed by leatherbacks to navigate in the open seas is still a mystery to scientists. Upon reaching the age of sexual maturity – typically by 15 to 30 years of age – female leatherbacks navigate

Photo 4

This is a photo of a female leatherback in the process of laying

her eggs in a nest. When she has finished egg-laying, she will use

her paddle-shaped hind flippers to cover the nest with sand, and

return to sea. The entire process only occurs at night and takes

about 2-3 hours. (Photo provided by Solvin Zankl, Sandy Point

National Wildlife Refuge)

back to the beach where they hatched; and both male and female leatherbacks navigate back to the beach where they hatched; and both male and female leatherbacks follow jellyfish migration routes worldwide. Leatherbacks do not rely heavily on their eyesight because they “can raise their heads only a few inches above the surface, and there are often no visible landmarks”. A theory proposed by researchers is that sea turtles, in general, can detect the angle and intensity of the earth’s magnetic field,” giving them the ability to determine latitude and longitude (FL Travel Guide, 2002).

 

 Diet and Feeding Habits

 

The leatherback’s diet consists primarily of jellyfish and other gelatinous invertebrates. The upper jaw has two tooth-like protrusions, but the mouth has no teeth on the palette. They are “one of the few animals that feed exclusively on jellyfish” (CRESLI, 2002). Through evolution, the leatherback turtle has developed “long backward pointing spines [in their esophagus] which aid in their swallowing such soft, slippery food” (CRESLI, 2002). Jellyfish and other gelatinous organisms tend to have stinging cells (nematosysts) within their tentacles. However, leatherbacks have grown to be immune to these, and they are known to eat the deadliest of jellyfish – the Portuguese Man-O-War and the Lion’s Mane. In addition, “young leatherbacks in captivity can eat twice their weight in jellyfish each day” (FL Travel Guide, 2002). A main factor contributing to the decline of the leatherback population is pollution in the oceans. Leatherbacks cannot adequately distinguish between a jellyfish and a floating plastic bag. Ingestion of marine debris can cause choking, strangulation, and blockage of the airway and/or esophagus.

 

Aside from jellyfish, leatherbacks found in around islands and continents are known to forage for pelagic crabs.

 

<TOP>

 

 

à Evolution

Turtle evolution is well documented. Its hard shell and skeleton have been well-preserved through fossilization.

 

Turtles evolved along with other reptiles some 200 million years ago. At about 180 million years ago during the Late Triassic to Early Jurassic Periods, the turtle order, Chelonia, deviated from the main line of reptile evolution.

 

The first turtle species, Proganochelys quenstedi, lived at this time (Steel and Harvey, 1989). It had a shell, but its head and limbs could not be retracted into it. The development of a hard shell was probably brought on by “times of extreme environmental change” (ORF.org) that allowed the turtles to be better suited to the environment.

 

Turtles, for the most part, have not drastically changed from their ancestors. However, many subtle, but vital changes in physiology have occurred. For instance, the ancient turtles “had teeth rather than sharp jaws” (ORF.org). Also, the sea turtle species

Photo 5

Protostega, an ancient marine turtle’s skeleton at the Carnegie Museum in Pittsburgh. Notice the long front flippers and pointed head – these are features shared with the modern leatherback turtles to aid in long-distance swimming.

(Photo provided by John Hutchinson)

Archelon ischyros, which lived 65 million years ago in the Paleocene, grew to “9 feet 10 inches” (ORF.org). At 7 feet, today’s leatherbacks are comparably smaller, even though they are the largest turtle species.

 

During the same time, many scientists believe a meteor struck the earth causing the extinction of many flora and fauna. However, the turtles survived this dramatic event, probably with the use of their hard shells as protection. Nevertheless, only 2 suborders of turtles survived – the “side-necked turtles (Pleurodires) and the arch-necked turtles (Cryptodires)” (Turtle Pages).

 

It was not until the Late Jurassic that sea turtles occurred. “It is believed that sea turtles are the descendants of turtles that inhabited swamps and marshes during the Late Triassic.” During this time, the United States “was covered by the large

Niobara Sea” (Turtle Pages). The leatherback’s ancestor is believed to be the Archelon because it too had a “weak” shell – as supposed to a “hard” shell. Photo 5 shows the fossilized remains of Protostega, an ancient sea turtle that lived 97-66 million years ago (Carnegie, 1999). This photo shows some of the features shared with modern-day sea turtles – proportionately long front flippers, a streamlined skull, and a wide, flat body. Its skeletal structure suggests that this is a “hard”-shelled turtle which could not dive to great depths as the modern leatherbacks. Photo 6 is an artist’s rendition of what a Protostega  (probably a land species) may have looked like. The pronounced bony ridges, long tail, and stocky legs are not seen in modern turtle species. Also, notice the large unprotected area just behind its head. Through evolution, turtles have grown their shells closer to their heads to provide greater protection to their shoulder and neck areas.

 

Figure 1 shows a cladogram of the turtle order. Of the 28 families, only 13 are extant today. The leatherback is the only species in the Dermochelyidae family.  Despite surviving times of extreme weather change, shortage of food supply, and other catastrophic events brought on by the meteor strike some 65 million years ago, many turtle species are becoming extinct, and the leatherback is one of them.

 

The majority of the extinct turtle families shown on this cladogram died off millions of years ago. It is likely that most families become extinct because they could no longer compete for resources with the more evolved descendants.

Photo 6
This photo is an artist’s rendition of the ancient turtle species, Protostega. It is believed to be the ancestor of all modern sea turtle species. (Photo provided by
Eugene Gaffney of the AMNH)

 

The purpose of this diagram is to show the closeness of the derived traits between extinct and extant turtle families. The majority of turtle families progressively evolved, gradually developing evolutionary advantages over their predecessors. These families were well-suited to their environment and propagated. However, there are two families, Proganochelyidae and Australochelyidae that did not evolve as rapidly as other families, and consequently became extinct in the late Triassic (Gaffney, 2002).

 

Dermochelyidae, the leatherback turtle family, has no living relatives except for Chelonidae. This close relative includes sea turtles such as the green sea turtle. But by visual inspection alone, there are obvious differences in size, structure,

appearance, and features between the leatherbacks and the green sea turtles.

 

                                                                                 â

 

Figure 1

Phylogeny of all living turtles and some well-known extinct species. The leatherback family, Dermochelyidae (marked with blue arrow above), is one of only 13 living families of the turtle order, Testudines. (Figure provided by the Encyclopedia of Life Sciences)

 

<TOP>

 

Photos 7 and 8

Turtles evolved to two general categories: side-necked (pleurodires), top; and arch-necked (cryptodires), bottom. Leatherbacks are of the arch-necked variety. (Photos from Eugene Gaffney of the AMNH)

 

 

 

 

 

 

 

 

 

 

 

 

 

à Distribution

 

Understanding where the leatherback turtle occurs naturally means that we must first understand its basic physiology.

 

Contrary to popular belief, being a reptile doesn’t necessarily mean that it must be cold-blooded. Having a large, barrel-

shaped body allows the leatherback to “maintain their core (deep) body temperature considerably higher than their surroundings” (CRESLI, 2002). This explains why the leatherback can survive in ocean temperatures as low as 30 to 40˚F, from “as far north as Newfoundland, Greenland, and Iceland” (CRESLI, 2002).

 

Though they can survive in cold waters, the leatherback can be found most often in the low- to mid-latitudes. This is due to the fact that their primary diet consists of jellyfish. Geographically speaking, their migration routes run east-and-west, alongside areas of high jellyfish concentration. This route can extend far west to the British Isles and far south as the Cape of Good Hope and Australia. However, leatherbacks are most commonly found along the east coast of continents, namely, from Nova Scotia, to Florida, and further south to Puerto Rico, Mexico, and the Virgin Islands. Many are also found close to the Hawaiian Islands, which explains why so many are killed by boat strikes. Malaysia, Senegal, Madagascar, Ceylon, Thailand, and Papua New Guinea are the breeding grounds for this internationally-protected sea turtle.

 

Its streamlined and well-adapted body is suited for long distance travel in the open seas. The leatherback’s migration route in the Pacific Ocean runs along the boundary of warm and cold ocean currents. The “cool water [is] rich in plankton and the warmer water [is] low in plankton. As the cool water sinks beneath the warm, it traps buoyant creatures like jellyfish” (National Geographic, 2000). Jeffrey Polovina, of the National Marine Fisheries Service, says that the turtles will cross the Pacific in the next two to six years along the route described.

 

Leatherbacks thrive in all oceans of the world, except at the coldest near the poles. This species has “the most extensive range of an extant reptile (71˚N to

Map 1

This map shows the distribution of leatherback turtle nesting sites at the Parque Nacional Las Baulas in Costa Rica, one of the most active nesting sites for Pacific Leatherbacks. This beach region has also been designated as a national reserve, preventing urbanization. (Map provided by ENN)

47˚S)” (Eckert, 1997). They are most often found in reefs, and temperate and tropical coastal aquatic biomes, but can be also found in cooler boreal waters.

 

Leatherback turtles rarely venture to land except to lay eggs on shallow tropical beaches. Though leatherbacks venturing to land to feed is very rare, there have been some sightings of this behavior. (VA F&W, 2002).

Map 2

This is a thermal satellite image of the Pacific Ocean showing the areas of cool water (green) and warm water (blue) currents. Leatherbacks usually occur at the boundary of these water currents where jellyfish, their main prey, are abundant. (Image scanned from National Geographic, December 2000 Issue)

 

<TOP>

 

 

à Conservation

 

Worldwide Conservation

 

The leatherback turtle is listed as an endangered species as of June 2, 1970 (NOAA, 2001). There are an estimated 70,000 to 115,000 breeding females worldwide, but this number is decreasing rapidly (NOAA, 2001). In the US and Mexico, the leatherback population is declining at a rate of 22% annually along the Eastern Seaboard (NOAA, 2001).

 

The major causes for the decline of the leatherback population is the over-harvesting of unhatched eggs, the direct harvesting of adults, the incidental mortality from fishing, and the loss of habitat by urbanization or human disruption. Unhatched eggs are an easy target for humans and small mammals along nesting sites. In the US, as much as “95% of turtle nests were destroyed by raccoons” looting the nests even before the females had returned to sea (FL Travel Guide, 2002). Today, the Florida Marine Patrol (FMP) installs cages around turtle nests to prevent raccoons from digging into them. The cages have spaces that are wide enough for the hatchlings to pass through. Additionally, the FMP installs fences around beaches to further isolate the turtles from any human activity during nesting seasons.

 

Many countries have implemented laws to counteract the illegal smuggling of unhatched eggs. However, very little is being done to enforce these laws, especially in the remote areas of developing countries. Many countries aware of the leatherback’s endangerment of extinction have established natural reserves as a means to deter theft of unhatched eggs and development of beachfronts.

 

Human Impact

 

For centuries, humans have killed sea turtles for their meat and oil. However, “it has been reported that the leatherback is one of two turtles that are toxic to humans and other animals. The flesh of this animal supposedly contains a substance called chelonitoxin whose chemistry is unknown. Reported symptoms of poisoning are nausea, vomiting, diarrhea, burning

sensation of lips, tongue and mouth, tightness of chest, difficulty in swallowing, hypersalivation, foul breath, skin rash, coma and death (Britannica 1986). However, these reports have been questioned because these turtles are regularly killed for food” (NOAA, 2001).

 

Today, the illegal poaching of eggs is the leading cause or the decline of the leatherback turtle population. In addition, the development of beachfronts causes sand erosion which creates an unsuitable condition for nesting. Artificial lights can also cause disorientation for hatchlings making tier way to sea, because they are attracted to the lights. Beach recreation also contributes to the decline of the leatherback population. Heavy machinery and cars moving through beaches can undoubtedly crush buried eggs.

 

Many leatherbacks have also been killed as pests. Such is the case in the waters off Chile, Peru, and Mexico, where leatherbacks were seen as “sea monsters” (Eckert, 1997).

Photo 9

A sea turtle (not leatherback) is caught during a fishing operation. Some 640 are unintentionally caught each year. (Photo and statistic provided by NOAA).

 

Marine Pollution

 

The leading cause of death among adult leatherback turtles is the ingestion of marine debris, and entanglement and drowning from fishing lines and nets. Ingestion of plastic bags, Styrofoam pieces, and other debris interferes with metabolism and bodily function causing malnutrition and/or ingestion of toxic components from these items.

 

Fishing operations usually unintentionally catch sea turtles – an estimated 640 every year (NOAA, 2001). In addition, boat impacts can seriously injure the layer of skin on the carapace, which will lead to infection and eventually, death. Oil spills, one of the most destructive events to occur in oceans, can disrupt the turtle’s entire physiology – its respiration, skin, blood, behavior, instincts, etc.

 

Five Vital Steps to Preservation

 

According to Eckert’s 1997 publication, “Recovery Plan for US Pacific Populations of the Leatherback Turtle”, there are five tasks that need to be completed to preserve and increase the current leatherback turtle stock. These tasks include:

 

1.      Eliminate incidental take of leatherbacks in U.S. and international commercial fisheries.

2.      Support the efforts of Mexico and the countries of Central America to census and protect nesting leatherbacks, their

      eggs, and nesting beaches.

3.      Determine movement patterns, habitat needs and primary foraging areas for the species throughout its range.

4.      Determine population size and status in U.S. waters through regular aerial or on-water surveys.

5.      Identify stock home ranges using DNA analysis.

 

Because the leatherback turtle is “the most widely distributed reptile species in the world” (GA Wildlife Web, 2000), it will take the combined efforts of governments, environmental groups, and concerned individuals to conserve such an evolved and unique animal.

 

<TOP>

 

 

à Bibliography

 

All links will open in a new browser.

 

18th International Symposium on Sea Turtle Biology and Conservation. (1999). Genetics and Evolution. [Online]. Available: http://ola.icmyl.unam.mx/tortugas/abstracts/pos-genetics.htm [14 November 2002].

 

Bilinski, Joseph J., Reina, Richard D., Spotila, James R., Paladino, Frank V . (2001). “The Effects of Nest Environment on Calcium Mobilization by Leatherback Turtle Embryos (Dermochelys coriacea) During Development.” Comparative Biochemistry and Physiology. Part A 130: 151-162.

 

Brown, James H., Gibson, Arthur C. (1993). Biogeography. C.V. Mosby Company: St. Louis, Missouri.

 

Cannatella, David. (1997). University of Texas: Herpetology. [Online]. Available: http://cluster3.biosci.utexas.edu/courses/herpetology/turtlecroc/turtlecroc.html [18 November 2002].

 

Carnegie Museum of Natural History. (1999). Protostega gigas. [Online]. Available: http://www.carnegiemuseum.org/cmnh/exhibits/jurassic/fctprost.html [21 November 2002].

 

Coastal Research and Education Society of Long Island, Inc (CRESLI). (2002). Leatherback Sea Turtle (Dermochelys coriacea). [Online]. Available: http://www.cresli.org/cresli/turtles/leaback.html [17 October 2002].

 

Drexel University. (2002). Las Baulas Leatherback Turtle Project. [Online]. Available: http://www.leatherback.org/lasbaulas/costa-rica/Las_Baulas/Results_progress/2001_02%20Main_project.html [31 October 2002].

 

Drexel University. (2002). Leatherback Task Force. [Online]. Available: http://www.coas.drexel.edu/environ/leatherback/core.html [14 November 2002].

 

Eckert, Scott A. (1997). Recovery Plan for U.S. Pacific Populations of the Leatherback Turtle (Dermochelys coriacea). [Online]. Available: http://ecos.fws.gov/recovery_plan/pdf_files/1998/981201d.pdf [21 November 2002].

 

Emling, Shelley. (1999). Egg-Citing Stuff! Endangered Sea Turtles Nesting in Record Numbers. [Online]. Available: http://www.coxnews.com/washington/TURTLES.HTM [14 November 2002].

 

FL Travel Guide. (2002). Leatherback. [Online]. Available: http://www.2fla.com/leatherback.htm [13-20 November 2002].

 

Fontanes, Fermin. (1995). Dermochelys Coriacea (Leatherback Turtle) Narrative. [Online]. Available: http://animaldiversity.ummz.umich.edu/accounts/dermochelys/d._coriacea$narrative.html [29 September 2002].

 

Gaffney, Eugene S. American Museum of Natural History: Phylogeny of Turtles. [Online]. Available: http://research.amnh.org/users/esg/ [11 November 2002].

 

Georgia Wildlife Web. (2000). Turtles. [Online]. Available: http://museum.nhm.uga.edu/gawildlife/reptiles/testudines/dermochelyidae/dcoriacea.html [24 October 2002].

 

Green Nature. (2002). Leatherback Turtle (Dermochelys coriacea). [Online]. Available: http://www.greennature.com/article178.html [25 October 2002].

 

Hutchinson, John. (1996). Testudines: More on Morphology. [Online]. Available: http://www.ucmp.berkeley.edu/anapsids/testudines/testudinesmm.html [20 November 2002]

 

National Oceanic and Atmospheric Administration Fisheries Office of Protected Resources. (2001). Leatherback Sea Turtle (Dermochelys coriacea). [Online]. Available: http://www.nmfs.noaa.gov/prot_res/species/turtles/leatherback.html [13 October 2002].

 

Oceana. Leatherback (Dermochelys coriacea). [Online]. Available: http://www.oceana.org/index.cfm?sectionID=6&campaignID=3&fuseaction=bio.detail&bioID=4 [13 October 2002].

 

Reeds, Kate. (2002). Marine Life Information Network for Britain and Ireland – MarLIN: Leatherback Turtle. [Online]. Available: http://www.marlin.ac.uk/index2.htm?demo/Dercor.htm [24 October 2002].

 

Roach, John. (2000). Environmental News Network (ENN): Leatherback Turtles on Verge of Extinction. [Online]. Available: http://www.enn.com/enn-news-archive/2000/06/06012000/leatherback_13506.asp [10 November 2002].

 

Stanback, Mark. (2000). Biology 322: Vertebrate Field Zoology. [Online]. Available: http://www.bio.davidson.edu/Biology/mastanback/vfz/200.html [12 November 2002].

 

State of California Department of Fish and Game. (2002). State and Federally Listed Endangered and Threatened Animals of California. [Online]. Available: http://www.dfg.ca.gov/whdab/TEAnimals.pdf [29 September 2002].

 

Steel, R. and Harvey, A. (1989). The Encyclopedia of Prehistoric Life. Gramercy Publishing Co.

 

Thomas, Ellen. (2002). History of Life on Earth [Online]. Available: http://ethomas.web.wesleyan.edu/ees104/lect4clad.htm [20 October 2002].

 

The Turtle Pages. (Date). The Turtle Pages – Anatomy of a Turtle. [Online]. Available: http://theturtlepages.crosswinds.net/anatomy/index.html [22 November 2002].

 

Turtle Time, Inc. (2002). Sea Turtle Anatomy. [Online]. Available: http://www.turtletime.org/anatomy.html [1 November 2002].

 

Turtle Time, Inc. (2002). Species: Distribution, Attributes and Diet. [Online]. Available: http://www.turtletime.org/lthrback.htm [21 November 2002].

 

University of Texas, Austin. (2002). Digimorph. [Online]. Available: http://www.digimorph.org/specimens/Chelus_fimbriatus/whole/ [15 November 2002].

 

US Fish and Wildlife Service Division of Endangered Species. (1994). Leatherback Sea Turtle, Dermochelys coriacea, U.S. Fish and Wildlife Service. [Online]. Available: http://endangered.fws.gov/i/c/sac0d.html [3 November 2002].

 

The Virginia Fish and Wildlife Information Service (VA F&W). (2002). Turtle, Leatherback Sea. [Online]. Available: http://www.vafwis.org/BOVA/BOOKS/030075.HTM [18 October 2002].

 

 

à Please send comments to bholzman@sfsu.edu.

 

 

 

Photo 10

Leatherback sea turtle. (Photo provided by Scott Eckert)

 

“Because they are still living, turtles are commonplace objects to us. Were they entirely extinct, their shells – the most remarkable defensive armor ever assumed by a tetrapod – would be a cause for wonder.”
 

                                                                       -A. S. Romer

 

 

<TOP>

 

Click to See Other Biogeography Projects

 

Biogeography Homepage |  Geography Homepage | SFSU Homepage