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Known to some as the “green” map turtle to differentiate it from the similar Texas map turtle, the threatened Cagle’s map turtle in endemic to three Texas waterways—the Guadalupe, San Antonio and San Marcos rivers—but can also be found in associated creeks and tributaries. Named for Fred R. Cagle, an eminent herpetologist from Tulane University who passed away in 1969, Cagle’s map turtles are smaller than the other Graptemys species, with males typically reaching less than 5 inches and females averaging 7 inches in length. Both genders are greenish brown and have black heads marked with cream-colored stripes.
Once populous along the entire Guadalupe River Basin, Cagle’s map turtle numbers have waned, and remaining populations have been forced southward by habitat loss due to reservoir construction, water diversion, degradation of water quality and the impact of human development.
In 2005, a small population of Cagle’s map turtles was discovered in the Blanco River by scientists from Texas State University. The discovery, which was made during a project partially funded by the Conservancy, represented the first grouping of Cagle’s map turtles found upstream of the confluence of the San Marcos and Guadalupe rivers in some time.
Considering the scarcity the species, and new population represents a significant find and foster hope that suitable habitat still remains in the upper reaches of the Guadalupe River Basin. The Conservancy's Blanco River Project seeks to address the long-term health and conservation of the river where this population was found.
Tidbit: Little is known about the life span of the Cagle’s map turtle, but one adult male lived more than 14 years in captivity.
Nature picture credits: Thomas Simpson; TNC.
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