Creature Feature!

 Cetaceans (Dolphins, Whales & Porpoises)
Pinnipeds and Others (Seals, Sea Lions, Walruses and the Sea Otter)
Reptiles - The Sea Turtles
Fish
Invertebrates
Birds

Marine Reptiles - The Sea Turtles!

Kingdom: Animalia
Phylum: Chordata
Class: Reptilia

How do reptiles and amphibians compare?

• they are both cold blooded (ectothermic)
• reptiles have scales and amphibians do not
• they are both vertebrates (they have a spine or backbone)
• amphibians lay their eggs in the water and reptiles lay their eggs on land

What is a reptile?

Unlike frogs, salamanders and other amphibians, many reptiles live on land. The Class reptilia is a very diverse group. It includes snakes, lizards, turtles, tortoises, crocodiles and even the extinct dinosaurs.

All reptiles have scales for skin. They have lungs like mammals, but they have a three chambered heart (mammals have 4 chambers). The young of most reptiles hatch from eggs that are incubated in sand, moss and other substrates. Some eggs are incubated inside the mother's body and the young leave the mother with no shell.

Turtles (Order: Testudines)!

Turtles are interesting creatures that have a protective shell built around their body. When threatened by another animal most turtles can pull their entire body inside the shell. The "upper shell" is called the Carapace, the "lower shell" is called the Plastron and the section of the shell joining the upper and lower halves is known as the Bridge. Their shell is made of Scutes, which are also called bony plates.

Turtles belong to the Order Testudines. They occur on all continents except for Antarctica. There are more that 240 species of turtles living today.

Did You Know?... Turtles are the only group of reptiles that do not have teeth. Instead they have a strong horny beak that is good at crushing hard food.

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Where do turtles live?

Turtles have managed to adapt to many different types of habitats:

• land
• freshwater
• saltwater

Land or terrestrial turtles are known as tortoises. Tortoises are found in warmer parts of the globe, for example the Galapagos Islands.  They are not found in  Canada. Aquatic turtles can be found in lakes, rivers, and in the ocean. Freshwater turtles are found all around the world. Examples of freshwater turtles found in Canada include; the eastern painted turtle, the spotted turtle, the musk turtle and the snapping turtle. The third type of turtle lives in the ocean, including the green turtle, the loggerhead turtle, the hawksbill turtle and others.

Aquatic turtles (fresh and saltwater) do not stay in the water at all times. They do venture on land at certain times. Freshwater turtles climb onto land for breeding and for sunning and oceanic turtles travel to beaches for breeding.

The main difference between freshwater turtles and sea turtles is that sea turtles have limbs modified into flippers and freshwater turtles have webbed feet. Both types of limbs assist the turtles in swimming, but freshwater turtles who must often venture far onto land to find a nesting site have retained limbs that can travel well enough on land. Sea turtles simply have to use their flippers to move themselves onto a flat beach for nesting. In this case, the flippers do the job. For sea turtles who spend most of their lives in the ocean, flippers allow them faster and more accurate movement.

All turtles have scales called scutes on some or all parts of their body. The scutes may become worn out with age and therefore they would not be as visible on older turtles.

Scientific Classification of Sea Turtles!

Order - Testudines

Scientifically speaking the Order Testudines consists of the following three suborders:

1. Amphichelydia - living turtle and tortoise species
2. Pleurodira - includes side-necked turtles
3. Cryptodira - includes all species that are extinct
   

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Suborder - Amphichelydia

This suborder includes the freshwater turtles, snapping turtles, tortoises, soft-shelled turtles, and sea turtles.

Did You Know?... Sea turtles can stay underwater without surfacing to breathe for up to two hours while resting. They must surface frequently when active.

Family - Cheloniidae or Dermochelyidae

Sea turtles fall into one of the following two families:

• The family Cheloniidae includes sea turtles which have shells covered with scutes (horny plates).
• The family Dermochelyidae includes only one modern species of sea turtle, the leatherback turtle. Rather than a shell covered with scutes, leatherbacks have leathery skin.

Sea Turtles!

There are 5 types of sea turtle: Leatherback, Green, Loggerhead, Hawksbill and Ridley. These turtles differ from all other turtles because they have modified their limbs (arms and legs) to act as flippers. They nest (lay their eggs) on shore and then the females return to the sea leaving the young to fend for themselves. Naturalists and biologists often patrol sea turtle nesting grounds during nesting season to make sure that people do not accidentally step on nests.

Did You Know?... Arribada is the term for the mass nesting of sea turtles that occurs when they come onto land and lay their eggs.

How do Sea Turtles eat?

Sea turtles have a mouth and strong jaw that is specially shaped to help them eat their food. Their upper and lower jaws act as a clamp on unsuspecting prey. They have no teeth, but their bite is very strong. The two large muscles at the back of the skull contract as the turtle eats its food. Once these muscles have contracted, it is very difficult to escape from a turtles mouth.

Turtles have a very slow metabolism, which does not require lots of food every day. They can go for periods of time without eating.

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What Sea Turtles Eat

The hawksbill sea turtle has a narrow head and its jaws are shaped like a beak. These features allow the hawksbill to get food from the cracks and crevices in coral reefs. These turtles eat sponges, anemones, squid and shrimp. Loggerhead sea turtles are mostly carnivorous and they feed on shellfish that live on the ocean floor. These turtles eat horseshoe crabs, clams, mussels, and other invertebrates. The powerful jaws of this species are designed to help them easily crush the hard shell of shellfish. Atlantic ridleys and Pacific ridleys sea turtles are also carnivores. Like the loggerheads, the ridleys have strong jaws that help them to crush and grind shellfish such as crabs, clams, mussels, and shrimp. The ridleys also like to eat fish, sea urchins, squid and jellyfish.

Did You Know?... Sea turtles that eat jellyfish often confuse plastic bags with jellyfish. This is very harmful to their digestive system. It is therefore very important to these creatures and many others that we do not litter.

Canadian Species of Sea Turtles!

Leatherback Turtle, Dermochelys coriacea

Did You Know?... the leatherback sea turtle has been listed as an endangered species by COSEWIC, the Committee on the Status of Endangered Wildlife in Canada, since 1981?

The leatherback is the largest living turtle. Its' plastron and carapace have no scutes, instead they are covered by a dark blue-black leathery skin. The plastron and some parts of the body have white markings. Long backward-projecting spines (like shark teeth) inside their mouth and esophagus help them swallow the slimy food that they eat. This turtle has an amazing ability to maintain its deep body heat high above the temperature of cold seawater, allowing it to venture into the colder waters of Canada in the summer.

Nesting occurs on beaches of tropical coasts. The female adult leatherback digs a hole in the sand where she lays her eggs. She then covers the hole and goes back to the ocean. When the young hatch they venture out into the sea. Young sea turtles are at risk of being eaten by predators such crabs on land and sharks at sea. The hatchlings are covered in beady scales which are shed. Their tail has a keel and they measure 6-7.5 cm (2.4 - 3 inches) in length.

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Interesting Facts About Leatherbacks

Leatherbacks are known to be actively swimming in water below 40 degrees Fahrenheit (below 4 degrees Celsius). This turtle is the only reptile that is known to still be active at such a low temperature. This species of sea turtle has a very high oil content in their body.

Habitat: Open water.
Length: 135-178 cm (53-70 inches)
Weight: 295-544 kg (650-1200 lbs)
Diet: Jellyfish (mostly), sometimes seaweed, sea urchins, squid, and molluscs
Range: Atlantic: Western Atlantic, from Newfoundland to Argentina.

Loggerhead Turtle, Caretta caretta

The loggerhead is one of the larger sea turtles. It is a reddish brown colour, with a middorsal keel which becomes less pronounced in old turtles. Adult females nest regularly on the beaches of the Carolinas in the United States. The young have 3 dorsal keels and two plastral keels. They measure 4.1-4.8 cm (1.6 - 1.9 inches)

Links!

Canada's Turtles
http://www.aquatic.uoguelph.ca/reptiles/books/book3/bookframe1.htm

Checklist of North American Turtles
http://www.nearctica.com/nathist/reptile/turtlist.htm

The Nova Scotia Turtles website
http://ednet.ns.ca/educ/museum/mnh/nature/turtles/index.htm

Sea Turtles - Species of the World
http://www.cccturtle.org

Turtle Trax - Marine Turtles
http://www.turtles.org

References

Microsoft Encarta. 1996 Edition. Microsoft Corporation.

Microsoft Oceans.1995 Edition. Microsoft Corporation.

Petersons Field Guides - Reptiles and Amphibians (Eastern/Central North America) by Roger Conant and Joseph T. Collins. Copyright 1991.

Artwork:
Clipart by the Corel Corporation
Clipart by Microsoft Creative Writer
Original Art by Jennifer Lalonde