Turtles are reptiles that have existed on Earth for over 200 million years. There are around 356 known species of turtles in the world today. Turtles can be found on every continent except Antarctica and in all types of habitats from deserts to oceans. The main characteristics that all turtles share are a protective shell, a beak-like mouth without teeth, and a slow metabolic rate. Beyond these common features, different turtle species have evolved for specialized environments and vary greatly in size, color, diet, behavior, and more. In this article, we will look at the major categories of turtles and highlight some of the most fascinating turtle species from around the world.
Freshwater Turtles
Freshwater turtles live in ponds, lakes, rivers, streams, and other bodies of fresh water. There are around 257 known species of freshwater turtles which accounts for the majority of all turtle species. Some key features of freshwater turtles include webbed feet for swimming and a streamlined shell shape. Their sizes range from just a few inches to over 6 feet long. Here are some examples of common freshwater turtle species:
– Red-eared slider turtle – This is likely the most popular pet turtle. They have red stripes around their ears and can grow up to 12 inches long. Native to the southern U.S. and northern Mexico.
– Common snapping turtle – These turtles have a jagged shell and long, thick tail. They can reach over 18 inches in length and have a powerful bite. Widespread across eastern U.S. and Canada.
– Painted turtle – Named for their brightly colored shells with red, orange, and yellow markings. They are small to medium-sized turtles less than 10 inches long. Found throughout much of North America.
– Softshell turtle – These turtles lack the hard, protective shell that most turtles have. Instead they are covered in leathery skin for camouflage at the water’s bottom. Distributed across North America, Asia, and Africa.
Sea Turtles
Sea turtles, as their name suggests, live in ocean habitats around the world. Their streamlined shells and large flippers make them excellent swimmers. Of the 7 species of sea turtles, most are endangered or threatened due to human activities. The largest sea turtles can reach over 6 feet long and 500 pounds. Some key sea turtle species include:
– Green sea turtle – Named for the green color of their fat and cartilage. They are herbivores that graze on sea grass and algae. Populations are endangered from overharvesting their eggs and meat.
– Loggerhead sea turtle – The most abundant species of sea turtle but still threatened. They have a large head and powerful jaws to crush hard-shelled prey like clams and crabs.
– Leatherback sea turtle – The largest species that can weigh over 2,000 pounds. They lack a hard shell and feed on jellyfish and other soft-bodied animals. Their numbers are rapidly declining.
– Hawksbill sea turtle – Distinguished by their tapered head shape and stunning gold and brown shell. They are critically endangered due to demand for their shells for decorative purposes.
Land Tortoises
Land tortoises are turtles that live entirely on land. To survive on land, they have domed shells, stumpy legs, and thick forelimbs for digging burrows. They are found in warm, dry habitats like deserts and are herbivorous, feeding on grasses, fruits, and vegetables. Some remarkable land tortoises include:
– Galápagos tortoise – The largest species that can weigh over 800 pounds and live over 100 years. They are native to the Galápagos Islands and helped inspire Darwin’s theory of evolution.
– Gopher tortoise – Lives in sandy upland habitats in the southeastern U.S. They dig deep burrows for shelter which provide a habitat for over 300 other species.
– Aldabra giant tortoise – From the Aldabra Atoll in the Indian Ocean. They can live over 150 years and weigh 550 pounds making them one of the longest lived animals.
– Desert tortoise – Inhabits the Mojave and Sonoran Deserts in the southwestern U.S. Adapted to survive in hot, dry conditions and able to live up to 80 years.
Semi-aquatic Turtles
Semi-aquatic turtles live both on land and in the water. They typically live in fresh water habitats but will leave the water to bask on land. Semi-aquatic turtles have webbed feet but are more agile on land compared to fully aquatic turtles. Some examples include:
– Red-bellied turtle – Often basks on logs and rocks near the water’s edge. Named for the reddish plastron on their belly. Found from Virginia to Florida.
– Yellow-spotted Amazon River turtle – Spends more time on land than most semi-aquatic species. Has bright yellow spots on its head and legs. Native to South America.
– Malayan flat-shelled turtle – Has a flat, rounded shell and webbed feet. Often found buried in mud on riverbanks. Native to Southeast Asia.
– Chicken turtle – Has an unusual high-domed shell and long, striped neck. It makes grunting sounds like a chicken. Found in the southeastern U.S.
Oddities and Ancient Turtles
In addition to the major groups, there are some turtles that are truly one-of-a-kind or represent ancient turtle lineages:
– Matamata turtle – This bizarre species has a flattened, triangular head and carapace that looks like fallen leaves for camouflage. It’s found in the Amazon and Orinoco Basins in South America.
– Pig-nosed turtle – The sole living member of an ancient turtle family, it has a distinctive pig-like nose. It flaps its nose like a snorkel to breathe while staying submerged. Found in freshwaters of Australia and New Guinea.
– Alligator snapping turtle – The heaviest freshwater turtle that can weigh over 170 pounds. It has powerful jaws, spiked shell, and a worm-like tongue used as a lure to catch fish. Found in the southeastern U.S.
– Big-headed turtle – Recognized by their disproportionately large head. They use their powerful jaw muscles to crush mollusks and snails. Found in Southeast Asia.
– Leatherback sea turtle – As the last surviving member of an ancient turtle family, it represents a highly distinct evolutionary lineage over 100 million years old.
Turtle Shells
One of the most distinguishing features of a turtle is its shell. There are two main parts – the upper carapace and lower plastron. The shell is made up of over 50 bones covered in keratin, the same material that makes up human fingernails. Turtles cannot crawl out of their shell because it is actually part of its skeleton. There are two main types of turtle shells:
| Shell Type | Description |
|---|---|
| Domed Shell | Curved carapace shape common in tortoises and box turtles. Offers protection from terrestrial predators. |
| Flattened Shell | Flatter streamlined shell suited for swimming. Seen in most aquatic and semi-aquatic turtles. |
In addition to the main shell types, the plastron on the turtle’s underside displays variation:
| Plastron Type | Description |
|---|---|
| Hinged Plastron | Allows the shell to partially close for added protection. Present in box turtles and tortoises. |
| Reduced Plastron | Smaller or absent plastron to aid in swimming. Seen in softshell turtles and sea turtles. |
Turtle Life Cycle
Turtles undergo a fascinating life cycle that starts on land but takes place largely in the water:
1. **Mating** – Occurs in water for most species. Male turtles mount the female’s back to copulate.
2. **Nesting** – Female turtles leave the safety of water and travel over land to dig nests and lay eggs. Nest locations vary by species.
3. **Hatching** – After incubating for 50-70 days, the eggs hatch and the hatchlings emerge. Their sex is determined by nest temperatures.
4. **Maturation** – Hatchlings head to water where they will spend years maturing before reaching sexual maturity. Lifespans are long, often 30-70 years.
5. **Migration** – Reproductive migrations between land and water continue in cycles throughout adulthood. Some turtles migrate thousands of miles.
This life history means that turtles face threats during both their vulnerable terrestrial and aquatic phases from predators, habitat loss, road mortality, and human consumption.
Turtle Conservation
Over 60% of the 356 known turtle species are listed as vulnerable, endangered, or critically endangered by the IUCN Red List. Some major threats facing global turtle populations include:
– **Habitat destruction** – Development, agriculture, and water diversions destroy wetland habitats and nesting sites.
– **Over-collection** – Wild turtles are unsustainably overharvested for the pet trade and food markets, particularly in Asia.
– **Invasive species** – Invasive plants, fish, and other animals outcompete or prey on native turtles.
– **Road mortality** – Turtles crossing roads to migrate and nest are often hit by vehicles.
– **Hunting** – Turtles are illegally poached for their meat, shells, and use in traditional medicines.
There are several conservation actions that can help protect turtles:
– Protecting habitat corridors and preserves for migration and nesting
– Using wildlife-friendly underpasses and barriers at roads
– Better regulating the harvest and trade of turtles
– Reducing invasive species through ecosystem restoration
– Raising awareness and supporting anti-poaching programs
With concerted conservation efforts, the long legacy of these ancient reptiles can continue.
Conclusion
From tiny musk turtles to giant Galápagos tortoises, the world’s turtles display an amazing diversity suited to habitats across the planet. But they also share common traits like protective shells, strong jaws, and long lives that have enabled the evolution and persistence of these reptiles for over 200 million years. Learning about the differences and similarities across turtle species highlights their evolutionary adaptations and underscores the importance of conserving these fascinating creatures. While turtles face severe threats from humans, protecting them offers an opportunity to safeguard critical wetland and coastal ecosystems that provide enormous benefits to both wildlife and people.
