Q. I know tortoises live on land. Does that mean box turtles (which also live on land) are tortoises? How many true tortoises are there, what parts of the world do they live in and how big do they get?
A. All tortoises are turtles, but not all turtles (including box turtles) are tortoises. The distinction is based on their evolutionary history. Tortoises arose about 50 million years ago. Box turtles evolved more recently within a family of aquatic species. All tortoises are terrestrial, but not all terrestrial turtles (thanks to box turtles) are tortoises.
“Tortoises of the World: Giants to Dwarfs” by George R. Zug and Devin A. Reese (Johns Hopkins University Press, 2024) provides an overview of the currently recognized tortoise species around the globe. Tortoises of one kind or another are found on all continents (except Australia and Antarctica) and on many large islands, such as Madagascar, the Galapagos and the Seychelles. The list includes 47 living species in addition to 8 that have become extinct in modern times. An alarming number of species are classified as endangered or—even worse—critically endangered. Only a half dozen are ranked as being of “least concern” from a conservation perspective.
The book begins with a chapter explaining how tortoises are structurally different from their aquatic relatives, as revealed by a body plan suitable for living on land. The authors note that “it would be hard to mistake a tortoise for any other animal.” Most tortoises are built like an armored tank. The front legs are muscular and stocky. The columnar hind legs resemble those of an elephant more than those of other turtles. Spending a lifetime on land, tortoises do not have webbed hindfeet or flippers like many freshwater and marine turtles. The shell is solid and sturdy; the tough skin of the limbs and long neck is dry and scaly. A tortoise threatened by a predator pulls in its legs so that only its shell and surfaces with thick scales are exposed. Contrary to conventional wisdom, a tortoise lying on its back is eventually able to right itself.
Most tortoises are herbivores, eating seasonal vegetation and fruits. They also eat mushrooms when available. Like many animals, tortoises will consume carrion on occasion. I once watched a shameless gopher tortoise amble onto a blacktop highway in Georgia and begin eating a road-killed armadillo. The book discusses general behavioral traits of tortoises as well as the many threats wild tortoises face throughout the world. Some are the standard hazards faced by most wildlife due to habitat modifications. Tortoises also must deal with removal from the wild by the illegal pet trade. Other exploitations include being captured for food and for traditional (which often means worthless) medicine.
Several pages are dedicated to informative accounts for each species that include geographical distribution and general ecology. Exceptions are always my favorites when reading about various groups of animals; hence, the speckled dwarf tortoise of rocky landscapes in west coastal South Africa caught my attention under its billing as “the world’s smallest tortoise.” Imagine an adult tortoise that does not exceed 4 inches in length! Africa is also home to the largest tortoise found on the mainland of any continent. The spurred tortoise, native to the region south of the Sahara across northern Africa, reaches a length of more than 3 feet and can weigh over 200 pounds. But for size records, even it does not compare to that of the lumbering giants of the Galapagos documented at greater than 4.5 feet.
With “Tortoises of the World,” Zug and Reese have produced an exemplary natural history book. The superb mix of entertaining and informative writing coupled with exquisite photographs will mesmerize all readers—children to adults, amateurs to professionals. The book is destined to become the consummate authority on these appealing creatures.
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