World Turtle Day: Celebrating the Remarkable Resilience of Earth’s Oldest Reptiles

It has been said that turtles and tortoises have covered vast distances on the Earth over millions of years, playing a vital role in the natural world and human cultures balancing marine habitats.

The Origins of Turtles

Turtles first emerged over 200 million years ago during the Triassic period, making them one of the oldest living groups of reptiles. Their distinct shell, fused to their backbone and ribcage, is one of their most iconic features and has helped them survive for so long. This hardy adaptation has allowed turtles to thrive in various environments, from tropical rainforests to tundra.

Over the millennia, turtles have evolved into an incredibly diverse group, with over 300 known species found on every continent except Antarctica. From the massive leatherback sea turtle that grows as long as eight feet and weighs up to two thousand pounds, to the tiny spotted turtle that fits in the palm of your hand, these reptiles come in a remarkable variety of shapes, sizes, and habitats.

These remarkable species can breathe through their cloaca. While most turtles breathe through their lungs, some species have developed the ability to extract oxygen from water through a process called cloacal respiration, which allows them to remain submerged for extended periods, making them highly efficient swimmers.

Moreover, turtles have a significant ability to navigate during their migrations. Some sea turtles use the Earth’s magnetic fields to navigate. They have geomagnetic abilities that serve as an internal GPS. The turtles have particles of magnetite, a magnetic mineral, in their brains, which likely plays a role in orienting them to the Earth’s magnetic poles, like a compass. Baby sea turtles imprint on the unique magnetic signature of the beaches where they hatch. This magnetic map can guide them to the same beaches several years later to lay their eggs.

The Importance of Turtles in Ecosystems

Turtles play vital roles in the delicate balance of ecosystems around the world. As both predators and prey, they help to regulate the populations of many other species. Sea turtles, for example, are crucial for maintaining healthy coral reefs and seagrass habitats, which provide food and shelter for countless other marine organisms.

In freshwater environments, turtles act as natural scavengers, helping to break down and recycle organic matter. This nutrient cycling is essential for the overall health of lakes, rivers, and wetlands. In addition, turtles are crucial food sources for larger predators, which maintains the energy flow in food webs. Beyond their ecological importance, turtles also hold deep cultural significance for many human societies. In various traditions and mythologies around the world, turtles are revered as symbols of wisdom, longevity, and the interconnectedness of all life. Their slow, steady movements and remarkable lifespans have inspired stories, art, and legends that have been passed down for generations. Some species of turtles are known to live for incredibly long periods of time. For example, the famous Galapagos tortoise is known to have lived for over a hundred years, with some individuals reaching the age of 150 years or more.

Threats to Turtle Populations

Despite their long evolutionary history, turtles today face a range of threats that are putting their survival at risk. Habitat loss and degradation, due to factors such as deforestation, urbanization, and pollution, are some of the primary drivers of turtle population declines. Many species are also targeted for the illegal wildlife trade, where their meat, shells, and eggs are highly sought after.

Climate change also poses a significant threat to turtles, particularly sea turtles, which rely on specific nesting beaches for reproduction. While these ancient mariners periodically come ashore to either bask or nest, they spend the rest of their lives in the oceans. Marine turtles can lay more than 150 eggs at a time. Called the clutch, these large egg deposits help ensure the survival of sea turtle hatchlings. Once a female lays her eggs, she returns to the sea, leaving her hatchlings to fend for themselves. Fewer than 0.1% of hatchlings survive to adulthood, in part due to the numerous predators on the beach. Emerging in large numbers increases the chance that some will survive.

Unlike most vertebrates, a sea turtle’s sex is not determined by sex chromosomes. Instead, the temperature of the nest determines the sex of the hatchlings. When temperatures are warm, at about 88 degrees Fahrenheit, most of the hatchlings will be female, while when temperatures are cooler, less than around 82 degrees Fahrenheit, most of them will be male. Thus, rising temperatures and sea levels can disrupt nesting patterns and lead to the loss of critical nesting habitats. Once abundant, turtle populations have dramatically declined in the past two centuries. Fishing is a major threat to sea turtles as they become caught in fishing nets as bycatch or accidental catch in commercial fishing operations, leading to high mortality rates. This issue is especially prevalent for endangered species, such as the hawksbill and Kemp’s ridley sea turtles.

However, policies have been enacted to reduce bycatch, protect turtle habitats, and prohibit the killing of sea turtles and their eggs. By continuing this kind of intervention, humans can help stop the decline of sea turtles, helping keep these ancient mariners in the world’s oceans. In conclusion, turtles are truly remarkable creatures with a range of interesting and rare characteristics. From their extraordinary longevity to their unique reproductive strategies and impressive navigational abilities, turtles continue to captivate the imagination of people around the world. On this World Turtle Day, let’s gain a deeper understanding of these fascinating reptiles and appreciate the importance of protecting their natural habitats.

Written by:

Apoorwa Amarathunga

3^rd Year

Business and Environment, Hons. Undergraduate,

Faculty of Science,

University of Colombo.

References:

• Gibbons, J. Whitfield. “Temperature-Dependent Sex Determination in Turtles.” Journal of Herpetology, vol. 20, no. 3, 1986, pp. 353–361.
• Spotila, James R., et al. “Temperature-dependent sex determination in sea turtles.” Conservation Biology, vol. 1, no. 2, 1987, pp. 149-154.
• The Editors of Encyclopaedia Britannica. (n.d.). Habitats, diets, and characteristics of turtles. Encyclopedia Britannica. https://www.britannica.com/summary/turtle-reptile
• The IUCN red list of threatened species. (n.d.). IUCN Red List of Threatened Species. https://www.iucnredlist.org/search?query=turtles&searchType=species
• Turtle Conservancy. (n.d.). Turtle Conservancy. https://www.turtleconservancy.org/

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