Cagle’s map turtle  (Graptemys caglei)

Cagle's map turtle is classified as Endangered (EN) on the IUCN Red List (1) and is listed on Appendix III of CITES (3).

Map turtles are 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 (4). Like most turtles found in the green-tinted rivers it occupies, Cagle’s map turtle is a distinctive greenish colour (5) (6). The upper shell is serrated at the back, bears a steep keel of sharp spine-like projections down the centre, and is brightly patterned with black and yellow-green concentric lines and circles (2) (6).

The head, limbs and tail of Cagle’s map turtle 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) (6). Female Cagle’s map turtles are larger than males and also have broader heads (6) (7).

Cagle’s map turtle has been recorded in the Guadalupe River and its tributaries, the San Marcos and Blanco Rivers, of south-eastern Texas, United States (2) (8). Its range appears to now be restricted to a single stretch of about 120 kilometres along the lower Guadalupe River (1).

Generally found in shallow limestone and mud-bottomed streams with moderate currents, and in pools up to three metres in depth (2) (6) (9).

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 (9). Hatchlings have been collected from September through November, indicating that the nesting season likely occurs in late spring to early summer (2) (6). 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) (6) (9). Sex is temperature-dependent, with lower nest temperatures producing males and higher temperatures producing females (6) (9).

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 (6) (10). This difference in diet is correlated to the difference in head-width between the sexes (7). Plant remains have also been found in specimen’s stomachs, but are thought to have been ingested incidentally (2) (6) (9).

Relatively little is documented on the threats that face Cagle’s map turtle (1), other than the fact that its habitat is constantly being threatened by siltation, impoundment and other forms of habitat alteration (1) (11). It is also likely to be affected by disturbance by humans and by the effects of groundwater depletion (1).

Cagle’s map turtle was uplisted from Vulnerable to Endangered by the IUCN in 2011, as its range was found to have reduced by half to two-thirds since 1974. This species is now restricted to a 120 kilometre stretch of river, where it faces continued threats from habitat degradation, water diversion and human disturbance (1).

Cagle’s map turtle is listed as Threatened in Texas and is therefore protected within the state (1) (5). It is also listed on Appendix III of the Convention on International Trade in Endangered Species (CITES), meaning international trade in this species should be carefully regulated (3).

Further information is needed on the distribution and population trends of Cable’s map turtle, and a population monitoring programme has been recommended. A greater understanding of the threats facing this species would also help to inform appropriate conservation measures (1).

View information on this species at the UNEP World Conservation Monitoring Centre.

More information on Cagle’s map turtle:

• 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