I recently wrote about salamanders, one of the most poorly known groups of animals. Turtles (including about 50 kinds of tortoises) are much better-known. But aside from their iconic shell, what sets the more than 350 recognized species apart from other animals?
Like any group of plants or animals, they possess a variety of distinctive traits. I asked Jeff Lovich, lead author of our book “Turtles of the World” (Princeton University Press, 2021), what he considered to be intriguing facts about turtles. Following are his top 10.
• 1. Extended longevity of individuals is one of the foremost traits that makes turtles distinctive as a group compared to most other vertebrates. A common snapping turtle may take a dozen years to reach maturity, while a white-tailed deer population will have gone through an entire generation or more. A small percentage of Galápagos tortoises may live to be 200 years old!
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• 2. In addition to turtles living longer as individuals, they have one of the longest fossil records among the vertebrates. The oldest known turtles walked beneath the feet of dinosaurs 200 million years ago.
• 3. The largest turtles, now extinct, had shell lengths approaching 10 feet. The largest living turtles are the leatherback sea turtles, with a record length of 8 feet and a weight of more than a ton. Giant tortoises from the Galapagos Islands can weigh more than 800 pounds.
• 4. All turtles lay eggs — as few as one at a time in the five-toed padloper of South Africa to as many as 200 in the leatherback sea turtle. Among their unusual reproductive traits, many turtle species have environmental sex determination, meaning whether an individual becomes a male or female is determined by nest temperature and moisture. Some female turtles can mate once and produce fertile eggs for years.
• 5. The hip and shoulder joints are located outside the rib cage of amphibians, birds, mammals and all reptiles, with the exception of turtles. In turtles, the limb girdles are inside the rib cage, which is part of the formation of the protective shell characteristic of the group.
• 6. Eye color among turtles is highly variable compared to most other animal groups. Among the more dramatic are male box turtles with red eyes, Mississippi map turtles with white eyes, and the aptly named Sahara blue-eyed pond turtles.
• 7. Though living turtles are toothless, all of them can bite. A big alligator snapping turtle can easily chomp off a person’s finger with its powerful head muscles and knife-sharp jaws. Based on fossil records, more than 150 million years ago, turtles had teeth.
• 8. The first animals to orbit the moon and return safely to Earth were two Russian tortoises aboard a spaceship in 1968. Although provided with food, they could easily have made the trip without eating a bite. All turtles can fast for long periods.
• 9. Turtles play a significant ecological role in many habitats. In both terrestrial and aquatic systems they disperse seeds, enhance germination of seeds and recycle nutrients. Like many birds, turtles eat seeds that pass through their bodies and are later deposited elsewhere. Leopard tortoises of South Africa are known to disperse seeds from more than 75 different kinds of plants.
• 10. Some turtles are keystone species, which means they influence an entire ecological community. The burrowing habits of gopher tortoises in the Southeast and the African spurred tortoise create underground refuges for many other animals.
Almost everybody likes turtles, which constitute a captivating part of our natural heritage in much of the country. To make sure they stay around, we need to be aware of the hazards they face. Highways, degraded wetlands and illegal removal from their wild habitats by unscrupulous commercial pet trade collectors continue to threaten many turtles. Anything we can do to limit their impact will help assure we have turtles around for many generations to come.
Whit Gibbons is professor of zoology and senior biologist at the University of Georgia’s Savannah River Ecology Laboratory. If you have an environmental question or comment, email [email protected]