By Stacey Venzel
When it comes to water, turtles have a number of aquatic homes to choose from. Habitat preference among aquatic individuals is relative to water flow and type, among other determining characteristics.
Of the more than 300 members of the Testudines family, most live in rivers, with many of the river species inhabiting lakes, brackish water or opting for a semiaquatic lifestyle, but only a small percentage are found in the ocean. Two countries outshine the rest in their diverse concentration of turtle species.
Roughly half of the total turtle population can call a river home. Examples include the alligator snapper in the United States, the pig-nosed turtle of Australia and Central American river turtle. Though riverine species are most often found in rivers, they might be generalists, meandering into stagnant, river-fed freshwater habitats, both man-made and natural, similar to the red-headed river turtle’s preference for black water of the Amazon and Orinoco rivers. A handful are endemic to only a specific stream, such as the Fitzroy River and Mary River turtles, with turtles like the Magdalena River turtle exploring into lagoons, floodplains and swamps of this South American river.
Over half of the global turtle count can survive in lakes or ponds, but no species is a distinct lake-dweller. Typically, these species are also found in low flow regions ranging from creeks to quarries and, of course, rivers. Certain lakes make more suitable homes than others based on variables including their accessibility and amount of vegetation, as with the Blanding’s turtle preferring heavy plant life. Pond turtle species of Europe and North America as well as the bog turtle are found in small bodies of water associated with rivers.
Only seven marine species exist, surprisingly few considering saltwater covers 70 percent of the globe. However, the marine environment is harsh—just think how much faster a bike left outside will rust in Florida versus Ohio. Physiological adaptations like salt glands help flatback, hawksbill, Kemp’s ridley, olive ridley, loggerhead, green and leatherback sea turtles regulate bodily salt concentration to adapt to life in the sea.
When discussing aquatic habitats, it is important to remember the small number of non-marine turtles that can still tolerate saltwater to some degree. On all but two continents, many terrapins thrive in estuaries, tidal creeks and saltwater marshes, including the mangrove and painted terrapins of Asia and the North American diamondback terrapin.
Some species, like spiny-necked and twist-necked turtles, are better classified as semiaquatic, splitting their time between water and land. They might thrive in seasonally water-logged wetland habitats or simply live in and out of rivers. Around 25 species of U.S. turtles fall into this category, while still more semiaquatic species are found throughout the world. The savanna side-necked turtle crawls in and out of streams, ponds and wetlands along grassy plains in Venezuela and Colombia.
Regions of the United States and Asia rank highest when it comes to turtle diversity. In the U.S., 18 species are concentrated in a pocket of the southeastern states surrounding Alabama’s Mobile basin. That is more than the total number of species found in some countries. With approximately 60 species, the Unites States has more turtle species than any other country. Asia at large hosts around 30 percent of the world’s species, more than 15 times that of Europe and about double the species count in other continents. Regionally, Southeast Asia has even more native species than the Mobile basin but spread over a wider area. Sadly, the Asian turtle trade is threatening this natural diversity.
Roger Bour, John B Iverson, Anders GJ Rhodin, Et. Al., “Turtles of the world, 7th edition: Annotated checklist of taxonomy, synonymy, distribution with maps, and conservation status,” Chelonian Research Foundation, June 16, 2014, .
Karen Eckert, David Gulko, Sea Turtles: An Ecological Guide (Honolulu, Mutual Publishing, 2004), 23.
Carl J Franklin, Turtles: An Extraordinary Natural History 245 Million Years in the Making (St. Paul, Voyageur Press, 2007), 25, 56, 58, 67-68, 96-98, 104.
Whit Gibbons, Judy Greene, Turtle: The Animal Answer Guide (Baltimore, The John Hopkins University Press, 2009), 2, 4, 43-45.