Turtles are easy to tell apart from other animals, whether they’re swimming in the open ocean, sunning themselves on a snag in a creek, or trying to cross the road. All turtles have four legs, a tail, and a shell that extends over their back and belly.
To avoid predators, they can pull their limbs and head into the shell. Some species can even close the shell entirely.
Keep reading to learn about the ways turtles have adapted. You’ll discover the physical traits that make them unique, as well as how they survive in environments with extremes of heat, cold, and water.
Key Takeaways:
- Natural selection over millions of years gave rise to the turtle’s shell, which is actually made up of the animal’s own ribs.
- Most of the turtle’s unique traits came about as ways to help the animal hide or flee from predators.
- Turtles have adapted to thousands of environments and all but the harshest of biomes; they are found in tropical, temperate, and saltwater environments.
How Have Turtles Adapted?
Turtles have adapted to a semi-aquatic lifestyle by developing a shell, the ability to hold their breath for minutes at a time, and fast swimming abilities. These adaptations are all ways they defend themselves and evade predators. Every turtle species has specific adaptations to its environment that help it survive and thrive.
Turtles can hibernate to avoid cold weather, bask in the sun to raise their body temperatures, see in more colors than humans, and navigate while migrating.
Before we discuss further, it’s important to note the difference between a tortoise and a turtle. Turtles are more reliant on water sources than tortoises. Some turtles have soft shells, while all tortoises’ shells are hard and bony.
How Have Turtles Evolved Over Time?
Turtles didn’t always look the way they do now. Over millions of years, natural selection promoted the reproduction and survival of better-adapted turtles. The turtle you see sunning itself on the creek bank is the product of over 250 million years of evolution.
The turtle body plan first appeared, probably due to a mutation, during the middle of the Triassic Period. This turtle’s ribs spread over its back in a hard, bony protrusion. It didn’t look like the turtle shell we see today. The external plates were still separated.
Scientists discovered what they believe is the earliest fossilized turtle as we know it in Proganochelys, which lived about 210 million years ago. Ever since the first known turtle, the shell body plan has stayed pretty much the same. Other changes, such as neck morphology and limb shape, adapted to environmental conditions.
What Are The Adaptations of A Turtle?
A turtle has different adaptations depending on what environment it lives in. However, there are some major traits that make a turtle a turtle. We’ll list several of them and explain why they’re important.
- A soft or hard shell
- A toothless beak
- Good vision
- 8 neck vertebrae
- Abdominal breathing mechanism
Many turtles hide from predators by retracting their limbs and head into their shells. Some box turtles can even flip down a ‘lid’ on a hinge to cover their head! This deters predators from trying to eat them since they can’t get past the bony shell.
While prehistoric turtles had teeth, they lost them over millions of years. Since most turtles eat vegetation and soft-bodied prey, the lack of teeth isn’t a problem. Today, most turtles have a parrot-like beak.
The predatory alligator snapping turtle even has a tiny pink lure on its tongue. It waits at the bottom of a water body with its mouth wide open until an unsuspecting fish mistakes the lure for a worm.
Turtles have surprisingly good vision for reptiles. Some can see UV light, which humans cannot. They also have 8 neck vertebrae, which gives them added flexibility and movement of their heads.
Breathing is a big issue for turtles. Its shell prevents the turtle from expanding and contracting its lungs, the basic formula for breathing. Another method of respiration had to be developed.
Today’s turtles use the movement of their abdominal muscles while walking or swimming to help them breathe. With each leg movement, the muscles act as a lever to inflate and deflate the lungs.
What Adaptations Do Turtles Have For Surviving in Water?
The level of a turtle’s water-related adaptations depends on what species of turtle it is, how much time it spends in the water, and whether it lives in saltwater or freshwater.
Sea turtles have more water-related behavioral and morphological differences compared to the average freshwater-dwelling box turtle. Even freshwater turtles that spend the majority of their lives in the water have more flattened limbs.
Their limbs act as paddles to help them glide along the currents. These make locomotion easier underwater.
Most turtles can hold their breath for at least 10 minutes. Sea turtles, which are almost completely reliant on the ocean for their entire life cycle, can hold their breath for over 40 minutes.
Even semi-aquatic turtles are well adapted to living in water. Even though their primary source of oxygen is from respiration using their lungs, some freshwater turtles engage in a practice called ‘cloacal breathing.’
They have specialized vascular tissue in this region that absorbs dissolved oxygen straight from the water. Others have vascularized tissue around their noses that helps them breathe air and absorb dissolved oxygen simultaneously.
How Do Turtles Survive in Winter?
Turtles are ectotherms, meaning they can’t maintain a constant body temperature of their own accord. In warmer months, they stay warm by basking in the light of the sun. Things change when it gets cold.
Some turtles hibernate through the winter by using a process called brumation. Brumation is similar to hibernation, but it describes a behavior where the animal can wake up and drink water for short periods before returning to sleep.
A turtle that is preparing to brumate looks for an abandoned burrow or nook underground. They choose underground spots because they are easy to access and have fewer temperature extremes than the soil’s surface.
Underground burrows deeper than 6 feet usually maintain a temperature of about 55F, warmer than most ambient winter conditions in North America. Other types of brumation include burying oneself in mud, or hibernating at the bottom of a frozen pond in the winter.
Don’t worry if a brumating turtle will run out of air! Turtles, unlike mammals, have comparatively slow metabolisms. They don’t require as much energy to support their day-to-day lives, especially when brumating.
Can a Turtle Live Without Its Shell?
No, a turtle cannot live without its shell. Turtles’ shells’ are fused to their bodies. They can’t be separated from their shells without perishing.
Some species of shelled animals can live without their shells. Hermit crabs, for example, spend their lives going from shell to shell as they grow. Turtles are different. They grow their own shells that are part of their body.
The bones that make up a turtle’s shell are actually the animal’s ribs. They are coated in a layer of keratin, the same material that makes up hair and fingernails.
Conclusion
Turtles have adapted to a myriad of environmental conditions. They can shut their shells to keep predators out, hold their breath for over half an hour, and hibernate in cold conditions. These long-lived reptiles may be slow-moving on land, but they are agile and swift in the water.
And remember, if you see a turtle in the wild, don’t take it home!
Anna is a wildlife biologist who graduated from Texas A&M in 2020. She enjoys studying and learning about wild birds and wildlife of all types.