Cagle's map turtle  (Graptemys caglei)

Map turtles are so named for the distinctive fine lines covering their skin and upper shell (carapace), which somewhat resemble a road or contour map, and lend an air of beauty and elegance to these species that is hard to equal (3). Like most turtles found in the green-tinted rivers it occupies, Cagle's map turtle is a distinctive greenish colour (4), and arguably one of the most attractive of all map turtles (5). The upper shell is serrated at the back, bears a steep keel of sharp spine-like projections down the centre (2), and is brightly patterned with black and yellow-green concentric lines and circles (5). The head, limbs and tail are black with numerous cream to yellow lines, and there is a cream-coloured bar on the chin and a yellow ‘V'-shaped mark on the top of the head (2) (5). Female Cagle's map turtles are larger than males and also have broader heads (6).

Restricted to the Guadalupe River and its tributaries, the San Marcos and Blanco Rivers, of south-eastern Texas, U.S. (2) (7).

Generally found in shallow limestone and mud-bottomed streams with moderate currents, and in pools up to three metres in depth (2) (8).

Cagle's map turtle is a diurnal species that spends much of the day basking on logs and rocks in the water. A predominantly aquatic species, this turtle rarely comes onto land other than to nest (8). Hatchlings have been collected from September through November, indicating that the nesting season likely occurs in late spring to early summer (2). As many as three clutches of one to six eggs may be laid by a single female each year, deposited in nest-cavities approximately 15 centimetres deep near the water (2) (8). Sex is temperature-dependent, with lower nest temperatures producing males and higher temperatures producing females (8).

Female Cagle's map turtle feed almost exclusively on Asian clams, while the males predominantly consume caddisfly larvae, and occasionally other insects and small molluscs (9). This difference in diet is correlated to the difference in head-width between the sexes (6). Plant remains have also been found in specimen's stomachs, but are thought to have been ingested incidentally (2) (8).

Relatively little is documented on the threats that face Cagle's map turtle, other than the fact that its habitat is constantly being threatened by siltation, impoundment and other forms of habitat alteration (10).

Cagle's map turtle is listed as Threatened in Texas and is therefore protected within the state (4).

For more information on Cagle's map turtle see:

• Ernst, C.H., Altenburg, R.G.M. and Barbour, R.W. (1997) Turtles of the World. ETI Information Systems Ltd, Netherlands. Available at:
  http://ip30.eti.uva.nl/BIS/turtles.php

Authenticated (28/02/2008) by Professor Peter Lindeman, Professor of Biology, Edinboro University, Pennsylvania.
http://users.edinboro.edu/plindeman/