PUBLICATION 420-529 Sustaining America’s Aquatic Biodiversity Turtle Biodiversity and Conservation Joseph C. Mitchell, Department of Biology, University of Richmond, Richmond, Va. Kurt A. Buhlmann, Conservation International, Center for Applied Biodiversity Science,Washington, D.C. urtles are freshwater, marine, and terrestrial oriental food markets. Throughout the world, many vertebrates with a shell. There are about 300 people eat turtles and/or their eggs. The demand for living species worldwide in 12 families and turtles of all kinds in the oriental food markets, espe- Tabout 89 genera. Of these, eight species are marine, cially in China, is driving many species to the brink of 49 are land, and about 250 are freshwater to semi- extinction. Environmental and landscape changes in aquatic. North America threaten many populations. Pollution (e.g., contamination by pesticides) is known to disrupt The inexact numbers reflect changing taxonomy and endocrine function and cause sex reversal in some descriptions of new species. Forty-eight species oc- species. cur in the United States and Canada, with the highest diversity in the Southeastern United States. Most of Turtles are some of the longest-lived vertebrates. these are freshwater species, including the well- Among the reptiles, turtles, crocodilians, and some of known box turtles that are primarily terrestrial. Of the large snakes are longer-lived than most lizards and the remaining species, three are tortoises and five are small snakes. In studies of North American fresh- marine (sea) turtles. water turtles, Blanding’s turtle appears to be one of the longer lived species, as individuals older than 55 Turtles are found worldwide except in the coldest years are known to be reproductive. The oldest known regions. Their diversity is greatest in the tropical and age for painted turtles in a Michigan population was lower temperate regions. They have colonized many 34 years old. Yellow-bellied slider turtles and eastern habitats from deserts (several tortoises), forests, mud turtles in South Carolina were both estimated wetlands, ponds, and rivers (freshwater species) to the to live for about 35 years. The fact that most turtles oceans (sea turtles). are long-lived, with most living for several decades and some known to live as long as a century, makes it Many species of turtles worldwide and in the United difficult for these unique animals to sustain losses of States are in need of conservation and some are close individuals from populations. to extinction, particularly in Asia. The primary threats to turtles are habitat loss, alteration, and fragmenta- A primary reason why many tortoise and freshwater tion; mortality from road traffic, urban predators such turtles are endangered is their life history strategy. as raccoons and introduced species; and the collec- They take a long time to reach sexual maturity (i.e., tion of wild turtles for the commercial pet trade and some species require 20 years). This is in sharp con- www.ext.vt.edu Produced by Communications and Marketing, College of Agriculture and Life Sciences, Virginia Polytechnic Institute and State University, 2009 Virginia Cooperative Extension programs and employment are open to all, regardless of race, color, national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. An equal opportunity/affirmative action employer. Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Rick D. Rudd, Interim Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; Alma C. Hobbs, Administrator, 1890 Extension Program, Virginia State, Petersburg. trast to traditionally-hunted North American wildlife swimming and walking. However, variation within species such as rabbits or white-tailed deer that can freshwater turtles is still great. The soft-shell turtles reproduce at six months to one year of age; these ani- are fast and powerful swimmers, the snapping and mals may only live to be 2 or 3 years old. Conversely, musk turtles, often called “stinkpots,” are underwater turtles spend their juvenile years building hard shells “bottom walkers,” while the colorful spotted turtle is that will enable them to survive for many years; confined to shallow wetlands. perhaps a century for a few species, such as the giant tortoises of the Galapagos Islands. All turtles are included in the Order Testudines. Modifications of the unique Eastern box turtles, for example, shell and other body parts characterize possess a life history much each of the 12 families worldwide. Of these, like humans; they reach seven families occur in North America. maturity in their teens, They include sea turtles, tortoises, soft- produce few off- shell turtles, snapping turtles, box turtles, spring, and live for map turtles, mud turtles, cooters, sliders, decades. The significant and painted turtles, among others. differences are that in turtles there is no known curtailment of the ability to repro- All turtles lay shelled eggs. Most deposit them in duce and egg and juvenile mortality is high. Thus, nests constructed in the ground by the female par- loss of the older individuals in a population causes ent and a few lay eggs in leaf litter and on stumps in major negative effects. Many box turtles are killed wetlands. Most turtle species (and all crocodilians) on roads annually and many are collected for the pet possess temperature-dependent sex determination trade. Consider that this and other species cannot (TSD); the sex of the baby turtle is determined by withstand losses of adults and one will realize that the nest temperatures at a sensitive time during embry- killing and removal of even one old individual has onic development. There are no sex chromosomes as serious consequences. in most other vertebrates. Conservation efforts on behalf of turtles include Structure and appearance protecting habitat, controlling or preventing collect- ing, and reducing mortality through management of The distinctive shell is the most unique feature of tur- habitats and predators. Some efforts are local, some tles. The leatherback sea turtle has the largest known are national, and others are international. The list of shell with a length of over six feet. Turtle body armor resources at the end of this publication provides a is made up of 59 to 61 dermal bones organized into an window into these activities. upper part (carapace) and lower part (plastron) of the shell that are connected together by extensions (bridg- es) of the plastron. Many bones (ribs, vertebrae, and What Is a Turtle? sternum) are modified and expanded to form the shell. No one mistakes a turtle for anything else. One sees Another unique aspect of turtles is that the pectoral them basking on logs in lakes and ponds, walking in and pelvic girdles are positioned inside the rib cage the forest or other terrestrial habitats, or nesting on (shell); they are outside in all other vertebrates. This beaches along the shoreline. Some species are secre- body plan has been in existence for over 200 million tive and seldom seen. Turtles are incredibly diverse. years, and has served turtles well, until now. Other They come in all shapes and sizes, and each species features include a sharp-edged beak without teeth, is unique. The massive sea turtles have limbs that hard, keratinized (fingernail-like) plates that overlap are modified to resemble paddles. They can, and do, the bony shell, and the ability of some species to pull travel across an entire ocean, but have great difficulty their heads and necks inside the protective shell. hauling themselves up on an ocean beach to dig a nest. At the opposite end of the spectrum are the land Sea turtles are the largest of the North American tortoises which have club-like feet that resembling turtles. Their forelimbs are modified into flippers and those possessed by elephants. Tortoises may drown if rear limbs are formed as paddles. Freshwater turtles they fall into water over their heads. in the Family Emydidae all have hard shells and are Most freshwater turtles, including the ubiquitous highly variable in color and pattern. They include box turtle, have limbs modified to allow for both the largest freshwater turtles, the snapping turtles 2 eat both animal prey and plants as adults and juveniles include common snapping turtles, box turtles, painted turtles, and spotted turtles. Box turtles eat slugs, car- rion, fruits, berries, and leafy plants. The estuarine diamondback terrapin specializes on snails and clams. How do they reproduce (life cycle)? Adults of most species (e.g., painted turtles, cooters, sliders) engage in elaborate courtship rituals, although some, such as mud and musk turtles, have relatively simple mating rituals. Fertilization is internal. Fe- males of small species lay one to ten eggs, medium- that have large heads, massive jaws, sharp claws on sized females lay ten to 30 eggs, snapping turtles can powerful limbs, and flexible shells. Mud and musk lay 75 eggs, and sea turtles can lay up to 200 eggs turtles in the Family Kinosternidae are small, rela- in each nest. Sea turtle females may deposit sev- tively drab species with dark shells and skin and scent eral clutches in a single season but most turtles will glands that produce foul-smelling odors in some spe- lay only one clutch in a year. Many will skip years cies. Soft-shell turtles lack the hard shell and instead between reproduction depending on food resources in have a flexible, leathery skin covering a reduced bony previous years. structure. These highly aquatic species have long necks and powerful limbs with expanded feet for Most species in North America lay eggs in late spring swimming fast. Tortoises have hard, relatively high- and embryos develop within the eggs for about 60 to domed shells, rear feet modified like elephant’s feet 90 days.