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Description: The riverine Barbour's map turtle displays
a high degree of sexual dimorphism. Typically, males have a carapace
length of less than 12 cm (4.7 in) while females may reach 33
cm (12.9 in) long. Females also have a much larger head than males
of the same species. In addition, females darken markedly once
they reach maturity, retaining few signs of the patterning of
juveniles and males. The color of the carapace is greenish or
olive brown, though adults found in the wild will usually be covered
in algae. Skin coloration of the head, legs, and tail ranges from
dark olive to nearly black with faint yellow or yellowish green
markings. The plastron is yellow, although the transverse seams
are lined with dark pigmentation. Barbour's map turtles have keeled
carapaces that contain black-tipped spines or knobs. Both the
pleural scutes and upper surfaces of the marginal scutes have
yellow, semi-circular markings that resemble the letter C. The
lower parts of the marginal scutes have dark markings on a light
background. A defining characteristic of this species is an interorbital
blotch on top of the head. This blotch ends in a point above the
nose and is connected to blotches or crescents immediately behind
each eye. A light transverse or curved bar can be found on the
underside of the chin.
Distribution and Habitat: Barbour's map turtles can be
found in the Gulf Coastal Plain in the Apalachicola and Choctawhatchee
River systems. This limited range includes parts of southeast
Alabama, southwest Georgia, and the Florida Panhandle. The Chattahoochee,
Flint, and Chipola Rivers in which these turtles reside are clear
flowing with limestone rock and cobble bottoms. They are also
rich in mollusks and contain many fallen trees and exposed rocks
for basking.
Reproduction and Development: The nesting season for Barbour's
map turtles is from June to August. The only reports of mating
have been during the winter months from captive turtles. Nests
are laid on sandbars or riverbanks as far away as 200 m (656 ft)
from the water. They typically contain 4-11 eggs that hatch in
late August and September. The temperature during incubation determines
the sex ratio of hatchlings as with many turtle species; warmer
temperatures result in a higher number of females. Males become
sexually mature at 4 years, while females reach maturity at 15-20
years.
Habits: Basking is a common occurrence in this species
of map turtle and usually takes place on rocks, tree branches,
or tree stumps at a safe distance from shore. They have been recorded
to bask at temperatures as low as 10°C, but in general there
is not much activity in colder months. Wary Barbour's map turtles
will dive into the water at the slightest disturbance. Due to
their powerful jaws, females maintain a diet of primarily aquatic
snails and freshwater mussels. Females have also been known to
scrape freshwater sponges off hard substratum. Males and juveniles
tend to ingest softer-bodied invertebrates such as caddisflies
and dragonfly nymphs. Raccoons and other mammals cause the most
harm to eggs and hatchlings, but introduced fire ants have also
become a major problem. Fire ants are likely to pose a problem
for many egg-laying reptiles, but we have few data quantifying
those impacts.
Conservation: The Barbour's map turtle is listed as a
vulnerable species by the IUCN. A number of conservation issues
have contributed to their decline. First, free-flowing rivers
that comprise the natural habitat of these turtles are slowly
but surely being replaced by deep reservoirs with silt bottoms.
Siltation destroys native mussel populations. Non-native Asian
clams have invaded some streams within the Barbour's map turtle's
range, providing a replacement food source. Various cases of unexplained
shell rot is likely due to river pollution, and collection for
the pet trade has also impacted populations of map turtles. Invasive
plants have taken their toll on suitable nesting locations by
colonizing sandbars, especially those that no longer flood.
Pertinent References:
Buhlmann, Kurt, Tracey Tuberville, and Whit Gibbons. Turtles
of the Southeast. Athens: University of Georgia, 2008.
Conant, Roger, and Joseph T. Collins. A Field Guide to Reptiles
& Amphibians: Eastern and Central North America. 3rd ed. Boston:
Houghton Mifflin, 1998.
Jensen, John B., Carlos D. Camp, Whit Gibbons, and Matt J. Elliott.
Amphibians and Reptiles of Georgia. Athens: University of Georgia,
2008.
Account Author: Lindsay Partymiller
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Hatchling
Note cross-shaped marking on underside of lower jaw
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